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Weeds in Christmas tree plantings are often the most difficult
pests to control. They can reduce growth rates in young trees
and affect the shape of older ones. They can provide a refuge
for insects and create microclimates that diseases love. And
they just get in the way of shearing, spraying and harvesting.
Planning before planting is always the best strategy. Map
the planting area for differences in soil type, drainage, and
elevation (for temperature differences). At the same time, map
the area for the major weeds present. Take particular note of
whether you have summer annuals, winter annuals or perennial
weeds, as that information will help you plan your weed control
practices.
Cultivation is most practical and effective before planting.
Use a labeled post-emergence herbicide to kill weeds before
cultivation. Especially target any weeds that are likely to
be problems once the trees are planted. Vines and woody perennials
are weeds to look out for!
Improving fertility levels is also easiest when preparing
the field before planting. Have your soil tested to determine
what you need to apply. Applying nutrients in the rows rather
than broadcast will make them more available to the trees and
less available to the weeds between the rows. Your trees will
reward you with faster growth and better weed competition.
Even species selection can help in your fight against damage
due to weeds. Choose tree species best adapted to the site and
environment, as well as desirable to the consumer. Trees grown
under stressful conditions are more likely to have pest problems
of all sorts, and those slower growing trees are more likely
to be out grown by weeds.
Keep weed control in mind when you plant your trees. Any
equipment you use for mowing or spraying needs to fit between
the rows and perhaps between trees in the row when they are
mature.
If you are renovating an area or replanting in between existing
trees, you can still do some weed control in advance. A summer
mowing will result in actively growing weeds for a fall spot
treatment of herbicide. Check to make sure the herbicide is
labeled in your location for the weeds and the surrounding tree
species, and is appropriate for the site and soil conditions.
Even labeled pesticides can cause damage, especially on young
trees, so be sure to shield them if you are not sure.
Not too many growers are still growing their own transplants
in seed or transplant beds. If you do, weed control is essential.
Even though the high density of planting would seem to help
crowd out weeds, seedling evergreens don‚t offer much ground
cover and may be slower growing than the weeds. Younger trees
are more susceptible to herbicide damage so seed/transplant
beds are the one place in Christmas tree production where mulches
to exclude weeds are practical.
Once you are in the full swing of production, weed control
is based on scouting -- just like disease and insect control.
Scout before tree budbreak in the spring and again in July/August
to identify weed problems. Spring, early summer and late summer
mowings are the backbone of the weed management program. Where
needed, spring pre-emergent herbicide and fall post-emergence
herbicides are used for problem weeds based on the results of
your scouting. Being especially vigilant during the first few
years of tree growth will pay off in faster growth rates and
fewer losses to other pests.
Ground cover management is of growing interest as a weed
management tool. In effect, if you are promoting low growing
weeds, like chickweed, between rows with mowing and suppressive
rates of herbicides, you have a ground cover. You can also plant
low-growing fescues or clover between the rows when you plant
the trees or overseed them in an existing field. Ground covers
suppress the growth of less desirable weeds, keep soil temperatures
cooler, and reduce the need for mowing. Bear in mind that a
groundcover can also compete with the trees so a weed free area
at the base of very young trees is advisable.
Specifics on herbicides for New York State can be found in
the Annual
Pest Management Guide for Commercial Production and Maintenance
of Trees and Shrubs or through the
NYS
Pesticide Product, Ingredient and Manufacturer System. Additional
information on weed control in Christmas trees can be found
in:
2007 New England Guide to Chemical Weed and Brush Control
in Christmas Trees
Ohio
Christmas Tree Producers Bulletin 670
Christmas Trees in Pennsylvania
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