Archive for Wednesday, June 3, 1998


June 3, 1998


I witnessed something shocking the other day in one of our local garden centers. It's not often that what goes on in a retail greenhouse can strike me speechless, and perhaps this admission is really just a testimonial to how mundane my life has become.

I smelled it first, wafting toward me on the breeze, and when I located the source I couldn't believe what I saw. There -- among the tomato plants, no less -- was a greenhouse employee, garden hose in one hand and cigarette in the other.

Being a former smoker myself, I can be fairly tolerant of another person's tobacco habit just about anywhere but in the nightshade section of a greenhouse. The reason I draw the line there is tobacco mosaic virus, which attacks tomatoes, eggplant, peppers and potatoes.

I do a fair amount of reading about vegetable gardening and occasionally run across references to tobacco mosaic virus and the perils of handling nightshades after smoking. Given the dire warnings in the literature, it never occurred to me that I'd ever see anyone smoke in a greenhouse.

While the development of virus-resistant cultivars has reduced the incidence of this disease, the pathogen that causes it has not been eliminated and can be transmitted to plants by smokers. Not only is it taboo for someone to smoke in a greenhouse, but many commercial growers flatly refuse to hire people who smoke at all, on the outside chance that they will bring the disease to work.

The leaves of tomato plants infected by the virus will be mottled with yellow and new leaves will have curled edges. The fruit will have yellow and brown patches and, if it matures, will do so unevenly.

With all the chemical processing that tobacco leaves undergo to become cigarettes, it seems hard to believe that a mere pathogen could survive. However, even current gardening manuals that discuss the use of nicotine as a natural insecticide caution against using the alkaloid on tomatoes, eggplants, peppers and potatoes.

The warning holds for both tobacco dust and liquid nicotine sulfate, which are toxic to soft-bodied insects, such as aphids and mealybugs.

If your garden is going to be tended by someone who also touches cigarettes, you need to be choosing nightshade varieties that are bred to withstand tobacco mosaic virus. The most disease-resistant varieties carry the VFTN designation.

The T refers to tobacco mosaic virus. The other resistances, which are the most basic and common, are to verticilium and fusarium, two fungi, and nematodes. Although you needn't confine your choices to resistant plants if these diseases aren't present in your garden, many people simply choose to eliminate the risk.

Look for the letters V, F, N and T, next to individual listings in seed catalogs and occasionally on seed envelopes and on the plastic markers that greenhouses use to label their plants. Not all plants have any or all of these resistances. If the information is missing from plants you want to buy, greenhouse employees should be able to advise you.

Happily, some of the best-tasting varieties of nightshade are resistant to all the ``alphabet'' diseases. I'm thinking of the Celebrity tomato, for example.

Unfortunately, some of the other diseases that are common to this central category of vegetable haven't been ``bred out'' of nightshades. I'm thinking particularly of early blight, which popped up in a number of area gardens after the cool, wet springs we've had in recent years, and anthracnose, which I've occasionally seen on tomatoes in my garden.

Anthracnose is a fungus that produces distinct markings and is an easy diagnosis. On tomatoes, a dark, sunken spot appears on the fruit, surrounded by a second lighter circle. Anthracnose also afflicts beans and eats into the pod, leaving a pattern that looks something like the etchings of acid.

-- When she's not writing about foods and gardening, Gwyn Mellinger is teaching journalism at Baker University. You can send e-mail to her at mellinger

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