About 10 days ago we harvested a few pumpkin trials at the research station. After weighing and grading the fruit, they were set back in the row but not in the leaf canopy. Last week I drove by some of the plots and noticed some fruit were sunburned. Such is the fate of many pumpkin fruit exposed to direct sun and not covered by leaf canopy. Sunburned fruit have a reddish area facing the sun which will eventually soften and rot.
Over the year’s growers have asked me, how long into the season should they treat the foliage with fungicides? I would respond as long as you plan to harvest fruit. Avoiding sunburned fruit is the primary reason to keep the foliage healthy later into the season. Given our increasingly warmer and sunnier fall season, growers should expect to incur significant losses if the foliage is degraded by bacterial or fungal pathogens.
Conditions that favor sunburn include thin leaf canopies, fruit that have been clipped off of the vine but left in the field to cure or be packed at a later date, and clear sunny days with highs above 80-85F. The weather forecast for the next week in southwest Ohio include max temperatures in the mid 80’s to low 90’s…let’s hope periodic cloud cover spares growers from excessive fruit losses.