Control of powdery mildew on pumpkin leaves by experimental and registered fungicides: 2007 trials
University of California, Davis, CA
Christopher N. Janousek, Jacob D. Lorber, and W. Douglas Gubler
Department of Plant Pathology
Objective: Powdery mildew, caused by the pathogens Podosphaera xanthii, Golovinomyces orontii and G. cucurbitacearum, is an important global disease of cucurbit crops, with many pumpkin, squash, cucumber, and melon varieties being particularly susceptible to infection. Pathogen resistance to chemical fungicides, particularly benomyl and trimefon (a DMI), has been documented in the field (McGrath et al. 1996), suggesting that new materials or novel cultural practices may need to be eventually integrated into current control regimens.
Method: Two adjacent trials were conducted at the University of California, Davis Plant Pathology Farm (Solano Co., CA) to test the efficacy of different fungicide products against foliar occurrence of Powdery mildew on pumpkin cultivars of Cucurbita pepo. This trial tested the efficacy of microbial-based biofungicides and organic products. Treatments consisted of unsprayed and water only controls, two concentrations of Actinovate (Streptomyces lydicus) and Companion® Biological Fungicide (Bacillus subtilis) applied with and without Quintec.
Results: Following 6 weeks of fungicide application, powdery mildew colonies were ubiquitous in both trials. Disease incidence in the Wee-Be-Little pumpkins approached 80% on the upper leaf surfaces of unsprayed plants and exceeded 50% on the upper leaf surface of most treatments. Like the Merlin variety, disease incidence generally appeared to be greater on the lower surfaces of leaves. Quintec applied alone, or with Companion Biological Fungicide, greatly reduced disease incidence and markedly outperformed other biofungicides and organic products.
Companion® is a registered trademark of Growth Products, Ltd., Quintec® is a registered trademark of Dow AgroSciences, LLC., Sporan® is a registered trademark of EcoSMART Technologies, Inc., Actinovate® is a registered trademark of Natural Industries.