How to Manage Pests

UC Pest Management Guidelines

Pear foliage damaged by a heavy infestation of European red mite, Panonychus ulmi.

Pear

European Red Mite

Scientific name: Panonychus ulmi

(Reviewed 11/12 , updated 11/12 )

In this Guideline:


DESCRIPTION OF THE PEST

European red mites overwinter as eggs at bases of buds and spurs on smaller branches and twigs, or in wounds. Eggs are globular and red with a slender stalk (stipe) rising from the top center. During the growing season, eggs are laid on leaves. There are three instars before the adult stage. Immature mites are bright red, except just after molting when they appear bright green. The green color turns to red after the mites resume feeding. Adults are dark red and have white spots at the base of six to eight hairs on the back.

DAMAGE

The feeding of European red mites on leaves causes the leaves to lighten in color and become mottled or stippled. Prolonged feeding by heavy populations eventually causes leaf bronzing, and under high temperatures portions of the leaf blade or its entire surface may turn brown and dry. This kind of damage, referred to as mite burn, can occur even after mites have been controlled if high temperatures occur soon after mites are controlled.

MANAGEMENT

European red mite occasionally becomes troublesome in pear orchards. Dormant oil treatments and natural enemies usually keep them below damaging levels. Monitor during the season to assess need for treatment.

Biological Control

If European red mite populations are reduced to low levels by treating with oil during the dormant season, predators usually can effectively maintain these low levels during the growing season. Minimize the use or dosages of materials disruptive to predators, especially predaceous mites. Major European red mite predators include green lacewings, brown lacewings, minute pirate bugs, and the predatory mite Zetzellia mali.

Cultural Control

Minimize the potential for mite problems by reducing dusty conditions within the orchard.

Organically Acceptable Methods

Biological and cultural controls and approved oil sprays are organically acceptable methods.

Monitoring and Treatment Decisions
Dormant to delayed-dormant period

Apply a dormant or delayed-dormant oil spray yearly. Sample during dormancy to determine overwintering population levels of this pest: collect 100 fruit spurs, one from the treetop and one from eye level of 50 trees in a 20-acre block. Use a 10 or 14X hand lens to examine the bases of buds and spurs. If more than 10% of the spurs are heavily infested, monitor European red mite throughout the growing season. If less than 10% of the spurs are infested, European red mite probably won't be a problem in the coming year, provided the dormant oil treatment was properly applied. If no dormant treatment was applied, European red mite should be monitored throughout the growing season if three or more spurs are infested in the sample of 100. For information on monitoring other pests at this time, see DORMANT/DELAYED-DORMANT SAMPLING.

Finger bud to petal fall

Sample again after egg hatch, usually during the period from finger bud to petal fall, by examining 100 flower clusters, one from the treetop and one from eye level, of 50 trees. If more than 5 clusters are infested, treat with oil immediately. If more than 10 are infested, add a miticide to the oil. If between 1 and 5 clusters are infested, adding oil to the first codling moth spray may be adequate. For information on monitoring other pests at this time, see SAMPLING AT BLOOM.

Late spring

European red mite infestations can begin either in the tops or bottoms of the tree canopy. To detect populations, take two samples in each of 20 trees: one from the top of the tree (in spring these are spur samples and later are shoot samples) and one shoot sample from eye level. Examine five leaves per shoot. If 10 or fewer European red mites or eggs are found per 100 leaves sampled, don't treat. If 11 to 50 European red mites or eggs are found, treat with oil. If more than 50 European red mites and eggs are found, add a miticide with the oil. For information on monitoring other pests at this time, see SAMPLING DURING FRUIT DEVELOPMENT.

Summer

Continue monitoring European red mite when monitoring shoot samples for pear psylla and twospotted spider mites. Examine five leaves from each of the 20 top shoots with a hand lens (10 to 14X) and count the number of European red mites. Use the above thresholds to determine treatment needs if only European red mite is present. If both twospotted and European red mites are present, use the thresholds given in WEBSPINNING MITES.

Harvest and postharvest

Sample again during harvest and following harvest. Use the lower thresholds listed below when predators are absent to determine if a postharvest treatment is required.

  • Bottom sample: 50 to 150 mites and eggs per 100 leaves
  • Top sample: 50 to 200 mites and eggs per 100 leaves
Common name Amount to use** R.E.I.+ P.H.I.+
(trade name) (conc.) (dilute)
(hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
 
DORMANT TO DELAYED-DORMANT
Note: All orchards should be treated; the delayed-dormant timing gives better results.
A. NARROW RANGE OIL# 8 gal 2 gal 4 0
  . . . or . . .
  DORMANT FLOWABLE EMULSION 6–8 gal 2–3 gal 4 0
  . . . or . . .
  DORMANT PLUS 6–8 gal 4 gal 4 0
  MODE OF ACTION: Contact, including smothering and barrier effects.
  COMMENTS: Apply oil sprays before February for best results. For narrow range oil, check with your certifier to determine which products are organically acceptable.
 
