First results on population dynamics and chemical control of Aleyrodes proletella in Germany

Abstract: The cabbage whitefly Aleyrodes proletella is a well known pest of vegetable brassica species. Since more than a decade, it is a constant and relevant pest in Germany with mass reproduction in several cabbage species. Damages occur particularly on Brussels sprouts, kale, kohlrabi, and savoy. Produce quality is affected by the sole presence of the insects; furthermore, the produce is contaminated by honeydew and sooty mould fungi.Until now, there is only little information available on the population dynamics of A. proletella. It seems that the enormous reproductive potential is a result of at least four generations, with the first generation developing on overwintering brassica species. In northern Germany oilseed rape offers an exclusive hibernation habitat for the cabbage whitefly. With the ripening of the rapeseed plants in May/June, the young adults leave the crop searching for new host pants. After invading Brussels sprout in June, a mass reproduction of whiteflies with up to 60,000 larvae per plant until to September could be observed in 2010.From 2008 to 2009 studies were undertaken to test two different methods of chemical control with different insecticides. The first step was to drench seedlings of Brussels sprouts with systemic insecticides before transplantation. The second step was to test field spray applications. Best insecticides for drench application were imidacloprid and thiamethoxam. For spray application flonicamid and spirotetramat revealed best efficacy. Adding rapeseed oil or a wetting agent improved efficacy of some insecticides.