Endophytes as Novel Pest Control Agents: Myth or Reality?

Endophytic fungi are ubiquitous in nature and their potential for pest control in grassland systems is well understood. However, their role as novel pest control agents in herbaceous crops is far less clear. These fungi can be broadly split into two groups: unspecialized species (including saprotrophs and latent pathogens) and entomopathogens. The literature on the interactions of these fungi with herbivorous insects is biased towards studies in a few plant families and with a few insect species. This fact notwithstanding, we suggest that infection of plants by these fungi elicits dramatic chemical changes within their hosts, which have the potential to reduce insect and pathogen attack. However, the effects of fungal infection on insects are context-specific, being influenced by the identity of the insect and plant, the existing community of fungi within a plant, the habitat in which it is growing and the plant age.
Unspecialized endophytes can reduce the performance of sucking insects, but effects are only seen when seeds are inoculated. This result may reflect poor experimental technique but corresponds well to fungal biology, as these endophytes can be transmitted through seeds from one plant generation to the next. Endophytic entomopathogens show more consistent detrimental effects on insects and plant pathogens and can even provide growth benefits in the absence of antagonists.
We conclude that a better understanding of the biochemical and molecular changes elicited by endophytes in plants is required, so that these can be harnessed in future pest control strategies. Endophytes will not replace conventional pesticides in the near future, but could be incorporated into future integrated control programmes, thereby reducing the reliance on synthetic chemicals.