Grape Cane Borer (Alias: Apple Twig
Borer)
By Paul E. Read, Professor
University of Nebraska Viticulture Program
Recently, several growers have reported infestations of the
grape cane borer, originally named the apple twig borer (Amphicerus
bicaudatus). With the assistance of UNL Department of Entomology
scientists Fred Baxendale and Jim Kalisch, it has been identified and the
following recent article written by Cornell University (New York) scientists has
been found. Information about this insect is sparse, but the following
approaches are suggested.
1.
Remove and destroy all infested and damaged canes and other plant parts.
Incineration, where legal, finely chopping or burial are recommended.
2. As noted in the following article
(Dr. Baxendale concurs with this suggestion), control of adults by spraying with
Imidan in early to mid-May is suggested, with a follow-up spray in late May or
early June to kill recently hatched larvae.
3. Treat and/or remove other host
species near the vineyard (apples, scrub trees, etc.). This insect is not
easy to control because once it is inside the canes, no kill can be effected by
insecticidal sprays. If you have experienced problems with this insect,
please let me know. Dr. Baxendale and I will be trying to learn more about
this insect's abundance, relative severity, and distribution, with the ultimate
goal of reducing or eliminating damage caused by this pest.
Paul Read,
Professor
Horticulture/Viticulture
Grape Cane Borer Biology and Control
by Timothy E. Martinson and Greg English-Loeb
Grape Cane Borer, Amphicerus bicaudatus, has once again been a topic of
discussion
among growers in the Finger Lakes. The consensus among growers I have spoken
with is
that problems seem to be increasing in area vineyards, not just in the Keuka
area but also
in some locations on Seneca Lake.
For those of you who are unacquainted with the cane borer, the damage comes from
adults
that bore into live canes -generally but not always in nodes near the base of
the cane.
Although these holes are about 3/16" in diameter, they are hard to see without
searching
closely. Retained canes often die past the entrance hole, and canes with borer
in them often
break during the typing operation. In a cane pruned vineyard with '4 cane'
vines, loss of
one cane would amount to 25 percent of the potential crop. In cordon/spur
trimmed
vineyards, damage would be somewhat less, but may make it more difficult to
maintain
permanent cordons.
Biology
What we know about cane borer comes from a study done by Dr. George Shaefers and
Zeke
Mendel, of Taylor Wine Company, between 1981 and 1983. In a literature search,
we found
on a couple of papers on this pest, along with a reference to an unpublished
thesis from
Texas. Dr. Shaefer's study looked at economic impact in an' Aurore' vineyard,
and
included a very preliminary laboratory insecticide trial.
Life Cycle
Adults are brown to black in color, shaped like a cylinder, and 3/8" long. Cane
borer
overwinters in the adult stage, within burrows made in live canes. As weather
warms, they
become active in late April and early May, and tend to fly around in evening
hours near
dusk (the report mentions 8:30 PM). At this time, they are thought to make few
new entries,
with most limited to dry wood. Presumably adults mate around this time of the
year.
Egg laying starts in mid May, and peaks in mid-June. Eggs are reportedly laid
singly under
loose bark -either on live vines or pruned wood on the vineyard floor. Eggs
hatch around
mid-June, and larvae burrow "directly into the dead or dying canes." Early
feeding is just
below the bark, while older larvae enter the pitch (spongy area in the middle of
the cane),
leaving a sawdust-filled channel behind. Larvae complete their development and
form
pupae in mid-August, and adults emerge in mid-September. As canes harden off and
form
periderm, the adults enter one-year-old wood and the current year's canes, and
again feed
in channels in the middle of the canes. This is when the economically
significant damage to
healthy wood occurs.
Economic Impact
Shaefers reported that in one heavily infested Aurora vineyard,
30 percent of the dead
canes showed evidence of cane borer feeding, while a less-heavily infested area
within the
same vineyard had about 19 percent of the dead canes attacked. He also reported
that
"Counts revealed that one out of nine vines had a dead cane, and one out of 47
vines had
one cane attacked by borer." What I interpret this to mean is that although 1/3
of the 'dead
canes' may have died due to borer feeding, only 10 percent of the vines had a
dead cane,
and only two percent of vines had one cane borer in them. If these figures were
accurate for
a calle-prulled vineyard with four canes per vine (the training system was not
mentioned),
the potential crop loss would have been one of 188 = 0.5 percent crop loss.
