Plant disease & stress

Recognize the signs

Pattern

Record whether symptoms affect one plant, a species, an irrigation zone or many unrelated plants. Distribution helps frame questions but does not prove a cause.

Signs versus symptoms

Wilt or discolouration is a symptom. Fungal growth, an insect, an entry hole or a root lesion offers more specific evidence; photographs may still be insufficient.

Look more closely

Compare the labeled examples and their limits. Images are independently enlarged, not shown at a common scale.

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Differences that change the decision

A similar-looking organism can need a different response. Compare the evidence and what it changes.

Compare every column. On a narrow screen, scroll the table sideways.

What else could it be?

Sap feeders and mites

Look beneath leaves for live colonies and corresponding fresh feeding.

Compare spider mites ↗

Caterpillars, slugs or beetles

Chewed tissue, frass or slime directs a different investigation.

Compare caterpillars ↗

Root nematodes

Galls or laboratory findings may explain root-related decline.

Compare nematodes ↗

Inspect the right places

1. Build a diagnostic record

   Record plant and cultivar, planting date, affected parts, first symptoms, recent weather, irrigation, fertiliser and pesticide use. Take whole-plant, site and close-up images.

2. Compare roots and growing conditions

   Check the root zone and drainage, not only the leaves. Compare a healthy plant nearby. Ask a clinic how to collect a useful sample before cutting or shipping material.

3. Keep wilt alternatives open

   For squash, inspect the lower stem for borer entry and frass, leaves for squash bugs and the root zone for moisture problems. Cucumber-beetle-associated bacterial wilt is another possibility.

Choose a proportionate response

For pesticides, the local product label determines the allowed pest, site, precautions and timing. Check safety and regional guidance.

1. Correct a verified care problem

   Repair drainage or uneven irrigation and match light, planting depth and nutrition to the plant. Do not add water or fertiliser simply because leaves look weak.

2. Contain likely disease

   Separate affected movable plants, clean tools and use host-specific sanitation advice. Remove clearly decayed seedlings; avoid spreading suspect soil or plants.

3. Choose prevention or treatment after diagnosis

   Resistant cultivars, sound spacing and appropriate irrigation often matter more than rescue sprays. Any fungicide must be permitted for the host and diagnosed disease; protectants do not repair existing tissue.

Avoid these mistakes

• Do not label every brown lawn patch as grubs or every wilted squash as vine borer.
• Do not use calendar pesticide mixtures to cover all possible diagnoses.
• Do not assume all white leaf growth is the same mildew or that every fungal disease needs wetter or drier leaves.

Check whether it is working

Prevent a return

• Choose locally adapted, resistant plants and healthy stock.
• Use clean propagation materials, suitable spacing and irrigation that avoids prolonged saturation or unnecessary leaf wetness.

Common questions