Home & Garden

How to minimize the effects of diseases in the garden

Dark green peppers that turn pale can indicate a serious disease problem or nutritional deficiencies in certain soil conditions.
Dark green peppers that turn pale can indicate a serious disease problem or nutritional deficiencies in certain soil conditions. TNS

When I was a horticulture student, I was urged to never smoke cigarettes around tomato plants. At the time I considered this advice an old wives’ tale. It wasn’t until I discovered tobacco mosaic virus on my tomatoes that I took a closer look at the disease. Lo and behold, that old smoking-around-tomatoes link came up on the University of Minnesota website:

“Cigars, cigarettes and pipe tobaccos can be infected with tobacco mosaic virus. Handling these smoking materials contaminates the hands, and subsequent handling of plants results in a transmission of the virus. Therefore, do not smoke while handling or transplanting plants.”

This past year, every one of my carefully selected heirlooms declined and died. A postmortem at season’s end revealed they were afflicted with root knot nematodes that had reached critical mass the third year after the garden’s creation. Like many other diseases, it’s due to small space gardens where crops can’t be rotated sufficiently to prevent disease propagation. In small spaces, diseases build up over two or three seasons to critical levels before they strike.

There are two ways to minimize the effects of diseases. First, expand the size of the garden to allow crop rotation, which allows sufficiently different arrangements of plants each year. Solution number two is to find vegetable varieties resistant to the disease. These won’t be in my favorite heirloom catalogs because breeding for disease resistance is a modern thing. It’s a hybridization thing. It may even be a GMO (genetically modified organism) thing. These varieties are the salvation of farmers in regions where certain diseases are epic.

Keep in mind these are “resistant” varieties, not completely disease-proof. In areas of very high concentrations of disease organisms, the resistance may not be enough to overcome these odds. To maximize results, let the infected area lie fallow (unused) for a year to break the reproductive cycle. Bake the ground in summer under a sheet of black plastic to kill them off. This intermediate step will give resistant varieties greater advantage the following season.

Johnny’s Selected Seeds has always impressed me as the working farmer’s seed catalog. Maybe it’s because they sell in bulk for farmers, not just seed packets for home gardens. It’s our starting point for finding tomatoes and other vegetable varieties specially bred to resist diseases without chemical controls.

It helps to know what to look for in disease resistant seed stock. These varietal names are followed by abbreviations that indicate resistance to specific diseases. For example, TMV means it’s resistant to tobacco mosaic virus. Other common viral designations for tomatoes are F for fusarium wilt resistance, V for verticillium wilt, L for grey leaf spot and N for nematodes, a type of root-damaging roundworm.

I was thrilled to find a master list of plant disease resistance codes on the Johnny’s Selected Seeds website. This is a highly valuable feature for home gardeners who have met with disease problems in the past. The list tells you what every suffix abbreviation means. This is a universal code for the seed industry developed by the U.S. Department of Agriculture.

To access the list, go to www.johnnyseeds.com and click on Growing Center in the left side navigation bar. Scroll down to Plant Disease Resistance Codes. Use it online or print it out to keep on hand for reference as you shop seed varieties for next year’s garden. Order a print catalog online or by phone by calling 877-564-6697.

The saying goes: Insanity is doing the same thing over and over expecting a different result. If your plants are suffering from diseases, if yields are poor or they just lack vigor, don’t replant these same varieties. Instead, try something new with an edge against disease. Shop Johnny’s catalog to study new tomatoes that solve problems like the nematode resistant ones I’m buying. Then come spring you won’t be insane; you’ll have tried something new and therefore have earned the right to expect a different result.

Maureen Gilmer is an author, horticulturist and landscape designer. Learn more at www.MoPlants.com. Contact her at mogilmer@yahoo.com or P.O. Box 891, Morongo Valley, CA 92256.