Efficacy of drench and spray applications of insecticides to control cabbage whitefly Aleyrodes proletella

Abstract: For several years, the cabbage whitefly Aleyrodes proletella Linnaeus has been an important pest affecting the production of Brussels sprouts, kale, savoy and kohlrabi in Germany. From 2008 to 2009 studies were undertaken to test two different methods of chemical control with different insecticides. The first method was to drench seedlings of Brussels sprouts with systemic insecticides before transplanting. The insecticides included were acetamiprid, clothianidin, dimethoate, emamectin, flonicamide, imidacloprid, pymetrozine, spirotetramat, and thiamethoxam. The most efficient insecticides for drench application were the neonicotinoids imidacloprid and thiamethoxam, resulting in a remarkable efficacy even 16 weeks after treatment. The second method was to test field spray applications. The insecticides included were acetamiprid (sole and in combination with rapeseed oil or a wetting agent), azadirachtin A, bifenthrin, chlorpyrifos-methyl, clothianidin, emamectin, flonicamid plus methylated oil, pymetrozine plus methylated oil, potassium soap, plant oil, pyrethrine plus oil, and spirotetramat. For spray application spirotetramat showed the best efficacy. Adding oil or a wetting agent improved efficacy, e.g. for acetamiprid and flonicamid.