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2. What types of vegetation commonly
interfere with forest regeneration efforts?
The three most common types of interfering understory vegetation found
in Pennsylvania are ferns, beech brush, and striped maple. Other species
such as spicebush, mile-a-minute vine, honeysuckle, bittersweet, mountain laurel, multiflora rose, poison ivy,
grasses and others may present problems for forest regeneration on certain sites.
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3. What herbicides are frequently used
in Pennsylvania?
DUPONT™ OUST® XP is a preemergent and postemergent herbicide. Preemergence treatments
control or suppress weeds through root uptake during seed germination.
Postemergence herbicide control is through root and foliar
translocation. OUST® XP will provide a diminishing residual effect
for a period of 9 to 12 months. OUST® XP cannot be applied to surface
water or wetland areas that include surface water. Generally, use OUST®
XP when ferns are present. OUST® XP has better control on young ferns
earlier in the season. OUST® XP is best applied alone when a.) The
target species is light to moderate fern cover b.) Significant amounts
of advanced regeneration are present. Note however, that OUST® XP
can kill a significant percentage of existing desirable regeneration in some
instances. OUST® XP will not kill many species of established grasses.
Dow Agro Sciences manufactures ACCORD® Concentrate, a postemergent
herbicide that controls or suppresses vegetation primarily through
foliar uptake. Unlike OUST® XP, ACCORD® Concentrate exhibits no
residual action to control vegetation. ACCORD® Concentrate is best
applied alone when the target species are primarily beech brush and
striped maple.
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4. Are the herbicides safe?
ACCORD® Concentrate and OUST® XP provide the greatest levels of
control and the lowest levels of toxicity of all herbicides suitably labeled
for forest applications in Pennsylvania.
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5. Where can I find herbicide label
and MSDS information?
Visit www.cdms.net/manuf/manuf.asp,
or our Links page.
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6. I've always heard that ACCORD®
and OUST® have been used in the past. What is the difference between
these products and the products being used today?
Herbicide formulations, concentration levels of active
ingredients, and labeled uses for the products are always changing.
This is particularly true since the patent for glyphosate (the active
ingredient in ACCORD®) has expired. Many new "generic" formulations
of glyphosate are now available. The old formulation for OUST® has also
changed. Therefore, the herbicide applicator must exhibit a keen
knowledge of current formulations and application technologies that
minimize herbicide loads on the environment while achieving the desired
level of vegetative control.
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7. When to apply ACCORD® Concentrate
and OUST® XP in combination?
ACCORD® Concentrate and OUST® XP will be most effective at controlling
mixed understory vegetation. Heavy fern cover also requires a mixture
of OUST® XP and ACCORD® Concentrate.
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8. What is the best way to control
striped maple?
Striped maple can reach heights greater than 20 feet and form particularly
dense stands. These growth traits present special problems that inhibit
adequate coverage of herbicide during the spray application. Reducing
the spray swath distance from 80 feet to perhaps 60 feet in moderate cover
or 40 feet in very dense cover can compensate for stand density. However,
mechanical limitations prohibit the control of striped maple that exceeds
20 feet in height. In stands where a significant percentage of striped
maple is greater than 20 feet tall it may be necessary to a.) Cut all
the stems greater than twenty feet in height, then herbicide the site
one or two spray seasons following the cut, b.) Herbicide the stand, then
cut and/or basal spray all stems that survived the initial herbicide spray
application, or c.) Conduct a shelterwood harvest which includes the cutting
of all understory trees down to 1" DBH, then herbicide 2 seasons
following the harvest. Option C is probably most cost effective.
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9. Can planted conifers be released
from competing hardwood and herbaceous vegetation by using herbicides?
Yes, ACCORD® Concentrate can be applied to conifer stands after buds set in August. Other herbicides
are also available depending on specific situations. It is best to
release pines before they are three feet tall so as to minimize
mechanical damage during the spray application.
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10. When is the best time to spray
herbicide?
Begin spraying ferns and beech brush around the first of July. Begin spraying striped maple in
August or whenever terminal growth stops and buds are set. Generally:
spray ferns early, spray striped maple later, when a combination of
species are present spray at the time best suited for striped maple.
