Fighting Plant Diseases in the Garden

Strong, healthy plants are less susceptible to disease. To keep your plants healthy, take care of the basics first; this will make everything easier. You know, “An ounce of prevention. . .”

The basics include:  Provide sufficient light, good soil, adequate moisture and employ thoughtful garden hygiene practices. Use mulch to prevent soil splashing on to plant leaves.

Should disease strike, here’s a helpful checklist to identify what’s going on.

 

Fungus

One of the most common problems with plants is fungal disease. It takes many forms – mildew, mold, blight, rust, smut, scab, wilt and more. If your garden had any form of fungi last year, it will likely have it again this year.  This stuff is persistent. What can you do?

Cherry tomato plant with late blight fungal disease

Cherry and standard tomatoes are susceptible to fungal blights.

Water plants before noon. Fungi spores can germinate in just 6 to 8 hours. So while watering at night may limit evaporation, it allows fungus to grow in moist conditions.

Rotate crops. Never plant the same kind of vegetable or flower in the same place two years in a row.

Stop it before it starts. If your garden had a fungi in the past, the spores are still around and odds are good the disease will be back. It usually occurs at the same time every year. The best time to start using fungicides, such as Physan 20, is early in the season. Repeat every seven to ten days throughout the growing season to keep spores from multiplying.

Solarize the soil. Lay black plastic sheeting on your garden preseason and let the sun cook the soil. This helps kill fungus spores.

Powdery mildew frequently attacks garden phlox.

Powdery mildew frequently attacks garden phlox plants.

Use drip irrigation to prevent fungal diseases.  This keeps the foliage dry and helps avoid spreading fungal diseases.  Don’t work with plants when they are wet.

Plant disease resistant varieties. If problems have existed in previous years, choose disease resistant cultivars.

Other tips: Mow under fruit trees. Move fallen leaves to the compost pile. Basically, remove dead or dying plant material that represents a hospitable site for fungus growth.

 

Bacteria

Other common plant diseases are bacterial based. These are spread through water and soil. Bacteria can enter a plant through wounds or through the natural openings in the epidermis (stomata). Generally, bacterial diseases cause rotting and wilting.

Sadly, bacterial diseases cannot be cured. The recommended action is to immediately remove the infected plant(s) from the garden. ALL of the affected plants must be removed to the trash can, even if they have only slight symptoms of bacterial disease.  Do not place diseased plants in your compost pile; the disease will be spread through the use of tainted compost.

To prevent the spread of bacterial disease, clean your pruning tools with a bleach solution made up of one part household bleach to four parts of water, or use Physan 20. Wash your hands after handling infected plants to avoid transmitting the disease to healthy plants.

 

Viruses

Viral diseases damage the plant by destroying the chlorophyll in cells, causing yellowing of the leaves. If a plant becomes sick and dies within a few days, suspect a virus. (Remember how fast the flu virus knocked the wind out of your sails the last time you got it?)

Insects often carry viruses to plants, especially aphids, leafhoppers, mealy bugs and whiteflies.  Aphids are the worst offenders; the green peach aphid can carry more than 50 different plant viruses. Viruses can also be transmitted on your hands or on garden tools.

Once they have taken hold, viral diseases cannot be cured. Remove and destroy the infected plants. Viruses can live on dead plant material for 50 years so never add infected plants to your compost pile.

Raspberry rust is a fungal disease that manifests as yellow or orange spots on leaves.

Raspberry rust is a common fungal disease in many parts of the country.

And finally:  Always use Physan 20 at the first sign of disease. We are huge fans of this product!

 

10/22/2013    Plant Diseases: Identification & Solutions, Uncategorized