Many arthropods are considered to be pests and can cause negative impacts on agricultural and nursery plants. The majority of these arthropods are insects. On the other hand, not all arthropod pests are insects and some of them may be confused for insects, such as the case of spider mites.

What Are Spider Mites and How Can I Identify Them?

Spider mites are among the most important agricultural pests of many plants. Although spider mites are arthropods, they are not insects. Compared to insects that have 3 body parts (head, thorax, and abdomen) and 6 legs, mites have 2 body parts (head and thorax fused with the abdomen) and 8 legs. Like spiders, these mites generate a thin webbing on the plants they infest. Spider mites are small red arthropods (0.8mm) that look like red spots on top of the plant leaves and the webbing they generate.

What Is Their Life Cycle?

Spider mite infestations are more common to occur when is dry and hot. A typical life cycle of spider mites comprises 4 stages: egg, larva, nymphs (protonymph and deutonymph), and adult. They undergo gradual metamorphosis, meaning the larvae and nymphs look like mini versions of the adults (but without their reproductive capacities), although the larva stage only has 3 pairs of legs instead of 4. The females deposit the eggs on the thin webbing they generate, and it takes approximately 3 days for these eggs to hatch. The length of the cycle will vary depending on temperature, but under optimal conditions (approximately 80°F) the cycle can be completed within 5 – 20 days.

How Do They Damage My Plants?

Like other arthropods, spider mites have a piercing-sucking mouthpart which they use to extract plant sap. This feeding behavior can cause yellow or discolored spots on the leaf surface. This damage causes a decrease in photosynthesis and a premature drop in the leaves. Furthermore, some species of spider mites are vectors of plant diseases. In severe infestations, spider mites can cause plant death.

How Do I Control These Pests?

There are several methods we can use in combination to control spider mites:

• Monitoring – monitoring for spider mites or any other pest is extremely important for any Integrated Pest Management (IPM) program. Using a 10X magnifying lens could be efficient in identifying these arthropods. Observing any cast skins or webbing could be an indication of the presence of spider mites. It is also important to check the underside of the leaves since this is where some mites may be hiding. Acting before an infestation happens could help you save money and avoid unnecessary damage to your plants. On large crops, monitor selected plants representing the total of acres under production and estimate the amounts of mites to determine if control is needed. A good practice is to take a white paper, place it under the plant leaves, shake it, and count how many mites fall into the paper.

• Biological Control – There are plenty of natural predators of mites. These include lady beetles, lacewings, bigeye bugs, minute pirate bugs, and predatory mites, among others. Having this species around your crops may help maintain the mite population under control.

• Chemical Control – There are plenty of pesticides designed to control mites. It is important to understand that mites are not insects, so insecticides are not effective when controlling mites unless the product functions as a broad-spectrum insecticide that also has miticidal activity. Always read the label of any pesticide to verify if mites are listed as species controlled by the product. Furthermore, mite eggs are very resistant to pesticides, so secondary applications are often needed. Verify the label for proper application timing, rates, and how often these applications need to be done. Also, if you are depending on biological control try to use pesticides that will not harm the predatory species of mites.

Conclusion

Spider mites are a common pest of many crops and nursery plants. Early detection and proper monitoring methods are essential when controlling these pests and avoid before an infestation. Remember to use the proper products when controlling spider mites since they are not insects. Normal insecticides will not be effective, you must use a product that has miticidal activity to control these pests.

For more information about Spider mites access the following “Ask IFAS” publications:

Twospotted Spider Mite, Tetranychus urticae Koch (Arachnida: Acari: Tetranychidae)

2024–2025 Florida Citrus Production Guide: Rust Mites, Spider Mites, and Other Phytophagous Mites

Mite Pests of Southern Highbush Blueberry in Florida

Managing Spider Mites in Florida Hops

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