Hail is typically accompanied by driving rains and wind and can physically damage even the strongest plants. Depending on the extent, plants can usually recover from hail damage. However, these injuries may serve as sites of infection for various fungal and bacterial diseases. There are no “cures” for disease once the tissue is infected – it is all downhill from there, just at variable slopes. That is why I usually refer to our options using the term “disease management,” rather than “disease control,” since most actions are taken to minimize the effects of disease, or flatten the downhill slope. By responding appropriately to hail, the impact of disease on both injured and uninjured vegetable plants can be reduced.
Here are some tips for preventing disease from taking hold in vegetable plantings damaged from hail.
Clean Up Damaged Plant Material
Bring a bag or bucket into the field to carry detached or hanging debris to be trashed. Damaged plant tissue left in the field is more susceptible to fungal and especially bacterial diseases, so removing these materials will help protect the rest of the crop.
Only prune or trellis plants when they are physically dry, to avoid causing further injury. Prune with a sharp blade; dipping the blade in a 10% bleach solution (one part bleach, nine parts water) is recommended to avoid spreading bacteria between each cut. Some vegetables should be pruned minimally or not at all; see ID-36 for more information.
Spray With Copper or Another Bactericide
Copper is the primary chemical control against bacterial diseases. Bacteria require a wound or a natural opening to initiate disease in plants, and bacteria can easily be spread by splashing rain, which makes hailstorms convenient events for bacterial disease epidemics. Copper will protect plant tissue from new infections from bacteria.
Tank-Mix Copper with A Fungicide
Ideally, choose a fungicide labeled for Botrytis gray mold. Botrytis gray mold particularly affects damaged plant tissue, and a single diseased area has the ability to produce hundreds to thousands of spores that can start new infections in unprotected plants. Some fungicide suggestions are mancozeb, chlorothalonil, or fungicides in FRAC groups 1, 2, 3, 7, 9, 11, or 14. See ID-36, ID-128, and the product label for chemicals for specific crops, since not all fungicides are labeled for use on all vegetables. Ensure product compatibility any time you tank-mix.
This is a decision to be made on a farm-by-farm basis. Some factors to consider include the age of plants when affected, extent of plant damage, existing disease pressure in the field, the timeline of when produce needs to be marketed, the cost and/or availability of additional transplants, and other production aspects unique to individual farms. Some examples of hail damage on snap bean, cabbage, and tomato are shown in Figures 1, 2, and 3.
- Vegetable Production Guide for Commercial Growers (ID-36)
- Home Vegetable Gardening (ID-128)
- Homeowner’s Guide to Fungicides (PPFS-GEN-07)
By Emily Pfeufer, Extension Plant Pathologist
(The author thanks Brenda Kennedy, Plant Disease Diagnostician, for her review.)