PETAL FALL TO HARVEST
A. NARROW RANGE OIL 4 gal 1 gal 4 0
  MODE OF ACTION: Contact, including smothering and barrier effects.
  . . . PLUS . . .
  ABAMECTIN*
  (Agri-Mek 0.15EC) 10–20 oz 2.5–5 fl oz 12 28
  MODE OF ACTION GROUP NUMBER1: 6
  COMMENTS: Apply early when leaf tissue is tender and good coverage is easier. Do not apply to blooming plants, including fruit trees and broadleaf weeds.
 
B. PYRIDABEN
  (Nexter) 4.4–5.2 oz 1.1–1.3 oz 12 7
  MODE OF ACTION GROUP NUMBER1: 21A
  COMMENTS: Most effective with use of a silicone spreader.
 
C. ACEQUINOCYL
  (Kanemite 15SC) 21–31 fl oz 5.25–7.75 fl oz 12 14
  MODE OF ACTION GROUP NUMBER1: 20B
  COMMENTS: New material: there is little experience in California regarding efficacy and effect on beneficials.
 
D. ETOXAZOLE
  (Zeal) 2–3 oz 0.5–0.75 oz 12 14
  MODE OF ACTION GROUP NUMBER1: 10B
  COMMENTS: Preliminary research indicates etoxazole has an effect on the reproductive capacity of predatory mites. Most effective with use of a silicone spreader.
 
E. SPIRODICLOFEN
  (Envidor 2SC) 16–18 fl oz 12 7
  MODE OF ACTION GROUP NUMBER1: 23
  COMMENTS: Do not apply to blooming plants, including fruit trees and broadleaf weeds.
 
F. FENPYROXIMATE
  (FujiMite 5EC) 2 pt 0.5 pt 12 14
  MODE OF ACTION GROUP NUMBER1: 21
  COMMENTS: New material: there is little experience in California regarding efficacy and effect on beneficials. Most effective with use of a silicone spreader.
 
G. CLOFENTEZINE
  (Apollo) 4 oz 1 oz 12 21
  MODE OF ACTION GROUP NUMBER1: 10A
  COMMENTS: Kills eggs. Need to apply early, before monitoring indicates a need; use in orchards where European red mite is a chronic pest. Good coverage is a must; use a minimum of 50 gal water/acre for concentrate sprays and a maximum of 400 gal water/acre for dilute. To delay development of resistance, use only once per season.
 
H. HEXYTHIAZOX
  (Savey 50DF) Low-to mid-label rate 12 28
  (Onager) Low-to mid-label rate 12 28
  MODE OF ACTION GROUP NUMBER1: 10A
  COMMENTS: Kills eggs. Need to apply early, before monitoring indicates a need; use in orchards where European red mite is a chronic pest. Apply only once per growing season.
 
I. BIFENAZATE
  (Acramite 50WS) 1 lb 0.25 lb 12 7
  MODE OF ACTION GROUP NUMBER1: 25
  COMMENTS: Only one application per crop per year. Preliminary observations indicate may not be as effective as other materials for European red mite. Most effective with use of a silicone spreader.
 
POSTHARVEST
A. NARROW RANGE OIL# 4 gal 1 gal 4 0
  MODE OF ACTION: Contact, including smothering and barrier effects.
  COMMENTS: Apply this spray according to monitoring guidelines. Check with your certifier to determine which products are organically acceptable.
 
** Dilute rate is the rate per 100 gal water; use 400 gal solution/acre. Apply concentrate in 80–100 gal water/acre, or less if the label allows.
+ 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 REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
# Acceptable for organically grown produce.
* 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 are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at www.irac-online.org.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Pear
UC ANR Publication 3455

Insects and Mites

L. G. Varela, UC IPM Program, UC Cooperative Extension, Sonoma County
R. B. Elkins, UC Cooperative Extension, Lake County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
C. Ingels, UC Cooperative Extension, Sacramento County
Acknowledgment for contributions to Insects and Mites:
C. Pickel, UC IPM Program, UC Cooperative Extension, Sutter/Yuba counties
P. W. Weddle, Weddle, Hansen & Associates
R. Hansen, Weddle, Hansen & Associates
P. Chevalier, United Ag Products, Ukiah
M. Hooper, Ag Unlimited, Lakeport
B. Knispel, Pest Control Adviser, Upper Lake
T. Lidyoff, Purity Products, Healdsburg
G. McCosker, Harvey Lyman Agservices, Walnut Grove
B. Oldham, Ag Unlimited, Ukiah
J. Sisevich, AgroTech, Kelseyville (retired)
D. Smith, Western Farm Service, Walnut Grove
B. Zoller, The Pear Doctor, Inc., Kelseyville

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