TIMING OF MOLLUSCICIDE APPLICATIONS FOR RELIABLE CONTROL IN NO-TILLAGE FIELD CROPS

With the increase in conservation tillage practices, especially no-til lage, growers in the eastern corn belt are experiencing increasing pro blems with slugs. Many growers are reluctant to use conservation tilla ge practices if slugs cannot be managed. The usual control is a mollus cicide applied on a therapeutic basis. However, some growers are consi dering the use of a molluscicide preventive treatment, applying the ma terial at planting to reduce the need for additional trips across the field later in the spring. This study was conducted to examine the eff ectiveness of molluscicide applications during the spring, starting at the beginning of planting season, in providing slug control. Mollusci cide was broadcast weekly from early May to early June to corn, Zea ma ize L., plots, after which slug populations were sampled weekly with b eer traps. Two additional samples were taken in mid-June, defoliation injury ratings and in situ counts of the number of juvenile slugs on c orn plants at dusk. The predominant slug species in this study was the gray garden slug, Derocerus reticulatum (Muller). All 3 sampling proc edures indicated that molluscicides applied in early May did not preve nt juvenile gray garden slugs from becoming numerous in mid-June and, subsequently, causing defoliation injury similar to that observed in c ontrol plots. Only late May and early June molluscicide applications s ignificantly reduced the number of juvenile slugs and prevented defoli ation injury, probably because the molluscicides were applied near, or following, egg hatch.