Effectiveness and persistence of six insecticides for control of lettuce aphid on field lettuce in Canterbury New Zealand

Abstract

Since its arrival in March 2002 lettuce growers in New Zealand have been struggling to control the lettuce aphid (Nasonovia ribisnigri) using topically applied insecticides Potter tower tests have shown there is some level of resistance in New Zealand to two insecticides (acephate and methomyl) at the recommended field rate A field trial was set up to examine the effectiveness and persistence of six insecticides on autumn sown seedling lettuces for control of the lettuce aphid Acephate and methomyl failed to give complete kill of lettuce aphids unlike the other four insecticides tested The synthetic pyrethroid lambdacyhalothrin gave a higher level of protection having both a longer persistence period than the other insecticides tested and a significantly lower rate of increase in aphid numbers