Carbofuran was applied at planting to study the influence on alfalfa (Medicago sativa L.) growth, potato leafhopper, Empoasea fabae (Harris), and seedcorn maggot, Hylemya platura (Meigen). No increases in radicle length, trifoliate leaf development, or dry matter resulted from carbofuran application to alfalfa seedlings grown in a growth chamber using plastic pouches. High rates of carbofuran produced toxicity symptoms, reduced growth and increased protein content of plants. No-till alfalfa was seeded with granular carbofuran into a cereal rye cover crop in late March and late April of 1982. Conventional alfalfa plantings were made in March and April of 1981 and 1982 using granular and flowable formulations of carbofuran. Soi 1 samples were screened for soil-dwelling insects. Potato leafhopper populations were monitored by sweep net sampling. Severe seedcorn maggot damage and high larval populations were associated with conventionally planted fields prepared by disking a small grain cover crop, and were effectively controlled by carbofuran. Conventional plantings without a previous cover crop and no-till plantings were not visibly affected by seedcorn maggots. Potato leafhopper populations were not affected by carbofuran applications at planting, however, results may have been influenced by insecticide applications surrounding the study area. The use of carbofuran increased seedling populations on three occasions, only one of which was associated with visible insect damage. Yield increases associated with carbofuran were observed in the first harvests of three conventional plantings and one no-till planting, indicating that early growth stages of alfalfa were the most susceptible to pest damage. Total yields were increased by carbofuran applications in only two of nine plantings, both conventionally established. Carbofuran applications greater than 1. 1 kg ai/ha were of no benefit and should not be recommended for alfalfa establishment. / M.S.