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University of Nebraska–Lincoln

UNL Extension in Lancaster County

Horticulture

Helping Nebraskans enhance their lives through research-based education.

Plant Diseases Can Be Devastating

by Don Janssen, UNL Extension Educator

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Plant diseases can be very destructive. Often there's no treatment for infected plants. But there is a way to prevent many common plant diseases through built-in disease resistance. Disease resistance is one of the traits that plant breeders seek to incorporate in new varieties. Combined with crop rotation, disease resistance can go a long way to minimizing crop losses and yield reduction.

Crop rotation is moving related groups of crops each year so that plants susceptible to the same diseases don't follow one another in the same soil. Following tomatoes, pepper and eggplant with snap beans the next year, then corn, then squash means that disease organisms that afflict one family of plants don't have year after year to build up in the soil. Soil-borne diseases such as Verticillium and Fusarium wilts can't be treated but they can be eliminated with a combination of built-in disease resistance and crop rotation.

Some diseases are transmitted by viruses, bacteria and fungi on seeds or plants. Seeds and plants acquired from reputable dealers are less likely to be carrying disease problems than seed saved from last year's garden. Saving seed is a questionable practice unless you're perpetuating a heritage variety.

Environmental conditions can make plants more prone to develop disease. For instance, plants in low-lying or poorly drained areas often develop root rots. High humidity in such areas may mean foliage is slow to dry after dew, rain or irrigation making them prone to foliage diseases. Place your garden where cool, moist air will drain away from plants and where plants will receive eight to 10 hours of direct sun each day and air can circulate freely around them.

Some diseases are carried by insects that feed on crops. In this case, controlling the insect controls the disease. Bacterial wilt of cucumbers and squash is a good example. The only way to keep it from killing your cucurbits is to prevent the cucumber beetles that carry it from feeding on the plants.

Remove diseased plant materials from the garden during the growing season and after harvest and burn or bury them some distance from the garden. Control weeds that can serve as alternate hosts for disease organisms and pests and provide plants with the water and nutrients they need to grow vigorously. These are cultural factors in garden disease control.

Some diseases may occur in spite of best efforts to prevent them. For example, tomato plants frequently develop leaf spots or blights caused by fungi. Applying fungicides labeled for leaf diseases on tomato as soon as symptoms appear should prevent serious losses of foliage or fruit.

Powdery Mildew on Lilac

(This resource was added May 2007 and appeared in the Lincoln Journal Star Newspaper Sunday edition. For information on reproducing this article or using any photographs or graphics, read the Terms of Use statement)

University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office


Contact Information

University of Nebraska-Lincoln
in Lancaster County
Web site: lancaster.unl.edu
444 Cherrycreek Road, Suite A,
Lincoln, NE 68528
| 402-441-7180