How to Manage Pests

UC Pest Management Guidelines

Pistachio

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.

DAMAGE

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.

MANAGEMENT

No precise guidelines are available for when to treat. Populations can be initially spotty and in following years become more widespread in the orchard.

Biological Control

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.

Common name Amount per acre** R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
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. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. WETTABLE SULFUR# 15–20 lb 24 0
  MODE OF ACTION: Unknown. An inorganic miticide.
  COMMENTS: May be applied by ground or air. Check label to confirm product is labeled for pistachio.
 
B. SULFUR DUST 98%# 50 lb 24 0
  MODE OF ACTION: Unknown. An inorganic miticide.
  COMMENTS: Best results are obtained by ground treatments; however, aerial treatments are effective. Use higher rates by air. Check label to confirm product is labeled for pistachio.
 
** Unless otherwise noted, apply with enough water to ensure adequate coverage.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the R.E.I. exceeds the P.H.I.. The longer of two intervals is the minimum time that must elapse before harvest.
# Acceptable for organically grown produce.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Pistachio
UC ANR Publication 3461

Insects and Mites

D. R. Haviland, UC Cooperative Extension, Kern County
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
R. H. Beede, UC Cooperative Extension, Kings County
K. M. Daane, Biological Control, UC Berkeley and Kearney Agricultural Center, Parlier
Acknowledgment for contributions to Insects and Mites:
R. E. Rice, Kearney Agricultural Center, Parlier

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