Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
Many pumpkin fields in the mid-Atlantic have poor foliage cover and weak vines at this time due to foliar diseases such as powdery and downy mildews (Fig. 1). Some growers are looking at their pumpkin field wondering if they should harvest now and store the pumpkins or wait a little longer. Maintaining vine health through harvest is one of the most important considerations for good fruit and stem hardiness. Once the fruit is mature (you can test to see if the pumpkin is mature by pressing the end of your thumbnail into the flesh of the fruit, if little indentation is left in the fruit the pumpkin is mature) the pumpkins can be harvested at any time. The best time to harvest mature fruit is while foliage is still green and relatively healthy. If there is poor foliage cover before pumpkins reach full maturity the fruit and stem quality will be diminished leading to premature fruit breakdown. This includes fruit rotting in the field, sunscald and collapsed stems. Fruit can appear healthy, but the stems still collapse (Fig. 2).
Over the last 2 weeks I have seen a great deal of sunscald damage to pumpkins. Sunscald starts as a reddish area on the fruit that becomes sunken and appears flat (Fig. 3). Over time, this area usually becomes tan with secondary pathogens often invading the area oftentimes causing a black ‘mold’ to cover the damaged spot. If you do have reduced foliage due to disease or insect damage it is best to harvest the fruit and store. Although some growers use chlorine solutions as a post-harvest dip to protect pumpkins taken early from fields our research has shown no value from these dips. Pumpkins can be stored in a well-ventilated shaded area with temperatures between 50-70°F. In general, fully mature, disease free fruit can be stored for months under these conditions. I have kept healthy pumpkins (not jack-o-lanterns) in good shape on my front door step from mid-September until mid-December (yes I like pumpkins a bit too much). Pumpkins should not be stored around apples as the apples emit ethylene gases that accelerate the ripening process, which could lead to premature breakdown.
Figure 1. Loss of foliage due to downy mildew
Figure 2. Healthy looking fruit, but rotting stem
Figure 3. Sunscald damage to pumpkin fruit