Jerry Brust, IPM Vegetable Specialist, University of Maryland, jbrust@umd.edu
After visiting pumpkin fields over the last few weeks it seems that in some of the fields there could be a reduction in yields of around 15-30%. I reached this very unscientific conclusion based on walking around in the fields. Normally I end up stumbling over fruit that is underfoot and unseen under the pumpkin canopy. But this year I stumbled around very little as pumpkins –large orange ones—were spaced greatly apart from one another. Much of the reduction in the number of pumpkins could be due to flower or fruit abortion (Fig. 1) that occurred sometime in late July or early August during our severe heat wave, which greatly reduced pollination success. An indication of this possible flower/fruit abortion is that in many of these fields there were large orange fruit found and small-medium green fruit also being found that look quite good. However, there are no, or at least very, few pumpkin fruit in-between these two sizes. Unfortunately, these small to medium sized fruit will not be harvestable in time as they were formed later in the season.
Figure 1. An aborted pumpkin fruit in early August
The other thing I observed was that the fields that kept their foliage up and in good shape (Fig. 2) had excellent quality fruit. This entails pumpkins with good color and unblemished skins and good dark green firm handles (Fig. 3). I have not seen such good looking foliage this late into the season in quite a while and it is paying off in these fields as pumpkins are well covered with foliage and are not exposed to any possible sunburn we might see now because we are experiencing clear sunny days with highs in the mid to upper 80s, which are perfect settings for sunburn/sunscald. In addition to sunburn protection the good foliage will allow the large green fruit that is present in these fields to ripen to mature orange fruit over the next week or two.
Figure 2. Pumpkin field in mid-September with excellent foliage
Figure 3. Pumpkin fruit with excellent skin and handles in mid-September