1 - Viral and fungal diseases are potential causes for problems with tomato plants.

Yard and Garden July 19, 2014

Q.

I want to ask about a problem with a tomato plant. It is a large plant and the leaves are curling. I have checked several things, including your column. All the other plants in the bed are good, except for the tomatillas that have potato bugs on them; but they are only on the tomatillos and I keep treating with neem.

I got the tomato plant of concern from an organic market. Most of my other plants are from seed or another nursery.

We have had horrid winds, but only the one plant is affected. I sent you a few pictures to help.

-Kathy M.

Albuquerque

A.

From looking at the pictures you sent, I think your one tomato plant may have a virus disease. Curly top virus is the most likely candidate, but there are other viral diseases. Your local NMSU County Extension Service agent can help you determine the specific virus by sending a sample to NMSU for analysis if you wish.

While it is possible that the plant was infected when you bought it, it is more likely that it was infected after you planted it in your garden. Virus diseases are spread by insect vectors. The beet leafhopper is the primary agent for spreading curly top virus. Most viral diseases do not persist in the soil, rather must overwinter in living plants and be spread from the overwintering host to garden plants by insects. There are no cures for viral diseases; prevention is the best course of action. Removal of infected plants to prevent spread of the disease is a common recommendation. You can find good information about curly top virus disease on the ACES website - Guide H-106: Curly Top Virus. You may also find other relevant information at ACES Publications.

I have also seen some tomato plants that appear to be infected by fungal diseases also. There are several fungal diseases of concern in New Mexico. Once again your NMSU County Extension Service can be of assistance in determining the specific fungal infection and recommended treatment. Fungal diseases often plug up the vascular tissues in stems. This results in symptoms that suggest lack of water when the soil has adequate water. Identification of such vascular diseases may reveal themselves by discoloration of the vasculature at the base of the stems. A longitudinal cut through the base of the stem of infected plants after removal from the soil can help confirm fungal vascular disease.

Fungal diseases often persist in the soil and can cause infections in subsequent years if susceptible plants are grown in the same location year after year. Crop rotation with resistant plants helps to manage fungal diseases. Once again your local NMSU Extension Service office can help you identify appropriate rotation crops.

Fungal diseases may also be spread by putting infected plants in the compost pile if the compost does not heat to a temperature sufficient to kill pathogens.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

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