The Belowground–Aboveground Interactions of Zucchini: The Effects of Trichoderma afroharzianum Strain T22 on the Population and Behavior of the Aphid Aphis gossypii Glover and Its Endoparasitoid Aphidius colemani Viereck

: Fungi belonging to the genus Trichoderma have received high consideration in agriculture due to their beneficial effects on crops from their plant promotion effects and protection from disease. A role of Trichoderma fungi in triggering plant defense mechanisms against insect pests, either directly or by natural enemy attraction, has been proposed, even if the results in different studies are controversial. In this present study, using zucchini plants as a model species, we investigated the effects of Trichoderma afroharzianum strain T22 plant inoculation on the cotton aphid Aphis gossypii and its endoparasitoid Aphidius colemani. Our results showed that the inoculation with T. afroharzianum T22 promotes A. gossypii population growth and makes zucchini more attractive to the aphid. The higher abundance of aphids on Trichoderma-inoculated zucchini was compensated for by a higher presence of the mummies of Aphidius colemani. In this present study, we recorded a higher zucchini biomass, thereby confirming that Trichoderma can act as a plant growth inducer.