Gardening catalogs have been arriving daily. As you browse through them this winter, you might notice that some of the plant descriptions contain information about disease resistance or tolerance. The use of resistant or tolerant varieties is an inexpensive and easy means of controlling plant diseases in crops where such varieties are available. Their use can also help cut down on the use of pesticides for disease control.
The term resistance or tolerance does not mean that the plant is completely immune to disease. It refers to a plant's ability to overcome to some degree the effect of the pathogen. Also, no variety is resistant or tolerant to all diseases. For instance, the initials VF by a tomato variety indicates resistance to the fungal diseases Verticillium wilt and Fusarium wilt, but does not mean that the variety is also resistant to the common leaf diseases.
If you have had a particular disease problem on a crop in the past, check to see if resistance to this disease is available. Many catalogs clearly list information on resistance or tolerance to specific diseases.
The following list gives some examples of host plants and diseases to which resistance or tolerance is available:
|rose||black spot, powdery mildew|
|apple||scab, cedar-apple rust, fireblight, powdery mildew|
|beans||powdery mildew, downy mildew, rust, various viruses|
|broccoli||black rot, downy mildew|
|cucumber||bacterial wilt, powdery mildew, downy mildew, various viruses|
|pea||Fusarium wilt, powdery mildew, downy mildew, various viruses|
|pepper||Verticillium wilt, various viruses|
|sweet corn||rust, smut, Stewart's wilt, anthracnose, other foliar diseases|
|tomato||Fusarium wilt, Verticillium wilt, Tobacco Mosaic virus, early blight|
Remember to select plants that are suitable for Iowa's hardiness zones and suitable for the site where they will planted. Pm-607 "Suggested vegetable varieties" lists suitable vegetable varieties for Iowa. Plants that are healthy and growing vigorously are better able to resist infection by disease organisms.
This article originally appeared in the January 13, 1995 issue, p. 6.