Spider Mites on Cucumbers
Spider mites are tiny and easy to miss at first — pale stippling on the leaves is usually the earlier sign, with the fine webbing they're known for showing up only once the infestation grows.
How to spot them
Spider mites feed mostly on the underside of leaves. Early feeding shows as tiny white-to-yellow specks that can turn into a yellowish or bronze stippling. Fine webbing on the underside of the leaves usually follows as their numbers grow.
A quick test
Hold a sheet of white paper under a leaf and tap the leaf firmly. Tiny specks that start crawling are mites. A magnifying glass helps.
Why hot, dry weather matters
Mites build up fastest in hot, dry, dusty conditions — roughly temperatures above 27 °C (80 °F) and humidity below 50%.
What to try, step by step
- Confirm with the paper test before treating.
- A strong jet of water on the undersides of the leaves can knock mites off. It is not suitable for very young or delicate plants, and wet leaves can encourage disease.
- Insecticidal soap or horticultural oil have shown some effectiveness for home gardeners. Follow the product label.
- Avoid broad-spectrum insecticides: they kill the natural enemies that keep mites in check. For most gardeners, encouraging natural enemies works better than buying them.
When it is not mites
Pale, faded leaves without webbing or moving specks are more likely sun scorch, underwatering, or a nutrient problem.
Possible Causes
- Spider mites — tiny, barely visible pests that cause pale stippling on leaves and fine webbing once the infestation grows
- Nutrient deficiency or underwatering, which can cause similar pale, faded leaves without any webbing
- Sun scorch from intense direct light
What to Check
- Fine webbing on the underside of leaves or around the stem
- Tiny moving specks up close (a magnifying glass helps)
- Recent weather — hot, dry conditions favor mites
- Whether the fading is even across the plant or shows up in patches first
In a light infestation, webbing can be hard to spot at first — pale stippling on the leaves is often the earlier sign.
Sources
This guide was checked against the public references below. It is general background, not a diagnosis of a specific plant.
- Washington State University HortSense — Cucumber, Pumpkin, Squash: Spider mites
- University of Delaware Cooperative Extension — Two-Spotted Spider Mite
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