Research progress in the interactions of fungal pathogens and insect pests during host plant colonization

Microbial pathogens and insect pests frequently share the same host plant, and both can cause severe damage. When surviving on the same host, the fungal pathogens and pests can have positive effects, negative effects, or no effect on each other. Plant pathogens influence feeding preference, oviposition, growth, development, dispersal, and population dynamics of pests by inducing the accumulation of volatile compounds, soluble sugars, starch, free amino acids, secondary metabolites, and antioxidant enzymes. Insect pests, as vectors, transmit pathogens; reduce the incidence of diseases by directly feeding on fungal spores, mycelium, or toxic fungal compounds; or increase plant susceptibility to pathogens by consuming plant tissues and afford access for pathogens that is enhanced by wounding. Pests and pathogens also activate plant defense systems as mediated by defense-related chemicals, such as jasmonic acid and salicylic acid, which subsequently regulate the expression of defense-related genes. The underlying mechanisms of "tripartite" interaction of pathogens, insect pests and host plants remain unclear, and detailed genomic and proteomic analyses using molecular biology techniques will provide more basic information for the integrated management of fungal pathogens and pests.