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UC Pest Management Guidelines

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Grape

Branch and Twig Borer

Scientific name: Melalgus (=Polycaon) confertus

(Reviewed 6/06, updated 10/08)

In this Guideline:

Description of the pest
Damage
Management

Important links
Publication
Glossary

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. 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. Flagging 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 carpocasae, 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 used as compost 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 wilted shoots (flagging) and drying leaves when you monitor your vineyard during the period of rapid shoot growth. 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.

In the North Coast, adults continue to emerge through April. 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, particularly after pruning. 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.

Common name		Amount/Acre**	R.E.I.+	P.H.I.+
(trade name)			(hours)	(days)

The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.

A.	CARBARYL*
	(Sevin) 80S	2.5 lb	12	7
	MODE OF ACTION GROUP NUMBER¹: 1A
	COMMENTS: May cause mite outbreaks; do not use where mites are a chronic problem. Extremely toxic to honey bees.

B.	STEINERNEMA CARPOCAPSAE#	Label rates	NA	NA
	COMMENTS: Nematodes are perishable, so store them under cool, dark conditions. Use hand sprayer to aim spray at infected cordons. Most effective when applied during January and February.

**	Apply with enough water to provide complete coverage.
+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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). For additional information, see their Web site at http://www.irac-online.org/.
#	Acceptable for use on organically grown produce.
NA	Not applicable.

IMPORTANT LINKS

PUBLICATION

UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Research Center, Parlier
L. G. Varela, UC IPM Program, Sonoma County
F. G. Zalom, Entomology, UC Davis
R. J. Smith, UC Cooperative Extension, Sonoma County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
P. A. Phillips, UC IPM Program, Ventura County
D. R. Haviland, UC IPM Program, Kern County
K. M. Daane, Kearney Agricultural Research Center, Parlier
M. C. Battany, UC Cooperative Extension, San Luis Obispo County
Acknowledgment for contributions to Insects and Mites:
J. Granett, Entomology, UC Davis

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