Getting Started on a Garden Disease Control Plan for 1998

Plant Pathology Infobytes

December 22, 1997

Thumbing through the garden supply catalogs is a favorite activity of gardeners at this point in the season. Planning for the upcoming season is a lot of fun, but your "to do" list won't be complete unless some thought is given to developing a game plan for some of the diseases which may have caused problems in the 1997 crop.

Although improved vegetable varieties are available, that "magic" variety hasn't been developed which is resistant to all garden pests. For example, the "Better Boy" and "Celebrity" tomato varieties are resistant to Verticillium and Fusarium wilts, and root-knot nematodes. However, they are still susceptible to southern blight, early blight leaf spots, and other disease problems, not to mention insect pests.

This goes for other types of vegetable as well, and gardeners must rely on a well-balanced defense against diseases which can reduce vegetable yield and quality, or in some cases kill plants before they've had a chance to produce a crop.

It's not too early to start on your vegetable disease defense program, and while no gardener will achieve the perfect pest-free garden, the following are steps which will lead to healthier vegetable plants next spring.

Site Selection. To reduce chances of damping-off, root rot, and other problems associated with wet soils, choose a well drained garden site. If such a site is not available, plant on raised beds to promote drainage and faster warming of soil. Divert surface water from flowing across the garden. This will help prevent disease-causing organisms from coming into the garden from outside areas.
Sanitation. Since many disease organisms live through the winter in old plants, plow under debris at least six inches deep before planting in such areas. Sanitation is also effective for tobacco mosaic virus of tomato. This virus, a common problem each season, can be transmitted through tobacco products. Wash your hands with soap and water before working in the garden if you use tobacco. Or, better still, if you can find varieties which are resistant to this virus pest, give them a try.
Seed Treatment. Most seeds are treated with a fungicide, as indicated by their red, blue, or purple color. If they have not been treated with a fungicide, treat them yourself. Treat large seed, such as lima, green bean, or corn, in a jar. To treat small seed, tear off one corner of the seed packet. Lift out as much of the seed treatment fungicide (thiram or captan) as is held on the tip of the blade of a penknife, and insert the dust through the hole in the seed packet. Fold down the corner of the packet and shake thoroughly. Plant immediately; do not eat treated seed or feed it to livestock.
Healthy Transplants. When you make your transplant selections, choose healthy, vigorous plants, and purchase them from a reputable dealer or grow your own.
Collect a soil sample for fertility and nematode analysis. If you have a soil acidity or alkalinity problem, now's the time to spot it, and correct the problem. Also, the analysis report will tell you what needs to be added to your soil in the way of nitrogen, phosphorus, potassium, and other plant nutrients. Remember that well-fed plants are healthier and less likely to be attacked by disease pests. Also, don't overlook nematodes. These microscopic critters can attack a wide range of vegetables, so checking your soil to find out if you have root-knot and other parasitic types present in your garden soil is a must. If it turns out, there is a problem, check with the County Extension Office for a free copy of the "Garden Tabloid" which will help you plan a program for fighting nematodes.
Crop Rotation. An easy and economical way to reduce soilborne diseases and nematode problems is to rotate vegetables. Corn and members of the cabbage family can be alternated with other vegetables from one year to the next. If space permits, move the garden to a new location every 3 to 4 years, preferably to a site that was in grass.
Resistant Varieties. Make every effort to purchase varieties which resist disease pests. Consult the list of recommended varieties, seed catalog variety descriptions, or refer to the "Garden Tabloid" for variety suggestions.
Plant Spacing. Plant your growing areas carefully. More is often less when plants are crowded together, since too close spacing allows moisture from rain or dew to remain on plant surfaces. Such a situation promotes disease development and should be avoided.

There is a lot more that goes into growing healthier disease-free garden plants, but the steps listed should help get you get your garden off to a better start. And remember, personnel from your county Extension office are always available to provide assistance, so drop for a visit if you have questions about planning for the 1998 gardening season.

Infobytes newsletter was written by the late Dr. Frank Killebrew, Extension Specialist.