Probing the problem of insect pests
Date: 01 Aug 2016
Cost-effective detection of beetle pests in grain silos is best achieved by combining a couple of simple methods, a Queensland study has shown.
By using shallow probe traps in the grain at the top of the silo and sieving samples from the bottom, beetles can be detected quickly, cheaply and safely, so that timely treatments can be administered.
The conclusions emerged from a pilot study conducted by the Queensland Department of Agriculture and Fisheries (DAF) that compared several straightforward methods of pest detection.
As growers increasingly move to on-farm storage of grain, there is corresponding requirement to manage pest incursions for the protection of grain marketability and profitability, according to DAF principal research scientist Greg Daglish.
“There is an urgent need for appropriate sampling methods to help farmers manage the risk of insect infestation and minimise marketing delays,” Dr Daglish said.
“Simple, safe, cost effective and easy to interpret sampling options will enable growers to make informed decisions about pest management.”
Speaking at a recent Grains Research and Development Corporation (GRDC) Grains Research Update in southern Queensland, Dr Daglish outlined findings from the pilot study which tested the use of probe traps in the top and side hatches of the silos and sieving grain samples from the top and bottom of the silos, to determine the most effective and cost efficient combinations of the two.
“In beetle-infested silos, sieved grain from the bottom of the silo yielded 82 per cent of the beetles known to be present, compared to just 20pc from samples taken from the top of the silo,” Dr Daglish said.
“When comparing shallow and deep probe traps, the shallow traps captured 82pc of beetles and the deep traps just 18pc.
“Probe traps inserted from the top hatch captured 76pc of pests, and those inserted from the side hatch collected 24pc.”
Dr Daglish said the results demonstrated that combining the use of probe traps in the top of a silo with sieving a grain sample from the bottom was an effective insect detection method.
“The trial work has resulted in some key preliminary recommendations. If sieving grain is to be limited to one location, then a sample from the bottom of the silo is preferable to one from the top of the silo,” he said.
“Probe traps should be inserted into the grain bulk so that the top of the trap is level with the grain surface.
“If trapping is limited to one location then inserting the probe trap into the grain through the top hatch is preferable to inserting it through the upper side hatch.
“In terms of frequency, probe traps should be initially inspected after one day in case there is a heavy infestation which risks large numbers of beetles clogging the traps. If no or few beetles are trapped in the first instance a longer trapping period can be used.”
Dr Daglish advises that checks not be done after early morning. As the sun rises, heat in the silo head space becomes too great for beetles to survive, so a midday check may show little signs of life in a silo that is infested at depth.
While the research didn’t distinguish the significance of one beetle compared to many beetles in a sample; the presence of beetles straight after harvest compared to later during storage; or the habits of the five different beetle pests of grain - some of which may prefer living deep in the grain bulk, some on the surface – it provides a vital first step towards efficient assessment and detection.
“There are many beetle species that can infest stored grain and at least five pest species were detected in this study,” Dr Daglish said.
“From a scientific perspective, knowing the identity and exact numbers of beetles in grain samples or probe traps is valuable.
From a grower perspective however, the presence of any beetles in stored grain is a problem.”
Probe traps are available from Graintec, visit their website. Or telephone 1300 640 299.
DAF Manager (Media)
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Sarah Jeffrey, Senior Consultant Cox Inall Communications