An Integrated Pest Management Approach to Controlling Powdery Mildew on Curcurbits in Florida
Project description and objectives:
Powdery mildew (PM) caused predominantly by the fungus Podosphaera xanthii causes wilting and premature senescence of cucurbits. Talcum-like fungal growth develops on leaf surfaces, petioles, and stems when temperatures are cool, relative humidity is high, and light intensity is low. Since the 1800’s, PM has been recognized worldwide as a major problem in both the field and greenhouse. PM is present in 70% of all squash acreage in Florida and impacts yield by decreasing the size and/or number of fruit, diminishing the quality of fruit, and shortening the length of time fruit can be harvested. There are 7 races of P. xanthii which are identified based on the disease response of 6 muskmelon differentials. Race 1 has been most commonly found in the eastern U.S. and many commercial cultivars have resistance to this race. Recently in the southeast, cucurbits have become severely infected with PM. It is not known if the race structure of PM has changed and resulted in the breakdown of cultivar resistance. We propose to elucidate the race structure of PM on cucurbits in FL by planting the 6 muskmelon differentials and 10 additional cultivars of various cucurbits and evaluating for disease in 3 locations.
Cultivar disease resistance, when available, can manage PM. However, when disease resistant cultivars are not available or the targeted pathogen changes and conditions favor disease, fungicides are critical. Systemic products are particularly effective for PM control; however, fungicide resistance has been documented worldwide. We propose to investigate the efficacy of currently registered fungicides of varying modes of action for control of PM in FL.
Our objectives are to:
1) To characterize the powdery mildew (S. fuliginea) races at 3 locations in FL using 6 muskmelon differential lines. The 3 UF research locations include Live Oak at the
NFREC – Suwannee Valley, Citra at the Plant Science Research and Education Unit, and Wimauma at the GCREC. The 6 muskmelon differential lines are ‘TopMark,’
‘PMR 45,’ ‘PMR 5,’ ‘Edisto 47,’ PI 414723, and ‘MR-1.’
2) To evaluate 10 cultivars total of Cucurbita moschata, C. maxima (both winter squash), and C. pepo (summer squash) for susceptibility to powdery mildew at 3
locations in FL (Live Oak, Citra, and Wimauma).
3) To compare 14 registered fungicides for the control of powdery mildew on butternut squash at 3 locations in FL (Live Oak, Citra, and Wimauma). The 14 fungicides
may include the following: azoxystrobin, chlorothalonil, copper, mancozeb, mancozeb & fixed copper, maneb, myclobutanil, pyraclostrobin, pyraclostrobin &
boscalid, sulfur, thiophanate-methyl, trifloxystrobin, triflumizole, and zoxamide.
Project leaders:
- Dr. Amanda Gevens, Assistant Professor, Plant Pathology, UF
- Dr. Eileen Kabelka, Assistant Professor, Horticultural Sciences Department. UF
- Dr. Gary Vallad, Assistant Professor, Plant Pathology Department, Gulf Coast Research and Education Center (GCREC)
- Robert Hochmuth, Multi-County Extension Agent - Vegetables, North Florida Research and Education Center (NFREC) – Suwannee Valley