As summer progresses into late summer, many parts of Texas experience prolonged periods of hot, dry weather with fewer rainfall events. These conditions not only place ornamental plants under drought stress but also create the perfect environment for spider mites to thrive. Unlike many insect pests that are suppressed by frequent rain, spider mite populations often explode during extended periods of dry heat, making August and September a critical time for greenhouse and nursery growers to intensify scouting efforts.

The two-spotted spider mite (Tetranychus urticae) is one of the most common and economically important pests of ornamental crops. Feeding on more than 200 plant species, it attacks popular nursery and greenhouse crops including roses, hibiscus, lantana, marigold, salvia, verbena, hydrangea, and many bedding plants. Spider mites feed by piercing individual plant cells and removing their contents, producing characteristic yellow or white stippling on leaves. As infestations worsen, foliage develops a bronze appearance, leaves become dry and brittle, and severe infestations produce fine webbing that can cover leaves, stems, and flowers.

Warm temperatures accelerate spider mite development, allowing a generation to be completed in as little as 7–10 days under favorable conditions. This rapid life cycle means that a few mites can quickly develop into damaging populations if left undetected. Dry weather also reduces the natural washing effect of rainfall, allowing mites to survive and reproduce unchecked.

Routine scouting is the most effective defense. Inspect susceptible crops weekly, paying particular attention to the undersides of leaves where mites feed and lay eggs. A 10× hand lens can help detect early infestations before visible damage becomes widespread. Early detection allows timely intervention and greatly improves management success.
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An integrated pest management (IPM) approach provides the best long-term control. Maintain adequate irrigation to minimize plant stress, remove heavily infested plant material, and eliminate weeds that can serve as alternative hosts. In greenhouses, reducing excessive heat and maintaining appropriate humidity can help slow spider mite population growth.
Biological control can be highly effective, especially in protected environments. Predatory mites such as Neoseiulus californicus provide excellent suppression when released early, before pest populations become established. Conserving these beneficials by selecting compatible pesticides is essential for successful biological control.

When chemical control is necessary, rotate miticides with different modes of action to delay the development of resistance. Thorough coverage of the undersides of leaves is critical, as both mites and their eggs are concentrated in these protected areas.
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Late summer is the time when spider mites can quickly turn from a minor nuisance into a serious production problem. By combining vigilant scouting with cultural, biological, and chemical management tactics, growers can protect plant quality and minimize losses during one of the most challenging periods of the growing season.

​Rafia Khan, Ph. D.
Texas A&M AgriLife Research and Extension Center
Overton, TX.