Agriculture: Pear Pest Management Guidelines

Green Fruitworms

  • Humped green fruitworm: Amphipyra pyramidoides
  • Speckled green fruitworm: Orthosia hibisci
  • Description of the Pest

    Immature larvae of both species are light green. Mature green fruitworms have green bodies and green heads. Speckled green fruitworms have cream-colored lines down the back and sides of the body. Humped green fruitworms are distinguished by a prominent hump on the last segment, bright yellow lines on the side, and less distinct white lines on the back. They have only one generation; larvae hatch from cluster to after petal fall.

    Damage

    Young green fruitworm larvae feed on leaves, occasionally tying them together. Fruit feeding usually begins at petal fall when fruits are about 0.25 inch (6 mm) in diameter. At harvest, these fruit are misshapen and have large, roughened, russetted cavities.

    Management

    Green fruitworm populations in an orchard are usually spotty; often they occur near borders where windbreaks and other trees serve as sources of infestation. Generally this is a minor pest of pears; monitor during the cluster sample at bloom.

    Organically Acceptable Methods

    Sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are organically acceptable.

    Monitoring and Treatment Decisions

    Because populations of green fruitworm are often spotty within an orchard, look for its presence when taking the cluster sample at bloom. Examine 100 flower clusters from the tops and eye level of trees located throughout the orchard. If any green fruitworm larvae are found, a treatment may be necessary. For more information on monitoring pests at this time, see SAMPLING AT BLOOM.

    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. BACILLUS THURINGIENSIS ssp. KURSTAKI#
      (various products) Label rates 4 0
      MODE OF ACTION GROUP NUMBER1: 11A
      COMMENTS: Least harmful to beneficials. Must be applied when worms are small. Apply starting at cluster bud to start of bloom. A second application may be required 7-10 days after the first. Occasionally a third treatment may be required. Most effective if applied when weather forecasts predict 3 to 4 days of warm, dry weather. Larvae are more active and feed more in warm weather than in cooler or rainy weather.
     
    B. METHOXYFENOZIDE
      (Intrepid 2F) 16 fl oz 4 14
      MODE OF ACTION GROUP NUMBER1: 18A
      COMMENTS: Treat at early egg hatch. Spray coverage is extremely important. Ground application should use 200 gal water/acre with a sprayer speed of 1.5 mph. The addition of a spray adjuvant is recommended to enhance spray coverage.
     
    C. SPINOSAD
      (Entrust)# 2–3 oz 0.5–0.75 oz 4 7
      (Success) 6–10 fl oz 2–3.3 fl oz 4 7
      MODE OF ACTION GROUP NUMBER1: 5
      COMMENTS: To prevent the development of resistance to this product, rotate to a material with a different Group number after treating two consecutive generations. Residual efficacy is affected by pH but initial efficacy is not; verify that water pH is greater than 6 and less than 8.
     
    D. CHLORANTRANILIPROLE
      (Altacor) 3–4.5 oz 4 5
      MODE OF ACTION GROUP NUMBER1: 28
      COMMENTS: Do not apply dilute applications of more than 200 gal/acre; use 100–150 gal/acre for best results.
     
    E. SPINETORAM
      (Delegate WG) 4.5–7 oz 4 7
      MODE OF ACTION GROUP NUMBER1: 5
      COMMENTS: Residual efficacy is affected by pH but initial efficacy is not; verify that water pH is greater than 6 and less than 8.
    ** Dilute rate is the rate per 100 gal water; use 400 gal solution per 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.
    # Acceptable for organically grown produce.
    Not recommended or not on label.
    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).
    Text Updated: 07/18
    Treatment Table Updated: 07/18