With substantial yields expected across much of the Australian grain growing area and wet weather hampering harvesting efforts, growers are being encouraged to consider how they will manage on-farm storage to preserve grain quality.
Storing cereals and pulses with an average moisture content above 12.5 per cent can cause a range of issues, including mould and insect outbreaks in storage facilities.
Grains Research and Development Corporation (GRDC) National Grain Storage Extension Project Coordinator Chris Warrick said aeration cooling could play a critical role in successful on-farm storage this season.
“Aeration cooling allows grain that was harvested slightly over moisture to be stored for up to three to four weeks before it is dried or blended with dry loads,” he said.
Recent survey data has revealed that aeration cooling is widely underutilised in Australian on-farm grain storage, with two thirds of growers not using it, not realising it can be retro-fitted to their existing silos, or not ordering it as part of new storage capacity.
Mixing over-moist grain with drier loads will lead to a lower average moisture once the two loads are properly blended.
“Ideally, the blended load will be put back into storage with aeration cooling to help redistribute moisture evenly among the grain,” Mr Warrick said.
“The cooling fans need to be run continuously if the grain has a moisture content above 12.5 per cent, unless the ambient relative humidity is above 85 per cent for an extended period. Even air-distribution through the silo and open lids or vents are essential, as is monitoring the grain-temperature daily.
“The fans must deliver at least two litres of air per second per tonne of grain (l/s/t) just to hold over-moist grain safely.
“Drying grain out requires much higher airflows, in excess of 15 litres of air per second per tonne, which is only possible with high capacity systems specifically designed for aeration drying.”
Grain drying facilities have the benefit of being able to dry grain down to a safe moisture content for storage but are different systems to aeration cooling, which is important to understand.
Aeration cooling can enable over moisture grain to be held temporarily until it can be dried or blended. The longer-term benefits of aeration cooling are preserving grain quality including germination characteristics, grain colour in pulses and creating unwelcoming conditions for mould and insects.
Mr Warrick said the most common cooling mistake was not running the fans for enough hours to thoroughly cool the entire silo and push fresh cooling air right through the store. This could result in grain at the top of the silo remaining warm.
Grain that has been harvested, dried or blended below 12.5 per cent moisture content can be managed with a three-step cooling process.
Cooling fans should be run continuously from as soon as the aeration ducts are covered until three to five days after the silo is filled, or until the air coming out the top of the silo smells clean and fresh.
They should then be run for the 12 coolest hours of the next five to seven days.
And then for the 100 coolest hours of each subsequent month. To optimise this process an automated aeration controller is recommended.
This identification guide provides a snapshot of common pests found in stored grain in Australia. The tolerance for live storage pests in grain sold off-farm either for the domestic, humanconsumption market or for the export market is nil. With more grain being stored on-farm growers need to identify pests early and monitor – at the very least – monthly. Regular inspection by sieving grain from the top and bottom of silos will provide an early warning of insects present.
A serious pest of most stored grains: the Lesser Grain Borer has developed resistance to a number of grain insecticides.
Dark brown cylindrical shaped beetle (up to 3mm long) with club-like antennae
Viewed from the side the beetle’s mouth parts and eyes are tucked underneath the thorax (chest)
Adult beetles are strong flyers.
Life cycle completed in four weeks at 35°C and seven weeks at 22°C. Breeding stops below 18°C
Females lay between 200 – 400 eggs on grain surface. Young larvae (white with brown heads) initially feed outside then bore into the grain
Adults live for 2 – 3 months.
Their habit is to remain hidden in grain. Regular sampling and sieving is required for detection.
Rust-Red Flour Beetle
Commonly found in stored cereal grain, processed grain products, oilseeds, nuts and dried fruit.
Adult beetles (3 – 4.5mm long) bright reddish-brown in colour when young and a darker brown when older
Three larger segments on end of end of antennae
Similar species: Tribolium confusum – confused flour beetle, more common in cool, temperate regions.
Life cycle completed in 4 weeks at 30°C, 11 weeks at 22°C and reproduction stops below 20°C
Adults live from 200 days to 2 years and fly in warm conditions
Up to 1000 eggs per female, loosely scattered throughout the commodity
Cream-coloured larvae feed externally on damaged grain
Beetles infest whole grain, but breed more successfully on processed products (i.e. flour).
Beetles move quickly and are strong flyers. When in low numbers use sieving and probe traps to detect
Prefered habit is around storage areas with poor hygiene, broken grain, gradings or bulk cottonseed.
Major pest of whole cereal grains.
Adults are dark brownish black (2 – 4mm long) with a long weevil ‘snout’
Have four small light coloured patches on its rear wing covers
Rarely flies, but climbs vertical surfaces (e.g. glass jar)
Similar species: Sitophilus zeamais – maize weevil, and Sitophilus granarius – granary weevil.
Adults live 2-3 months
Larvae generally not seen – they feed and develop inside single grains
Life cycle completed in four weeks at 30°C, 15 weeks at 18°C, breeding stops below 15°C.
Under warm conditions or when grain is moved rice weevils are often observed climbing out of grain up vertical surfaces. Sieving & probe traps recommended to detect low numbers.
Flat Grain Beetle
Infests most stored grain and feeds on damaged grain. Some populations have high levels of phosphine resistance.
Smaller than other major stored grain pests (2mm long), very flat,reddish brown colour with long thin antennae
Fast moving, seeking cover under grain or trash
Adults fly readily and can live for several months
C. ferrugineus most common in Australia, but there are several closely related Cryptolestes species with similar appearance.
Life cycle completed in 4 weeks at 30 – 35°C with moist conditions, 13 weeks at 20°C, breeding stops at 17.5°C
Larvae, with characteristic tail and horns, feed and develop externally on damaged grains
Females lay up to 300 eggs loosely in the grain stack.
Sieving and probe traps usually required for detection
Some populations of flat grain beetles have developed very high levels of phosphine resistance. Send in insect samples for testing after a fumigation failure.
Saw-Toothed Grain Beetle
Infests cereal grains, oilseeds, processed products, peanuts and dried fruits.
Dark brown-black beetle (up to 3mm long), fast moving
Thorax (chest) has saw-toothed pattern on each side and three distinct ridge lines on top
Adults climb vertical surfaces (glass jar) and fly in warm conditions.
Prefers damaged or processed grain to establish in significant numbers
Adults can live for several months, females laying 300 – 400 eggs loosely throughout the grain. White larvae feed and develop externally
Life cycle completed in 3 weeks at 30 – 33°C, 17 weeks at 20°C, reproduction stops below 17.5°C.
Sieving and probe traps are recommended for detection
Has developed resistance to a number of grain insecticides.
Psocids – Booklice
Infests a wide range of grains, commodities and storage facilities.
Very small, soft-bodied and opaque, pale coloured (up to 1mm long), often appear as a ‘moving carpet of dust’ on grain or storage structures
A secondary pest, feeding on damaged grain and moulds
There are three main species of psocids in Australia, often in mixed populations.
Thrive under warm, moist conditions – optimum 25°C and 75% relative humidity. Life cycle 21 days
Eggs are laid on grain surface, hatching to nymphs that moult through to adult stage.
Warm, humid conditions increases activity. Usually observed in storage or on grain surfaces. Sample and sieve to detect when in low numbers.
BRUCHIDS: Cowpea weevils
Callosobruchus spp are pests of most pulse crops, including mungbeans, cowpeas, field peas, chickpeas, soybeans and lentils.
Adults (up to 4mm long), emerge through perfectly round holes in the seed
Globular, tear-shaped body is reddish brown with black and grey markings
Wing covers (elytra) do not fully cover the abdomen
Adults have long antennae, climb vertical surfaces (glass jar) and are strong flyers.
