Systemic resistance induced by Trichoderma hamatum 382 in cucumber against Phytophthora crown rot and leaf blight

Phytophthora root rot, crown rot, leaf and stem blight, and fruit rot of cucumber can cause serious losses, and are difficult to control. Although composts can be used successfully for control of Phytophthora root rots, little is known about their effects on Phytophthora diseases of above-ground plant parts. This research shows that the severity of Phytophthora root and crown rot of cucumber caused by Phytophthora capsici was suppressed significantly in cucumber transplants produced in a composted cow manure-amended mix compared with those in a dark sphagnum peat mix. In split root bioassays, Trichoderma hamatum 382 (T-382) inoculated into the compost-amended potting mix significantly reduced the severity of Phytophthora root and crown rot on paired roots in the peat mix. This effect did not differ significantly from that provided by a drench with benzothiadiazole (BTH) or mefenoxam (Subdue MAXX). Based on area under disease progress curves, T-382 also significantly reduced the severity of Phytophthora leaf blight in transplants produced in the compost mix compared with controls not inoculated with T-382. Efficacy of T-382 did not differ significantly from that provided by a drench with BTH. T-382 remained spatially separated from the pathogen in plants in both the split root and leaf blight bioassays, suggesting that these effects were systemic in nature.