Extension Report

Baldwin County Extension Office

302A Byrne Street

Bay Minette, AL  36507

Telephone (251) 937-7176 or

928-0860/943-5061 ext. 2222

FAX (251) 937-7285

Mike McQueen

Regional Extension Agent

Home Grounds, Gardens & Home Pests

May 25, 2010

Common Diseases of Vegetables

Blossom end rot, early blight, and powdery mildew are some common diseases you might find in your garden.                                                                                                                   

Blossom end rot starts as a water-soaked spot near the blossom end of the fruit. This spot soon gets larger and turns dark, just as the green fruit begins to ripen. This darker area may become leathery and crack, which increase the chances of other diseases taking hold.

Blossom end rot sounds like a disease that would be caused by an infection, but it is not. It is caused by a calcium deficiency and often associated with drought or too little water. It often occurs after rapid growth early in the season, followed by hot and dry weather, or conditions alternating between the two. This physiological “disease” is most common on the earliest plants to set fruit, put out early in cool soil, or plants spaced too close together.                                                                                                                                                                                      

Blossom end rot can often be prevented by:

·         Keeping the soil’s pH at 6.0 to 6.5. Perform a soil test and apply the recommended rate of lime, using dolomitic or high-calcium limestone. Lime should be applied two to four months before planting crops.

·         Keeping soils uniformly moist, and deeply watered during drought. Using mulches can help.

·         Avoiding root damage by not cultivating too close to plants.

·         Spraying plants early in the season, especially after heavy rains, with a diluted calcium chloride solution at the rate of one level tablespoon per gallon of water.

Another disease which attacks stems, leaves, and fruit of tomatoes, but also those of potatoes and eggplant, is early blight. Early blight is caused by either of two fungal organisms, beginning as circular or irregular shaped spots ¼ to ½ inch in diameter. If the spots have a yellow halo on the outside and concentric lines inside, they are most likely from the fungus Alternaria. This fungus can also cause dark, sunken areas (cankers) in stems. Fruit that is infected will have dark, sunken leathery spots on the stem end. If the leaf spots are gray with dark centers, they are likely from the fungus Septoria. This fungus may also infect stems. A secondary problem caused by this fungus is sunscald from the infected leaves dropping off and exposing the fruit to excess sunlight.

Ways to minimize or prevent early blight include:

·         Selecting resistant varieties

·         Growing tomatoes in a different part of the garden each year (crop rotation).

·         Watering early in the morning if using overhead watering, to allow the leaves to dry during the day

·         Using fungicides labeled for this disease. If using fungicides, please make sure to read and follow all label directions for the best control, protecting the environment, and for your safety.

Powdery mildew can attack many plants, but is seen more often on cucurbits such as squash and pumpkins. High humidity conditions are favorable for this disease. Many diseases are spread by rain, but powdery mildew does not need rain to spread. Once a leaf is infected, it can produce tens of millions of spores.

The symptoms of powdery mildew are a white spotting or growth on the leaves, eventually causing them to turn yellow, then brown, and finally die.

Some methods for controlling this disease are:

·         Choosing resistant varieties

·         Planting in areas with good air circulation

·         Proper use of the appropriate fungicides

More information about plant diseases, pests, and controls can be found at: http://www.aces.edu/pubs/docs/indexes/anripm.php

 Source: Dr. Leonard Perry, Extension Professor, University of Vermont

Email address: mcquegj@aces.edu

Phone number: 937-7176 or 943-5061, 928-0860, ext. 2222

The Alabama Cooperative Extension System (Alabama A&M and Auburn Universities) in cooperation with the U.S. Department of Agriculture is an equal opportunity educator and employer.