Injury levels for soil-dwelling insects in sunflower in the Central Highlands, Queensland

Abstract

Soil-dwelling insects cause poor establishment of summer crops, especially sunflower, in the Central Highlands of Queensland. Laboratory studies established that adults and nymphs of cockroaches, Calolampra spp., and Pterohelaeus alternatus beetles were most damaging to sunflower seedlings. Field trials were used to define an econonic injury level (EIL) for these insects in sunflower, but a comparison of yields from untreated and treated plots (where baits were used to control soil-dwelling insects) was inconclusive. However, based on seed costs alone, 1.34 insects/mound.night was established as an EIL. Injury equivalents were used to refine the EIL to account for multiple species attacking seedling crops. At the recommended baiting rate of 2.5 kg/ha, the EIL was 1.97 insect equivalents/mound.night.