----- Original Message -----
Sent: Thursday, November 13, 2008 8:20
AM
Subject: [NAFEX] screening apples
Rodent and borer control at Fedco:
In central and southern Maine non-commercial growers
must all deal with apple tree borers. Some areas of Maine(and other
apple districts) do not have problems with borers. If new to planting
apples and wondering if you will have a problem, check with anyone growing
apples near you, they'll know. Commercial growers who use a
conventional spray program generally have limited problems with
borers. The Fedco recommendations are based on our experiences on our
farm in Palermo over the past 25 years.
In our orchard we have tried a number of
approaches. Using window screen seemed like a great idea since the
screen would double as rodent deterrence and borer control. For those
who do not have a borer problem, using window screen is highly
effective. I recommend, however, removing the screen during the
times of year when you do not need it. That way the tree trunk will have
an opportunity to breath and dry out. Screen removal can also be
an opportunity to be sure the screening is not girdling or growing into the
trunk.
Using window screen as borer control is
problematic. If the screen top edge is not tight to the trunk, the borer
beetles will simply scoot down the trunk behind the screen and lay eggs where
you will never see them. The beetles can also lay an egg through the
screen if it lays flat against the trunk. With screen around the trunk
it is also very difficult to see if you have borers in the trunk. But
the time you realize you have a problem, it may be too late.
We tried stapling the "top" of the screen to
itself tight around the trunk to prevent borers from getting behind the
screen. We also tried a foam "gasket". Both of these approaches
have their own problems. You can never really get the screen tight
enough, and if you do, then you are likely damaging the trunk. The
gasket works well, but foams and rubber, etc do not mix well with tree
trunk tissue and we found that the trunks were rotting under the gasket.
Where we are currently:
Rodents:
In early November we "screen" all of our fruit trees
up to 16" diameter. For the small ones, we generally use those spiral
tree guards. For larger trees we use old window screening, hardware
cloth, etc. With the screening, we wrap it around the trunk and tie it
off with a piece of baler twine. In April, we remove all the
screens and guards. We keep our trees "weeded" around the base during the
growing season. We have never experienced any rodent damage during the
growing season.
Borers:
All trees are weeded and mulched with chipped
brush. Eventually the brush bits disappear and more is laid down
as available. The mulch is kept back about 3 inches from the
trunk. This leaves a "moat" of soil around the trunk. We then
paint the trunk up to about knee-high with a mixture of interior white latex
paint and "sheetrock" joint compound. The mixture is like a thick paint,
not a paste. It paints on. We dig down into the soil a little bit
- say 1/2"- and paint right down to the soil. Then, gently pull the soil
back over the paint up against the trunk. We don't wait until the paint
is dry to do that last step. The paint and joint compound are cheap and
easily accessed. Hardwares stores occasionally have "returned" gallons
of paint for $5. We prefer interior (rather than exterior) paint.
Exterior contains ingredients that might damage trees.
(This mixture is NOT organically
certifiable. We also developed a certifiable mixture using linseed oil,
milk and quick lime. This also works, but does not adhere to the trunk
very well and therefore requires more frequent re-application. Although
we use organic practices in our orchard, we are not certified. We vastly
prefer paint/joint compound.)
Using either paint method is an excellent
deterrent. However, the paint does not kill the borers, so they will be
around. Over time, the population may decline, but in high-pressure
areas, they may not do so. It is critical to continue to regularly check
all trunks for the "frass" that is the sign of borer activity inside the
trunk. They do occasionally still get into our trees. The paint
must be reapplied every year. It wears off, etc. When we do find
borer sign, we dig/cut out the borer. Even serious surgery on the young
tree is better that leaving the borer inside. Having the trunk painted
white makes it very easy to spot borer activity.
Best regards,
John Bunker
Fedco
www.fedcoseeds.com
PO Box 520
Waterville ME 04903
207-873-7333
fax: 207-872-8317
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