Climate change and pesticides: (no) need for concern?

Higher temperatures and more intense rainfall are seen as the major climate change-factors influencing pesticide residues. Pesticide use will change in two ways. First, where the effect of rain intensity on pesticide residues was assessed, the residues on crops decline faster when temperature increases or when heavy rainfall comes within a couple of hours after the spray application. Secondly, for some pests and diseases the pest or disease pressure will increase in future. In the context of climate change an increased use of chemical crop protection products is assumed. Effects will differ strongly for different regions, crops and pesticide types, with variable consequences for pesticide efficiency and food safety. The objective was to assess the impact of climate change on the pesticide use crops. The development rates and emergence of pests and diseases were estimated by the use of current ‘Pest Warning models’ applicable in Belgium. Analyses were carried out on the basis of the climate and weather data from the Royal Meteorological Institute of Belgium, located in Ukkel (Longitude 4.35° E, Latitude 50.79° N). Climate change statistics were generated using the CCSM4 and HadGEM2-ES model. A pest warning model of the codling moth (Cydia pomonella L.) calculating the degree-days was used in this study to predict future pest outbreaks. Looking at the reference period 1981-2000, the pest warning model predicts the reproduction of two generations adult codling moths a year. The second generation adults is able to produce eggs and larvae, but they are unable to develop into a third generation adults. In contrast, due to climate change in the period 2031-2050 and 2081-2100, a third generation of adults can easily be reproduced. In this study, increasingly favourable conditions for the codling moth in the future will occur, allowing more generations to be developed in one growing season due to shorter generation time cycles