Adults do not feed, but lay 100 white eggs clearly visible on the outside of seed. Adult short lifespan 10 –12 days. Unlike most storage pests, adults may also lay eggs on mature seed pods in a standing crop
Larvae feed and develop within individual seeds and emerge as adults leaving a neat round hole.
A common problem in warmer months for mungbeans. Fortnightly thorough sampling and sieving is important to prevent serious losses.
Both a field pest and storage pest (appears in storage after emergence). In WA it is a major pest of field peas.
Adult globular body length (4 – 5mm long) with long legs and antennae
Wings (elytra) are patterned with white/cream spots
Do not breed in stored dry peas, adults lay and glue eggs onto pods in standing pea crops before harvest
Adult emerges through a neat round hole in the seed
Adults are strong flyers, they reappear in spring to visit flowers to feed on the nectar then seek out new field peas crops to lay eggs.
Hatching larvae bore through the seed pod and into a single seed where they feed, grow and pupate
Breed one generation per year. Adult is long-lived and overwinters but does not feed on field peas.
Adults migrate into crops from seed sources and nearby trees where they shelter under the bark
Field peas should be regularly checked, in and around the crop edges when first pods are forming using a sweep net when temperatures are above 18°C
Check pea seed for neat round holes (evidence that adults have emerged).
MOTHS: Angoumois Grain Moth
A pest of whole cereal grains which only infests surface layers of bulk-stored grains. Infestation of standing maize crops before harvest is quite common, occasionally in other cereal crops.
Silvery grey to grey brown wings which taper to a point
Wings have a long fringe of fine hairs along the posterior edge
Adults (5 – 7mm long) are unable to penetrate grain, therefore only infest surface layers of bulk grain.
Adult moths do not feed but lay 150 – 300 eggs on or near the grain surface. This pest does not create webbing
Larvae burrow into a single grain and feed and develop until the adult moth emerges in 10 – 14 days through a visible hole
Life cycle takes around 5 – 7 weeks in warm conditions.
Take regular monthly samples and look for moths near grain surface. When adults emerge pupal cases are often found protruding from grain.
Indian Meal Moth
A pest in flour mills, processing plants, dried fruit and on the surface of all types of grains.
Adults (5 – 7mm long), distinctive bicoloured wings – dark reddish brown on rear half of the wing and grey at the front.
Female month lay 200 – 400 eggs on the foodstuff
Larvae create webbing as they feed. They then pupate in several grains webbed together in a clump
In summer life cycle takes about 4 weeks.
Take regular monthly samples and look for webbing and moths near grain surface
Also check in residues on grain harvesting and handling equipment.
A pest of flour mills, food processing plants, cereal grains and oilseeds.
Adult moth body length is 8 – 10mm
Moth has grey wings with many fine, dark wavy markings, including lighter stripes extending horizontally across each forewing
Extensive webbing created by larvae is visible on the grain surface.
Adult moths do not feed and are short-lived. Female lays between 100 – 270 eggs over a two week period on or near grain
Caterpillar is coloured light pink with a small black spot at the base of each hair
Full life cycle 30 days under ideal conditions, 30°C and 75% relative humidity.
Take regular monthly samples and look for webbing and moths near grain surface. All moths are typically active at dusk and dawn.
Saw-Toothed Grain Beetle and Lesser Grain Borer have developed some resistance to a number of grain insecticides.
Flat Grain Beetle: some populations (Rusty Grain Beetle) have developed high level of phosphine resistance.
A range of stored grain insects are becoming harder to kill with phosphine fumigations.
Threatens exports, as phosphine may become ineffective against some pests.
Poor fumigation practices increase resistance (e.g. repeated fumigations in unsealed or poorly sealed storages).
Strong phosphine resistance is also found in overseas countries.
Live insects detected following fumigation should be tested for resistance.
Resistant insects can fly between stores or be transported in machinery.
EXOTIC PESTS: NOT PRESENT IN AUSTRALIA
BE ON THE LOOKOUT
The following pests have serious potential impact on the value of grain if detected in Australia. If you see anything unusual, report it to your local state department of primary industries or phone the Exotic Plant Pest Hotline, 1800 084 881
Can infect wheat, durum and triticale.
Usually only part of each grain is affected. Infected stored grain will have a sooty appearance and will crush easily, leaving a black powder.
Infected grain often has a rotten fish smell, flour quality is seriously reduced.
Symptoms are similar to common bunt.
Attacks most stored grains.
Larvae are covered in fine hairs.
Looks identical to the warehouse beetle to the naked eye.
Causes grain loss in storage.
Larvae skins contaminate grain and cause allergies on consumption.
Phosphine fumigation is not reliably effective.
How to monitor and identify grain pests
Identify pests early by regular fortnightly/monthly sampling
Sieve (with 2mm mesh) grain samples taken from the top and bottom of stores onto a white tray. Hold tray out in sunlight to warm for 10 to 20 seconds to encourage insect movement to identify them.
Also use grain probes or pitfall traps to monitor for insects. These are pushed into the grain surface and then pulled up for fortnightly/monthly inspection. Place 1 or 2 traps in the top of a silo or several traps in a grain shed.
If live insects are found, identify them and select the appropriate treatment for the grain type and insect. Always check product labels. Ensure potential grain buyers & end-users also accept treatments selected.
To check insects for resistance, send samples for testing
FOLLOW THESE BASIC STEPS:
Use a small, strong plastic container which is well sealed. DO NOT provide air holes – insects will escape
Place 20 to 100 insects with clean untreated grain into container
Do not overfill the container – leave some air space
Label container with the date, your name and the silo/storage identification
Provide all your contact details (address, phone and email) and a brief explanation of why you are seeking a resistance test, the storage type and details of any grain treatments details
If possible post early in the week so the insects are not left in the mail over the weekend.
SEND SAMPLES TO YOUR RELEVANT REGIONAL AUSTRALIAN LABORATORY:
NORTHERN REGION (QLD AND NORTHERN NSW): Dr Manoj Nayak DAF Ecosciences Precinct GPO Box 267 Brisbane Qld 4001 E: firstname.lastname@example.org
SOUTHERN REGION (SOUTHERN NSW, VIC, SA AND TAS): Please phone 02 6938 1605 before sending sample Dr Joanne Holloway NSW DPI / Wagga Wagga Agricultural Institute Pine Gully Rd Wagga Wagga NSW 2650 E: email@example.com
WESTERN REGION (WA): David Cousins DPIRD Entomology 3 Baron-Hay Court South Perth WA 6151 E: firstname.lastname@example.org For WA Biosecurity only WA insects to be sent to this lab!
Grain storage systems come in a range of shapes and sizes to meet farm requirements and careful planning is needed to optimise an on-farm grain storage facility investment. According to the option selected, on-farm grain storage systems can provide a short-term or long-term storage facility. Depending on the goal of on-farm storage, whether it be access to improved markets or simply to maximise harvest efficiency, there are a number of options available.
Harvest is the ideal time to plan future grain storage system requirements, as it can help identify issues and opportunities for future harvest operations that may otherwise be forgotten once next year’s crop cycle gets underway. Costs and storage flexibility can vary between grain storage options as can longevity of the investment. Table 1 identifies the major on-farm grain storage options, their advantages and disadvantages.
Silos are the most common method of storing grain in Australia, constituting 79% of all on-farm grain storage facilities nationally (see Figure 1).
