CHAMBERSBURG, Pa. — It is the time of year when children have gone back to school, leaves are starting to turn colors, and we have had some cooler weather upon us. Among these signs of summer coming to a close and autumn being on its way, one that I look forward to every year is seeing pumpkins for sale at roadside stands and other markets. However, with the heavy rain we have had this week, pumpkin fruit rots could end up being a concern. If you are growing pumpkins or other winter squash, here are some tips to protect your crop.
Don’t let off the gas on your fungicide program yet. Conditions are currently suitable for both downy mildew and powdery mildew to spread into pumpkins, in addition to the many fungal pathogens that cause fruit rots. Both of these mildews can lead to rapid defoliation if they are not managed. Powdery mildew can also spread into vines and fruits, weakening handles. Maintain an effective weekly fungicide program including products for both powdery and Downy mildew. Be sure to rotate FRAC groups to prevent the development of fungicide resistance.
Be sure to scout your fields for evidence of fruit rots, particularly Phytophthora. Phytophthora fruit rot symptoms will begin as water-soaked, sunken lesions on mature fruit, followed by a white-ish gray powdery mold, which can spread easily in water. Thus, heavy rainstorms increase the risk of spread. Fungicides at this time of year will not help as much for controlling fruit rots but you should practice good sanitation and cleanup practices to reduce further spread. If you start to see fruit rots develop in one area, harvest from that area last and sanitize your harvesting equipment afterward.
Wait until pumpkins and winter squash are fully ripe to harvest them and handle them carefully. Any wound that is caused due to rough handling or handling of rinds that have not fully hardened will provide easier entry to pathogens that cause fruit rots. When fully mature, the rind of squash should be difficult to pierce with your nail.
Once vines are cut, make sure to cure the fruit to extend its storage life. The curing process helps ensure rinds have hardened, helps heal any cuts or scratches, and allows the handle to dry down, reducing access to rots. Winter squash and pumpkins should be cured between 80-85° F. This can be done in the field or in a dry barn or other location.
Once cured, winter squash and pumpkins should be stored somewhere cool, dry, and well-ventilated. Storage temperature for most winter squash should be between 50-55° F. If you produce tree fruit crops, such as apples, keep your squash storage away from where your fruit is stored.
If you suspect you have Phytophthora or another fungal fruit rot, consider holding harvested fruit on your farm for a week or so before selling it. Fruit appearing clean when picked from infected fields can quickly develop symptoms quickly once placed in packing bins, as the crowding creates favorable conditions for disease development. By holding risky fruit on your own farm, you prevent rot from developing on site for a customer you have sold it to and souring the customer’s relationship with you.
–Karly H. Regan, Penn State Extension