There have been a number of recent reports of two-spotted spider mites on tomatoes, both in high tunnel and field production. Spider mites are favored by hot dry weather, and we have had several periods fitting this description since mid-April. To prevent yield loss to spider mites, producers are encouraged to monitor their fields weekly to catch infestations when populations are still low.
Spider Mite Damage
Initial spider mite damage develops as stippling to leaves (Figure 1), appearing as tiny light colored spots on infested leaves. When noticing this, producers should flip over the leaves and search for mites with a hand lens. As infestations increase, webbing increases. Damage to the leaves progresses from silvering to bronzing and eventually to leaf death. Heavy infestations may result in gold flecking on fruit (Figure 2).
The University of Florida uses an average count of 10 mites per leaflet as the threshold for treatment. Note that this is per leaflet, not the entire leaf.
There are several miticides listed in Vegetable Production Guide for Commercial Growers (ID-36) that can be used to control mites on commercial tomatoes, but Movento and Portal cannot be used in high tunnels or greenhouses. Coverage is critical to controlling spider mites with these products. Several products are limited to one or two applications per crop.
By Ric Bessin, Extension Entomologist