Description of the Pest
The branch and twig borer, also known as the grape cane borer, occurs throughout California. Adult borers are dark brown beetles, cylindrical in shape with a pronotum that is wider near the head than the posterior end. Females are about 0.7 inch long; adult males are smaller, about 0.3 to 0.4 inch long. Larvae have white bodies that are typically curved in a C-shape and enlarged at the anterior end; the head is brown. Branch and twig borers have one generation per year. Adult emergence starts in March and continues through April. Larvae spend up to 10 months in tunnels they excavate.
Damage
Both adults and larvae injure grapevines. Larvae bore into wood at dead or dying parts of vines, often in old pruning scars. Adults burrow into fruiting canes at the base of the bud or shoot, or they burrow into the crotch formed by the shoot and spur. Feeding is often deep enough to completely conceal the adult in the hole. Feeding at the base of shoots on spurs will cause shoots to wilt (flagging) and fall. This pest is most serious in cane-pruned vineyards where feeding on canes can cause them to break when shoots reach a length of 10 to 12 inches, if a strong wind occurs. Shoot wilting can also be caused by Botrytis.
Management
Establishment of branch and twig borer in a vineyard may be attributed to one or two factors: (1) proximity to habitat suitable to the insect, such as riparian or woodland areas, old orchards, or unmaintained vineyards, and (2) failure to destroy or adequately remove dead or damaged parts of vines that may have resulted from disease (such as Eutypa and Pierce's disease) or cultural practices such as T-budding, lowering the vine head, or mechanical pruning.
Chemical control is normally not necessary if good cultural controls are practiced. April treatment of carbaryl for cutworms offers some measurable control of adult borers but may cause mite outbreaks later in the season.
Biological Control
The many species of general predators found under the bark of grapevines may assist in maintaining lower populations. Treatments with commercial formulations of the entomopathogenic nematode Steinernema carpocapsae, which can move through frass tubes to infect larvae, may be of some benefit.
Cultural Control
The best way to manage branch and twig borer in vineyards is to prevent invasion and establishment of the beetles through cultural methods. Wood and brush piles of any kind of tree or shrub should be completely removed from the vineyard or burned before emergence of adult beetles in March. Remove dead or dying portions of vines and destroy them with other prunings. Do not leave grapevine prunings in the vicinity of the vineyard. All prunings must be removed from berms on the vine rows and destroyed to optimize sanitation. If mechanical cane chipping or cutting is used for pruning disposal, the residue should be incorporated into the soil or composted before adult emergence. Good vine health is important for reducing sites of borer establishment in vineyards.
Organically Acceptable Methods
Biological and cultural controls are organically acceptable, including the use of beneficial nematodes.
Monitoring and Treatment Decisions
Look for shoot wilting (flagging) and drying leaves when you monitor your vineyard during the period of rapid shoot growth. In coastal regions, adults continue to emerge through April. Examine the base of these shoots for a 0.4 inch diameter hole. If no holes are present, another possibility is a Botrytis infection. Cut the shoot in half and look for brown discoloration.
After pruning, examine old pruning scars and dead parts of vines for brown frass and fine wood dust filling the holes that were made by borer larvae. Borer holes are detected more easily during the dormant season. No control action thresholds have been established. It is unlikely that borer injury in cordon-pruned vineyards would ever justify chemical treatment if good vineyard pruning and sanitation is practiced. Cane-pruned vineyards with a history of borer injury may require treatment.
Pesticides and Natural Enemy Releases
Not all registered pesticides are listed. The following are ranked by their IPM value, with the most effective and least harmful to natural enemies, honey bees, and the environment listed at the top of the table. When choosing a pesticide, consider information related to water and air quality, resistance management, and the pesticide's properties and application timing. Use PestManage to compare summarized management options for different pests in the same crop. Always carefully read the label of the product being used and take all necessary precautions when handling pesticides.
| Rank | Active ingredient | Example trade name | Group | Group Order | MoA 1 | Amount per acre | REI (hours) ‡ | PHI (days) ‡ | Comments | Selectivity 2 | Bees 3 | Predatory mites 4 | Predators 5 | Parasitoids 5 | Residue duration 6 | Leaching(fish) 7 | Adsorbed runoff(fish) 8 | Solution runoff(fish) 9 | Leaching(human) 10 | Solution runoff(human) 11 | Last updated 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
Steinernema carpocapsae # | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
NA |
Label rates | NA | NA | Nematodes are perishable, so store them... | — | — | — | — | — | — | — | — | — | — | — | 07/2015 | |
| Sevin XLR Plus | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
1A |
1–2 lb | 144 (6 days) | 7 | May cause mite outbreaks; do not use whe... | broad | moderate/high | high | high | long | low | low | intermediate | low | low | 07/2015 |
Legend
- ‡ a b Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest.
- * a Permit required from county agricultural commissioner for purchase or use.
- # ↩ Acceptable for use on certified organic crops. Check with your certifier to confirm before application.
- 1 ↩ Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Insecticides with unknown modes of action are assigned mode-of-action group numbers (MoAs) that begin with UN. Rotate pesticides 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; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B.
- 2 ↩ Range of insect and mite groups affected by a pesticide. Broad means the pesticide affects most groups of insects and mites; narrow means the pesticide affects only a few specific groups.
- 3 ↩ Risk of harm to honey bees. For more information, see Bee Precaution Pesticide Ratings.
- 4 ↩ Risk of harm to predatory mites. Toxicities are generally to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain or native strain.
- 5 a b Risk of harm to parasitoids and general predators. Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific insecticide depends on factors including the application rate, environmental conditions, and the life stage and species of a parasitoid or predator.
- 6 ↩ Length of time residue affects natural enemies. Short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
- 7 ↩ Risk of harm to fish from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 8 ↩ Risk of harm to fish from adsorbed runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 9 ↩ Risk of harm to fish from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 10 ↩ Risk of harm to humans from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 11 ↩ Risk of harm to humans from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 12 ↩ Date information was last updated in the UC IPM Pest Management Guidelines.
Important Links
UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448
L.G. Varela (emeritus), UC IPM and UC Cooperative Extension Sonoma County
D.R. Haviland, UC IPM and UC Cooperative Extension Kern County
W.J. Bentley (emeritus), UC IPM and Kearney Agricultural Research and Extension Center, Parlier
L.J. Bettiga, UC Cooperative Extension Monterey County
K.M. Daane (emeritus), Kearney Agricultural Research and Extension Center, Parlier
R.J. Smith (emeritus), UC Cooperative Extension Sonoma County
L.R. Wunderlich, UC Cooperative Extension Central Sierra
F.G. Zalom (emeritus), Entomology, UC Davis
Acknowledgement for Contributions to Invertebrates
M.C. Battany, UC Cooperative Extension San Luis Obispo County
J. Granett (emeritus), Entomology, UC Davis
P.A. Phillips (emeritus), UC Cooperative Extension Ventura County
A.H. Purcell (emeritus), Environmental Science, Policy, and Management, UC Berkeley
