Description of the Pest
The redhumped caterpillar is easily recognized because of its striking appearance: the main body is yellow and is marked by longitudinal reddish and white stripes; the head is bright red, and the fourth abdominal segment is red and enlarged. Redhumped caterpillars pass the winter as full-grown larvae in cocoons on the ground. In early summer, moths lay egg masses on the undersides of leaves. Eggs hatch into larvae that begin feeding on leaves. There are at least three generations each year in northern California.
Damage
Redhumped caterpillars are mainly a problem on young trees where they skeletonize leaves, leaving behind only leaf veins. They do not web leaves.
Management
Redhumped caterpillar can be a pest of cherry orchards in the Central Valley but is rarely found in the Central Coast. Biological control and pruning are often sufficient to manage the pest; use the monitoring guidelines below to determine need for treatment.
Biological Control
The most common parasite species are Hyposoter fugitivus, which forms a single pupal case that is white with a black band around the middle, and Apanteles sp., which forms a fluffy white mass of pupal cases.
Organically Acceptable Methods
Biological control and sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable for use on an organically certified crop.
Monitoring and Treatment Decisions
On small trees, cut out and destroy infested twigs. Insecticide sprays applied for leafhoppers often keep these leaf-eating caterpillars in check. When monitoring, look for the presence of parasites. If 80% or more of the larval population is parasitized, no treatment is needed. If insecticide treatments are required, localized treatments on individual trees applied when evidence of caterpillars is first observed are generally all that is necessary. Mature trees usually don't require controls.
| 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: Most effective on small caterpillars. Does not destroy natural enemies. Make 2 applications during bloom: the first at early bloom and the second 7–10 days later, but no later than petal fall. Compatible with fungicide sprays. Good coverage is essential. | |||||
| B. | METHOXYFENOZIDE | ||||
| (Intrepid 2F) | 8–16 fl oz | 4 | 7 | ||
| MODE-OF-ACTION GROUP NUMBER1: 18 | |||||
| COMMENTS: Most effective when applied at petal fall. Do not apply more than 16 fl oz/acre per application or 64 fl oz/acre per season. Coverage is extremely important; sprayer speed should not exceed 2 mph. | |||||
| C. | SPINOSAD | ||||
| (Entrust)# | 1.25–2.5 oz | 0.42–0.83 oz | 4 | 7 | |
| MODE-OF-ACTION GROUP NUMBER1: 5 | |||||
| COMMENTS: Do not apply more than 29 oz/acre per year of Success or 9 oz/acre per year of Entrust. Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | |||||
| D. | SPINETORAM | ||||
| (Delegate WG) | 4.5–7 oz/acre | 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. | |||||
| E. | DIAZINON* | ||||
| (Diazinon 50W) | 1 lb/100 gal water | 96 (4 days) | 21 | ||
| MODE-OF-ACTION GROUP NUMBER1: 1B | |||||
| COMMENTS: Avoid drift and tailwater runoff into surface waters. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | |||||
| F. | CARBARYL* | ||||
| (Sevin 4F) | 3–4 qt/acre | 12 | 1 | ||
| MODE-OF-ACTION GROUP NUMBER1: 1A | |||||
| COMMENTS: May cause increased spider mite problems or leaf yellowing under some conditions. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | |||||
| ** | For concentrate applications, use the amount given in 80–100 gal water/acre, or lower if the label allows; for dilute applications, amount is per 100 gal water to be applied in 300–400 gal water/acre, according to label. |
| ‡ | 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. |
| 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). |
| # | Acceptable for use on organically grown produce. |