The Influence of UC-21149 and the Aphidiid Parasite Aphidius smithi on Populations of the Pea Aphid1234

Abstract

The influence of Aphidius smithi Sharma & Subba Rao alone or in combination with applications of the systemic insecticide Union Carbide UC-21149 (2-methyl-2-(methylthio) propionaldehyde O -(methylcarbamoyl) ox-ime (Temik®) on populations of the pea aphid, Acyrthosiphon pisum (Harris), was studied on 3 plant-growth cycles of ‘Buffalo’ alfalfa seedlings in 3 small greenhouses. were suppressed throughout all 3 growth cycles. This When only parasites were used the populations of aphids during the 1st growth cycle were high but lower than those in the controls; by the end of the 2nd cycle they were reduced 80%. During the 3rd cycle the aphid population remained at less than 5% When only UC-21149 was applied (0.56, 1.12, and 2.24 kg/hectare) populations of aphids were low during the 1st growth cycle, but during the 2nd and 3rd cycles they increased greatly. This increase correlated with the reduction in the concentration of the sulfoxide metabolite of UC-21149 in the plants. When UC-21149 and parasites were used in combination, the populations of aphids method of control was the most effective and allowed the best alfalfa growth. At the doses used UC-21149 had no apparent effect on the activity of the parasites. Thus, the aphidiids were able to parasitize a higher percentage of the initial density. of the reduced populations of aphids than when no insecticide was applied.