Description of the Pest
Omnivorous leafroller larvae are cream-colored with black or brown head capsules and resemble other leafrollers, except that they have white oval tubercules at the base of each bristle along the dorsum. Omnivorous leafrollers are more common in interior valleys and southern California mountain orchards, especially those next to vineyards, than in orchards in coastal areas or at higher elevations of the Sierra Foothills. Adults may migrate from host plants outside the orchards. Infestations are often spotty, making monitoring difficult. They have three to four generations per year.
Although omnivorous leafroller feeds on both fruit and foliage, it is a minor pest in pear orchards. When larvae feed on fruit, they cause irregular, shallow scars similar to those caused by orange tortrix. Larvae feed where fruit are touching, so entire clusters frequently are damaged.
Omnivorous leafrollers commonly develop on host plants outside the orchard and may move into the orchard in early summer. They are a minor pest of pears. Infestations often are spotty, making monitoring difficult. Watch for leafrollers throughout the season when monitoring for other pests.
Organically Acceptable Methods
Sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are organically acceptable.
Monitoring and Treatment Decisions
If more than one omnivorous leafroller is found when sampling during the cluster stage (see SAMPLING AT BLOOM), consider treating. If only one larva is found, look for this pest again in a week when monitoring for other caterpillars (see SAMPLING DURING FRUIT DEVELOPMENT). One spray should keep omnivorous leafroller under control for the remainder of the season. Treatments are most effective when made around cluster bud.
|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: 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. Apply starting at cluster bud. 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: Apply with oil. 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).|