Recent rain and cold conditions have brought detrimental effects to some of the early planted vegetables. In southwest Indiana, air temperatures have dropped into the 40s °F and soil temperatures have dropped into the 50s °F in early May. The low temperatures would have greatly inhibited absorption of water and mineral nutrients for many warm season vegetables. In one of our fields where watermelon and cantaloupe were transplanted on April 26, almost all the plants showed wilt symptoms on May 3. The wilt was caused by decreased water absorption from roots. The plants were dead due to the extended cold weather. Peppers and tomatoes that were planted about the same time maintained turgid and survived the cold period (Figure 1). But they showed symptoms similar to nutrient deficiency due to the reduced function of roots in the cold soil. The plants should start new growth when the temperature rises. Growers using low tunnels are more likely to see the benefits in a year like this.
Figure 1. A tomato plant showing nutrient deficiency symptoms.
What exacerbates the situation is the extended heavy rainfalls since the end of April. Some growers report the running water washed away some of the newly planted seedlings, and flooding occurred in some field. If the soil is flooded, oxygen in the soil would be depleted within 24 hours. Plants are injured in the water saturated soil. Symptoms usually include wilt; yellowing and drop of older leaves; epinastic curvature that is most commonly seen on tomatoes. If flooding lasts for more than 48 hours, there is little chance vegetable crops could recover. Re-planting would be the only option left. On the bright side, the majority of vegetable fields have not been planted although fertilizers were applied and plastic was laid in several fields in the Southwest Indiana. In this scenario, the heavy rainfall did not directly affect plants, but we should caution that they may leach already applied fertilizers that would affect crops in the middle or late of the season. If field were flooded or ponded with water, they may not be replanted right away even after water recedes because of food safety concerns.