How to Manage Pests
UC Pest Management Guidelines
Citrus Flat Mite
Scientific name: Brevipalpus lewisi
(Reviewed 10/14, updated 10/14)
In this Guideline:
DESCRIPTION OF THE PEST
Citrus flat mite is smaller than tetranychid (spider) mites. It is slow-moving, flat, and oblong in shape, being wider at the anterior end. Coloring ranges from red brown to reddish.
Citrus flat mite is a warm-season pest with populations increasing in June and peaking in late July and August, then gradually declining.
Mite feeding damages the stems (rachis) of clusters as well as nuts. Feeding on the stems causes a browning that gradually develops into a severely roughened, black area that resembles a scab. This feeding damage is usually on the inside or back portion of nut clusters. Under heavy population pressure, stems and nuts begin to shrivel. Damaged nuts remain on the tree and can provide an overwintering source for navel orangeworm. Close examination will reveal citrus flat mite. They are most easily observed around shriveled and damaged areas.
No precise guidelines are available for when to treat. Populations can be initially spotty and in following years become more widespread in the orchard.
A predaceous phytoseiid mite, Metaseiulus mcgregori, which is common in several crops throughout California, feeds on citrus flat mite. Its numbers begin increasing in August and reach their highest level at the same time as citrus flat mite, but experience has been that their numbers are insufficient to reduce flat mite populations below economic injurious levels.
Organically Acceptable Methods
Sulfur sprays are acceptable for use in an organically managed orchard.
Monitoring and Treatment Decisions
During fruit development monitor for fruit scabbing and rachis darkening caused by citrus flat mite. Before harvest monitor for flat mite damage to nut clusters, while monitoring for other pests. If detected, consider a pesticide application. Begin treatments before nut shriveling.
UC IPM Pest Management Guidelines: Pistachio
Insects and Mites
D. R. Haviland, UC Cooperative Extension, Kern County