Silos come in a variety of configurations, including flat-bottom or cone base, and both are available as gas-tight sealable or non-sealed, aerated and non-aerated. The balance of on-farm grain storage facilities can be split between grain storage bags (9 per cent) and bunkers or sheds (12 per cent). Grain-storage bags are increasing in popularity as a short-term storage solution to assist harvest logistics. With careful management growers can also use silo bags to provide short-term marketing opportunities. For similar storage time-frames to grain storage bags, and where options are limited, growers can also use sheds to temporarily store grain during harvest — provided they have been well prepared.
Superior silo: The dominant on-farm grain storage option is the silo in either a flat-bottom or cone-base configuration.
Benefits and pitfalls of various storage types
Silos: fumigation options
A gas-tight sealable silo will ensure phosphine, or other fumigants and controlled atmospheres, are maintained at a sufficient concentration to kill insects through their complete life cycle of eggs, larvae, pupae and adult. Be aware of cunning marketing terminology such as ‘fumigatable silos’. Although such a silo might be capable of sealing with modifications, a gas-tight sealable silo needs to be tested onsite to meet Australian Standard (AS 2628-2010) after installation. Gas-tight sealable silos also can be used for alternative methods of insect control including controlled atmospheres of inert gasses, such as carbon dioxide or nitrogen. Current costs of using these gases (between $5 and $12/tonne to treat stored grain compared with $0.30 per tonne using phosphine) carbon dioxide and nitrogen atmospheres will arguably be used solely by niche growers, such as organic growers, until gas is less expensive.
There is significant work being carried out in lower-cost nitrogen gas generation and if buying a silo, ensure it is gas-tight for future proofing of the investment.
Silos: sizes and construction
Silos can be transported fully constructed and ready to stand, or can be built onsite. While intra-state variations apply, transportable silos are typically limited to 140 tonnes capacity due to road transport regulation limitations. Most smaller, 50–70t, cone-bottom silos are prefabricated and transported. Cone-bottom silos are easier to clean than flat-bottom silos due to their self-emptying design, but are limited to capacities less than 300t. Some growers require gas-tight storage facilities of greater capacity and increasing silo capacity requires quality materials and design. Silos can be built onsite and are available in sizes up to 3000t. The increased surface area of a larger silo requires more sheet metal joins, providing more opportunity for gas to escape.
TABLE 2 Typical Grain Bulk Densities Per Cubic Metre
Silo lifespan is another advantage delivered through investment in gas-tight sealable silo storage infrastructure. A well-built, aerated, quality gas-tight sealable silo constructed to meet the Australian standard (AS 2628-2010) with a thorough maintenance regime could be expected to provide around 25 years of serviceable life before major repairs may be required. Silos: aeration While some preliminary research has been carried out using other grain-storage methods, silos permit simple administration of aeration after harvest to cool grain.
Aeration cooling of grain in-storage creates uniform moisture conditions and slows or stops insect pest life cycles.
Depending on the temperature reductions achieved; this can deliver significantly-reduced insect numbers.
For older, unsealed silos, consider retro-fitting aeration as the first option. Aeration cooling requires airflows of at least 2-3 litres of air, per second, per tonne. For example, a 100t silo will require 200-300 litres per second (l/s) of air to cool the grain effectively. Aeration fans also require well-designed perforated ducts or a plenum to assist in dispersing airflow evenly throughout the silo. Selecting the coolest air for the grain is best done using an aeration controller, but aeration fans should be run continuously for at least three days for smaller silos (less than 100t) and up to a week for large silos (over 100t) as soon as grain covers the aeration ducting. This initial process removes the harvest heat and equalises grain moisture. After initial harvest heat has been removed, the controller can be switched on to continue the cooling process.
Silos: aeration drying
Specific drying silos are designed to maximise drying efficacy and have minimum air-flow rates of between 15–20 litres per second per tonne (l/s/t) of storage. Specially-designed drying silos often have a truncated, or secondary, base cone to assist in the efficiency and efficacy of drying stored grain. Drying with ambient air requires a relative humidity well below that of the equilibrium relative humidity of the grain. Drying silos often allow the addition of heat at the air intake to improve the moisture removal capacity of the air flowing through the grain.
Silos: capital investment
As a permanent infrastructure fixture on a farm, silos are initially one of the most expensive options of grain storage at around $100 to $140/tonne for transportable sealed silos. To this can be added foundation requirements, which can vary between $2500 for a 70t transportable silo to considerably more for a flat-bottom silo with aeration ducting incorporated into the floor. Larger silos built onsite typically have an outlay cost of about $80 per tonne of stored grain. But looking at this investment over the life of the storage can see this figure drop significantly to being one of the cheapest forms of on-farm grain storage.
Working at heights can be dangerous without the appropriate safety precautions. In the case of silos, this can mean working up to 16m off the ground. A climb to the top is required for regular inspection through the top hatch if grain is stored for more than a month. Silo designs now incorporate ground-operated lids, caged ladders, platforms and top rails to minimise the risk of operators falling. Facilities for harness attachments, which should be worn by all operators climbing silos, are also fitted.
To meet the requirements of fumigation and utilising existing silo infrastructure, some growers have invested in retro-sealing older silos. In most instances these silos are high capacity (> 500t), flat-bottomed silos. Retro-sealing specialists use an array of rubber, specialised rubberised cements and silicon compounds to seal sheet joins, bolts, rivets, lids and openings on older silos. These are typically sprayed on with an air-operated gun with coarse flows to handle the heavy product viscosity.
[box]The interface between the pad and the bottom sheet of the silo and the top sheet meeting the roof should be given special attention as they are commonly points of limited seal integrity. Customised sealing plates can also be fabricated for doors, vents and openings. Oil-filled pressure-relief valves will also be fitted. The cost of retro-sealing an older style silo can be significant, often totalling as much as 50 per cent of the cost of a new sealed unit. Ensure the retro-seal contractor includes a guarantee that when completed the silo will meet the Australian Standard for sealed silos AS2628. After sealing, consider ongoing maintenance costs. Check coating integrity annually and patch as required to maintain an effective seal. Particular vigilance is needed around the storage base, and where the walls meet the lid, as expansion and contraction of the metal can damage the retro-seal finish.[/box]
Silo buyers’ checklist
Aerated, gas-tight sealable silos should always be the preferred option.
Ask the manufacturer to provide a guaranteed pressure test in accordance with AS2628-2010 on-site after construction or delivery. Pressure testing a storage when full of grain is also important.
Ensure a pressure relief valve capable of handling the maximum air-flow in and out of the silo due to ambient temperature variations is fitted.
A silo aeration fan can be used with care to pressurise a sealable silo to carry out the annual pressure test for leaks.A tyre valve or a larger fitting may also be installed to determine the volume of air required for the test.
Seal mechanisms on inlets and outlets should be simple to operate and provide even seal pressure.
Seal rubbers should be quality high-density EPDM (ethylene-propylene-diene-monomer) rubber, maintain a strong memory and be UV resistant.
Look for ground-operated lids that provide an even seal on the silo inlet.High-quality ground-opening lids will provide a gas-tight seal, but some will still require a climb to the top of the silo to lock down the lid for fumigation.
Aeration cooling fans are a must-have accessory for a new silo and provide significant benefits for stored grain.Buy these with the silo or as an aftermarket accessory and specify airflow rates of at least 2–3l/s for every tonne of grain storage capacity of the silo.
Aeration drying silos are an option, but are typically shaped to maximise drying efficiency.Drying fans need to deliver between 15 and 20l/s for every tonne of grain storage capacity of the silo and additional sealable venting in the roof should be fitted.
Outlet access for unloading should be simple to operate and permit ample auger access.
