There have been several reports of spider mites on high tunnel tomatoes this past week. This coincides with the onset of some much-needed warmer weather in the Commonwealth. Generally, higher levels of mites are more common with warmer weather. Ideally, producers should be scouting for signs of mites and insect pests at least once a week in their high tunnels.
Scouting for Mites
Usually, when scouting for spider mites, I look for signs of their initial damage, rather than for the tiny mites themselves. Mites are small and often found underneath leaves, making them hard to find. As they feed on the tomato leaves with their piercing-sucking mouthparts, mites leave clusters of tiny, light-yellow spots on leaves. This damage is called stippling. Once I find this type of damage, I examine the area to see if spider mites are still active, as the damage remains long after mites may have disappeared.
In terms of sprays for mites on tomato plants, page 104 of Vegetable Production Guide for Commercial Growers (ID-36) breaks out those products that can be used in high tunnels. Most tunnels are into a period of harvest now, so producers need to select a product with a pre-harvest (PHI) interval that fits their picking schedule. PHIs for high tunnel tomato miticides range from 0 to 7 days.
By Ric Bessin, Extension Entomologist