Sustainable Management of Phytophthora Root Rot and Ambrosia Beetles under Stress Conditions

Phytophthora root and ambrosia beetles were the important disease and pests of flowering dogwoods in the United States. In this study, different fungicides, biofungicides, host plant defense inducers, and fertilizers were used to manage Phytophthora root rot in different flooding durations, application methods, and time interval applications. Similarly, different fungicides and host plant defense inducers were compared for their efficacy against Phytophthora root rot in drought conditions in the greenhouse. Selective fungicides, insecticides, and crop protectants along with their different combinations were also tested for the integrated management of Phytophthora root rot and ambrosia beetle attacks in nursery container production system under flooding conditions. The fungicides Empress Intrinsic, Pageant Intrinsic, Segovis, and Subdue MAXX, applied as preventative and curative treatments, were able to suppress the disease severity compared to the inoculated control in all 1-, 3-, and 7-day flooding durations. Similarly, all fungicides and host plant defense inducers applied preventative or curative, were able to suppress the Phytophthora disease significantly, except Orkestra Intrinsic. However, net photosynthesis, stomatal conductance, and leaf moisture potential were significantly greater in seedlings treated with Subdue MAXX, Signature Xtra, and Empress Intrinsic in preventative or curative application trials. For the integrated management of Phytophthora root rot and ambrosia beetle attacks, the combination treatment of Subdue MAXX and Permethrin was significantly more effective compared to the Phytophthora-inoculated control treatment. The results of this study can be useful for ornamental growers to combat Phytophthora root rot and ambrosia beetle in trees under abiotic stress conditions