APS Homepage

Poster: Biology & Disease Mgmt: Biological Control


Efficacy of synthetic and biorational products against powdery mildew of flowering dogwood
P. LIYANAPATHIRANAGE (1), T. Simmons (1), M. Kabir (1), K. Addesso (1), F. Baysal-Gurel (1) (1) Tennessee State University, U.S.A.; (2) Tennessee State University, U.S.A.

Flowering dogwood (Cornus florida L.) is a popular ornamental plant in home gardens and commercial settings. Powdery mildew, caused by Erysiphe pulchra, may cause cosmetic damage on flowering dogwood by attacking tender shoots and leaf surfaces that cause for dead patches and premature defoliation or kill seedlings. Various products are available or in development that have the potential to contribute to the management of powdery mildew of dogwood. In this study the effect of biorational products (Triact 70-neem oil, thymol and cedar oil) and fungicide (Cleary's 3336F) on dogwood powdery mildew severity was evaluated. Treatments were applied using hand-held sprayer every 7 days for a total of five applications. The experiments were done twice, each with three replicates per treatment. The severity of powdery mildew on foliage and phytotoxicity were evaluated using a scale of 0-100% foliage affected. In both experiments, the severity of powdery mildew was low to moderate (~15 and 30% foliage affected-non-treated control). Triact 70, thymol and Cleary's 3336F provided significant control of powdery mildew compared to the non-treated control in both experiments. Powdery mildew disease progress was lower in dogwood plants treated with Triact 70, thymol, Cleary's 3336F and the high rate of cedar oil than in those non-treated control and the low rate of cedar oil. However, thymol and the high rate of cedar oil were slightly phytotoxic on dogwood foliage.