How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Adult flies are somewhat smaller than house flies and have clear wings with characteristic black bands, a pronounced white spot on the back of the thorax, and a black abdomen with light-colored crossbands. Female flies have four crossbands on the abdomen, and males have three. Larvae are cream-colored maggots with a blunt posterior and a tapered front end that contains two black mouth hooks. The apple maggot is closely related to the walnut husk fly and cherry fruit fly. The adult fly can be distinguished from these other pests by the banding on its wings. It is difficult to distinguish apple maggot from snowberry maggot, a close lookalike that occurs throughout California but does not attack apples and pears.

DAMAGE

Apple maggot is a native pest of the eastern United States and Canada. In 1979 it was discovered in Oregon and later in California (Mendocino and Lake counties), Washington, and other western states. Hawthorn and apples are favored host plants, but cherries, pears, and other fruits have also been attacked.

Apple maggot may infest pears that are adjacent to infested apple trees. Female apple maggot adults deposit eggs singly under the pear skin, using a needlelike ovipositor at the tip of the abdomen. Principal injury is caused by burrowing larvae that feed on pear flesh. Browning of the trails occurs as the pear responds to this injury and bacteria associated with maggots cause fruits to rot internally.

MANAGEMENT

Apple maggot is a minor pest of pears. If spray treatments are needed, they are aimed at the adult stage.

Biological Control
Because the apple maggot feeds within fruit, biological control agents have not been very effective.

Organically Acceptable Methods
Baited sprays such as GF-120 are organically acceptable.

Monitoring and Treatment Decisions
Emergence and dispersal of adult flies must be carefully monitored to effectively time treatments. Sticky traps, including yellow rectangles and red spheres, are used in other areas to monitor adults and time treatments. Unfortunately, only provisional economic thresholds are available for apple maggots, even in areas where it has long been a pest. You can detect the first emergence of adults by hanging yellow sticky traps in abandoned orchards or unsprayed apple trees in infested areas. To detect the beginning of egg laying, hang red sticky spheres in apple trees, then treat as soon as the first fly is found. In Oregon, where some orchards are treated regularly for apple maggots, the first maggot spray is applied 7 to 10 days after the first fly has emerged. Later sprays follow at 10- to 14-day intervals as long as adults are active and are being caught in traps.

Common name		Amount to Use**		R.E.I.+	P.H.I.+
(trade name)		(conc.)	(dilute)	(hours)	(days)
The following materials are listed in order of usefulness in an IPM program, taking into account impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
A.	SPINOSAD
	(GF-120)#	Label rates		4	0
	MODE OF ACTION GROUP NUMBER1: 5
	COMMENTS: Most effective for small populations
B.	CORN GLUTEN MEAL
	(Nu-Lure Insect Bait)	1-3 pt/acre		N.A.	0
	. . . PLUS . . .
	SPINOSAD
	(Entrust)	2-3 oz	0.5-0.75 oz	4	7
	(Success)	6-10 fl oz	2-3.3 fl oz	4	7
	MODE OF ACTION GROUP NUMBER1: 5
	COMMENTS: Do not apply more than 9 oz/acre/crop of Entrust or 29 fl oz of Success/acre/crop.
C.	PHOSMET
	(Imidan) 70W	4 lb	1 lb	24	7
	MODE OF ACTION GROUP NUMBER1: 1B
	COMMENTS: Apply alone or tank-mixed with Nu-Lure Insect Bait.
** Dilute rate is the rate per 100 gal water; use 400 gal solution/acre. Apply concentrate in 80-100 gal water/acre, or less if the label allows. + Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment until the harvest may take place. In some cases the R.E.I. exceeds the P.H.I. The longer of these two intervals is the minimum time that must elapse before harvest may take place. # Acceptable for organically grown produce. 1 Rotate chemicals 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; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/. N.A. Not applicable.

PUBLICATION

UC IPM Pest Management Guidelines: Pear
UC ANR Publication 3455

Insects and Mites

L. G. Varela, UC IPM Program, UC Cooperative Extension, Sonoma County
R. B. Elkins, UC Cooperative Extension, Lake County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
C. Ingels, UC Cooperative Extension, Sacramento County
Acknowledgment for contributions to Insects and Mites:
C. Pickel, UC IPM Program, UC Cooperative Extension, Sutter/Yuba counties
P. W. Weddle, Weddle, Hansen & Associates
R. Hansen, Weddle, Hansen & Associates
P. Chevalier, United Ag Products, Ukiah
M. Hooper, Ag Unlimited, Lakeport
B. Knispel, Pest Control Adviser, Upper Lake
T. Lidyoff, Purity Products, Healdsburg
G. McCosker, Harvey Lyman Agservices, Walnut Grove
B. Oldham, Ag Unlimited, Ukiah
J. Sisevich, AgroTech, Kelseyville (retired)
D. Smith, Western Farm Service, Walnut Grove
B. Zoller, The Pear Doctor, Inc., Kelseyville

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