Efficacy of chemical and biological agents against pepper blight (Phytophthora capsici Leonion) in East Asia: a meta-analysis of laboratory and field trial data

Pepper blight caused by Phytophthora capsici Leonian is one of the most economically important plant diseases worldwide. In East Asia, pepper blight is a serious disease that is capable of decimating entire chili crops resulting in high economic losses. Management strategies undertaken to control the disease include the use of chemical and biological agents alongside soil fumigation and improved cultural practices. In recent years, biological agents are considered to be preferable to the use of chemicals due to the lower risk of resistance evolution and harm to the environment. Using meta-analysis, we synthesised the literature on the efficacy of different types of controls on pepper blight in East Asia. The studies were almost all conducted in Korea and China. We found that phenylamides (FRAC group 4), Xenorhabdus sp., Pseudomonas sp., and plant extracts were generally more effective against the pathogen in pepper; while soil amendments, Bacillus sp., Chryseobacterium sp., unidentified antagonists, and carboxylic acid amides (FRAC group 11) tend to be less effective. Overall, chemical agents were 50% more effective than biological agents. However, the benefits of using biological agents may outweigh the reduction in efficacy, particularly if used as a part of mixed treatments. Interestingly, control agents were 58% more effective on the disease in Korea compared to China, highlighting potential differences among pathogen genotypes or the resistance of cultivars to disease. Avenues for future research on biological forms of control and novel control strategies for plant pathogens are discussed.