DBM and Caterpillar Infestation Hits WA Grainbelt

Western Australia's grainbelt is experiencing an infestation of diamondback moths (DBM) and caterpillars, particularly in the upper Kwinana Port Zone. According to DPIRD researcher Cindy Webster, pheromone traps have detected high numbers of DBM and caterpillars around Wongan Hills, Kalannie, Bolgart, and Cascade in the Esperance Port Zone.

The traps are checked every two weeks, accompanied by sweep netting in surrounding crops. Growers are advised not to panic if they find caterpillars but rather follow recommended thresholds for control. High moth trap catches do not necessarily indicate a need for immediate action, but rather an increased risk of caterpillar activity in the coming weeks.

Webster emphasized the importance of growers inspecting crops regularly and basing spray decisions on caterpillar numbers and established economic thresholds. While native budworm moth and caterpillar detections remain low, they have been reported in some locations, with numbers expected to increase and/or spread in the coming weeks.

DPIRD's surveillance staff have detected DBM activity across the grainbelt through their trapping network at 22 sites. Webster noted that DPIRD staff had recently recorded higher numbers of DBM caterpillars (over 100 per 10 sweeps) in canola at Ogilvie and Nabawa, as well as Wongan Hills and Kalannie traps having upwards of 500 moths per 10 sweeps collected in a fortnight.

Growers are encouraged to monitor susceptible crops from flowering through to pod maturity using sweep nets or other monitoring methods. The PestFacts WA team has received reports of DBM caterpillars in canola near Geraldton, Mullewa, Latham, Moorine Rock, and Salmon Gums.