Look for a sturdy base and frame on elevated cone base silos with quality weldments. Galvanised tubing has a heavier coating than galvanised rolled hollow section (RHS) but is more difficult to shape and weld joins.
Ensure wall sections incorporate a positive seal between sheets and sealed riveting where rivets are exposed.
Always consider access and safety features, including roof rails, ladder lockouts, platforms and ladder cages. It can be argued that a ladder should always be fitted, as inspection of the grain in the top of the silo should be carried out regularly.
A quality outside finish will provide a superior life. White paint reduces heating of grain in storage. It comes at a cost premium but is superior to zincalume finishes over time.
A chalk-board patch painted on the silo base can be useful for recording grain and treatment details, including variety, protein and moisture content, fill date and fumigation details.
Check silo design inside and outside for ease of cleaning. Check walls and aeration ducting including the floor for grain trap points.
Ensure adequate venting is fitted to the roof of silos with aeration fans to permit adequate air-flow without restriction. These vents should be easy to clean. Check seals and lock down if it is a sealable silo.
As a relatively new on-farm grain storage option, silo bags have been widely used in Australia since the early 2000s, although they have been used overseas for much longer. As with most things new, numerous disasters, mostly due to operator error and lack of inspection vigilance, have earned grain bags a bad name. They can provide useful short-term storage (less than three months) and a logistics management tool during harvest. They must be installed on a well-prepared site away from bird habitats, including trees and water sources.
Grain-storage bags: capacity
Typical storage capacity is around 240 tonnes, but other sizes including 200t and 150t bags are also available.
Take care when buying bags. Quality of bag materials varies and using bags for grain storage that have been designed for silage storage is not recommended.
Grain-storage bags: using them successfully
Successful use of grain bags as an on-farm grain storage option requires a carefully-prepared pad. Anecdotally, an elevated, well-drained pad provides optimal results where no stubble (which can harbour vermin) or rocks can tear the grain storage bags as they are being filled and unloaded.
Fill rates are typically 3–4 tonnes per minute. Always fill bags up-the-slope and ensure brake settings on the filler are set to ensure the appropriate stretch of the bag is achieved. While typically a 10 per cent stretch, this can be adjusted down for hot weather conditions or up for cool ambient weather. When full, regularly and vigilantly check the bags for cuts, nicks and holes and patch these with silicon or bag sticky tape available from the bag supplier.
Grain-storage bags: costs
The two pieces of equipment required for loading and unloading grain storage bags can cost around $27,000 each. This equipment can be hired, although having your own can reduce the pressure of having to get grain in and out of the bags within a specified timeframe as demand for this hire equipment is high at the peak of harvest. The bags themselves are single-use and cost around $5 per tonne stored, or $1000 plus for a 240t bag. Consider site-preparation, including any earthworks and fencing requirements, time and labour costs for maintenance when calculating the comparative costs of using grain bags.
Grain-storage bags: useable lifespan
Grain-storage bags are best used for short-term storage only. While longer-term storages are possible, three months is regarded as a maximum storage period. Beyond this, there is considerable risk of grain losses and spoilage in many of Australia’s grain production regions.
Grain-storage bags: pest and insect control
Fumigation with phosphine in bags has been recently proven in Australia as an option if the correct method of application and venting is followed. Alternatively, fumigation of grain-storage bags can also be performed using gases like ProFume. But this is only available for use by licensed fumigators and the cost is generally considerably higher than phosphine. In addition to insects, vermin including mice and birds can attack grain bags. Outside baiting, reducing habitat provision and food sources (including regular checking and patching of bags where required) is the best way to reduce vermin risk. Grain storage bags: access One often-overlooked aspect of using grain-storage bags in the paddock is their accessibility after harvest. Unless the bags are placed on, or near, an all-weather access road, they can be difficult to unload if wet weather conditions prevail post-harvest. The pad site needs to be large enough for trucks and machinery for bag unloading and allow access in wet conditions.
Sheds and bunkers
Bunkers are commonly used by bulk handling companies, but require careful site preparation, labour for handling large tarp covers and machinery to move grain on and off the grain stack. Effective treatment of insect infestation is difficult in sheds and bunkers. For on-farm storage, grain bags may be a more suitable short-term alternative. Sheds can provide dual-purpose functionality for storage of other products including fertiliser and machinery. But the risk of grain contamination requires a focus on impeccable hygiene practices. As a permanent infrastructure investment, sheds can be continually used and have a retained value on-farm with a service life expected to exceed 30 years.
Specialist grain-storage sheds can be constructed to make filling and unloading simpler. Aeration and sealing methods for fumigations are best considered in the early shed design phase.
Sheds are most useful as a short-term storage solution to assist harvest logistics. They can be a useful component of an on-farm grain storage system that incorporates other gas-tight sealable grain storage facilities
Cost of grain storage in sheds varies widely depending on footing and slab requirements as determined by soil type. Method of construction and alternative uses can also vary the cost of construction. Sheds: aeration Aerating grain stored in a shed is difficult due to the open design of most shed structures. But customised ducting and air manifolds can be designed by grain aeration specialists to aerate grain stacked in a shed.
Sheds: pest and insect control
Given the open nature of most sheds on-farm, pest and insect control presents some challenges. Fumigation with gas-proof sheeting placed over the stack is difficult. Bulk handlers, including CBH in Western Australia, have invested heavily in sealing gas-tight bulk storage sheds to permit fumigation. On-farm, sheds are also prone to spoilage by mice and birds.
Sheds: loading and unloading
One of the biggest drawbacks of sheds used for grain storage is the ease of getting grain in and out. Using an auger or belt conveyor to fill the shed from the truck is common practice. For out-loading, some operators opt for bulk-handling buckets on front-end-loaders or tele-handlers to fill direct into trucks. Some grain trade operators use this approach to minimised grain damage when handling grains prone to splitting, such as lentils. Sump load points are occasionally used, with a lowered section of the floor utilising gravity to assist in sweeping grain into a loading point. Grain vacuums can also be used to out-load grain from sheds. Regardless of the out-loading options, inevitably, a final clean is performed with a broom and grain shovel, which can take time if hygiene is to be maintained.
On-farm grain storage facility considerations
Depending on budget and expectations, investing in and planning a grain-storage facility requires a range of considerations, regardless of the storage type.
Access for in-loading and out-loading
Continuous loop roads around the grain-storage facility requiring minimal, or no, reversing are ideal and can dramatically improve loading and out-loading rates as well as minimising damage to equipment through accidental collision. Dedicate an ample-sized pad to permit auger or grain conveyor access and ease of shifting grain loads. Where steeper slopes exist, some growers have terraced the slope with a retaining wall, to allow them to reduce the lift height (and auger size) for loading the silo. Where retaining walls exceed 1m in height, consider guard rails and access steps.
Proximity to resources (power sources — electricity and fuel)
Whether the facility is to be powered for aeration, i.e. using petrol or electricity, consider the proximity to these resources, particularly if the facility will be built in stages as each stage becomes affordable. Connection to mains power can be expensive depending on the distance to the line. Some large drying fans also require three-phase power which requires a specific pole transformer.
With augers, machinery and tipping trucks in use around the facility, placing power underground is expensive, but can significantly improve safety.
It is worth considering fuel sources and fuel lines for dryer installations, or future dryer installations, when planning the facility layout and constructing the pad.
Health and safety considerations
Operational safety considerations should be key to the facility design. Allow plenty of space for auger transport and movement around the facility.Ensure overhead power-lines are located nowhere near the pad where augers, conveyors or trucks might be operating — ideally locate power underground.
Pads should be flat, hard-packed stands that allow tipping trucks to elevate without risk of toppling over sideways.
