How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Orange tortrix, also called apple skinworm, is a pest in California coastal areas. The moths are 0.5 inch long with tan to rusty brown forewings. The fully grown larvae are about 0.5 inch long, straw colored to green, with light brown heads. They are active and quickly wiggle backwards when disturbed, dropping to the ground or spinning down a silken thread.

DAMAGE

Orange tortrix is an occasional pest in apple orchards. The principal damage caused by orange tortrix larvae is feeding on the surface of fruit, where they leave shallow, irregular scars. Generally they feed within a fruit cluster; occasionally they tie a leaf to the fruit's surface and feed under it.

MANAGEMENT

Orange tortrix is frequently controlled by parasites, especially in warm years when high temperatures slow its development. In cool years, higher populations occur, and natural enemies may not be able to hold populations below economically damaging levels; additional control measures may be needed.

Biological Control
Several parasites and predators attack orange tortrix. Two parasitic wasps, Apanteles aristolilae and Exochus sp., are the most common. Hormius basalis, an external parasite, also occurs. Brown lacewing, Hemerobius pacificus, is a general feeder on orange tortrix.

Cultural Control
Thin fruit to one or two fruit per cluster to reduce available habitat and to increase exposure of larvae to parasites, predators, and insecticides. Remove and dispose of mummy fruit to reduce overwintering orange tortrix. Orange tortrix feeds on many weeds found in orchards, such as mustard. Plant low-growing grass cover crops to reduce overwintering hosts of orange tortrix.

Organically Acceptable Methods
While rarely a significant pest in organic orchards, biological and cultural controls and sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are organically acceptable methods for pest control.

Monitoring and Treatment Decisions
Usually orange tortrix does not appear in apple trees until June when eggs from the first summer generation are laid. Sample trees for larvae once a month in June, July, and August; take the first sample no later than mid-June. Examine 10 trees of each variety in each block for 4 minutes each. Each larva found, whether orange tortrix, apple pandemis, or eyespotted bud moth. Correlates to about 1% fruit damage at harvest.

Common name		Amount to use**		R.E.I.+	P.H.I.+
(trade name)		(conc.)	(dilute)	(hours)	(days)
When choosing a pesticide, consider information relating to the impact on natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
A.	BACILLUS THURINGIENSIS ssp. KURSTAKI#
	(various products)	Label rates	—	4	0
	MODE OF ACTION GROUP NUMBER1: 11.B2
	COMMENTS: Least harmful to beneficials. Bt is a stomach poison and must be consumed by the leafroller; therefore it is most effective when applied during warm, dry weather when larvae are actively feeding. Most effective against young larvae. Requires more than 1 treatment; apply second application 7–10 days after first.
B.	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: To prevent the development of resistance to this product, rotate to a material with a different mode of action after treating two consecutive generations. Do not apply more than 3 sprays/season directed at leafrollers. Do not apply more than 9 oz/acre/crop of Entrust or 29 fl oz of Success/acre/crop.
C.	METHOXYFENOZIDE
	(Intrepid) 2F	16 fl oz	—	4	14
	MODE OF ACTION GROUP NUMBER1: 18A
	COMMENTS: Functions both as an ovicide (when applied to eggs and when eggs are laid on residues) and as a larvicide (must be ingested to be effective). For each generation, begin applications at early egg hatch before webbing and sheltering begin. Make a second application in 10–14 days. Spray coverage is extremely important. Ground application should use 200 gal water/acre with a sprayer speed of 1.5 mph. The addition of a spray adjuvant is recommended to enhance spray coverage.
D.	CHLORANTRANILIPROLE
	(Altacor)	3–4.5 oz	—	4	14
	MODE OF ACTION GROUP NUMBER1: 28
	COMMENTS: Do not apply dilute applications of more than 200 gal/acre; use 100–150 gal/acre for best results.
E.	SPINETORAM
	(Delegate) WG	4.5–7 oz	—	4	7
	MODE OF ACTION GROUP NUMBER1: 5
**	For dilute application, rate is per 100 gal water to be applied in 300–500 gal water/acre, according to label; for concentrate applications, use 8–100 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.
#	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/.

PUBLICATION

UC IPM Pest Management Guidelines: Apple
UC ANR Publication 3432
Insects and Mites
J. L. Caprile, UC Cooperative Extension, Contra Costa County
L. R. Wunderlich, UC Cooperative Extension, El Dorado County
P. M. Vossen, UC Cooperative Extension, Sonoma and Marin counties
W. W. Coates, UC Cooperative Extension, San Benito County
H. L. Andris, UC Cooperative Extension, Fresno County
L. G. Varela, UC IPM Program, Sonoma County
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
Acknowledgment for contributions to Insects and Mites:
C. Pickel, UC IPM Program, Sutter and Yuba counties

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