The immature couch mite is a translucent bodied mite which is invisible to the naked eye at only 0.1-0.15mm in length. As they mature the adult stage is slightly larger with a creamy white elongated abdomen up to 0.2mm long. Infestations of mites are typically identified by the characteristic symptoms of plant injury in the field. Once visible injury has occurred, pest pressure must be considered to be extensive. Infected turf first exhibits a slight yellowing of leaf tips followed by shortening of internodes and leaves, producing a rosetted or tufted growth known as “witches brooming”. Severe infestations result in stand loss, and large dead areas soon become infested with weeds. Damage is usually most severe during hot, dry conditions.
Biology and Lifecycle
Couch mites are active primarily during late spring and summer. Development from egg to adult requires 5-10 days. After eggs hatch, they pass through 2 nymphal instar stages and molt to adults. All life stages live together, protected under the leaf sheath, and often 100-200 mites and eggs can be observed under a single leaf blade. Mites are spread on grass clippings and have been observed hitch-hiking on other turf insects. Dispersal in wind is also common.