Effects of different pesticide management options on the population dynamics of aphids, Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) (Hemiptera: Aphididae), their natural enemies and the yield of cabbage

Abstract

Cabbage is a popular vegetable grown in Ghana and it serves as an important source of livelihood for smallscale farmers. Aphids are major pests of cabbage in the field and as such, farmers have resorted to the indiscriminate use of insecticides which have had adverse environmental and health implications. The current study sought to investigate the effect of commonly used management options on the population of aphids, Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) (Hemiptera: Aphididae), their natural enemies and the yield of cabbage. Cabbage seedlings were planted during the major and minor seasons of 2015 in 3 x 3 m plots and the treatments used included Chlorpyrifos, Lambda-cyhalothrin, hot pepper, Capsicum futescens fruit extract, neem, Azadirachta indica seed extract, solution of local soap (alata samina) with water as a control. Ten cabbage leaves per treated plot were randomly sampled weekly into 70% alcohol to obtain actual counts of aphids and their natural enemies. The least number of aphids was recorded in the neem treated plots, while Lambda-cyhalothrin treated plots recorded the highest number of aphids. The control and biopesticide treated plots recorded the highest numbers of the natural enemies (hoverflies, ladybirds and spiders). The highest yield and marketability was recorded in the neem treated plots for both seasons. The yield and marketability of cabbages obtained from plots sprayed with alata samina and pepper was also higher than that obtained from the control, Lambdacyhalothrin and Chlorpyrifos treated plots, with the insecticide treated plots recording the least number of marketable heads. It offered the most promising solution. The current findings suggest that the crude neem seed extract, and to some extent local soap, alata samina, and pepper, are effective and safe options for managing aphids on cabbage.