How to Manage Pests
UC Pest Management Guidelines
Kanzawa Spider mite (Hydrangea Mite)
Scientific Name: Tetranychus kanzawai
(Reviewed 2/17, updated 2/17)
In this Guideline:
Description of the Pest
The kanzawa spider mite is similar in biology to the twospotted spider mite, Tetranychus urticae. However, on citrus it often produces a bit more webbing, which is more prominent on the fruit than the leaves. Examine fruit and leaves with a hand lens for spider mites. Adult mites are greenish or cream colored, about 0.06 inch (1.5 mm) long, and have four pairs of legs. Spider mites produce webbing that is often filled with cast skins, dust, and other debris.
The first report of Kanzawa mite in California came from Hemet in 2002. Since then, its range has expanded into much of interior Southern California. Based on molecular work, this appears to be the same species of mite as the hydrangea mite, Tetranychus hydrangea: a species reported from citrus in Australia, China, Japan, Mexico, and South America. It is uncertain if its appearance in California is due to a relatively recent introduction or just host expansion of the same species reported in California in 1952, although the former seems more likely.
Kanzawa mite has been reported on a number of other hosts besides citrus, including hydrangea, beans, apples, strawberry, violets, and mulberry.
Kanzawa mite levels vary from year to year. Their numbers often become problematic late in the year (September to October) on late harvested Valencia oranges or red grapefruit. Extensive feeding can lead to rind bleaching and associated webbing.
Pest control advisors have reported that abamectin and fenbutatin oxide are effective in control of Kanzawa mite. However, replicated pesticide efficacy trials have not been conducted in California.
Little is known about biological control for the kanzawa spider mite. Predators that attack other tetranychid mites may also feed on Kanzawa mite.
Monitoring and Treatment Decisions
Check for kanzawa mites when you monitor for other citrus mites. High numbers in summer and fall may require insecticide applications, but thresholds have not been established.
UC IPM Pest Management Guidelines: Citrus
Insects, Mites, and Snails
E. E. Grafton-Cardwell, Lindcove Research and Extension Center, Exeter and Entomology, UC Riverside
Acknowledgments for contributions to Insect, Mite, and Snails:J. Barcinas, E.S.I., Corona, CA
R. Dunn, Badger Farming Co., Exeter, CA
J. Gorden, Pest Management Associates, Exeter, CA
C. E. Kallsen, UC Cooperative Extension, Kern County
D. Machlitt, Consulting Entomology Services, Moorpark, CA
C. Musgrove, retired entomologist, Riverside, CA
K. Olsen, S & J Ranch, Pinedale, CA
N. V. O'Connell, UC Cooperative Extension, Tulare County
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura County
T. Roberts, E.S.I., Corona, CA
T. Shea, UC Cooperative Extension, Riverside County
J. Stewart, Pest Management Associates, Exeter, CA
P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA