Sensitivity of Clonostachys rosea and Trichoderma spp. as potential biocontrol agents to pesticides

Clonostachys rosea 47 (CR47), Trichoderma atroviride 59 (TA59), T. atroviride 312 (TA312), Trichoderma harzianum 24 (TH24), Trichoderma longibrachiatum 9 (TL9), T. longibrachiatum 144 (TL144) and Trichoderma viride 15 (TV15) were tested to evaluate their in vitro sensitivity towards five fungicides (carboxin, guazatine, prochloraz, thiram and triticonazole) and four herbicides (chlorsulfuron, chlorotoluron, flufenacet and pendimethalin). All antagonists showed low sensitivity to carboxin and thiram and high sensitivity to prochloraz. For mycelial radial growth, TV15 was highly sensitive to guazatine, prochloraz and triticonazole and TH24 moderately insensitive to carboxin, guazatine and thiram. For conidial germination TL144 was the most sensitive to the fungicides, for mycelial radial growth and conidial germination CR47 was the least sensitive. None of the antagonists showed any mycelial radial growth inhibition in presence of the herbicides at field dose, except for TL144. Most antagonists did not show any conidial germination inhibition by the herbicides. The in vitro toxicity of prochloraz, guazatine and triticonazole towards the antagonists was confirmed by light and scanning electron microscope showing hyphal disruptions and extrusion of cytoplasmic content. A mixture of CR47 and/or TA312 with carboxin, thiram and triticonazole, applied to wheat seeds, was able to control Fusarium culmorum artificially inoculated to wheat seedlings in growth chambers. In the field, the antagonists applied along with triticonazole or thiram, at 1/10 of the field dose to seeds naturally infected by F. culmorum, gave a disease control comparable to that induced by triticonazole at full field dose. Our results demonstrate how an integration of microorganisms with pesticides makes the control of wheat foot rot possible.