Non-pesticide Materials on Control of Three Powdery Mildews in the Field

Powdery mildew is a serious disease of many important economic crops including cucurbits, apple, grape and rose. It causes great economic loses every year. Many fungicides had been developed for the control of powdery mildews. However, frequent use of fungicides has raised public concern regarding worker safety, consumer healths, and the environment pollution in recent year. Controlling the powdery mildews with non-pesticide method is an ideal strategy. In this study, sunflower oils emulsified with oil dispersant, Salatt, PAOS, or Tween 20, and narrow-range oil were tested to control the powdery mildews in the field. Results indicated that 1% sunflower oil emudified with Tween 20 has the greastest control efficacy against the powder mildews of common jasmin orange, common cosmos, and common crape myrtle with control rate of 78%, 61%, and 54%, respectively. The narrow-range oil at 300 fold dilution also decreased the desease severity for more than 50.4%. All oil treatments were more effect than benomyl on control of powdery mildews. In the conidial germination tests, all sunflower oil treatments decreased the conidial germination rate, significantly. The inhibitions of conidial germination were observed and may be the control mechanism of sunflower oil. Our data indicate that sunflower oil and narrow-range oil can be applied to the control the powdery mildews.