Description of the Pest
Obliquebanded leafroller overwinter as third instar larvae under bud scales. Larvae are yellowish green with brown to black heads. As they mature, larvae construct tubular shelters from a single leaf. There are two generations a year. Periodically, localized infestations of obliquebanded leafroller occur and the larvae of the summer generation can cause serious damage in July and August. Obliquebanded leafroller is rarely a pest in Central Coast orchards.
Larvae feed on flower parts and on fruit early in the season, causing deep depressions that eventually become rough and russeted by harvest. Damage from the summer generation is usually more serious and results in superficial skin tunnels or small holes near the stem portion of the fruit.
Obliquebanded leafroller can occur in orchards in spring and summer. Summer damage is most commonly seen in orchards where a switch is made to the use of highly selective materials (including mating disruption) against codling moth that do not control obliquebanded leafrollers.
The parasitic wasp Macrocentrus iridescens has been observed attacking obliquebanded leafroller larvae in the Central Valley and in Central Coast and North Coast apple orchards.
Organically Acceptable Methods
Sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are organically acceptable.
Monitoring and Treatment Decisions
The best time to treat obliquebanded leafrollers is in spring, around pink bud, before the larvae are sheltered under leaves and between fruit clusters. Apply materials before bees are placed in orchards or after they are removed. Control overwintering larvae with either a delayed dormant application of oil and insecticide or a bloom application. If orchards have experienced damage from this pest in previous years or if leafrollers were observed in spring, also monitor the summer generation. Take fruit and leaf cluster samples at pink bud and in July and August. Tentative thresholds are two or more live larvae in a 100 fruit cluster sample in spring, and four or more in summer.
|Common name||Amount per acre**||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.|
|PETAL FALL TO HARVEST|
|(Intrepid 2F)||8–16 fl oz||4||14|
|MODE-OF-ACTION GROUP NUMBER1: 18|
|COMMENTS: Functions as a larvicide (must be ingested for it 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.|
|(Entrust)#||2–3 oz||0.67–1 oz||4||7|
|(Success)||6–10 fl oz||2–3.3 fl oz||4||7|
|MODE-OF-ACTION GROUP NUMBER1: 5|
|COMMENTS: Most effective when applied at petal fall. 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 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. Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|C.||BACILLUS THURINGIENSIS ssp. KURSTAKI#|
|(various products)||Label rates||4||0|
|MODE-OF-ACTION GROUP NUMBER1: 11A|
|COMMENTS: Least harmful to beneficials. Bacillus thuringiensis 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.|
|MODE-OF-ACTION GROUP NUMBER1: 28|
|COMMENTS: Do not apply dilute applications of more than 200 gal/acre; use 100 to 150 gal/acre for best results.|
|(Delegate WG)||4.5–7 oz||4||7|
|MODE-OF-ACTION GROUP NUMBER1: 5|
|COMMENTS: Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|**||For dilute application, rate is per 100 gal water to be applied in 300 to 500 gal water/acre, according to label; for concentrate applications, use 80 to 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.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|#||Acceptable for use on organically grown produce.|
|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).|