Most garden crops can become infected with diseases caused by harmful fungi, bacteria, and viruses.

Inexperienced gardeners (and sometimes experienced growers) may have difficulty distinguishing plant diseases from nutrient deficiencies, insect damage, or environmental problems.

Identify the real problem before you attempt to treat it. Several of the online resources below contain extensive photo libraries.

10 Easy Steps to Prevent Common Garden Diseases Begin with the basics.

Vegetable MD Online Cornell's comprehensive online manual: disease fact sheets by crop, dianostic key, plant pathology glossary, lists of disease-resistant varieties.

Disease prevention: your best defense

Resource Guide for Organic Insect and Disease Management A technical manual developed for organic farmers and the professionals who work with them. Covers major diseases and insect pests of major vegetable crops. Excellent color photos of pest and disease damage.

Vegetable Disease Identification A comprehensive site from Penn State, with good photos and descriptions of vegetable diseases.

Plant Disease Control Oregon's online guide is searchable by host or disease and has good color photographs to help with diagnosis. A fact-sheet button creates easy-to-print fact sheets.

Ohioline-Yard & Garden Ohio State's yard and garden information site.  Primarily a site for fact sheets with a good search function.

Plant Problem Image Gallery The Virginia Cooperative Extension site has a good search feature and good photographs to help identify problems.

Key Vegetable Problems Chart detailing common problems on home garden crops.

Disease-resistant varieties for New Hampshire

Powdery Mildew Resistant Pumpkin and Squash Varieties

Pepper Varieties Resistant to Bacterial Leaf Spot

Not sure what kind of problem you have? Call our Info Line

If you notice a problem but can't determine the cause, call the UNH Cooperative Extension Education Center's toll-free Info Line (M-F, 9:00 a.m.-2:00 p.m.)

Before you call, record your answers to a few questions to help the person taking your call find the right answer to your question:

• Describe the damage (the symptoms).
• What part(s) of the plant is/are affected? When did you first notice the symptoms?
• How extensive is the problem?
• Do nearby plants or crops seem to have similar symptoms?
• Do you have the results of a recent soil test?
• How did you fertilize the soil the affected plants are growing in?
• Have you applied any pesticides or herbicides of any kind (including organic formulations) on or around the affected plants?

UNH Plant Diagnostic Laboratory When you can't tell for sure if your crop has a disease or some other problem, submit plant samples to our lab for diagnosis.