Agriculture: Pear Pest Management Guidelines

Aphids

  • Bean aphid: Aphis fabae
  • Cotton Aphid: Aphis gossypii
  • Green peach aphid: Myzus persicae
  • Description of the Pest

    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** REI‡ PHI‡
    (Example trade name) (conc.) (dilute) (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. 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 movement 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 (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.
    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).
    * Permit required from county agricultural commissioner for purchase or use.
    # Acceptable for organically grown produce.
    Text Updated: 11/12
    Treatment Table Updated: 11/12