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.
Damage
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.
Management
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.
Biological Control
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.
| Common name | Amount to use | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (type of coverage)** | (hours) | (days) | |
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used. | ||||
| A. | ABAMECTIN* | |||
| (Agri-Mek SC) | 2.25–4.25 fl oz/acre (OC or IC) | 12 | 7 | |
| RANGE OF ACTIVITY: Pests: intermediate (citrus thrips, mites, leafminers); Natural enemies: predatory mites and thrips | ||||
| PERSISTENCE: Pests: intermediate; Natural enemies: intermediate | ||||
| MODE-OF-ACTION GROUP NUMBER1: 6 | ||||
| . . . PLUS . . . | ||||
| NARROW RANGE OIL | ||||
| (415) | 0.25–1% | See Label | See Label | |
| RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most | ||||
| PERSISTENCE: Pests: short; Natural enemies: short | ||||
| MODE OF ACTION: Improves translaminar movement and persistence of insecticide. | ||||
| COMMENTS: For use on all varieties. Most effective in the spring when the trees are flushing. Certain formulations emit high amounts of volatile organic compounds (VOCs); use low-VOC formulations. Regulations affect use for the San Joaquin Valley from May 1 to October 31, 2020. Review the Department of Pesticide Regulation's updated fact sheet. | ||||
| B. | FENBUTATIN OXIDE | |||
| (Vendex 50WP) | 0.25–0.5 lb/100 gal (OC or IC) | 48 | 7 | |
| . . . or . . . | ||||
| 2–4 lb/acre (LV) | ||||
| RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites | ||||
| PERSISTENCE: Pests: short; Natural enemies: short | ||||
| MODE-OF-ACTION GROUP NUMBER1: 12B | ||||
| COMMENTS: For use on all varieties. Use higher rates during cool weather periods. Do not apply more than 1600 gal dilute spray/acre. | ||||
| ** | LV - Low-volume uses 20 to 100 gal water/acre. |
| OC - Outside coverage uses 100 to 250 gal water/acre. | |
| IC - Intermediate coverage uses 250 to 600 gal/acre. | |
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| * | Permit required from county agricultural commissioner for purchase or use. |
| 1 | Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers (un = unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee). |