by Ric Bessin, Extension Entomologist
University of Kentucky College of Agriculture
The codling
moth larva is one of the very destructive pests introduced from Europe by
settlers. Most pest management programs for apples a centered on management
of this pest. Female moths lay the scale like eggs singly on developing
fruit or adjacent leaves or stems just after sundown each night. Upon hatching
the larva enters into the calyx end or side of the fruit then tunnel to
the center where they feed and develop. Brown frass is often noticed near
the calyx end of the developing fruit. The larva is pinkish to white in
color with a brown head and can reach 3/4 inch. Larval development is completed
in 3 to 5 weeks. Larvae exit the fruit to pupate in a thick silken cocoon
on the bark or other protected areas. The fully developed larva is the overwintering
stage. Pupation occurs in spring beginning about the same time as bloom
with adults first active in late April or early May. In Kentucky, there
are three generations each year. The adult is about 3/8 inch, gray, with
distinctive bronze areas on the bottom 1/3 of the wing.
Control
of codling moth in commercial orchards relies on three tools: regular examination
of the trees and fruit (termed scouting), pheromone trapping, and the use
of weather monitoring and degree day models. Orchards should be scouted
twice a week early in the season and on a weekly basis for insects and mites
during mid season. Closer to harvest every other scouting trip may be omitted
such that visits are no more than two weeks apart.
Pheromone Trapping
Pheromone trapping uses chemical lures to attract male moths. These chemical lures are synthetic copies of the chemicals female moths use to attract males for mating. A trap consists of plastic top and bottom held together by a wire hanger with the lure placed inside. The inner surface of the bottom is coated with a sticky material to hold the insects once they land in the trap. Traps are hung in the southeast quadrant of the tree at eye level, usually one for each ten acres of trees (minimum of two traps per orchard) in commercial orchards.
Home owners have a few different options for controlling codling moths. Home owners can use pheromone traps to time insecticide sprays, or to "trap out" all the male moths. This involves using enough pheromone traps such that all of the male moths are captured before the female moths mate. Female moths are then able to lay only unfertilized eggs that will not develop. Typically, 2 to 4 traps per tree are required for this to be successful. This is less effective if there are additional sources of mated females, such as other trees in the neighborhood or wild hosts.
Traps should be put out at the pink stage of bud development. Every month, pheromone lures need to be replaced and the old lures discarded outside of the orchard. Codling moths can be distinguished from other insects in the traps by their bronze wing tips.
Degree Day Accumulation
Initial trap catches in the early spring are termed biofixes. This information will be used to predict when egg hatch will occur and synchronize insecticide sprays. This has become particularly important as different insecticides for codling moth control may need to be applied during different periods of egg laying or hatch. In commercial IPM orchards, inclusion of an insecticide in the cover sprays is recommended as long as pheromone trap catches exceed an average of five moths per trap per week.
The biofix for the codling moth is the starting date of the first sustained flight of male moths captured in pheromone traps. Generally, this is when the fifth moth has been captured in the trap. A few moths often emerge. This usually occurs just after petal fall. Codling moth traps need to be examined daily in order to know exactly when the biofix occurs. After the biofix has occurred, degree days are calculated on a daily basis and a running total is kept(see "Predicting Insect Development Using Degree Days" in EntFact 201, Controlling Apple Pests). The codling moth has a 50"F threshold temperature. These degree day accumulations are compared with the target values in the following table for different codling moth insecticides. Find the insecticide that will be applied then note the correct degree day target for optimal timing.
DD Target for Various
Codling Moth Insecticides |
|
|---|---|
Dimilin Rimon |
50
- 75 degree days |
Confirm Intrepid Esteem |
100 - 200 degree days |
Calypso Assail Clutch |
150-250 degree days |
Guthion Imidan Altacor Belt Avaunt Pyrethroids |
250 degree days (corresponds
to 3% egg hatch) |
Always
read the insecticide label to confirm degree day targets. |
|
Codling moth trap catch records need to be maintained throughout the summer to monitor additional generations. However, after the initial biofix it is only necessary to examine the traps twice a week. A threshold of five moths per trap per week is used to determine if there are sufficient levels of moths to warrant an insecticide application.
Trunk Banding
Another tactic that can be used by home owners is the use of cardboard bands placed around the trunk of the trees to serve as pupation sites for the wandering larvae. A four to six inch band encircling the trunk or scaffold limbs will attract the larvae. Bands should be in place before larvae begin to leave the apples in search of pupation sites and removed and destroyed before moth emergence begins. Bands should be placed on trees in August to capture overwintering pupae and removed and destroyed in December. Bands can also be used in the summer to capture pupae from the summer generations, but timing is more difficult.
Sanitation
Home owners should also pick up and destroy fallen fruit. Often fruit that drop prematurely are infested with either codling moth or plum curculio larvae. For more information on reduced insecticide apple management, see EntFact 201, Controlling Apple Pests.
Pesticide Resistance
Codling moth resistance to traditional organophosphate insecticides such as Imidan and Guthion is becoming more common on the east and west coasts, as well as in the Midwest. Fortunately, there are new labeled insecticide alternatives for codling moth control on apples with different modes of action.
Mating Disruption
Mating disruption relies on confusion to prevent codling moths from mating. Male codling moths locate female moths at night by following the sex attractant released into the air by the females. Mating disruption uses commercial dispensers of synthetic sex attractant to prevent male moths from locating females. Unfertilized moths are not able to lay viable eggs. Unlike other methods, codling moths are not killed with this technique. This technique is most successful in blocks of at least 5 acres and where initial populations of codling moth are low. Keep in mind that mating disruption for codling moth will not control other insects that are normally controlled with cover sprays (plum curculio for example).
Revised: 2/09
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!