Increased temperature is associated with reduced efficiency of insecticides

 

When discussing Climate Change, it is often said by people in northern latitudes that an increase in temperature is only beneficial, as plant growth will increase, whereby agricultural production will increase. Even if the temperature increase will cause some parts of the world to become completely unsuitable for agricultural production, the people, who say the above, do not care, as they maintain that it doesn’t matter what happens to the rest of the world, if the situation in their neighbourhood gets better. There are, however, two reasons why a temperature increase may not increase plant production without a marked increase in the use of insecticides. Since their use already affects, in addition to harmful insects, necessary pollinators, the use of insecticides should be decreased instead of being increased. Besides, the agricultural products from northern latitudes are always marketed as containing little pesticides and other exogenous substances. If temperature increases, this is not true any more.

There are two major reasons for the need of more insecticides. First, and this is virtually always mentioned, when the upsides and downsides of temperature increase to agricultural production in northern latitudes are discussed, the number of pest species increases and their populations become stronger. To be able to kill the harmful insects, more spraying of poisons is needed. In fact, one can think of severe winters as effective insecticides, they limit the growth of most pests. Second, and this is seldom considered, the insecticide concentration needed to kill the animal usually increases with increasing temperature. There are a couple of possible reasons for these. The most likely one is that the insecticide is detoxified more rapidly at high than at low temperature: the activity of all the detoxification enzymes increases with temperature. Also the excretion of insecticides is speeded up.  It appears that the neurobiological toxic actions are affected less than detoxification and excretion, because it is probable that also the toxic effects will be increased wit temperature. However, if the toxic action is increased less than detoxification and excretion, the overall effect is that more insecticide is needed for the same effect.

Notably, although the available results suggest that the insecticide concentration needed for a given toxic effect increases with temperature, interactions between abiotic environmental changes like Climate Change and environmental pollutants have been inadequately studied. For this reason our understanding of what causes the reduced effect of insecticides at higher temperature is deficient.