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Extension > Yard and Garden News > Diseases in the Vegetable Garden

Diseases in the Vegetable Garden

Michelle Grabowski, UMN Extension Educator



M. Grabowski, UMN Extension


Photo 1: Black rot is a bacterial disease of broccoli, cabbage, cauliflower and other brassicas.


This years frequent rains have created ideal conditions for many fungal and bacterial diseases in the vegetable garden. These pathogens need moisture to reproduce, spread and start new infections. Although gardeners can't change the weather, a few things can be done help plants dry out after rain or dew and to reduce the spread of disease.

1. Space plants to allow for air movement around the plants and through the foliage. Dense planting results in fruit and foliage that stay wet longer; a favorable condition for many pathogens.

2. Pull weeds. Weeds crowd the vegetable plant, steal nutrients and reduce air movement in the garden.

3. Completely mulch the soil with landscape fabric, plastic mulch, straw or wood chips. Many pathogens survive in plant debris and soil. Rain and irrigation splash water, soil and pathogens onto the lower



M. Grabowski, UMN Extension


Photo 2: Angular leaf spot on cucumber


leaves of the plant. Mulch provides a barrier that reduces splash dispersal of the pathogen from soil to plant. In addition, mulch keeps moisture in the soil and reduces humidity in the plant canopy.

4. Stake vining plants like tomatoes, cucumbers and runner beans. This will improve air movement around the plant and facilitate drying of the leaves and fruit.

5. Do not work in plants when leaves and fruit are wet. Fungal and bacterial pathogens reproduce under wet conditions and can easily be spread on a gardeners hands or tools at this time. Wait until plants have dried completely before working in the garden.

6. Pinch off heavily infected leaves and fruit and remove them from the garden. Many leaf spot and fruit rot diseases produce new fungal spores or bacteria in every leaf spot. These pathogens are easily



M. Grabowski, UMN Extension


Photo 3: Early blight on tomato



spread through the plant to new leaves and developing fruit. Infected plant material can be buried, placed in a compost that heats up or taken to a municipal compost facility.

Remember many plants tolerate some leaf infection and still produce a good crop. Use the steps above to reduce the spread of disease and minimize it's impact on your final harvest.

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