How to Manage Pests

UC Pest Management Guidelines

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. 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     Degree-day calculator    Degree-day table

Oriental fruit moth rarely causes significant 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. A harvest sample will help evaluate the effectiveness of your management program.

Adult oriental fruit moth populations can be monitored and treatments timed (if necessary) with pheromone traps. They 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 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, so trap catch numbers are generally not a good indicator of potential damage.

To determine optimum time to spray, accumulate degree-days beginning with the first male moth trapped from the second flight, which usually occurs in May. Use a lower threshold of 45°F and an upper threshold of 90°F. (For assistance in calculating degree-days, see "Degree-days" on the UC IPM Web site. The optimum time to treat for oriental fruit moth is 500 to 600 degree-days after first trapped male in any flight.

PUBLICATION

UC IPM Pest Management Guidelines: Almond
UC ANR Publication 3431
Insects and Mites
F. G. Zalom, Entomology, UC Davis
C. Pickel, UC IPM Program, UC Cooperative Extension, Sutter/Yuba counties
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
R. L. Coviello, UC Cooperative Extension, Fresno Co
R. A. Van Steenwyk, Insect Biology, UC Berkeley
M. W. Freeman, UC Cooperative Extension, Fresno Co.
Acknowledgment for contributions to the insects and mites section:
R. E. Rice, Kearney Agricultural Center, Parlier
L. C. Hendricks, UC Cooperative Extension, Merced Co.

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