Spider Mites (Tetranychus spp.)

Two-spotted spider mites.

Spider mite problems are most common in southwestern Kansas. Infestations develop on the undersides of lower leaves and may expand rapidly to include upper portions of the plant as it enters the reproductive stages, especially during periods of hot, dry weather that stresses plants and favors mite growth. Outbreaks of spider mites can also be created by applications of broad-spectrum insecticides targeting other pests, as these will also kill off the predatory mite species that normally suppress spider mite populations.

Effective mite management requires frequent inspection of fields, the prudent use of insecticides and miticides, careful timing of applications, and thorough coverage with sprays. Treatment is recommended when a majority of plants are infested with expanding colonies on lower leaves and some mites can be seen migrating up into the midsection of the plant. Do not delay treatment. Infestations that become established throughout the canopy are difficult to control.

Most eggs will survive chemical sprays, regardless of the kill rate achieved on adults and nymphs, so a second treatment is usually required, typically about 7-10 days after the first one. Examine infested leaves on several plants under a hand lens every few days post-treatment to determine when most eggs have hatched. If active life stages have also survived the initial treatment, consider changing to a different miticide and adjusting application techniques to achieve better coverage (for example, using a greater volume of water). The goal should be to maintain functional leaves in the upper 2/3 of the canopy until the hard dough stage.

Please refer to the most recent version of the Sorghum Insect Management Guide for specific control recommendations.

Page last updated on 10/16/2024 by J.P. Michaud.