We tested two cultivars of barley and one of wheat as living mulch for the retention of indigenous natural enemies of pests of winter-harvested Welsh onion. 'Hyakumangoku' barley withered earliest and was therefore most suitable to precede soil hilling for the blanching of the onions in early September; it supported populations of Rhopalosiphum padi (Linnaeus) and Anaphothrips obscurus (Müller), which are food sources for the indigenous natural enemy Geocoris proteus Distant, and various predatory phytoseiid mites.
We examined the effect of agrichemicals on an important predator, Geocoris proteus Distant, which has been observed in Allium crop fields. Adults and 3rd instar nymphs of G. proteus were dipped in 67 pesticide solutions at a practical concentration. As a result, two of ten organophosphorus insecticides, one of four carbamate insecticides, two of six neonicotinoid insecticides, two of six insect growth regulators IGRs , nine of eleven other synthetic insecticides, all microbial insecticides, all acaricides and all fungicides were determined to be harmless 30% mortality to adults and 3rd instar nymphs of G. proteus. The use of these pesticides should be recommended by integrated pest management IPM programs to control Allium insect pests, since they are regarded as being compatible with the conservation of G. proteus in the field.
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