How to Manage Pests

UC Pest Management Guidelines

Green peach aphid colony.

Pear

Aphids

Scientific names:
Green peach aphid: Myzus persicae
Cotton aphid: Aphis gossypii
Bean aphid: Aphis fabae

(Reviewed 11/12 , updated 11/12 )

In this Guideline:


DESCRIPTION OF THE PESTS

Several aphid species occasionally attack pears; the most common are green peach aphid, cotton aphid (also known as melon aphid), and bean aphid (also known as dock aphid). These aphids overwinter as adults on various weeds and field crops in or outside the orchards. Usually after pear bloom, when trees are growing rapidly, these aphids appear on foliage and shoots, establishing colonies, and several generations may occur in cool spring weather.

Green peach aphid is light green in color. On adults a dark blotch in the middle of the abdomen serves to distinguish this species from others. Cotton aphid is generally dark green, but immature forms may be yellowish. Bean aphid is dark-colored and seems to prefer sucker shoots in the center of the tree. Both green peach aphid and cotton aphid attack shoots all over the tree.

DAMAGE

Aphid feeding causes pear foliage to curl and the growth of shoots to be stunted. This type of injury is of minor importance. Most of the damage is caused from aphids feeding directly on fruit and producing honeydew, which falls on the fruit. Honeydew causes fruit lenticels to darken, giving the pear a russeted appearance. The presence of honeydew also makes the fruit sticky, and a black fungus grows in this honeydew, giving the fruit a sooty appearance. This contamination and russetting will cause fruit to be culled from fresh shipping.

MANAGEMENT

Aphids are infrequently encountered in pear orchards and seldom require special treatment unless the weather remains cool throughout spring and early summer. Aphids generally serve as a valuable early-season food source for insect predators. With the onset of warm weather, aphids leave pear trees for other hosts and do not reappear until the following spring.

Biological Control

Predators and parasites often reduce aphid populations, making chemical treatment unnecessary. Predators of aphids include lady beetles (Hippodamia convergens, Coccinella spp.), green lacewing larvae (Chrysoperla carnea), and brown lacewing larvae (Hemerobius spp.). Parasites of green peach aphid include Aphelinus semiflavus, Aphidius matricariae, Diaeretiella rapae, and Lysiphlebus testaceipes. A common cotton aphid parasite is Lysiphlebus testaceipes; parasites in the Lysiphlebus and Diaeretiella genera attack bean aphid. Delay chemical control as long as possible to allow biological control and hot weather to reduce aphid populations.

Organically Acceptable Methods

Use biological control and sprays of approved narrow range oils or neem oil to control aphids.

Monitoring and Treatment Decisions

When aphids are present in the spring and early summer, inspect fruit and foliage for fine droplets of honeydew to assess potential from honeydew damage. This can be done when sampling for other pests (see SAMPLING DURING FRUIT DEVELOPMENT). No specific criteria have been developed to project the severity of injury according to the honeydew found, so use your best judgment. Damaged fruit is not culled from No. 1 cannery shipment, so the decision for determining if a population requires treatment is not as critical as it is with pests that can cause the need for culling from both fresh and cannery markets. A spray is economically justified for fresh-market pears if a difficult and costly sorting will be required.

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 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.
 
A. THIAMETHOXAM
  (Actara) 4.5–5.5 oz 1.125–1.375 oz 12 see comments
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not apply to blooming plants, including fruit trees and broadleaf weeds. Preharvest interval is 14 days when 2.75 oz/acre or less is used and 35 days when more than 2.75 oz/acre is used.
 
B. IMIDACLOPRID
  (Provado 1.6F) 20 fl oz 5 fl oz 12 7
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not apply to blooming plants, including fruit trees and broadleaf weeds.
 
C. SPIROTETRAMAT
  (Movento) 6–9 fl oz 24 7
  MODE OF ACTION GROUP NUMBER1: 23
  COMMENTS: Allow 1 to 2 weeks for systemic movment through the plant. Must be applied with an adjuvant to improve penetration. Do not apply until after petal fall. Do not apply to blooming plants, including fruit trees and broadleaf weeds. For resistance management, do not apply more than once a year.
 
D. CLOTHIANIDIN
  (Clutch) 2–3 oz 12 7
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not apply to blooming plants, including fruit trees and broadleaf weeds.
 
E. DIAZINON* 50WP 3 lb 1 lb 96 (4 days) 21
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Avoid drift and tailwater runoff into surface waters. Do not apply to blooming plants, including fruit trees and broadleaf weeds.
 
F. NARROW RANGE OIL# Label rates 4 0
  MODE OF ACTION: Contact, including smothering and barrier effects.
  COMMENTS: Check with your certifier to determine which products are organically acceptable.
 
G. NEEM OIL#
  (Trilogy) 1% 4 0
  MODE OF ACTION: Unknown. A botanical insecticide.
  COMMENTS: Although research has not been conducted in pears, neem oil has been shown to be effective in apples and other crops for controlling aphids. Apply in at least 100 gal water/acre for adequate coverage.
 
** 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.
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.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for organically grown produce.

[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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