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UC Pest Management Guidelines

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Prune

Orange Tortrix

Scientific Name:Argyrotaenia franciscana (=A. citrana)

(Reviewed 6/06, updated 4/09)

In this Guideline:

Description of the pest
Damage
Management

Important links
Publication
Glossary

DESCRIPTION OF THE PEST

Orange tortrix is only found in coastal areas. Its larvae are light green caterpillars with brown heads; they resemble obliquebanded leafroller caterpillars. When disturbed, the larvae wiggle backwards and drop to the ground on a silken thread. Adults are fawn or gray-colored moths with a darker mottling on the forewings. The orange tortrix overwinters as larvae and there are two to four generations each year in coastal areas.

DAMAGE

Larvae feed on leaves, buds, and the surface of fruit, causing severe damage as well as contamination with their excrement in fresh market prunes.

MANAGEMENT

Orange tortrix is a cyclical pest in fresh market prunes. In coastal orchards, natural enemies and treatments for other pests usually keep this pest controlled. In other areas treatment is not needed.

Biological Control
Several parasites and predators attack orange tortrix. Parasites include the wasps Cotesia (Apanteles) aristolidae, Exochus sp., and Hormius basalis and a tachinid fly, Nemorilla pyste. Predators include spiders and brown lacewing larvae Hemerobius pacificus.

Cultural Control
Remove weed hosts such as mustard. The use of grass cover crops helps reduce overwintering hosts. Remove mummy fruit during the dormant season to help reduce overwintering populations.

Organically Acceptable Methods
Biological and cultural controls and sprays of Bacillus thuringiensis are organically acceptable management tools.

Monitoring and Treatment Decisions
If you suspect orange tortrix is a problem and your orchard is located in coastal areas, sample fruit on a weekly basis beginning in June for damage to determine spray timing. Sample 20 fruit on 15 trees for a total of 300 fruit. Treat if between 1 and 2% of fresh market fruit are damaged (check with cannery fieldman for damage acceptable for processing fruit).

Fruit damage sample. In mid-July, take a fruit damage sample to assess the overall effectiveness of the current year's IPM program and to determine next year's needs. For more information, see FRUIT EVALUATION AT HARVEST. Record on a monitoring form (84 KB, PDF) the number of fruit infested by larvae, type of larvae present, whether the damage is surface feeding only or if the larvae penetrated the fruit.

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 efficacy, impact on natural enemies and honey bees, and impact of the timing on beneficials. 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.	DIAZINON* 50WP	3 lb	1 lb	24	21
	4EC	3 pt	1 pt	24	21
	MODE OF ACTION GROUP NUMBER¹: 1B
	COMMENTS: Avoid drift and runoff into surface waters.

B.	CARBARYL*
	(Sevin) 80S	4 lb	1.25 lb	12	1
	MODE OF ACTION GROUP NUMBER¹: 1A
	COMMENTS: May cause increased spider mite problems; not recommended for routine use, especially early in the season.

C.	BACILLUS THURINGIENSIS# ssp. KURSTAKI
	(various products)	Label rates	—	4	0
	MODE OF ACTION GROUP NUMBER¹: 1A
	COMMENTS: Timing is important because of short residual period. Apply only during warm dry weather to control young actively feeding worms; may need to be applied more than once. Good coverage is essential.

**	For dilute applications, rate is per 100 gal water to be applied in 300-500 gal water/acre, according to label; for concentrate applications, use 80-100 gal water/acre, or lower 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 to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
*	Permit required from county agricultural commissioner for purchase or use.
#	Acceptable for use on organically grown produce.
—	Not recommended or not on label.
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/.

IMPORTANT LINKS

Final fruit damage form evaluation for caterpillars, scale, and aphids (84 KB, PDF)

PUBLICATION

UC IPM Pest Management Guidelines: Prune
UC ANR Publication 3464
Insects and Mites
C. Pickel, UC IPM Program, Sutter/Yuba counties
F. J. A. Niederholzer, UC Cooperative Extension, Sutter/Yuba counties
W. H. Olson, UC Cooperative Extension, Butte County
F. G. Zalom, Entomology, UC Davis
R. P. Buchner, UC Cooperative Extension, Tehama County
W. H. Krueger, UC Cooperative Extension, Glenn County
Acknowledgment for contributions to Insects and Mites:
W. O. Reil, UC Cooperative Extension Solano/Yolo counties

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