Agriculture: Almond Pest Management Guidelines

Oriental Fruit Moth

  • Grapholita molesta
  • Description of the Pest

    Oriental fruit moth is an occasional pest of almonds. It overwinters as a mature larva in bark cracks and in leaf litter. The small brown moths emerge in late February. Larvae are white to pink with a brown head capsule. There are five to six generations per year.

    Damage

    First- and second-generation larvae mine young, tender shoots, causing them to wilt and die. Third- and fourth-generation larvae feed between the hull and shell; this damage is difficult to distinguish from that caused by peach twig borer. Damage is rarely significant. Occasionally, larvae have been found feeding on nut meats. They may feed in groups of several larvae within a nut. Larvae do not produce webbing but do produce a characteristic reddish brown frass in the hull.

    Management

    Oriental fruit moth rarely causes significant kernel damage to almonds. Sprays are usually only required if significant damage by this pest occurred the previous year or in orchards that are near to other sources of oriental fruit moth (e.g. infested peach and nectarine orchards, which are harvested before almonds). Monitor oriental fruit moth densities in late April to early May by opening shoot strikes and looking for larvae, as described in the monitoring section for peach twig borer. Oriental fruit moth larvae will look distinctly different from peach twig borer larvae (reddish-brown with white intersegmental banding) and strikes occur after peach twig borer strikes. A harvest sample will help evaluate the effectiveness of your management program.

    Monitoring and Treatment Decisions

    Adult oriental fruit moths can be monitored and a treatment timed (if necessary) with pheromone traps. These should be placed in orchards by February 15 in the northern or eastern quadrant of the tree, 6 to 7 feet high. Use three traps per orchard or varietal block less than 30 acres. Use one trap per 10 acres for 30- to 80-acre orchards and one trap per 20 acres for orchards larger than 80 acres. Monitor traps once a week. Replace pheromone lures according to manufacturer's directions, and replace trap liners when dirty, or after counting and removing an accumulated total of 150 moths. Oriental fruit moth traps usually catch many more moths than do peach twig borer traps, and like peach twig borer traps, trap catch numbers are generally not a good indicator of potential damage.

    Degree-days

    Calculate degree-days for oriental fruit moth in almond for your location using the oriental fruit moth pest model. To learn more about using degree-days to time insecticide applications, watch the degree-days video.

    To determine optimum time to spray, accumulate degree-days beginning with the first male moth trapped from the second flight, which usually peaks in late May. Use a lower threshold of 45°F and an upper threshold of 90°F. The optimum time to spray for oriental fruit moth is 500 to 600 degree-days after the first trapped male in any flight.

    Common name Amount per acre REI‡ PHI‡
    (Example trade name) (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. CHLORANTRANILIPROLE (RYNAXYPYR)
    (Altacor) 3.0–4.5 oz 4 10
    MODE-OF-ACTION GROUP NUMBER1: 28
    B. METHOXYFENOZIDE
    (Intrepid 2F) 12 oz 4 14
    MODE-OF-ACTION GROUP NUMBER1: 18A
    COMMENTS: Apply in sufficient water to ensure good coverage. Apply with Latron or similar surfactant at 0.125% volume by volume.
    C. SPINETORAM
    (Delegate WG) 3–7 oz 4 1
    MODE-OF-ACTION GROUP NUMBER1: 5
    COMMENTS: Apply at night to target active adult moths and to avoid foraging bees when blooming groundcover is present. May be disruptive of predaceous thrips and some parasitoids.
    D. PHOSMET
    (Imidan 70W) 4.33 lb 72 (3 days) 30
    MODE-OF-ACTION GROUP NUMBER1: 1B
    COMMENTS: Do not apply more than 1 foliar spray per season. Breaks down rapidly in water. Can be used where label restrictions prevent use of other organophosphates.
    E. SPINOSAD
    (Entrust)# 1.25–3 oz 4 1
    (Success) 4–10 oz 4 1
    MODE-OF-ACTION GROUP NUMBER1: 5
    COMMENTS: Apply in early morning or evening if bees are present in the orchard. May be disruptive of predaceous thrips and some parasitoids.
    * Permit required from county agricultural commissioner for purchase or use.
    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 these two intervals is the minimum time that must elapse before harvest may occur.
    # Acceptable for use on organically grown produce.
    1 Rotate pesticides 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; pesticides with a 1B group number should be alternated with pesticides that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).

    Important Links

    Text Updated: 08/17
    Treatment Table Updated: 08/17