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How to Manage Pests
UC Pest Management Guidelines
Grape
Branch and Twig Borer
Scientific name: Melalgus (=Polycaon) confertus
(Reviewed 6/06,
updated 6/06)
In this Guideline:
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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 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. To compare wilting symptoms of branch and twig borer damage to that
of Botrytis, view photos.
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 offer 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** |
P.H.I.+ |
| (trade name) |
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(days) |
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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.
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| A. |
CARBARYL* |
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(Sevin) 80S |
2.5 lb |
7 |
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MODE
OF ACTION: A carbamate (Group 1A)1 insecticide.
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COMMENTS:
Restricted entry interval: 12 hours. May cause mite outbreaks; do not use where mites are a chronic problem. Extremely toxic to honey bees. |
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| B. |
STEINERNEMA CARPOCAPSAE#
| Label rates |
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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. |
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![[Precautions]](/IMAGES/btn-precautions_bul.gif)
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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 the insects and mites section:
J. Granett, Entomology, UC Davis
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