Agriculture: Pear Pest Management Guidelines

Stink Bugs and Other Plant Bugs

  • Conchuela: Chlorochroa ligata
  • Consperse stink bug: Euschistus conspersus
  • Leaffooted Bug: Leptoglossus clypealis
  • Redshouldered stink bug: Thyanta accerra
  • Description of the Pest

    Stink bugs and other plant bugs occur throughout California, but only reach damaging numbers sporadically. Although they may differ in color and size, stink bugs all have the same overall shield-shaped body. The consperse stink bug is the most commonly found in all pear districts.

    Adult consperse stink bugs have gray brown to green bodies with yellow to orange legs, and antennae that have darkened tips. The body and legs are covered with small black specks and the undersurface of the body varies from gray to green. Consperse stink bug eggs are barrel-shaped, pearly white when first laid, turning pink before hatching, and laid in clusters on twigs and leaves. The conchuela is a large, grayish black stink bug with a reddish marginal border and a reddish spot in the middle of the back that distinguishes it from the bordered plant bug. Redshouldered stink bugs are green or brown and may have a red line across the shoulder. Leaffooted plant bug adults are about 0.75 inch long, yellowish brown and have yellow bands across the middle of the back. The back is flat and the hind legs have distinctive, leaflike enlargements.

    Damage

    Stink bugs damage the crop directly by feeding on fruit. Early season feeding results in dimples or irregularly depressed areas on mature fruit. If the feeding occurs after maturity, there is little external evidence other than excrement, which appears as small, brown, tear-shaped drops. Internally, stink bug feeding produces white, pithy areas that turn brown when fruit is peeled. If the spots are the result of stink bug feeding, these pithy areas will be concentrated near the stem end of the fruit. If they resulted from lygus bug feeding, they may be located anywhere on the fruit surface. In pears, these pithy areas are too deep to be removed by ordinary peeling practices and the fruit is unsuitable for canning or fresh market.

    Adult stink bugs move from tree to tree and can puncture large numbers of fruit. If they are migrating into the orchard, fruits on trees in outside rows will show the most damage. Frequently, damage by these pests is limited to specific areas in the orchard.

    Management

    Stink bugs and plant bugs may become more important pests in orchards where mating disruption is used for codling moth control. Infestations of stink bugs depend on the type of vegetation in and adjacent to the orchard. Most infestations occur in orchards with ground covers or adjacent to uncultivated areas; stink bugs move to ground covers in orchards when weeds in uncultivated areas dry. Consperse stink bug is rarely a pest in clean-cultivated orchards surrounded by cultivated lands, unless the land is planted in crops stink bugs favor: wheat, tomatoes, berries, alfalfa, or corn. Monitor weeds in spring and trees in early summer to determine need for treatment.

    Cultural Control

    Reduce weed host plants, listed below, both within and adjacent to the orchard to minimize stink bug problems.

    Organically Acceptable Methods

    Biological and cultural controls are organically acceptable methods of controlling these pests.

    Monitoring and Treatment Decisions

    If stink bugs are observed, monitor during the cluster stage in March or April by inspecting host plants located inside and along borders of sampling blocks. Spend about an hour checking the bases of plants for overwintered adult bugs. Favored host plants are mullein, mustard, and dock. If these are not present, bugs may be found on plantain, milkweed, mallow, morningglory, thistles, vetch, velvetgrass, beardgrass, bush berries, everlasting peas, and other broadleaf plants.

    If more than five stink bugs are found during the hour, apply a ground spray to the weeds immediately. Depending on the distribution of the bug population, a spot treatment may be adequate. If two to five bugs are found, and if bug damage has been experienced previously in the orchard, a ground spray might be advisable. If fewer than two bugs are found, resample in 7 to 10 days.

    Consperse stink bugs can also be monitored beginning in early April with double cone traps baited with an aggregation pheromone. Place traps just outside the edges of the orchard to determine if adults are migrating into the orchard. (For more information, see PHEROMONE TRAPS.) Cut fruit is attractive for feeding. Beginning in May, place cut fruit at the edge of the orchard next to unmanaged or alternate hosts. Check and replace weekly.

    In June and early July spend about 30 minutes sampling for adults starting from the edge of the orchard and working your way inward. Also inspect fruit for feeding damage. Examine fruit on the tree for the presence of bugs, excrement, or visible damage. To verify that damage is caused by stink bugs, peel the fruit. If more than three fruits per half-hour of inspection show feeding damage, spots of excrement, or active bugs, treatment probably is required to avoid economic loss by end of harvest. Be sure to take into account preharvest intervals when choosing the treatment material, and apply this treatment to the trees. (For information on sampling stink bugs in conjunction with other pests at this time, see SAMPLING DURING FRUIT DEVELOPMENT.)

    Harvest Fruit Sample

    At harvest, assess program by monitoring fruit in the bins for stink bug and other plant bug damage. Sample 200 fruit per bin from 5 bins per orchard (or 20-acre block in large orchards). (For more information regarding this sample, see HARVEST FRUIT SAMPLE.)

    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.
     
    FINGER BUD to BLOOM
    Note: Apply a thorough, drenching ground spray when adults begin activity. Dilution rates will vary from 100 to 300 gal/acre.
    A. DIMETHOATE Label rates see label 28
      MODE OF ACTION GROUP NUMBER1: 1B
      COMMENTS: Dimethoate can be applied with oil. Do not apply to blooming plants, including fruit trees and broadleaf weeds. Mow weeds before application. Not allowable by some processors.
     
    JUNE to PREHARVEST
    Note: Treatment is applied to trees.
    A. FENPROPATHRIN*
      (Danitol 2.4EC) 16–21.33 fl oz 4–5.3325 fl oz 24 14
      MODE OF ACTION GROUP NUMBER1: 3A
      COMMENTS: Harmful to beneficial insects and mites; will suppress spider mites. Do not apply to blooming plants, including fruit trees and broadleaf weeds.
     
    B. LAMBDA-CYHALOTHRIN*
      (Warrior with Zeon) 2.56–5.12 fl oz 24 21
      MODE OF ACTION GROUP NUMBER1: 3A
      COMMENTS: Harmful to beneficial insects and mites; will suppress spider mites. May cause outbreaks of pear rust mite. Do not apply to blooming plants, including fruit trees and broadleaf weeds.
    ** 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.
    Not recommended or not on label.
    Text Updated: 06/15
    Treatment Table Updated: 11/12