Diagnosing Plant Problems

"I think that any time of great pain is a time of transformation, a fertile time to plant new seeds."
- Debbie Ford

introduction

Every home gardener is, by necessity, also a plant doctor. Unfortunately, diagnosing plant problems is not always a quick and easy process. Many issues can be caused by more than one culprit; diseases and pests tend to work side-by-side.

diagnosing plant problems

To begin the process of diagnosing plant problems, it helps to note the signs and symptoms present, and take pictures if possible that document the spread of an issue. Information-gathering is a very important aspect of diagnosis, because it will help you document the problem, as well as be able to have answers There are four simple steps to follow in the initial symptom diagnosis.

Identifying your plant is the first crucial step in diagnosis. Is it deciduous or evergreen? What does it normally look like at this time of the year? Sometimes, the normal dormant stages of plant yearly growth cycles can mimic diseases. Research your plant to learn about its growth habit and life cycle, as well as the kinds of problems it is likely to develop.

Second, identify in depth the parts of the plant that are affected. Scrape away some of the dirt around the base of the plant and try to determine if the roots look as they should. Take care when doing this, as some plants really do not like having their root systems disturbed. If a number of plants are affected and it won't cause too much garden disruption, dig up one of the affected plants and examine the root system in full. Next, examine the leaves. Is the problem on the upper surface, lower surface, or both? Is the issue confined to lower, older leaves, or upper, younger leaves and shoots? Continue your investigation by answering the following questions:

Is the issue one one branch or many? On branches, does the damage begin at tips and progress back towards the trunk?
If you notice any leaf spots, describe the color, shape, size, and texture, and take photos, if possible.
Are leaves distorted? If some areas on leaves are yellowing or browning, is it towards the center of the leaf (at the midrib) at the tip (apex), or along the edges (margins)?
Are the leaf veins the same color of the leaf?
Is there any fungal activity present? If so, what color is it?
Are stems damaged in any way? If possible cut a stem and look inside. Is there any discoloration or distortion on the interior?
Examine the plant for oozes or cankers, and describe and photograph them if present.
Do you notice any galls (unusual plant growths) on the stems or trunks or mushrooms at the base of the plant? If so, describe them and photograph.
If there are damaged fruits or vegetables, cut them open and investigate the damage.

Third, identify any issues that may be affecting the garden as a whole, including abiotic diseases. Plants can incur a lot of damage from causes like frost or air pollution. If a variety of plants are affected, the problem is most likely environmental, as diseases and pests have plant family preferences. When only one type of plant is affected, a more likely culprit is pest or disease. As a last step, check the plant to see if you can find any signs of pest activity or see the pests themselves. If you can't identify the pest, check out the Pests and Pest Management page on this website, or take a photograph and bring it to your local cooperative extension agent.

Symptoms and causes at a glance

After you've gathered all of the information you need, This section is meant to provide you with a bit of a cheat-sheet when diagnosing commonly-encountered plant problems. For ease of use, it is divided into categories depending on the plant part that the issue is occurring in.

Roots

Blackened Roots
Can be caused by fusarium wilt or root rots, or from excessive watering.

Irregular Swelling
Caused by borer insects, grape phylloxera, root knot nemotodes, club rot, crown gall, or oak root fungus.

Rotting Off
Caused by verticillium wilt, or excessive watering.

White Fungus
Oak Root Fungus

Stems

Black Patches
Caused by fusarium wilt.

Blackening
Caused by cold temperatures.

Brittleness and Dieback
Caused by borers or bacterial wilt.

Cankers with Golden Ooze
Caused by bacterial canker.

Cottony Growth
Caused by fusarium wilt.

Discolored or Dead Patches
Caused by gray mold.

Dry, Brown Patches
Caused by cold temperatures.

Excrement Around Holes
Caused by squash vine borers.

Gnawed Stem Bases
Caused by cutworms.

Honeydew & Sooty Mold
Caused by scale and aphids.