Drift of Terrestrial Arthropods in an Irrigation Canal Following a Wide-Area Application of ULV Malathion

Numbers of arthropods drifting in an irrigation canal were recorded at 30-min intervals during and after an upstream application of ULV malathion. Flower-visiting and parasitic Hymenoptera were the first insects to increase; a bimodal drift pattern resulted from an interruption in the spray application. Diptera exhibited a delayed response but the numbers collected, especially Paracantha culta (Wiedemann), suggest high susceptibility. Ants occurred in large numbers over a long period, but mortality was probably low. Miridae and Cicadellidae were probably more susceptible than Orthoptera and adult Odonata but had similar delayed drift patterns. Tetragnathidae were the most, and Thomiscidae the least, susceptible spiders

The Effect of ULV Malathion on Spiders in Alfalfa

The purposes of this study were to determine the relative abundance and seasonal occurrence of spiders in alfalfa and to determine the effects of an insecticide (ULV malathion) on spiders in that environment. A wide-area spray program (“Project WASP”) was conducted in Dawson County, Nebraska, in 1968, 1969, and 1970. ULV malathion was aerially sprayed on one-half of the area, and the other half of the area was designated as control. Spider collections were made by sweeping in 1968 and 1969, and by taking drift samples in 1970. Spiders were significantly correlated with plant height in prespray and postspray samples. Crab spiders (Thomisidae) were the most abundant of the spider groups in alfalfa. Tetragnathidae were the second most important group of spiders collected in alfalfa. Advisors: K. P. Pruess and E. S. Rau