Description of the Pest
Fruittree leafroller overwinters in the egg stage in irregular masses of 30 to 100 eggs cemented over with a secretion. Young larvae are light green caterpillars with black heads and are first seen at bud break. The mature larva is about an inch long and has a green body and black head. The black head helps distinguish fruittree leafroller from other leafrollers. There is one generation per season.
The fruittree leafroller feeds principally on leaves, but also feeds on blossoms, flower buds, and fruits during bloom. Tiny larvae work their way into opening leaf buds to feed. Once the tree has leafed out, larvae tie up leaves and live within leafrolls, feeding on leaves or fruit. Larvae damage fruit in much the same way as green fruitworms, resulting in shallow cavities in the fruit. Damaged fruits that remain on the tree develop deep bronze-colored scars with roughened, netlike surfaces.
Generally fruittree leafrollers are the first caterpillars seen in samples taken after green tip and have about 2 weeks to feed before the first codling moth spray goes on. Young larvae are easiest to control because they have not yet constructed a nest out of leaves, which protects them from insecticides.
Natural enemies specific for fruittree leafroller are not known, but a number of general predators, such as lacewing and lady beetle larvae, and parasites feed on fruittree leafroller larvae. Although these natural enemies help keep fruittree leafroller populations at low, nondamaging levels; occasional outbreaks still occur, especially in the San Joaquin and inner coastal valleys.
Organically Acceptable Methods
Applications of approved narrow range oil, Bacillus thuringiensis, and the Entrust formulation of spinosad are organically acceptable.
Monitoring and Treatment Decisions
Fruittree leafroller usually is effectively controlled by a dormant oil spray. Make an application thorough enough to cover egg masses. Check results by sampling for leafrollers at green tip. Examine 100 fruit clusters per block. If no worms are found, resample in 1 week. If more than one worm is found, treatment before pink bud may be necessary to prevent damage. Often infestations are usually confined to small, localized areas of the orchard and can be spot treated.
|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.|
|B.||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. Effective against young larvae. Requires more than 1 treatment; apply second application 7–10 days after first.|
|(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: Apply 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.|
|MODE-OF-ACTION GROUP NUMBER 1: 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 NUMBER 1: 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).|