Description of the Pest
Orange tortrix, also called apple skinworm, is an occasional pest of pears in California. Moths are 0.5 inch long with tan to rusty brown forewings. Full-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 on a silken thread.
Not a major pest of pears, the principal damage caused by orange tortrix larvae is feeding on the surface of fruit, where they leave shallow, irregular scars. Generally the larvae feed within a cluster of fruit; occasionally they tie a leaf to the fruit's surface and feed under it.
A minor pest of pears, orange tortrix occurs in mostly coastal areas and 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.
Several parasites and predators attack orange tortrix. Normally these natural enemies keep orange tortrix under control. When these beneficials are disrupted by pesticide treatments, however, orange tortrix may become an occasional pest. Two parasitic wasps, Apanteles aristolilae and Exochus sp., are the most common naturally occurring enemies. Hormius basalis is an external parasite. Brown lacewing, Hemerobius pacificus, is a general predator of orange tortrix.
Orange tortrix feeds on many of the winter weeds that grow in orchards, such as mustard. Plant low-growing grass cover crops to reduce overwintering hosts of orange tortrix.
Organically Acceptable Methods
Biological and cultural controls and sprays of Bacillus thuringiensis and Entrust formulation of spinosad are organically acceptable methods.
Monitoring and Treatment Decisions
Usually orange tortrix does not appear in pear trees until June when eggs from the first summer generation are laid. Sample trees for larvae once a month in June and July. (See SAMPLING DURING FRUIT DEVELOPMENT.) Take the first sample no later than mid-June. Continue monitoring in combination with other pests. Treat if between 1 and 2% damage occurs on fresh-market pears (check with cannery fieldman for damage acceptable for processing fruit).
|Common name||Amount to use**||REI‡||PHI‡|
|(Example trade name)||(conc.)||(dilute)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|Note: Various pyrethroids are also registered for orange tortrix control in California, but are not recommended because they can cause severe mite problems and are not cost effective for control of orange tortrix.|
|A.||BACILLUS THURINGIENSIS ssp. KURSTAKI#|
|(various products)||Label rates||—||4||0|
|MODE OF ACTION GROUP NUMBER1: 11A|
|COMMENTS: Least harmful to beneficials. Bt is a stomach poison and must be consumed by the leafroller. Must be applied when worms are small. A second or third treatment may be required. Most effective if applied when weather forecasts predict 3 to 4 days of warm, dry weather. Larvae are more active and feed more in warm weather than in cooler or rainy weather.|
|(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. Larvae must ingest it for it to be effective. Treat at early egg hatch before webbing and sheltering begin. 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.|
|(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 3 sprays per season directed at leafrollers. Do not apply more than 9 oz/acre per crop of Entrust or 29 fl oz of Success/acre per crop. Residual efficacy is affected by pH but initial efficacy is not; verify that water pH is greater than 6 and less than 8.|
|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.|
|(Delegate WG)||4.5–7 oz||—||4||7|
|MODE OF ACTION GROUP NUMBER1: 5|
|COMMENTS: Residual efficacy is affected by pH but initial efficacy is not; verify that water pH is greater than 6 and less than 8.|
|**||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 (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) 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 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).|