Minimise any slopes and ensure they are of a constant grade. Position drainage lines and holes away from high-traffic areas to reduce the risk of equipment falling through while maximising drainage effectiveness. Electrical switch boards should incorporate residual current devices (RCDs) to prevent electrical shock if, for example, an electrical cable was accidentally cut. A qualified technician is required to carry out any 240-volt electrical work. They will ensure the components are safe to use in areas where combustible dusts are present.
The ability to get trucks in and around the grain-storage facility is paramount to its success. Sealed or hard, all-weather roads to the site from a main road are essential for year-round out-loading, which will ensure grain sale contracts are met in a timely manner and can deliver marketing advantages. Proximity to trees and insect or bird havens Avoid locating storage facilities near trees, haystacks and haysheds. All are havens for insects and birds, making migration from nature to the grain stored in the facility easier. Similarly, water sources are attractions for vermin and birds. Avoid water sources when selecting a site for a grain storage facility.
Proximity to harvest locations
One of the most important considerations of facility placement and layout is harvest logistics. While placing silos close to a house or existing infrastructure is most common, it may not be the most efficient placement from a logistics perspective. More often than not, storage facilities are located according to proximity to power and facilities, so a balance between ease of accessing services and optimising harvest logistics has to be struck.
Determining storage capacity requirements
Calculating ‘adequate storage capacity’ can involve an enormous range of variables. Consider what would be the ’ultimate‘ in on-farm storage capacity for the farm and then plan a series of stages to achieve this ultimate goal. For some growers, ultimate storage capacity is 100 per cent of their harvest, while others will always use an external bulk handling system to some extent. This is likely to vary between State bulk handling operators, dominant crop types, target markets and distance from the farm to bulk handlers. As an initial step, aim for a reasonable proportion of the total harvest and plan to expand the facility from there. Consider investing in a number of small silos as the first step and buy larger silos as the business expands. Smaller silos, for example around 70 to 100 tonnes, will always be valuable for segregation and blending or insect control in small parcels of grain. Fumigating a small amount of grain in a large silo can be expensive because treatment is based on silo volume, not grain volume.
Determining out-loading throughput rates
A standard out-loading rate is around 3-4 tonnes per minute and anything exceeding that will enable the driver to get back on the road to their delivery port quicker.
With fines for overloading increasing in severity and occurrence in most States, using a weighbridge could pay for itself quickly. Weighbridges can be incorporated into the silo load-and-unload loop with effective installations providing readouts for the driver when approaching from both sides. A weighbridge, fully installed will add a cost of about $130,000 to the facility.
The ability to blend grains and optimise specifications is one of the primary benefits of an on-farm storage facility. The ease of out-loading for blending is greatly improved by adding a belt or drag-chain grain conveyor and elevator system to the facility. Grain can be simultaneously out-loaded from multiple silos and loaded into another. The alternative is to blend into a truck and then auger back, which can be fiddly but effective if small batches are blended occasionally.
Keeping a record and sample of grain stored on-farm can be useful for subsequent testing and quality assurance. Owners of larger on-farm, grain-storage facilities commonly add a sampling shed where grain-quality specifications are collected and stored. Taking the sample from silos can be easier if sealed silo ports for sample collection can be easily accessed to obtain a cross section of the stored product. Truck sampling options include push spears and vacuum spears, which are designed to take a profile section of the load. They are used by many growers and are easier to operate from an elevated platform. If adding an elevated platform to the facility, remember to add handrails to minimise the risk of falling.
Cleaning and facility maintenance
Maintaining good site hygiene is easier with a quality hard surface. Concrete pads are essential for silos to sit on but extended aprons can also assist cleaning spilt grain from loading and unloading.
Common grain trap points include dump-pits, drainage or aeration channels and around silo bases.
Clean all grain off the site on a regular basis to avoid harbouring insects, which may infest stored grain. Ensure a water point is accessible for washing out silos after they are emptied. Grain vacuums are popular with owners of flat-bottomed silos to remove residual grain where sweep augers have not been able to reach.
When determining the requirement for earthworks, always allow a buffer around the pad for construction-vehicle movement. Raised pads are most common as they minimise the potential for water damage to the facility and stored grain. The height of the pad will typically vary according to the overall topography of the site relative to the landscape but 500mm above average topographic level is not uncommon.
Soil type impacts
Soil type can have a huge bearing on silo foundation thickness and requirements for facility earthworks. Foundations are normally engineered with depth of footing and reinforcing is determined according to the physical properties of the soil. Highly-reactive soils shrink and swell according to their level of moisture and typically require additional foundation engineering and reinforcing, which comes at a greater cost. As a rule of thumb, experienced silo-pad concreters assume soil type according to region for quoting purposes with slight variations dependent upon on-site requirements.
In addition to maintaining a raised, firm pad for the storage facility, plan for drainage to handle and direct run-off away from the pad. In some cases the natural topography of the site may assist free drainage while on flat sites, drainage channels may have to be formed to carry water away from the site. A well-designed pad for transportable cone-bottom silos will ensure water does not pool near the base structure, which can quickly rust out.
Loading and out-loading is often carried out at night during harvest and effective lighting not only makes the job easier for drivers but also improves safety at the site. Efficient and robust forms of lighting, including LED, are suitable choices for short-throw requirements. If laying electrical cables underground, for aeration or auger drives, consider laying electrical cables for lighting at the same time.
With numerous market opportunities and volumes of information and data detailing specifications of stored grain increasing, facilities for data transfer and communication add value to any site plan, particularly if the site is to be equipped with a sampling and testing shed.
Planning to expand
It is rare any grower would set out to build a complete on-farm grain storage system from scratch. The capital requirement would be enormous and in most cases grain storage facilities grow with increasing farm productivity. The careful planning of a facility to be built in stages can ensure design aspects of the larger site are not overlooked when constructing these stages. It can also lead to savings through coordinated placement of pipes, electricals and concrete pads. Expansion is most commonly, and simplistically, an extension of a single line of silos, although variations include circles with a central receival and out-loading point. Single lines of silos offer the ability to run a single out-loading belt, which can feed grain into an elevator for out-loading or transfer to other silos.
When planning to expand, consider drying options including the ability to undertake batch drying or dedicated drying silos with ample airflow rates.
Also plan for aeration controller placement and associated electricals.
Staking out the facility
Everything can look good on plans, but it is important to physically stake out the site of grain facilities to ensure proportions have not been underestimated or overlooked. Driving pegs onto the site to indicate silo placement, pad borders and the positioning of roads and weighbridges can help visualise the suitability of the plan for the site.
Adapting existing facilities
In many cases, existing facilities are worked into the design to use existing infrastructure.Upgrading, including retro-sealing silos and sheds, can be an option to reduce the overall cost of storage per tonne, but remember to include ongoing maintenance costs for retro-sealed facilities. Offset placement of silos in lines parallel to lines of existing silos can be an option and can offer out-loading efficiencies. Apart from fitting in around older storages, the first modification to older silos should be the installation of an appropriately sized aeration fan and ducting.
On-site office and sampling sheds
An on-site office is ideal for keeping records and samples of stored grain. It can house expensive, sensitive testing equipment and be used as a crib-room for drivers and employees. Portable site offices are a common choice as they can be fitted with air-conditioning and are often pre-wired for electrical outlets. Used site offices regularly come up for sale on mining sites and can be bought at a fraction of the new price. As a minimal alternative, an on-site cabinet for load documentation and records will ensure hard copies of silo contents and load specification details are kept on site.
Dump pits can be installed in combination with paddle or drag conveyors to quickly and easily take and elevate grain to load silos.
