Effect of temperature on microbial biocontrol agents of plant diseases

Biological control is an alternative to chemical control of diseases and a relevant tool for sustainable agriculture. Being living organisms, biocontrol agents (BCAs) are strongly influenced by the environmental conditions and climate change could hamper the use of biocontrol in areas where it is already a common practice. Commercial BCAs, which are negatively influenced by relatively high temperatures, may become useless if the temperature will increase above a limiting threshold. On the contrary, BCAs that are adapted to higher temperatures may be used under climate conditions that are warmer than it was in present time. The aims of our case study are to quantify and compare the effect of temperature and relative humidity (RH) on the survival of two BCAs (Y13 and B52) active against grapevine and tomato powdery mildew and isolated from a warm and a cold climates; to evaluate their survival in the grapevine or tomato phyllosphere under field conditions during the season in two climates; to estimate their biocontrol efficacy against grapevine tomato powdery mildew under field conditions. Y13 survived better than B52, even at high temperatures and low RH. B52 is positively affected by the presence of powdery mildew. In view of climate change with increasing temperatures particular attention should be posed in the development of commercial BCAs. Few degrees of difference in the temperature may negatively influence the survival of microbial BCAs, which could make the biocontrol activity ineffective. A BCA selected in a warm environment can better adapt to increasing temperatures, therefore, it may have a longer commercial life if temperature increase is forecasted in the future decades. The possible use of BCAs as adaptation tools to climate change will be discussed