Spider Mites

Spider mites are extremely small, typically 400–500 micrometers in length, but can reproduce rapidly and cause severe plant damage in a short period of time. They are most often found on the underside of leaves, where they pierce individual plant cells and feed on the contents. Unlike flat mites or broad mites, spider mites produce fine webbing, which can become extensive as populations increase.

Spider mite damage is often easier to recognize than the mites themselves. Feeding causes stippling—small yellow or pale dots on the leaf surface—which results from collapsed plant cells. As feeding continues, leaves may turn yellow or bronze, photosynthesis is reduced, and overall plant vigor declines. Under heavy pressure, leaves may dry out, drop prematurely, and plants can suffer significant yield or quality loss.

What to look for:

Fine stippling or speckling on leaves, yellowing or bronzing of foliage, webbing on leaf undersides or between leaves and stems, and reduced plant vigor.

Life Cycle of Spider Mites

Spider mites have a multi‑stage life cycle and can complete development very quickly under favorable conditions.

Egg – Eggs are laid on the underside of leaves, often attached to fine silk webbing.

Larvae – Larvae hatch with six legs and begin feeding shortly after emergence.

Nymphs – Spider mites pass through two nymphal stages (protonymph and deutonymph), both of which actively feed.

Adults – Adults have eight legs and continue feeding and reproducing.

All life stages feed on plant tissue. Development time is strongly influenced by temperature, with higher temperatures accelerating population growth.

Biology of Spider Mites

Spider mites have a high reproductive capacity, allowing populations to increase rapidly under favorable conditions.

They feed by piercing plant cells and removing cell contents, leading to cell death, reduced chlorophyll, and impaired photosynthesis.

Spider mites prefer warm, dry conditions, which favor faster development and increased reproduction.

Most spider mite species, including the two‑spotted spider mite, produce webbing, which protects them from predators and environmental stress.

Heavy infestations can result in leaf drop, plant stunting, and crop loss, particularly in ornamental and high‑value crops.

I see spider mites, now what?...

Spider mites can be effectively managed using biological control when detected early. Predatory mites, predatory gall midges, and predatory bugs are commonly used to target different life stages of spider mites.

Predatory mites form the foundation of control by feeding on spider mite eggs, larvae, nymphs, and adults. In cases of heavy or localized pressure, additional natural enemies may be used to suppress outbreaks more rapidly.

Early intervention is critical, as spider mite populations can increase exponentially under favorable conditions.

I don't see any spider mites, but I'd like to act preventatively....

Preventative biological control programs are commonly used to suppress spider mites before visible damage occurs. Slow‑release systems such as sachets can maintain a background population of predatory mites that respond quickly if spider mites appear.

Environmental conditions, crop type, and the presence of other pests influence which predators perform best. Preventative strategies are most effective when combined with regular scouting and avoidance of practices that disrupt natural enemies.

Additional Notes About Spider Mites

Spider mites primarily feed on the underside of leaves, but damage is often visible on the upper surface.

The presence of webbing is a key diagnostic feature that distinguishes spider mites from other plant‑feeding mites.

Because populations can increase rapidly, early detection and continuous monitoring are essential for successful management.