Description of the Pest
Cankerworm larvae are typical of the group of worms called inch or measuring worms.Both fall and spring cankerworms are similar in appearance except that the spring cankerworm has two pairs of prolegs (legs located towards the end of the abdomen) whereas fall cankerworms have three pairs with the pair furthest from the end being underdeveloped.
Cankerworms are green with three narrow, whitish stripes and one yellow stripe along the side of the body. When mature they are about 1 inch long, green to olive green, with stripes of a different shade of green along the sides. Cankerworms frequently stand on their posterior pair of prolegs in such a way that they resemble a small twig.
Fall cankerworms pass the winter in the egg stage on trees and hatch and feed on leaves in spring and summer. They pupate and develop into moths in fall. There is one generation per year.
Spring cankerworms overwinter in the soil as mature larvae and pupate in spring. Eggs are laid on bark and hatch somewhat later than those of fall cankerworm. Larvae feed on leaves later into the summer than fall cankerworms and then drop to the soil to pupate. There is one generation a year.
Damage
In spring, cankerworms occasionally cause damage in apricot. Larvae feed primarily on leaves, tending to skeletonize them. Occasionally they feed on young fruit by biting deep holes, which later heal, but leave large scarred depressions similar to the injury caused by green fruitworms. Larvae can be found feeding throughout the tree but tend to be more numerous along center scaffold limbs.
Management
Cankerworms may be observed in spring when monitoring leafrollers during bloom. Treatments of Bacillus thuringiensis or spinosad for peach twig borer, applied at bloom or petal fall, will help to keep these leaf-eating caterpillars in check. If cankerworms are detected on small trees, infested twigs can be cut out and destroyed.
Organically Acceptable Methods
Use sprays of Bacillus thuringiensis, selected narrow range oil formulations, and the Entrust formulation of spinosad in an organically certified orchard.
| 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. | |||||
| DELAYED DORMANT | |||||
| A. | NARROW RANGE OIL | ||||
| (Supreme) | 4–6 gal | 1–1.5 gal | 12 | 0 | |
| MODE OF ACTION: Contact including smothering and barrier effects. | |||||
| . . . PLUS . . . | |||||
| SPINOSAD | |||||
| (Entrust)# | 1.25–2.5 oz | 0.42–0.83 oz | 4 | 14 | |
| (Success) | 4–8 fl oz | 1.3–2.7 fl oz | 4 | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 5 | |||||
| COMMENTS: To avoid development of insect resistance, do not treat successive generations of the same pest with the same product. Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | |||||
| . . . or . . . | |||||
| SPINETORAM | |||||
| (Delegate WG) | 4.5–7 oz | 1.125–1.75 oz | 4 | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 5 | |||||
| COMMENTS: This product is toxic to bees for 3 hours following treatment; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. Apply in the late evening after bees have stopped foraging. Do not apply more than 28 oz/acre per year or make more than four applications per year. Use has not been researched on cankerworms in apricots. | |||||
| . . . or . . . | |||||
| DIFLUBENZURON* | |||||
| (Dimilin 2L) | 8–16 fl oz | 3 oz | 12 | 0 | |
| MODE-OF-ACTION GROUP NUMBER1: 15 | |||||
| COMMENTS: Apply in sufficient water to ensure good coverage. Apply with narrow range oil at 1.5% oil by volume. | |||||
| . . . or . . . | |||||
| METHOXYFENOZIDE | |||||
| (Intrepid 2F) | 8–16 fl oz | 2.5–4 fl oz | 4 | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 18 | |||||
| COMMENTS: Do not apply more than 16 fl oz/acre per application or more than 64 fl oz/acre per season. | |||||
| BLOOM | |||||
| A. | BACILLUS THURINGIENSIS ssp. KURSTAKI# | ||||
| (various products) | Label rates | — | 4 | 0 | |
| MODE-OF-ACTION GROUP NUMBER1: 11A | |||||
