Temperature is one of the most important mechanisms to control plant growth. On plant level, temperature effects photosynthesis, growth, evaporation and dissimilation. Additionally, temperature has also significant impact on pests and their natural enemies. These organisms cannot regulate their own temperature, but they depend on the environmental conditions. There are exceptions, of course. To some extent, bumblebees can influence the temperature of their body and the brood. Thus they depend less onthe environmental temperature. In general, however, one could say the speed of development of insects and mites largely depends of their average body temperature; a higher temperature shortens the life cycle (= quicker development). Each mite or insecthas its own specific minimum threshold temperature whereby its development starts. The difference between this threshold temperature and the actual temperature determines the speed of development. The relevant temperature is the one measured on the placewhere the organism lives. In most cases this is the leaf temperature on the place in the crop where the insect or mite occurs. Leaf temperature can be much lower than the air temperature in cold nights with a clear sky, or in case of strong evaporation. And higher in case of bright sunshine or assimilation lights.
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