Carefully cover dump pits when not in use to keep water out and keep pits and surrounding areas clean to minimise contamination and spoilt grain.
Numerous options for shifting grain around the site are available and each has benefits and disadvantages. Maximum angles of elevation vary between conveyors according to grain but figures are usually quoted for wheat. Augers are most common due to their portability and are one of the cheapest methods of elevating grain into a number of silos. Elevation angle and flight turn speed have a bearing on flow rates with higher elevation angles reducing throughput and impacting on hygiene. Hygiene can be compromised with lower throughput, as grain tends to sit between the auger flights. It is best removed by reversing the auger until all grain has been cleared.
Augers can occasionally damage split-prone grain — particularly old augers with worn flighting. Belted conveyors are the second most-commonly-used grain transfer method and are preferred by operators transferring damage-prone grain. Being a transportable unit, elevation angle is limited to the angle of repose of the grain. The angle of repose is a physical stacking property of a grain and varies between grain types. The repose angle is a measure of the angle of the sides of a conical grain pile from horizontal.
For example, the angle of repose for wheat is 27 degrees while canola is 22 degrees. Flow rates reduce as the angle of elevation increases to approach the repose angle. Belts are often cupped along the conveyor length to accommodate grain and hygiene is excellent with the design of a belted conveyor being self-cleaning. Bucket elevators are predominantly used to elevate grain vertically and are commonly used together with belted conveyors transferring grain horizontally, or splitters diverting grain down chutes through a gated manifold.
Bucket elevators are self-cleaning by design and are typically fixed position equipment Drag-chain conveyors or paddle conveyors use a series of paddles fixed to a loop of chain moving inside a conduit. Drag chains can elevate at any angle, including horizontal, and are largely self-cleaning, although corners of the chain-loop will normally require attention. Drag-chain conveyors are a permanent installation but are extendable for facility expansion.
Storing pulses successfully requires a balance between ideal harvest and storage conditions. Harvesting at 14 per cent moisture content captures grain quality and reduces mechanical damage to the seed but requires careful management to avoid deterioration during storage.
Pulses stored above 12 per cent moisture content require aeration cooling to maintain quality.
Meticulous hygiene and aeration cooling are the first lines of defence against pest incursion.
Fumigation is the only option available to control pests in stored pulses, which requires a gas-tight, sealable storage.
Avoiding mechanical damage to pulse seeds will maintain market quality, seed viability and be less attractive to insect pests.
Pulse crops most commonly grown in Australia include broad beans, faba beans, chickpeas, field peas, lentils, lupins, vetch and mungbeans.
Many of the quality characteristics of the grain from these crops are in the appearance, size and physical integrity of the seed. Mechanical seed damage, discolouration, disease, insect damage, split or small seeds will downgrade quality and market value.
Buyers prefer large, consistently-sized seed free of chemical residues for easy processing and marketing to consumers.
Optimum moisture and temperature
Research has shown that harvesting pulses at higher moisture content (up to 14 per cent) reduces field mould, mechanical damage to the seed, splitting and preserves seed viability. The challenge is to maintain this quality during storage as there is an increased risk of deterioration at these moisture levels. As a result, pulses stored above 12 per cent moisture content require aeration cooling to maintain quality.
Grain Trade Australia (GTA) sets a maximum moisture limit of 14 per cent for most pulses but bulk handlers may have receival requirements as low as 12 per cent. As a general rule of thumb, the higher the moisture content, the lower the temperature required to maintain seed quality (see Table 1).
Green pods and grains increase the risk of mould developing during storage — even at lower moisture content. Aeration cooling will help prevent mould and hot spots by creating uniform conditions throughout the grain bulk.
Weather damage hinders storage
Pulses exposed to weathering before harvest deteriorate more quickly in storage. Chickpeas stored for the medium to long term (6–12 months) continue to age and lose quality (see Table 2). Growers can minimise the effects of seed darkening, declining germination and reduced seed vigour by:
Lowering moisture content and temperature
Harvesting before weather damages the grain.
Aeration cooling — vital tool
Creates uniform conditions throughout the grain bulk.
Prevents moisture migration.
Maintains seed viability (germination and vigour).
Reduces mould growth.
Lengthens (and in some instances stops) insect reproduction cycles.
Slows seed coat darkening and quality loss.
Aeration cooling allows for longer-term storage of low-moisture grain by creating desirable conditions for the grain and undesirable conditions for mould and pests. Unlike aeration drying, aeration cooling can be achieved with air-flow rates of as little as 2–3 litres per second per tonne of grain.
High-moisture grain can also be safely held for a short time with aeration cooling before blending or drying. Run fans continuously to prevent self heating and quality damage.
Be aware that small seeds such as lentils will reduce the aeration fan capacity as there is less space for air to flow between the grains. For information on aeration cooling management, refer to the GRDC fact sheet, Aeration cooling for pest control.
Pulses stored for longer than three months at high moisture content (>14 per cent) will require drying or blending to maintain seed quality. Aeration drying has a lower risk of cracking and damaging pulses, which can occur with hot-air dryers.
Unlike aeration cooling, drying requires high airflow rates of at least 15–25 l/s/t and careful management. For more information on aeration drying refer to the GRDC booklet, Aerating stored grain, cooling or drying for quality control.
Handle with care
In addition to harvesting at high moisture content, growers can manage seeds quality at harvest by:
Minimising the number of times augers shift grain.
Ensuring augers are full of grain and operated at slow speeds.
Checking auger flight clearance — optimum clearance between flight and tube is half the grain size to minimise grain lodging and damage.
Operating augers as close as possible to their optimal efficiency — usually an angle of 30 degrees.
Using a belt conveyor instead of an auger where possible.
Silos fit the bill
Silos are the ideal storage option for pulses, especially if they are cone based for easy out-loading with minimal seed damage. For anything more than short-term storage (3 months) aeration cooling and gas-tight sealable storage suitable for fumigation are essential features for best management quality control.
Always fill and empty silos from the centre holes. This is especially important with pulses because most have a high bulk density. Loading or out-loading off-centre will put uneven weight on the structure and cause it to collapse. Avoid storing lentils in silos with horizontally corrugated walls as the grain can run out from the bottom first and collapse the silo as the grain bulk slides down the silo walls.
Pests and control options
The most common pulse pests are the cowpea weevil (Callosobruchus spp.) and pea weevil (Bruchids pisorum). The cowpea weevil has a short life span of 10–12 days while the pea weevil only breeds one generation per year.
The only control options are phosphine, an alternative fumigant or controlled atmosphere, all of which require a gas-tight, sealable storage to control the insects at all life stages.
For more information refer to the GRDC booklet, Fumigating with phosphine, other fumigants and controlled atmospheres.
Chemical sprays are not registered for pulses in any State. While there is a maximum residue limit (MRL) for dichlorvos on lentils, the product is only registered for use on cereal grains.
Weevil development ceases at temperatures below 20°C. This is a strong incentive for aeration cooling, especially if gas-tight storage is not available.
Keep it clean
The first line of defence against grain pests is before the pulses enter storage — meticulous grain hygiene. Because pest control options are limited, it’s critical to remove pests from the storage site before harvest.
Cleaning silos and storages thoroughly and removing spilt and leftover grain removes the feed source and harbour for insect pests.
Clean the following areas thoroughly:
Empty silos and grain storages
Augers and conveyers
Field and chaser bins
Spilt grain around grain storages
Leftover bags of grain
Chemicals used for structural treatments do not list the specific use before storing pulses on their labels and MRLs in pulses for those products are either extremely low or nil.
Using chemicals even as structural treatments risks exceeding the MRL so is not recommended.
