Description of the Pest
The 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.
Larvae feed on leaves, buds, and the surface of fruit, causing severe damage as well as contamination with their excrement.
Orange tortrix is a cyclical pest. In coastal orchards, natural enemies and treatments for other pests usually keep this pest controlled. In other areas treatment is not needed.
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).
Remove and dispose of mummy fruit to reduce overwintering orange tortrix. Also, remove weed hosts such as mustard. The use of grass cover crops helps reduce overwintering hosts.
Organically Acceptable Methods
Biological and cultural controls and sprays of Bacillus thuringiensis are organically acceptable controls.
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 for damage beginning in June to determine spray timing. Sample 20 fruit on 15 trees for a total of 300 fruit. Treat if between 1 and 2% damage occurs on fresh market fruit (check with cannery fieldman for damage acceptable for processing fruit).
Take a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program. See FRUIT EVALUATION AT HARVEST. Record results on a monitoring form .
|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.|
|A.||BACILLUS THURINGIENSIS ssp. KURSTAKI#|
|(various products)||Label rates||—||4||0|
|MODE OF ACTION GROUP NUMBER1: 11.B2|
|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.|
|B.||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. Where plums are grown near waterways, do not use diazinon.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|**||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 (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 use on organically grown produce.|
|—||Not recommended or not on label.|
|1||Rotate insecticides 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; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. Mode-of-action group numbers for insecticides and miticides (un=unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).|