The Effect of Nitrogen on Insect and Disease Pests of Onions, Carrots, and Cabbage

Abstract

ABSTRACT Mineral nutrition may affect the ability of plants to resist harmful insects or diseases. The effects of nitrogen (N) nutrition on pests of onions (Allium cepa L.), carrots (Daucus carota L.), and cabbage (Brassica oleracea var. capitata L.) were evaluated on organic and mineral soils in Ontario, Canada in 2000 and 2001. Onions (cvs. Norstar and Winner) and carrots (cvs. Indiana, Idaho, and Annapolis) were grown on both soil types, and cabbage (cv. Atlantis) was grown on mineral soil. Nitrogen was applied at 0,50,100,150, and 200% (carrots and cabbage) and 0, 100, and 200% (onions) of the rate recommended by the Ontario Ministry of Agriculture, Food, and Rural Affairs using calcium ammonium nitrate preplant and potassium nitrate for sidedress applications. In cabbage, onion thrips (Thrips tabaci L.) damage was rated at harvest. Onion thrips (OT) populations were monitored in onions weekly. In carrots, the combined leaf blight symptoms caused by Cercospora carotae and Alternaria dauci was evaluate...