Apple maggot

What is Apple Maggot?

Apple maggot (Rhagoletis pomonella Walsh) is a native pest of the Eastern United States and Canada. In 1979 it was discovered in Oregon and has since moved into California, Washington, and other Western states.

Commercial North Coast apple orchards under conventional pest management are less likely to have problems with apple maggot, because pesticides used for codling moth and aphids will control it. The presence of apple maggot in backyard orchards is considered a serious threat to organic apple production because organic growers would be adversely affected. The pest is capable of destroying fruit in organic commercial orchards. It is of the utmost importance to be able to identify the pest as early as possible, so that management strategies are more likely to succeed.

Fruit from backyard trees should not be moved offsite. Please, do not give away fruit from your orchard. Early stages of apple maggot damage are difficult to detect, as apples appear normal. They may be transported and discarded in apple growing areas where they will threaten commercial production. Apples are fit for consumption after discarding the damaged parts. Throw the damaged parts in the trash, do not compost unless you make sure that the maggots are dead (disposed of by cooking (over 160 Degrees F.), freezing or any method that will ensure the death of any larvae in the fruit).

When should I see apples damaged by apple maggot?

As early as mid-June. From late June through early July, female apple maggot adults deposit eggs singly under the apple skin. After 2-10 days, a small maggot hatches from the egg and starts burrowing and eating through the flesh, leaving a brown, thread-like trail. (Figure 1).

Figure 1. Small, brown decayed areas indicate sites where apple maggot laid their eggs.	Figure 2. Apple maggot larva burrow in the flesh and cause decay.

How do I know if I have maggots in my apples?

Cutting the apples in half will tell you if the apples are rotten or not. See figures 2 and 3

How do I know if my apples have apple maggots or codling moth worms?

If you find maggots or worms, look for the presence of legs. Apple maggots are leg-less, cream-colored cylindrical-shaped, and with a blunt posterior and a tapered front end that contains two black mouth hooks. Codling moth worms have a distinct brown-colored head, and several pairs of legs.

If maggots or worms are not found, the flesh of the fruit damaged by apple maggot has a mushy, brown appearance (Figure 2) while the apple core is left untouched. In contrast, codling moth worms tunnel and reach the apple core, where they feed actively, leaving behind abundant frass (i.e. fecal pellets that look like saw dust) (Figure 3).

Why do I have apples dropping under the tree?

All the fruit found under the tree is likely to be damaged by apple maggot or codling moth. See figure 2.

How do I control apple maggot?

There are several choices, depending if you want to apply insecticides or not.

Non-Chemical Control :

DISCARD FALLEN AND/OR WORMY APPLES. Fully grown maggots leave the apples to pupate in the soil. Very few maggots leave the apples while they are still hanging from the tree. After the fruit drops, maggots spend a few days inside the apple before leaving it to pupate in the soil. Usually a few days elapse between the time an apple maggot-infested apple falls to the ground and the maggots leave it. Clean up fallen fruit regularly so that larvae don't have a chance to burrow into the ground and pupate, becoming a problem the following season.

If dropped apples are collected and disposed inside plastic bags , the cycle will be interrupted and fewer flies will survive. Composting the fallen apples may not be sufficient to kill the maggots.

TRAP ADULT FLIES: Adult apple maggot flies are attracted to red sticky plastic spheres or yellow sticky panels. Flies get trapped in the sticky substance (Tanglefoot®) and die. The red spheres mimic ripening apple fruits to which flies are attracted for mating and egg laying while the yellow traps mimic apple leaves. Both types of traps may be improved with the addition of attractants ( i.e. apple volatile lures or ammonium acetate). Traps can be used to attract and kill adult flies or for monitoring when flies are present to time an insecticide application. Around mid June, place one to three apple maggot traps in the trees, about head height, surrounded by fruit and foliage, (but not obstructed from view).
CHEMICAL CONTROL: If you can not tolerate any damage, a spray program with Imidan® (phosmet) or Diazinon® will control apple maggot flies. Do not target the application to control maggots, the pesticide will not kill them while they are inside the apple. You should use at least one monitoring trap and only apply pesticides when the monitoring traps indicate the presence of apple maggot flies. WAITING TIME BETWEEN SPRAYING AND HARVESTING: When using an insecticide on edible fruits, a period of time must be observed when no spray is applied to prevent excessive residues of the insecticide on the harvested fruit. Examine your pesticide label to determine these day limitations.

WARNING. Pesticides are poisonous and must be used with caution. READ THE LABEL BEFORE OPENING A PESTICIDE CONTAINER. Follow all label precautions and directions, including requirements for protective equipment. Apply pesticides only on the crops or in the situations listed on the label. Apply pesticides at the rates specified on the label.

If you need more information, please contact the U.C.C.E. Master Gardeners at the Cooperative Extension office, (707) 565 2608.

Codling moth control information is available in the following references:

Integrated Pest Management for Apples and Pears, UC ANR Publication 3340; pgs 77-89;

Pests of the Garden and Small Farm; A Grower's Guide to Using Less Pesticide, UC ANR Publication 3332, pgs 53-57

Pest Note 13. Codling moth

Lucia Varela, Phd
North Coast IPM Advisor