Using diatomaceous earth (DE) as a structural treatment is possible but wash and dry the storage and equipment before using for pulses. This will ensure the DE doesn’t discolour the grain surface.
If unsure, check with the grain buyer before using any product that will come in contact with the stored grain. For more information see the GRDC fact sheet, Hygiene and structural treatments for grain storages.
Grain bags are best suited for short-term, high-volume grains to assist with harvest logistics.
Site planning and preparation is the first and most important step for successful storage.
Bulk grain bags are a higher risk form of storage compared with silos — requiring experience and best management practice.
Inspecting grain bags weekly, or more frequently, and patching holes will reduce the chance of spoilt grain from moisture or pests.
Bulk grain bags are best used for short-term storage (a few months maximum) to support harvest logistics.
Storing grain for longer periods requires:
A carefully prepared site
A method of sampling grain for quality monitoring
The capacity of grain bags varies with bag size, which generally ranges from 40 to 90 metres long, and anywhere from 100 to 300 tonnes depending on the type of grain and how much the bag is stretched during filling.
The material most commonly used for grain bags is a three-layer polyethylene — two white layers to protect against the ultraviolet rays and reflect heat and a black inner layer to block light.
Due to their short-term storage capacity and suitability for supporting harvest pressure, growers tend to use grain bags primarily for extending existing storage during high-yielding seasons of typically wheat, barley and sorghum.
Aeration cooling is not yet proven with grain bags. Storing canola or high-value legumes is not recommended.
Cereal grain quality is best preserved when the moisture content is below 12.5 per cent. Storing grain at higher moisture content in bags not only compromises grain quality but increases the risk of grain swelling and splitting the bag.
Being unable to aerate bags and having a large surface area exposed to heating from the sun means grain remains warm for months after harvest. This can affect seed germination rates and malt barley quality.
Storing grain at harvest temperatures of 30°C and above favours high insect reproduction rates, so take extra care with hygiene and monitoring.
Bulk grain bags are an effective form of storage when used in the right situations and when they are managed correctly.
Buying grain bags
Test bag quality by pushing your thumb through an edge of the bag — you will be able to make a subjective judgement as to whether it is high or poor quality. Test different brands before you buy.
Ensure the bag is UV stable for 12 months and complies with the ISO 9001 quality management system.
Make sure the bag has stretch indicators for accurate filling.
Ensure the grain bag is designed for grain not silage — different bags look similar and can be confused leading to disastrous results.
Choosing a site
Appropriate site selection is the first and most fundamental step in successful grain bag management.
Placing bags in different paddocks makes filling direct from the harvester or chaser bin easier but increases maintenance and monitoring time. This can compromise grain quality.
Bags located in individual paddocks can be challenging in wet weather.
A central, common storage site for bags is ideal for easier site preparation, monitoring, bag maintenance, vermin control and out-loading.
Select a hard, smooth, elevated site with a gentle slope where water can drain away.
Allow plenty of room around the grain bags for machinery access and trucks to turn around.
Preparing the site
Grade and roll the site, removing sticks, rocks or sharp objects.
Clear, firm ground makes operating the filling and emptying machines easier with less chance of brakes skidding.
A firmly-rolled site helps drainage and prevents water pooling where the grain bag has sunken into soft ground.
Anything that can puncture the bag is a threat and must be removed. Set up the site away from rocks, sticks, trees (they drop branches and harbour birds) and away from sand hills or long grass where rabbits, mice and foxes shelter.
Anecdotally, a thin sprinkle of urea can be spread on the ground where the bag is to be laid to deter mice from burrowing under it.
Setting up the filling machine
The most common filling machines are power take-off (PTO) driven, forcing grain into the bag, stretching it by about 10 per cent as it’s laid. A more recent development is the gravity filling design, which requires no power or tractor to operate and relies purely on gravity to fill and stretch the bag.
Make sure the machine is clean before filling the bags.
Grain pests, such as weevils and other insects, can survive in small amounts of grain left in equipment from the previous season. If the machine is not clean, these pests can infest the new season’s grain and will multiply and spread through the entire grain bag
Fitting the bag onto the machine with two people saves time and reduces the chance of injury. When setting up the bag on the filling machine, ensure the stretch markers are on a side where they can be seen and measured when the bag is filling. Once filled, any holes in the bag will allow grain to absorb moisture from the ground.
sealing the ends of the grain bag with a heat sealer, or
clamping the ends between two lengths of timber or steel, rolling each end around the timber then tucking the bag under itself with about a metre overlap.
The squarer the starting end of the bag, the easier it is to empty with less shovelling — a cable tie around the end is NOT a good idea.
Before filling the bag, use a string line to mark a straight path along the full length of the bag. A straight bag is a lot easier to empty than a curved bag.
Filling the bag
Patience and accuracy during filling will make emptying the bag much easier, reduce maintenance on the bag during the storage period and result in less spills and fewer stops to realign machinery.
Keep the bag filling evenly and straight to avoid creases — mice tend to attack creases.
Adjust the brakes and direction often and in small increments.
Avoid over-filling (over-stretching) the bag as extra strain makes it more prone to holes, splits and tears.
Remember, the polyethylene bags will stretch more easily when filled with warm grain on hot days.
Bags can be filled straight from the harvester, but operators may be tempted to rush, which leads to a poor job and increases the risk of an accident. (ie damage to machinery or operators).
Stop filling the bag while there is still plenty of bag to seal and re-attach to the emptying machine — about four metres is a good rule of thumb.
As with the starting end, heat seal or clamp the bag end to keep moisture out, then tuck the excess bag under itself and cover with soil to stop it flapping in the wind.
Site security and maintenance
Site security starts with hygiene. Cleaning the site after filling will not only remove harbours for grain insects, it will remove feed that attracts mice and wildlife. After cleaning up around the site, establish mice baiting stations along the length of each bag and put up signs to warn people of the poison.
Keep the site free of grass by spraying it regularly to remove cover for mice and wildlife. A sturdy fence, even an electric fence, around the bags can help prevent animals accessing the bags and chewing or walking on them. Even if there are no livestock in the paddock, remember there is always the potential for stray livestock or wild animals to cause a lot of damage in a short time.
Checking as often as twice daily may be required if vermin are plentiful during wet weather. During normal conditions check at least weekly. Patch any tears or punctures with quality tape or silicone to prevent moisture entering the grain bulk.
Emptying the bag
When making the initial cut in the bag for out-loading, place a piece of tape horizontally across the bag below where it is stretched tight at the top. Make the first cut perpendicular to the bag just below the tape. Do not make the cut parallel to the bag as there is potential for it to split up the entire length of the bag, exposing the grain and making it difficult to pick up.
As previously stated for filling the bag, frequent, small adjustments to align the machine and roller speeds are better than large adjustments. When the bag is almost empty and there’s not much weight left in it, the unloading machine may drag the bag towards itself. This can cause tears from the ground or from over stretching. To prevent this, drive the tractor slowly backwards as the last bit of the bag is emptied.
Clean grain residues from machinery used for grain handling to prevent reinfestation with insect pests next season. Structural treatments are a wise addition to a thorough clean down.
An inert dust such as diatomaceous earth (DE), can be blown into the machinery to prevent insects harbouring during the off season.
Site clean-up is vital for success. Spilt piles of grain and leftover small bags of grain provide an ideal harbour for insects to live and breed.
Safety around grain bags
Filling and emptying grain bags poses a number of safety hazards, exacerbated by the fact that during harvest people are usually tired and in a hurry. Always follow machinery manufacturer instructions and consult your State occupational health and safety authority for advice.
