New insights into the ecology of three major insect pests of stored grain have implications for farm hygiene practices.
By Dr Greg Daglish, Dr Andrew Ridley and Philip Burrill
The lesser grain borer (Rhyzopertha dominica), red flour beetle (Tribolium castaneum) and rusty grain beetle (Cryptolestes ferrugineus) are among the most common pests on farms; however, not much is known about how and when they travel through cropping areas.
A lack of relevant information on the ecology of these pests prompted a national research
effort coordinated by the Queensland Department of Agriculture and Fisheries (DAF) and supported by the Plant Biosecurity Cooperative Research Centre, of which the GRDC is a partner
Trapping studies show these beetles fly more than was previously thought. All three species have been trapped away from stored grain, sometimes more than 10 kilometres from the nearest farms. This means that beetles resistant to the fumigant phosphine or grain protectant insecticides can fly between farms. Flying beetles pose a threat for much of the year, highlighting the need to minimise the chances of infestation by eliminating places to breed. These beetles are long-lived and females can produce many offspring in small amounts of grain. There is strong seasonality in flight activity, with little or no flight occurring during the coldest months of the year. Limited flight during these months provides an opportunity for growers to get on top of infestations early. By undertaking their main storage facility clean-up during winter, growers can eliminate residual populations before rapid breeding and flight activity gets underway in spring.
Another study investigated the risk of newly harvested grain becoming infested on farms. The study showed that when there is an existing infestation in nearby silos, the risk of infestation is greatly increased. The risk is low on farms with no detectable infestations, emphasising the importance of managing pests in all storage areas. Grain located 2km from farm silos was also at risk of infestation, but much less so than facilities located close to farm silos (especially infested silos). The fact that flying beetles are not limited to the immediate storage environment and can infest grain located at least 2km away has implications for disposal of waste grain. It is common practice for many growers to dump badly infested grain by the road near their properties. The results of the field studies show that there may be no safe distance from farm silos to dump waste grain.
Although the risk of infestation from waste grain will be reduced with distance, the safest option will be to bury or burn the waste to reduce the risk to nil.
GRDC Research Code NPB00013
Plant Biosecurity CRC Codes 3039, 50089, 50149
More information: Dr Greg Daglish, greg.daglish@daf.qld.gov.au;
Dr Andrew Ridley, andrew.ridley@daf.qld.gov.au;
Philip Burrill, philip.burrill@daf.qld.gov.au;
Queensland DAF, 13 25 23, www.daf.qld.gov.a.