How to Manage Pests
UC Pest Management Guidelines
Branch and Twig Borer
Scientific name: Melalgus (=Polycaon) confertus
In this Guideline:
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.
Both adults and larvae injure grapevines. Larvae bore into wood at
dead or dying parts of vines, often in old
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.
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
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.
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.
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.
Biological and cultural controls are organically
acceptable, including the use of beneficial nematodes.
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.
|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.
OF ACTION GROUP NUMBER1: 1A
May cause mite outbreaks; do not use where mites are a chronic problem. Extremely toxic to honey bees.
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.
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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