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By Mark Carroll and Stephanie Kensicki

Do you have problems with your plants and don’t know what is causing them? Here are a few common causes of plant problems to help you get started. These are taken from information shared with the Master Gardener Training by Professor David Langston of the Tidewater Agricultural Research and Extension Center (AREC) in Suffolk (bio: https://www.arec.vaes.vt.edu/arec/tidewater/people/faculty/langston-biography.html).

First, it is important to understand the two main causes of plant problems:

Abiotic Stress

Abiotic stress is caused by events temporary in nature and which are not insect or disease related. For example: high winds, ozone concentrations, drift of chemicals from commercial fields, excessive drought, or sustained rain for days are all abiotic stressors. In some cases, plants can bounce back from the stressor event. In the case of drift, the plant may live but the foliage or growth that was exposed may die and be replaced by new healthy foliage. On the other hand, the plant may die completely.

Drift may occur from nearby commercial farms, but it also can occur if you are using chemicals in your yard. Dr. Langston suggests that if you can see vegetable plants from where you use glyphosate (weed killer commonly called Roundup), you could be exposing your vegetables to unwanted chemicals and could be causing them stress.

Plants are living things and they get stressed. You have likely heard of “transplant shock”, it is a common form of abiotic stress. Similar to human stress, it can lead to a weakened immune system and make plants more susceptible to harmful insects and diseases.

Harmful Insects and Diseases

Dr. Lanston is not an entomologist (an expert in insects), but he is frequently sent pictures and plants for pathological diagnosis where an insect actually created the damage or delivered pathogens (diseases) which killed the plant. A good first recommendation when diagnosing damage is to look for signs of abiotic stress or insect activity. His best advice for home gardeners is to select seed or plant varieties which are resistant to the types of diseases which frequent our area.

How to keep plants healthy

• Start with disease resistant varieties whether seeds or plant
• Do not over or under water, which is a very common cause of abiotic stress
• Plant in areas that drain well
• Plant in sunny areas and water in the mornings if possible, so the wet has a chance to dry before nightfall
• Practice crop rotation across plant families
• Do not over fertilize; READ the label
• Remove weeds which may harbor pathogens
• Improve air flow and space between plants

There is no use applying fungicide or bactericide after you see the signs of fungal or bacterial plant damage, these products are effective in preventing not treating already infected plants. As always, read and follow the labels on such products.

Abiotic stress, insects and diseases are a natural part of the ecosystem, but for gardeners, they are our constant enemies. When a plant is not healthy, nature doesn’t waste time recycling it. A stress event invites insects and disease in order to kill the weak plant and make room for new growth. Dr. Langston jokes “Tomatoes are a plant looking for a way to die.” But with a little knowledge and work, you can make sure your tomatoes – and whatever plants you choose to grow – can thrive.

Virginia Cooperative Extension programs and employment are open to all, regardless of age, color, disability, gender, gender identity, gender expression, national origin, political affiliation, race, religion, sexual orientation, genetic information, veteran status, or any other basis protected by law. An equal opportunity/affirmative action employer. Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.