Two-spotted Spider Mites have been observed on mums. They feed primarily on the undersides of leaves removing plant sap with their stylet-like mouthparts. The feeding damage causes the leaves to have a “stippled” appearance that appears on the upper sides of the leaves. Look on the underside of the leaves for the mites and their eggs.
Two-spotted spider mites are yellow-brown to dark-green with two dark spots on both sides of the body. You need a hand lens to see them. Spider mites can be a problem during dry and hot weather conditions. During periods of high temperature the mite population increases faster because they take less time to go from egg to adult. When numbers are high, they make a fine webbing on the undersides of leaves. Severe mite damage can cause leaf drop.
Treatments require good coverage to the undersides of the leaves and may need repeat applications during warm weather. Treatment options for mites include the following miticides: Sultan, Akari, Avid, Floramite, Hexygon, Judo, Kontos, Ovation, ProMite, Sanmite, Shuttle-O and Tetrasan.
Read and follow the pesticide label.
Geoffrey Njue
Resources
Two-spotted spider mites Umass Extension Greenhouse and Floriculture
Managing Two-Spotted Mites in the Greenhouse UConn Extension Greenhouse
