Insect Control on Seedling Alfalfa by Cultivars and Soil and Foliar Insecticides¹

Abstract

Control of insects on seedling alfalfa (Medicago sativa L.) is often desirable for stand establishment and forage production. The objective of these studies was to determine the use of cultivars and soil and foliar insecticides in controlling insects on seedling alfalfa. Three field studies were conducted on the use of preplant soil application of carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate) in spring seedings on a Typic Arguidoll soil. The studies also included foliar application of carbofuran alone and in combination with soil application, and cultivars that varied, in resistance to insect species. Insecticide was applied at 1.1 kg a.i./ha. Neither soil nor foliar insecticide application increased forage yield, protein and carotene concentration of seedling alfalfa. Potato leafhopper [Empoasca fabae (Harris)], pea aphid [Acyrthosiphon pisum (Harris)], spotted alfalfa aphid [Therioaphis maculata (Buckton)], and plant bugs [Lygus lineolaris (Beauv.)] and [Adelphocoris lineolatus (Goeze)] were controlled by carbofuran. The pea aphid resistance of ‘Arc,’ ‘Baker,’ and ‘Perry’ and spotted alfalfa aphid resistance of Baker were effective in controlling aphid populations. ‘Buffalo,’ susceptible to potato leafhopper, pea aphid, and spotted alfalfa aphid, was lower than Arc, Baker, and Perry in forage yield, protein and carotene concentrations. No residual effects of soil insecticide application prior to seeding were apparent on insect numbers in the second and third cuttings.