Diseases

Late Blight disease on Tomatoes

Late Blight disease is caused by the fungus-like organism Phytophthora infestans and can affect both tomatoes and potatoes. It should not be confused with Phytophthora blight (caused by P. capsici), which affects squash as well as tomatoes and peppers. Late blight has also been reported to affect petunias and nightshades.

Late Blight of Tomato

Late Blight disease is caused by the fungus-like organism Phytophthora infestans and can affect both tomatoes and potatoes. It should not be confused with Phytophthora blight (caused by P. capsici), which affects squash as well as tomatoes and peppers. Late blight has also been reported to affect petunias and nightshades.

Late Blight of Tomato Detected in Massachusetts

Late Blight of tomato has been detected in Massachusetts for the first time this growing season. This disease is caused by the fungus-like organism Phytophthora infestans and can affect both tomatoes and potatoes. It should not be confused with Phytophthora blight (caused by P. capsici), which affects squash as well as tomatoes and peppers. Late blight has also been reported to affect petunias and nightshades.

Geranium - Back leg (Pythium)

The first symptom of black leg is brown, water-soaked tissue at the base of the cutting. This turns shiny black and can quickly spread 3 or 4 inches up the cutting stem. Eventually the tops of affected cuttings and plants wilt, yellow and die. Fungus gnat larvae are often found in infected cuttings.

Peony Anthracnose

Peony anthracnose is caused by the fungus Gloeosporium. Symptoms seen in these photos include leaf spots, dieback, and dark lesions that may girdle stems.
Masses of salmon-colored spores may be observed in leaf spots and lesions. Buds and flowers may also be affected.

Prevent peony anthracnose by improving air circulation.
Avoid overhead watering. Remove and destroy all infected plant parts.
 

Pest Management Resources

The following pest management resources have recently been updated.

2017-2018 New England Greenhouse Floriculture Guide
300+ pages of current recommendations for nonchemical and chemical management of greenhouse insects, mites, diseases, weeds and algae, plus recommendations for using plant growth regulators.
$40 includes postage and handling: To Order: www.negreenhouse.org

Snapdragon - Pythium root rot

Pythium species cause damping-off, root rot, crown and stem rot of all plant species. The roots of these snapdragon transplants are infected with Pythium root rot resulting in stunted and wilted plants. Pythium is favored by high fertility and high moisture; avoid overwatering and overfertilizing. Pythium is a natural inhabitant of the soil and can survive there indefinitely as well as in dirt and debris in the greenhouse.

Cloudy Weather Greenhouse Tips

Here are some management tips especially important for periods of cloudy, rainy weather:

Clean Plants: Keep plants in retail areas clean. Remove dead and injured plants and spent flowers a couple times a day even during the busy season. Botrytis and high ethylene concentrations from decaying plant tissue will cause premature loss of foliage and flowers.

Mandevilla - Anthracnose

Anthracnose (Colletotrichum sp) was recently diagnosed on mandevilla. Anthracnose is common on many ornamental plants. The primary symptoms are leaf spots, leaf blights and dieback. Infected leaves develop tan to brown spots or lesions that are typically associated with leaf veins. In severe cases leaf drop may occur. Because anthracnose symptoms take on different forms and appearances it can be mistaken with other fungal diseases. Submit suspicious plants to a diagnostic laboratory for proper identification. 

Mandevilla - Anthracnose

Anthracnose (Colletotrichum sp) is common on many ornamental plants including mandevilla. Disease symptoms are leaf spots and dieback as seen in these photos. Infected leaves develop tan to brown spots or lesions that are typically associated with leaf veins. In severe cases leaf drop may occur. Because anthracnose symptoms take on different forms and appearances it can easily be mistaken with other fungal diseases. It is therefore beneficial to submit samples to a diagnostic laboratory for proper identification. 

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