Treat all operating machinery with respect — keep a distance from machines and always have room to take a step away if needed.
Think before you make any adjustments or movements on machinery.
Ensure anyone on-site is standing clear of the filling machine and tractor before adjusting the brakes as it can lurch forward at any time. Making small adjustments reduces the risk of the machine lurching.
The tolerance for live pests in grain sold off farm is nil. With growers increasing the amount of grain stored on farm, an integrated approach to pest control is crucial.
Caution: Research on unregistered pesticide use Any research with unregistered pesticides or of unregistered products reported in this document does not constitute a recommendation for that particular use by the authors or the authors’ organisations. All pesticide applications must accord with the currently registered label for that particular pesticide, crop, pest and region.
Effective grain hygiene and aeration cooling can overcome 85 per cent of pest problems.
When fumigation is needed it must be carried out in pressuretested, sealed silos.
Monitor stored grain monthly for moisture, temperature and pests.
Prevention is better than cure
The combination of meticulous grain hygiene plus well-managed aeration cooling generally overcomes 85 per cent of storage pest problems. For grain storage, three key factors provide significant gains for both grain storage pest control and grain quality – hygiene, aeration cooling and correct fumigation.
The first grain harvested is often at the greatest risk of early insect infestation due to contamination. One on-farm test found more than 1000 lesser grain borers in the first 40 litres of wheat passing through the harvester. Remove grain residues from empty storages and grain handling equipment, including harvesters, field bins, augers and silos to ensure an uncontaminated start for new-season grain. Clean equipment by blowing or hosing out residues and dust and then consider a structural treatment (see Table 2, page 3). Remove and discard any grain left in hoppers and bags from the grain storage site so it doesn’t provide a habitat for pests during the off season.
Freshly-harvested grain usually has a temperature around 30°C, which is an ideal breeding temperature for storage pests (see Table 1, page 2). Studies have shown that rust-red flour beetles stop breeding at 20°C, lesser grain borer at 18°C and below 15°C all storage pests stop breeding. Aim for grain temperatures of less than 23°C during summer and less than 15°C during winter. When placing grain into storage, run aeration fans continuously for the first 2-3 days to push the first cooling front through the grain and to create uniform moisture conditions. Then run the fans during the coolest 9-12 hours per day for the next 3-5 days. This will push a second cooling front through the grain bulk. Aeration cooling generally only requires air-flow rates of 2-4 litres per second per tonne. Finally the grain requires approximately 50 hours of appropriate quality air each fortnight during storage. Use an aeration controller that will perform the cooling process at the right time and continue to aerate the grain selecting the coolest air to run fans. An effective aeration controller will also ensure fans don’t operate when the relative humidity is higher than 85 per cent, which can re-wet and damage grain if operated for extended periods.
Fumigation with phosphine is a common component of many integrated pest control strategies. Taking fumigation shortcuts may kill enough adult insects in grain so it passes delivery standards, but the repercussions of such practices are detrimental to the grains industry. Poor fumigation techniques fail to kill pests at all life cycle stages, so while some adults may die, grain will soon be reinfested again as soon as larvae and eggs develop. What’s worse, every time a poor fumigation is carried out, insects with some resistance survive, and pass the resistance gene into their progeny making control more difficult in the future.
Using the right type of storage is the first and most important step towards an effective fumigation. Only use fumigants, like phosphine, in a pressure-tested, sealed silo. Research shows that fumigating in a storage that is anything less than pressure sealed doesn’t achieve a high enough concentration of fumigant for a long enough period to kill pests at all life cycle stages. For effective phosphine fumigation, a minimum of 300 parts per million (ppm) gas concentration for seven days or 200ppm for 10 days is required. Fumigation trials in silos with small leaks demonstrated that phosphine levels are as low as 3ppm close to the leaks. The rest of the silo also suffers from reduced gas levels. Achieve effective fumigation by placing the correct phosphine rates (as directed on the label) onto a tray and hanging it in the top of a pressuretested, sealed silo or into a ground level application system if the silo is fitted with recirculation. After fumigation, ventilate grain for a minimum of one day with aeration fans running, or five days if no fans are fitted. A minimum withholding period of two days is required after ventilation before grain can be used for human consumption or stock feed. The total time needed for fumigating is 10-17 days. As a general rule, only keep a silo sealed while carrying out the fumigation (for example, one to two weeks). If grain moisture content is low (8-12%) the silo can remain sealed after fumigating but regular monitoring is essential to check for insect infestation and moisture migration to the head space.
When grain is put into storage it needs monitoring just like it does when it’s in the paddock – regularly. Check stored grain at least monthly, taking samples from the bottom, and if safe, the top of the storage.
Things to monitor:
Grain moisture content
Grain quality and germination
When buying a new silo, buy a quality, sealable silo fitted with aeration and check with the manufacturer that it meets the Australian Standard for sealable silos (AS2628). Experience has shown that at least two sealable, aerated silos on farm provide the option for an effective fumigation and delivery program. Many older silos are not designed to be sealed and cannot be used for fumigation, however retrofitting aeration can reduce insect multiplication through grain cooling.
Seed held on farm (cereals — wheat, barley, oats)
Seed that is dry, cool and sound (not weather damaged) will remain viable for longer. In well-managed storage, germination percentages can be expected to reduce by only 5 per cent after six months. To achieve this, keep grain moisture content below 12%. Grain temperature also has a major impact on germination. Aim for grain temperatures of 20°C and below in seed storage by using aeration cooling (with auto control). Wheat at 12 per cent moisture content stored at 30-35°C (unaerated grain temperature) will reduce germination percentages and seedling vigour when stored over a long period. Position small seed silos in the shade or paint them reflective white to assist keeping grain cool. WA growers can treat seed with a grain protectant combined with a dyed grain fungicide in combination with aeration cooling to maximise insect control.
Pulse and oilseeds
Insect control options are limited for stored pulses and oilseeds. Aeration and phosphine fumigation are the main methods and controlled atmosphere (inert gasses such as carbon dioxide or nitrogen) may be an option. The effectiveness of phosphine fumigation on oilseeds is often reduced due to phosphine sorption during treatment. Monitoring gas concentrations with a gas monitor is essential to ensure the correct concentration is achieved for the correct length of time. Use sound grain hygiene in combination with aeration cooling to reduce insect activity. Small seed-size grains, such as canola, may need larger-capacity aeration fans to combat the greater amount of back pressure in the storage. Always store these grains at their recommended grain moisture content level.
Phosphine resistance is widespread – plan, monitor and control for clean grain
Dispose of grain residues and seed gradings. Clean empty storages and grain handling equipment, including harvesters, field bins and augers.
Sieve stored grain for the presence of insects at least monthly, or use pitfall traps. Also check grain temperature and moisture.
If grain temperature has been kept below 15°C by aeration, live insect numbers are likely to be low.
Sample grain three weeks before sale to allow time for any treatment.
For effective fumigations, pressure test sealable silos at least once a year to identify any leaks and ensure rubber seals are maintained.
Phosphine fumigation typically requires 7 to 10 days in a gastight sealed silo. When completed, open silo top with care, ventilate using aeration fan for one day; if not aerated, open silo top and ventilate for five days. The minimum withholding period is then two days after ventilation is completed. The total time needed for fumigation is therefore 10-17 days.
Sieve a half-litre sample onto a white tray. Hold tray in sunlight to warm for 20 to 30 seconds to encourage insect movement.
If live insects are found, identify them and fumigate in a gas-tight silo according to the label.
Take care when climbing silos to sample grain for insects and wear a safety harness. Sample from the base, and if safe, take a sample from the surface of the grain.