A novel heliothis trap-cropping trial on the Darling Downs showed encouraging results despite being plagued by weather and a few design flaws, according to Queensland Farming Systems Institute entomologist David Murray.
Trap crops are small areas planted specifically to attract and hold a target pest, keeping the insects awayfrom commercial crops in the area. Infestation numbers in trap crops may be controlled where necessary and eventually destroyed by cultivation. The Darling Downs trial was a first on the broadacre scale. The program involved some 80 growers in two major Downs production areas — Brookstead-Cecil Plains and the Jimbour floodplain — planting 1 per cent of their cultivated area to chickpea. Planting was timed to have the trap crops ready and attractive to moths when the major flights of heliothis occur in October and November.
"Results in 1998 were encouraging enough to make us want to do it again, but also showed us things we will do differently next year," Dr Murray said. "We won't plant close to cotton again, because when you plough out the trap crop, the heliothis migrate to the cotton.
"Because of the nature of the 1998 season, and its wet weather problems, we also had commercial crops of chickpeas overlapping the trap crops. Ideal planting time for trap crops is late July or early August, but the later you go in the season the bigger the risk of missing a planting rain.
"We also found heavy larvae infestations early in the life of some trap crops, with no treatment available to keep the numbers at an acceptable level. Resorting to the registered chemicals defeats the purpose (of keeping pesticide-use down in cottonmgrowing areas — Ed.).
"We may have to look at using [Gemstar] virus or some other control method, keeping in mind that we are not growing these trap crops for yield."
The project to knock down heliothis populations on the Darling Downs is jointly supported by growers through the GRDC and the Cotton Research and Development Corporation. The Rhone Poulenc company provided the chickpea seed for the trap-crop trial, some 20 tonnes.