Effect of nematicide on stem nematode (Ditylenchus dipsaci) populations and productivity, and survival of 3 lucerne cultivars in North Otago

Abstract

Abstract The effects of a pre-sowing application of ‘Mocap’ and regular post-harvest applications of ‘Furadan’ nematicides on stem nemotode (Ditylenchus dipsaci) were assessed in dryland and irrigated lucerne in North Otago. Populations in soil and herbage, and the production and survival of 3 lucerne (Medicago sativa) cultivars were measured. The pre-sowing application of nematicide reduced nematode populations in the soil by 98%. Post-harvest nematicide applications reduced nematode populations in soil and herbage, and significantly affected lucerne survival and production. By the end of the experiments, the nematicide applications had resulted in 30 and 45% increases in lucerne plant density at the irrigated and dryland sites respectively. Under irrigation, nematicide increased mean annual (3 years) yields of the lucerne cultivars Wairau (48%), Saranac (67%), and Nemasint (38%). Under dryland conditions, mean annual yields (4 years) were increased by 26, 29, and 8% respectively. At the dryland site, without nematicide applications, Nemasint (a stem nematoderesistant cultivar) produced about 20% more dry matter annually during the experiment than did the 2 susceptible cultivars. Under irrigation, where spread and reinfestations of stem nematodes by infested water maintained higher nematode populations than at the dryland site, mean annual yield of Nemasint was significantly greater than that of Saranac (17%) but not than that of Wairau (2%).