Aceria malherbae

BIOLOGY: A. malherbae are visible when viewed under a microscope. They are yellow to white in color. Nymphs are similar to adults. Mites are present in galls in the spring. During July, they move out of galls into the cool ground. Mites re-emerge in late August and are present until frost.

DESTRUCTIVE STAGE: Nymph and Adult (gall forming)

IMPACT TO HOST: Mites form galls on leaves and stems causing stunted growth and reduced flowering. Flowering is reduced by 60% in the first three years. Field bindweed plants can be reduced by 90% over 10 years. The mites are very slow movers and may take up to 10 years to impact an infestation of field bindweed, although in areas of Colorado, A. malherbae have exhibited outstanding control in 1 acre plots over a 10 year period.

REDISTRIBUTION: Mites are collected by pulling field bindweed containing galls and transported in breathable paper bags. To release, wrap healthy field bindweed around galls. Release sites should be well drained. A. malherbae fails to establish when exposed to early fall frost or late spring frost. Releases under shade trees or near structures can provide protection. Studies have shown that the labeled amounts of 2,4-D can be sprayed where A. malherbae are present. Mowing helps to distribute mites. Roadsides are an excellent area for release.