Insectary Evaluation of New Insecticides for Onion Maggot Control

Abstract

An insectary method to evaluate the potential field effectiveness of insecticides for control of the onion maggot, Hylemya antiqua (Meigen), was devised and proven by a series of experiments. This procedure will provide a means of eliminating noneffective new and untried materials from the field-testing program, thereby saving time and expense. The evaluation proceeded in 2 steps. First, activity of the new compound was determined by mixing the chemical into muck soil at predetermined dosages. The treated soil was apportioned and each portion placed into a pintsize plastic container, providing 4 replicates. The soil in each container was infested with 25 onion maggot eggs placed in the center and surrounded by 4 small onion bulbs as a food source for the larvae. After hatching, the young larvae moved to the bulbs and came in contact with the chemical in the soil. Survival of larvae after a 2-week period gave a measure of the potency of the chemical. If the new compound proved to have a high toxicity a second step was taken. The length of time that a chemical remained active in the soil was ascertained, because in the field the insecticide must be effective over a period of at least 6 weeks. To determine longevity, portions of treated soil were tested by the described means at intervals following treatment, over a period of 20 weeks. The information gained from these tests indicated the potential of a compound as an effective material in the field.