Shaefers
Insecticide Trial
Shaefers tested eight insecticides in the laboratory, several ofwhich are no
longer available.
The exact testing method was not indicated, and each material was tested on only
10 adults.
Of currently available insecticides, Imidall treatment after 48 hours resulted
in 10 dead
adults (100 percent of those tested), while Sevill (carbaryl) results in five
dead (50 percent)
mortality. It's important to keep in mind that these were laboratory tests, and
the results
may not translate into effective control at the field level.
Controlling Cane Borer
To my knowledge, no rigorous insecticide trials for cane borer have been done.
There are
reasons for this -the main one being that the life cycle of this pest does not
lend itself to
conventional small plot trials. The insect is protected for most of the year
within the vine
(and not likely to contact insecticide), and the only way to evaluate efficacy
(e.g. ofa spring
application) would be to look for adults the following winter. Presumably, they
move
around a bit, and they have several woody plant hosts (all common in the area),
so it's hard
to predict how large an area you would have to treat to see any effect.
Given the lack of research, the best guidelines we can offer at this time are
based on
educated guesses of what might be important:
* Remove or Chop Brush. Dead canes and wood remaining on the vineyard
floor may serve
as a reservoir for adults, and also may harbor larvae throughout the season.
Thoroughly
chop brush, or remove and destroy as much as possible before adults become
active in the
spring. Consistent with this recommendation is the result of a study conducted
in Italy
where they found that by burning pruning material before the next field season
helped
eliminate a cane borer problem. Note that hedged pruned vineyards, with an
abundance of
old, dead wood, may provide good places for larvae to develop.
*Timing Sprays. If you decide to try an insecticide, it makes sense to
target active adults
before they lay eggs. Recall that adults are active from mid to late May, and
are most active
in the evenings. Another potential target would be the larvae after eggs hatch
but before
they burrow into the wood. Again, Shaefers' study indicated that that the
peak timing for eggs
would be from early to mid June. It's possible that with thorough coverage, a
spray at this
time might significantly reduce the number of larvae that develop. Again, this
is all
guesswork.
*Insecticides. The only insecticide currently registered for cane borer
in New York is
Imidan 70 W, although we have conducted no trials to test its efficacy
-and thus no reason
to recommend it over other materials. It's possible that broad spectrum
insecticides applied
for other labeled pests might also provide some control of cane borer, if
applied at the
appropriate time. Narrow-spectrum materials such as miticides, BT (Dipel, biobit)
and
Provado (imidacloprid) will not provide control. As this pest has not been
exposed to many
insecticides, we presume that resistance is not a problem.
*Evaluate Objectively. Be careful in assessing the extent of the problem.
It's easy to
overestimate how many cane borers are out there and how much damage they
are doing.
It's dismaying to have a cane snap off during tying because of cane borer
injury. But it
makes a difference whether or not damage is present on one cane in 100 or five
in 100.
Remember that it's the infestation in the canes you leave, not in the canes you
trim off, that
will affect yield. Think of the numbers you find in relation to the size of your
vineyard, and
don't overreact. In the few vineyards I have surveyed, I've generally been
surprised at how
few I find, although I recognize that each individual can destroy a carefully
selected cane or
cut short the useful life of a cordon arm.
I understand that the information we have for this pest is incomplete,
particularly where
effective control measures are concerned. Greg English-Loeb is making some
information
observations of cane borer behavior at his lab in Geneva. I also think it would
be useful to
attempt to test a few of the registered insecticides at an appropriate site,
even if there's a
chance that a formal trial won't work. I'll be looking for cooperators to set up
an informal
trial this spring. If you think you have a block with enough cane borer damage
to attempt a
trial, please give me a call at (315) 536-5134, or e-mail at tem2@ cornelledu.
Source: Finger Lakes Vineyard Notes, April 2, 2002.
University of Nebraska
