Apple Maggot

Apple Maggot

The apple maggot (Rhagoletis pomonella) has recently been found in several locations in the Abbotsford area of British Columbia. This is the only area in British Columbia where the pest has been found, based on an annual survey throughout southern B.C. conducted by the Canadian Food Inspection Agency (CFIA). Every effort must be made to keep this serious pest from spreading to the interior of B.C., Vancouver Island and to the Gulf Islands.

female apple maggot fly Male apple maggot fly. Photo courtesy Agriculture & Agri-Food Canada

Apple maggot larvae in apple Apple maggot larvae in apple. Photo courtesy Agriculture & Agri-Food Canada

Hosts and Damage

The apple maggot attacks apple, especially early and thin-skinned varieties, crabapples, and native hawthorn (Crataegus spp.). Alternate hosts include pear, cherry, plum, apricot, chokecherry and cotoneaster, especially if present near heavily infested apple, crabapple or hawthorn trees.

Egg laying by females causes pitting and dimpling of the fruit surface. Fruit is rendered unmarketable as a result of larval tunneling throughout the fruit tissue.

Life Cycle and Appearance

Apple maggot overwinters as pupae in the soil under host trees. Adult flies emerge late June to September. Eggs are laid under the skin of host fruit and 20-30 days later, mature larvae drop from fruit to overwinter as pupae in the soil. There is one generation per year.

Adult apple maggot flies closely resemble in size and appearance other fruit flies present in the BC Interior such as the walnut husk fly, snowberry maggot, black and western cherry fruit flies. Apple maggot has a wing pattern that is different from all of these other species, except for the snowberry maggot, which is similar to the apple maggot. Adult flies are about half the size of house flies (about 5-6 mm long). The body is black with 3 (males) or 4 (females) white stripes across the abdomen and a prominent white spot in the middle of its back. Larvae are white legless maggots that measure up to 7 mm when mature. The oval yellowish brown pupae are half the size of a kernel of wheat.

Monitoring:

Set out yellow sticky cards baited with an ammonium carbonate lure by the end of June. Place traps within the canopy of trees. Commercial orchardists should place traps along margins of orchards adjacent to backyard and wild host trees. Inspect fruit for signs of damage and presence of larvae. Homeowners should take any suspicious flies captured on the traps to the nearest CFIA or BCMAL office, garden centre or Master Gardener to confirm if the flies are apple maggots. Orchardists should submit suspicious flies to their packinghouse fieldman, pest management consultant, or to the nearest CFIA or BCMAL office.

Controlling Apple Maggot:

Commercial orchardists should contact their packinghouse field service, pest management consultant or nearest BCMAL office for information on controlling apple maggot.

Owners of backyard host trees are encouraged to consider removing any host trees that will not be managed to control apple maggot. This is especially important if the trees are within 2 km of a commercial apple orchard. Non-chemical control options include stripping the trees of fruit before adult flies begin to emerge (by the end of June), or removing and destroying any infested fruit on the tree or ground (do not compost; bury at least 30 cm or take to local landfill for burial). Apple maggots can continue to develop in fallen fruit similar to codling moth. Placing several yellow sticky cards in trees as described above will aid in reducing apple maggot egg laying.

There are several control products containing the active ingredients phosalone, carbaryl, or permethrin available at local garden centres and nurseries for application to host trees (July - August) to kill adult flies when applied according to label instructions.

There are several web sites with useful information posted on apple maggot biology and management (see below).

Quarantine Regulations:

CFIA is exploring regulatory options to implement in consultation with the BC Ministry of Agriculture and Lands, stakeholders and industry groups.

To help prevent the spread of apple maggot to other parts of B.C., please contact the CFIA at 604-557-4500 if you are planning to move apples, apple trees or other host plants with soil, or nursery stock of apple, crabapple or hawthorn, out of the Abbotsford area. Soil under or adjacent to infested host trees may contain apple maggot pupae, thus any plants removed from the site with soil pose a risk of moving the apple maggot.

For more information on domestic movement and import regulations, please refer to the Canadian Food Inspection Agency policy directive D-00-07.

Further Information:

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