Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
As harvest approaches for some cucurbit crops and other plantings are beginning to flower this is the time to be planning controls if the crop is at risk from Phytophthora fruit blight. Although Gavel and Revus are not effective on cucumber downy mildew they do suppress Phytophthora fruit rot. To help suppress development, apply mefenoxam or metalaxyl at planting. The following materials will help provide suppression of the fruit rot phase only:
● Forum (dimethomorph, 40) at 6.0 fl oz 4.18SC/A – must be tank mixed with another fungicide active against Phytophthora blight on muskmelon, such as fixed copper
● Gavel (zoxamide + mancozeb, 22 + 3) at 1.5 to 2.0 lb 75DF/A (Note: some muskmelon cultivars are sensitive to Gavel)
● Tanos (famaxodone + cymoxanil, 11 + 27) at 8.0-10.0 oz 50DF/A
● Ranman (cyazofamid, 21) at 2.75 fl oz 400 SC/A plus an adjuvant, see label for details
● Presidio (fluopicolide, 43) 4.0 fl oz/A – plant back or rotation restrictions of 180 days for all crops other than cucurbits and fruiting vegetables. See label for details.
● Revus (was inadvertently omitted last week) (mandipropamid, 40) 8.0 fl oz/A – must be mixed with a fixed-copper fungicide.
Phytophthora fruit rot on pickling cucumber
Phytophthora fruit rot of watermelon