# Effects of Trichoderma harzianum Rifai and Chaetomium cupreum L.M. Ames on Biological Parameters of Myzus persicae (Sulzer) on Capia-Type Red Pepper (Capsicum annuum L.)

## TL;DR

A study found that a fungus called Trichoderma harzianum unexpectedly boosted aphid populations on pepper plants, showing that some beneficial fungi can actually make pest control harder.

## Contribution

The study reveals that Trichoderma harzianum can increase aphid population growth, challenging the assumption that endophytic fungi always suppress pests.

## Key findings

- Trichoderma harzianum increased aphid survival and reproduction, leading to faster population growth.
- Population projections showed aphid numbers could be 380 times higher on plants treated with Trichoderma harzianum.
- Chaetomium cupreum alone had minimal effects on aphid populations.

## Abstract

The green peach aphid is a small sap-feeding insect that causes serious damage to many crops and is difficult to control because it has become resistant to many insecticides. Endophytic fungi, which live inside plant tissues without causing disease, are considered a promising alternative for sustainable pest control. In this study, we tested how two such fungi affect aphid populations when they colonize pepper plants. Surprisingly, Trichoderma harzianum greatly increased aphid survival and reproduction instead of reducing it, leading to much faster population growth compared to untreated plants. When both fungi were applied together, aphid numbers also increased, while Chaetomium cupreum alone had only minor effects. Long-term projections showed that aphid populations could become hundreds of times larger on plants treated with the growth-promoting fungus. These results show that beneficial microorganisms do not always suppress pests and can sometimes make plants more favorable to them. Our findings highlight the importance of carefully testing plant–fungus–insect interactions before using endophytic fungi in sustainable pest management programs, in order to avoid unintended consequences for farmers and food production.

The green peach aphid, Myzus persicae (Sulzer), is a globally important agricultural pest whose management is increasingly challenged by widespread insecticide resistance, prompting interest in alternative and sustainable control strategies such as endophytic fungi. This study evaluated the effects of two endophytic fungi, Trichoderma harzianum and Chaetomium cupreum, applied individually or as a 1:1 mixture, on the population ecology of M. persicae feeding on capia-type red pepper (Capsicum annuum L.). Aphid development, survival, and reproduction were assessed using age-stage, two-sex life table analysis. Contrary to expectations, T. harzianum significantly enhanced aphid population growth, resulting in a higher intrinsic rate of increase (r = 0.42 d−1), finite rate of increase (λ = 1.52 d−1), and net reproductive rate (R0 = 87.67 offspring) compared to the Control (r = 0.32 d−1, λ = 1.37 d−1, R0 = 42.90 offspring). The Mixture treatment also increased population parameters, whereas C. cupreum showed limited effects on aphid life table traits. Population projections indicated that T. harzianum treatment could produce aphid populations approximately 380 times larger than the Control after 60 days. These results suggest that T. harzianum may improve host plant quality in ways that indirectly favor M. persicae. The findings highlight the importance of evaluating plant–fungus–herbivore interactions before incorporating endophytic fungi into integrated pest management programs.