Jack O’Lantern Pumpkin Response to Carfentrazone, Glufosinate, and Glyphosate Applied to the Distal Portion of the Vine

Chemical weed control in pumpkin ( Cucurbita pepo ) often relies on herbicide applications made at planting, which results in weed escapes later in the growing season. The use of postemergence herbicides in row middles is useful, especially in no-till pumpkin production, but there are limited effective options. We conducted field research in 2023 at Wanatah and Lafayette, IN, USA, to evaluate ‘Bayhorse Gold’ pumpkin response to carfentrazone, glufosinate, and glyphosate applied to 10% of the vine tip 5 weeks after planting. A non-treated control was included for comparison. Pooled across both locations at 1, 2, and 4 weeks after treatment, glyphosate resulted in greater visible foliar injury (32%, 21%, and 9%, respectively) than carfentrazone (16%, 8%, and 5%, respectively) or glufosinate (13%, 8%, and 6%, respectively). Injury did not differ among the herbicide treatments at 6 weeks after treatment; crop injury was 9% for glyphosate, 7% for carfentrazone, and 6% for glufosinate. The nontreated control yielded 2420 orange pumpkins/acre weighing 48,016 lb/acre, which was statistically similar to plots treated with glyphosate (2766 pumpkins and 50,684 lb/acre), carfentrazone (2593 pumpkins and 50,303 lb/acre), and glufosinate (3111 pumpkins and 54,495 lb/acre). All treatments resulted in 346 green and 173 nonmarketable pumpkin fruit (<3.3 lb) per acre. Our results suggest that the herbicide glufosinate, which is not currently registered for use in pumpkins, offers crop safety similar to carfentrazone and greater crop safety than glyphosate, which are both currently registered for use between pumpkin rows. Despite differences in visible crop injury, no herbicide treatment resulted in decreased pumpkin yield.