| COMMENTS: Treatments are timed by examining larval emergence from hibernacula. Treat when larvae activity is first detected —by bud feeding or emergence from hibernacula— and again 7 to 10 days later. This usually coincides with an application at the beginning of bloom and the second 7 to 10 days later, often full bloom to petal fall. In years when peach twig borer emergence is extended, make the second at petal fall. Compatible with fungicide sprays and can be tank mixed with them. Good coverage is essential. Ground application using a concentrate rate (80–100 gal water maximum) is preferred. If aerial applications must be made because conditions do not permit ground application, a concentrate rate (5 gal or less) is preferred. Fly material on at a height of about 20 feet over the canopy using appropriate nozzles to allow better deposition on the tree tops. Precede this treatment with an oil spray during the delayed dormant season to control San Jose scale and European red mite eggs. | |||||
| B. | CHLORANTRANILIPROLE | ||||
| (Altacor) | 3–4.5 oz | 0.75–1.125 oz | 4 | 10 | |
| MODE-OF-ACTION GROUP NUMBER1: 28 | |||||
| COMMENTS: Do not apply more than 9 oz/acre per year or make more than three applications a year. Do not apply with less than 100 or more than 200 gallons water/acre. | |||||
| C. | METHOXYFENOZIDE | ||||
| (Intrepid 2F) | 8–16 fl oz | 2.5–4 fl oz | 4 | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 18 | |||||
| COMMENTS: Do not apply more than 16 fl oz/acre per application or more than 64 fl oz/acre per season. | |||||
| D. | DIFLUBENZURON* | ||||
| (Dimilin 2L) | 8–16 fl oz | 3 oz | 12 | 0 | |
| MODE-OF-ACTION GROUP NUMBER1: 15 | |||||
| COMMENTS: Include vegetable oil at the rate of 1 qt/acre. Do not apply after petal fall. Do not exceed two applications in any given season. Allow 21 days between applications. | |||||
| PETAL FALL and AFTER | |||||
| A. | SPINETORAM | ||||
| (Delegate WG) | 4.5–7 oz | 1.125–1.75 oz | 4 | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 5 | |||||
| COMMENTS: This product is toxic to bees for 3 hours following treatment; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. Apply in the late evening after bees have stopped foraging. Do not apply more than 28 oz/acre per year or make more than four applications per year. | |||||
| B. | SPINOSAD | ||||
| (Entrust)# | 1.25–2.5 oz | 0.42–0.83 oz | 4 | 14 | |
| (Success) | 4–8 fl oz | 1.3–2.7 fl oz | 4 | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 5 | |||||
| COMMENTS: Most effective when applied at petal fall. This product is toxic to bees for 3 hours following treatment; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. Apply in the late evening after bees have stopped foraging. Do not apply more than 29 fl oz/acre per year of Success or 9 oz/acre per year of Entrust. | |||||
| C. | CHLORANTRANILIPROLE | ||||
| (Altacor) | 3–4.5 oz | 0.75–1.125 oz | 4 | 10 | |
| MODE-OF-ACTION GROUP NUMBER1: 28 | |||||
| COMMENTS: Do not apply more than 9 oz/acre per year or make more than three applications a year. Do not apply with less than 100 or more than 200 gallons water/acre. | |||||
| D. | METHOXYFENOZIDE | ||||
| (Intrepid 2F) | 8–16 fl oz | 2–4 fl oz | 4 | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 18 | |||||
| COMMENTS: Do not apply more than 16 fl oz/acre per application or more than 64 fl oz/acre per season. | |||||
| E. | PHOSMET | ||||
| (Imidan 70-W) | 2.125–4.25 lb | 1 lb | 168 (7 days) | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 1B | |||||
| F. | DIAZINON* | ||||
| (Diazinon 50W) | 1 lb/100 gallons | 96 (4 days) | 21 | ||
| MODE-OF-ACTION GROUP NUMBER1: 1B | |||||
| COMMENTS: Avoid drift and tailwater runoff into surface waters. Where apricots are grown adjacent to waterways, do not use this material. Do not apply more than 4 lb product per application. | |||||
| ** | For dilute applications, 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 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. |
| 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 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). |
| * | Permit required from county agricultural commissioner for purchase or use. |
| — | Not recommended or not on label. |