Viral diseases of greenhouse tomatoes in North Carolina occasionally cause serious damage and large economic loss. The amount of loss can vary depending on the virus disease involved, the variety of tomato, the age of the plant at infection time, the temperature during disease development, the presence of other diseases, and the extent that viruses have spread in the planting. The dense plant spacing, closed environment, and frequent mechanical contact that is inherent to greenhouse tomato production increase the chances of a viral disease outbreak. Keep in mind that symptoms will vary by strain of virus, age and health of host upon infection, and environmental conditions. The first step in controlling a disease is identifying the causal agent.

Though it has not yet been detected in North Carolina, the Tomato brown rugose fruit virus (ToBRFV) was first detected and eradicated in the United States in 2018 and its spread is currently being closely monitored by the USDA Animal and Plant Health Inspection Service (USDA-APHIS). Peppers, eggplants, tomatoes, and cut-leaf ground cherry are all hosts of the virus. It is transmitted by seed and spreads easily via mechanical contact. Symptoms often do not show up until fruit begins to ripen, but symptoms may include mosaic patterns on leaves, leaf narrowing, necrotic pedicles, calyces, and petioles, and smaller, discolored fruit that ripens later.

Control of viruses on tomato requires a complete program that is implemented all year.

Resistant varieties. When possible, plant resistant or tolerant varieties. There are varieties that have varying levels of resistance or tolerance to certain strains of TMV and TSWV.

Use clean seed. Obtain seed from reputable sources. Look for procedures such as fermentation or treatment with acid or bleach by the seedsman. If seed has not been treated, you can treat it yourself. Instructions can be found in the Southeastern US Vegetable Crop Handbook. There are several important things to keep in mind if treating seed yourself: (1) Beginners should try this seed treatment on a small number of seed prior to treating large lots; (2) Seed germination may be reduced with some lots of seed; (3) Research has shown that this seed treatment is enhanced by prewashing the seed for 15 minutes in a solution of trisodium phosphate (one ounce of TSP in two quarts of water); (4) Do not re-contaminate the seed by placing in used containers.

Sanitation. For transplant production, seed in individual pots (peat pots, etc.) and do not touch or handle plants prior to setting in the greenhouse. Discard pots with seedlings that show leaf twisting, mosaic, or unusual growth. Do not touch other seedlings while discarding them. Disinfest equipment, tools, and hands on a regular basis while pulling, pruning, trellising, harvesting, and spraying plants, and when moving from one row or area to another. Decontaminate stakes, tools, tables, etc. by washing them free of debris and then using a sanitizer. Use fresh solutions each time.

Manage insects and weeds. Control thrips and aphids early in the season to reduce initial infection and spread. For information regarding insecticide application, refer to the Southeastern US Vegetable Crop Handbook. All annual weeds in proximal areas should be destroyed. Greenhouses containing tomatoes should be bordered by at least 150 feet of turf or pavement.

Remove diseased plants. Remove and destroy diseased plants early in the season. Do not touch healthy plants with the diseased plants when removing them. Remove and destroy tomato plants as soon as possible after crop termination.