Managing Vegetable Diseases of the Home Garden

MANAGING VEGETABLE DISEASES OF THE HOME GARDEN
Janna Beckerman

Garden vegetables are perhaps the most popular summer garden plants, despite the fact that they are subject to numerous diseases. Preventing these diseases from occurring is the best management strategy available to ensure a healthy harvest. Try to implement these management strategies before reaching for a pesticide.

Preventing Disease

Some cultural practices that prevent and minimize diseases include:

Choose a sunny, well drained site for the garden.
Improve soil by adding compost and other organic amendments.
Choose disease-resistant or disease-tolerant varieties if disease has been a past problem.
Use healthy transplants to prevent disease introductions in your garden.
Water your garden in the morning to allow leaves to dry quickly, thereby preventing disease. Keeping the water on the roots by drip irrigation is the best available watering method. Do not irrigate gardens in the evening by overhead watering.
Do not work in the garden when the foliage is wet. This prevents spreading certain pathogens like bacteria, nematodes and "water molds."
Fertilize only to meet the needs of the plant, taking care to not over fertilize. Too much fertilizer, especially nitrogen, can predispose plants to disease.
Scout! Check the garden regularly for weeds, insect and disease.
Remove severely diseased plants during the growing season and do not compost them. Do not allow excess fruit and vegetables to rot in the garden.
Manage insect pests that can vector viruses and bacteria.
Control weeds that serve as sources for viral diseases.
At the end of the year, clean up all plant residues after the final harvest.
Practice crop rotation. Do not plant the same vegetable in the same location more than two times in three years.

Despite your best efforts, diseases can and do occur. If the above strategies haven’t successfully reduced disease pressures in previous years, then it’s time to consider the use of chemicals to control disease problems before they start.

The biggest mistake gardeners make is that they begin a spray program after the disease problem has become severe. Although environmental conditions can change over time, plant diseases do not "get better," any more than plants "heal." It is important to understand that fungicides work to prevent disease—similar to a vaccine in a person. They do not work like a drug, or silver bullet, to "cure" a problem after it has become established. In order to effectively use a fungicide, you need to make sure the plant is sprayed to prevent disease from occurring.

Chemical Management

Begin researching a fungicide spray program

Is your diagnosis correct? Incorrect diagnosis is the leading cause of failed chemical management.
When spraying, focus on disease prevention rather than "curing" infected plants. Improper timing is the second most common reason fungicides fail to control disease problems.

Always read the label before applying any pesticide. Follow the instructions and restrictions. Do not use any chemical when temperatures are above 85 degrees F, or under windy conditions. Note any restrictions and the time interval between application and harvest.

Table I. Fungicides labeled for disease management in backyard vegetable gardens.
Active Ingredient >	Commercial Product
chlorothalonil	Ortho Multi Purpose Fungicide, Dragon Daconil 2787, Ferti-lome Liquid Fungicide, Security Fungi-Gard, Pennington Multi-Purpose Fungicide
Copper*	Bonide Liquid Copper Fungicide, Acme Copper Fungicide, Acme Bordeaux Mixture, Dragon Tomato & Vegetable Dust, HiYield Copper Fungicide
Captan	Orthocide Garden Fungicide, Bonide Captan, Green Up Captan Garden Spray
Mancozeb	Bonide Manzate Flowable, Acme Tomato, Fruit & Vegetable Fungicide, Dragon Mancozeb Disease Control, Green Light Maneb Plus
Maneb	Maneb Tomato & Vegetable Fungicide
Sulfur*	Garden Sulfur Dust, Bonide Sulfur Plant Fungicide, Bonide Liquid Sulfur , Ferti-lome Rose, Flower & Vegetable Dust, Green Light Wettable Dusting Sulfur, Safer Garden Fungicide
* denotes accepted organic fungicide.

P261G
5/2004

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