Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Most areas of Delaware received significant rainfall over the last 7 days. For example, Bridgeville had over 3.7 inches of rain, Dover, over 3 inches, Blackbird over 3.3 inches, Laurel 2.2 inches, and Greenwood, 3.2 inches. While this was welcome for soybeans and helped to stop further yield loss in corn, it was a mixed blessing in vegetables. Certainly, crops such as dry land lima beans have benefitted greatly as have non-irrigated corners of pivots (pickles and sweet corn especially). However, heavy rainfall after a long, hot, dry period can lead to certain disorders in other vegetables and fruits. Common problems include:
Fruit Cracking and Splitting
This is most common in ripening tomatoes, peaches, and melons but also can be found in other fruiting crops, especially those that were water stressed prior to the rains.
Edema
Edema is water blistering and is causes when the plant takes up more water than it is transpiring. This is seen as raised bumps on leaves, stems, and sometimes fruits. If water pressure is great enough, these raised bumps will burst leaving small blisters.
Wilting
After heavy rains, in areas of the field that remain waterlogged, plants will wilt once the sun comes out. This is because roots are not functioning properly due to lack of oxygen. Wet conditions can also increase the susceptibility to root, crown, and stem rots due to organisms such as Pythium and Phytophthora, also leading to wilting.
Split Sets
Split sets are common in crops such as snap beans and lima beans where a crop under heat and moisture stress subsequently receives ample rain along with reduced heat. This induces re-flowering and a second pod or fruit set. Split sets complicate harvest timing as well as pest management programs in these crops.
Fruit Quality Reduction
Heavy rainfall along with cloudy weather can cause fruit quality problems in those fruits near ripening. Most common is reduced sugar content.