THE EFFECT OF PLANTING TIME INSECTICIDES AND LIQUID FERTILIZER ON THERUSSIAN WHEAT APHID (HOMOPTERA, APHIDIDAE) AND THE LESION NEMATODE (PRATYLENCHUS-THORNEI) ON WINTER-WHEAT

Organophosphate (OP) insecticides, disulfuton and phorate, applied in combination with liquid fertilizer (10-34-0) at planting, suppressed t he Russian wheat aphid, Diuraphis noxia (Mordvilko) (RWA) in 'Carson' winter wheat for a longer period of time than carbofuran used with and without liquid fertilizer. However, yields from carbofuran treated pl ots were greater (average of 631 kg/ha) than those treated with OP ins ecticides. Based on post-harvest soil samples, lesion nematodes (Praty lenchus thornei) were found to be the yield limiting factor in the OP + liquid fertilizer treatments, the untreated control and the treatmen ts with liquid fertilizer alone. Carbofuran provided increased yield, test weight and seed weight per head when compared with the other trea tments. The lesion nematode was the more economically damaging pest of winter wheat in this study, compared with the Russian wheat aphid.