Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Many vegetable fields on Delmarva have been impacted by heavy winds from Tropical Storm Isaias. Wind gusts of over 80 mph were recorded near Hurlock, MD. Damage to vegetable crops by severe wind includes plant defoliation, leaf tearing and shredding, stem lodging, stem breakage, loss of flowers and small fruit, and fruit bruising and wounding.
Effects of storm damage on vegetable crops and recovery of crops will depend on a number of factors including the type of vegetable, stage of growth, weather conditions immediately after storms, and prevalence of disease organisms. Continued hot, wet conditions after storm events pose the most risk by increasing disease incidence, particularly bacterial diseases.
Defoliation reduces leaf area and plants will need to grow new leaves from buds for vegetables such as vine crops where this is possible. It will take several weeks to replace the leaf area lost. This will cause delays in maturity. If crops are more advanced, loss of leaf area can reduce fruit or tuber/root quality because of reduced sugar production, however size may or may not be affected. Leaf area recovery (growing new leaves) will be aided by additional nitrogen applications after the storm event.
Stem breakage or injury can lead to major losses in some fruiting crops such as peppers by loss of fruiting area as well as increased sunburn as plants are opened up. Many vining crops will recover significantly from stem breakage by producing new branches, although production will be delayed and there will be potential for increased sunburn until leaf cover is restored. Losses of flowers or small fruit may limit yield potential and delay crop harvest in many vegetable crops.
Green snap in sweet corn is when the corn plant snaps off under the pressure of the wind. Sweet corn is most vulnerable to green snap during the rapid elongation stage (V8 – tasseling). Conditions favorable for rapid growth, good moisture and heat increase the risk of stalks breakage. If the stalk breaks near the ground, no ear will be produced. Some sweet corn varieties are susceptible to root lodging where the stalk is bent over by the wind. This corn will start to grow upright again giving it a U appearance. Harvest will be difficult in lodged sweet corn.
Of immediate concern after storms will be bacterial diseases on susceptible crops. Bacterial diseases have been shown to be more severe after storm damage as they can readily enter through wounds. Including copper products in spray programs after storm injury is recommended to limit bacterial diseases. There has been some recommendation to use peroxide based fungicide products after storm events. These products kill what they contact and have no residual. There may be some reduction in the numbers of disease organisms on plant surfaces; however, there is little research to show major benefits after storm damage.
General recommendations for storm damaged vegetables are to first evaluate the extent of the damage. Crop insurance adjusters are trained to evaluate storm damage in many crops and should be contacted immediately for insured vegetable crops. Consider applying additional nitrogen to encourage new growth where appropriate. Apply additional fungicides and include copper compounds where bacterial diseases are of concern.