Research and experience are showing that the dietary preferences of the much-maligned mouse may have had a positive effect on Darling Downs cropping. Queensland Department of Primary Industries and Fisheries principal entomologist David Murray says in-crop infrared spy cameras show mice like to eat larvae of the heliothis (helicoverpa), Australia"s major cropping insect pest.
Dr Murray says high numbers of mice with voracious appetites in Darling Downs" crops in autumn last year are thought to be among the reasons there were few heliothis around later in the year when the insect pest usually makes its presence felt.
He says the cameras show that when large heliothis larvae finish feeding on a crop, they drop to the ground and wander over the soil surface searching for a suitable site at which to burrow down and pupate. "Larvae are vulnerable to predation during this period of wandering," he says.
Dr Murray says that in GRDC-supported trials, four digital surveillance cameras with infrared lighting were set up to record night feeding on heliothis at seven Darling Downs sites of rain-grown crops of maize, mungbeans, sorghum and cotton. The trials involved tethering large heliothis larvae within the area covered by the cameras and playing back the results.
Last autumn, the cameras caught frogs, carabid beetles, earwigs and centipedes eating heliothis larvae, but mice were by far the most prolific larvae feeders. "The five larvae we"d put out below each camera at sunset disappeared within two hours or sooner, and the cameras at all seven sites showed mice were the main reason," he says.
The activities of predators seem to have had an impact on heliothis numbers this spring, although the situation was also helped by fewer host weed and crop plants because of dry weather.
"The low numbers are a good start to the heliothis season and will provide an opportunity to manage the pests well in summer crops," Dr Murray says. The research is part of an ongoing project to find what influences heliothis numbers on the Darling Downs and the relative importance of these influences.
"If natural enemies have a major impact on heliothis larval and pupal mortality we might be able to encourage a build-up in their numbers. Of course there are not going to be many farmers who want to encourage mice, even if they do destroy more than their fair share of heliothis."
Dr Murray says the research is linked to heliothis integrated pest management (IPM) that aims to achieve acceptable control of the pest with the minimum use of insecticides.
Darling Downs farmers are leaders in the adoption of area wide management of heliothis and IPM, he says.
GRDC Research Code: DAQ539.
For more information: Dr David Murray, 07 4688 1326 or 0428 442 616.
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