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Andy Wyenandt, Rutgers Cooperative Extension
As the summer heats up in New Jersey, the control of Phytophthora blight in cucurbit plantings can be
extremely difficult (even with the use of fungicides) as hot, wet weather finally sets in. Mitigating losses to Phytophthora blight in cucurbit crops begins with long crop rotations, where recommendations suggest crop rotations longer than 5 years if possible. Other cultural practices include avoid planting in low areas of the fi eld where water may persist after rain or overhead irrigation, rogueing out infected plants as soon as possible, cutting the plastic to help dry out the soil, proper weed control, and proper preventative fungicide programs.
Searching for sources of resistance to Phytophthora blight in cucurbit crops
Research is continually ongoing for discovering and introducing phytophthora-resistance into cucurbit
crops; where resistance has been identified and used breeding programs in crops such as bell pepper
for decades now. In cucurbit crops, ontogenic, or age-related resistance, to the fruit rot phase of
Phytophthora blight has been identified; however, its onset differs by crop. Where summer squash,
zucchini, and melon fruit remain susceptible over time; developing fruit of acorn, butternut, some
cucumber, and pumpkin become less susceptible to P. capsici as they age (i.e., mature) (Perla et
al., 2023). Pumpkin fruit with hard, gourd-like rinds are less susceptible to Phytophthora fruit rot than
pumpkins producing conventional (e.g., softer) rinds (Sanogo et al., 2023). Research for introducing
phytophthora blight resistance into squash is ongoing (LaPlant et al., 2020). Watermelon germplasm
with resistance Phytophthora blight has been identified and used in breeding programs in the past few
years, unfortunately, its been difficult to bring this resistance to market (Sanogo et al., 2023). Recently,
the USDA has developed and released five resistant germplasm lines which should prove useful for
developing watermelon cultivars with broad resistance to P. capsici (Kousik et al., 2022).