Spray beech brush anytime after full leaf expansion. If given a choice,
the herbicide spray application should be timed to take advantage of a
good overstory seed crop.
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11. Does drought alter the efficacy
of the herbicides?
Yes! Standards have been adopted by the PA Bureau of Forestry and the
PA Game Commission to cease spraying when the Palmer Drought Index drops
below (-2) in any given area. The Palmer Drought Index is explained and
can be monitored on the internet at: www.cpc.ncep.noaa.gov/products.
Scroll down to and select: Palmer Drought Severity Index Graphic (current).
Note that the vegetation within a stand in a given region may exhibit
signs of drought stress which are more or less than that which is indicated
by the Palmer Drought Severity Index. Therefore, it takes a trained and
experienced eye to judge whether the prescribed herbicide application
will achieve the desired effects when drought conditions threaten.
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12. Is it better to spray before or
after a timber harvest?
This is a question in which many factors must be weighed. Some factors to be
considered include: quantities of tree seed present, species of
understory vegetation being controlled, type(s) of herbicide needed to
control target vegetation, the presence of existing desirable advanced
regeneration, deer density levels, obstacles associated with stand
density vs. obstacles created by logging slash, adequate seed tree
distribution, the likelihood of abundant seed crops within several years
of herbicide and the all inclusive valuation of the probability that
successful regeneration will flourish.
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13. How long must the spray site remain
undisturbed before and after the actual herbicide spray date?
Do not conduct a harvest or otherwise disturb the spray site 4 to 8 weeks prior to the scheduled herbicide
application. Do not conduct a harvest or otherwise disturb the spray
site for at least 3 to 4 weeks after the herbicide spray application.
Wait till leaf fall before disturbing the site to maximize translocation
of the herbicide(s) to the root system.
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14. What special precautions must
be taken immediately after the herbicide spray application?
Stay out of the spray site for at least 12 hours after the spray application.
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15. How late in the season can you
spray?
Herbicide spraying can usually be conducted until mid to late September, depending on the
timing of the first hard frost or vegetation senescence. Also consider
the effects of drought and/or early signs of target vegetation
senescence (hardening off). All spraying must end after the first hard
frost.
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16. When can I expect to see results
after the herbicide spray application?
During favorable weather conditions, brownout typically
occurs within 2 to 3 weeks for fern, grasses, and beech brush. However,
near drought conditions may delay all outward signs of herbicide
activity until the following season. Review the overall efficacy of the
herbicide spray project near the end of the first growing season
following the herbicide spray operation. Even then, it may take two
growing seasons before you can determine the percent kill for striped
maple. Adequate levels of advanced regeneration may take 2 to 8 years
to become established.
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17. How much vegetation control is
enough?
Although it is desirable to achieve as high a percent kill as possible it is not necessary to
achieve 100% kill. Most sites will include areas of excessive slope,
rockiness, wetness, or other obstacles that prevents machinery from
traversing the site at recommended intervals. Even sites that have been
completely sprayed may have logging slash, windthrown trees, or other
barriers that shelter small areas from herbicide during the spray
application. After treatment, competing understory vegetation should be
present on less than 15% of the total area to be considered acceptable.
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18. How long will the herbicide treatment
remain effective?
If the competing vegetation has been reduced below the 15% post spray
threshold, the treatment should remain effective for 3 to 6 years. This
window may extend longer if used in conjunction with other measures such
as deer fencing. During this time advanced regeneration must become
firmly established.
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19. Have my goals been met by the forest
herbicide spray application?
This question should be answered in two phases:
1) Did the herbicide application succeed? Yes, if we achieve the 15% post
spray threshold as discussed in Question 17, above.
2) Did we achieve an adequate level of regeneration after the herbicide
application? A successful forest herbicide application in, and of itself,
will not assure that desirable results will be achieved. Your actual regeneration
success will depend on a number of different factors including, but not
limited to, deer browsing, seed crops, species composition, and weather
anomalies. Forest herbicide spraying is only one tool that can be used
to promote desirable regeneration within a forest environment. Consult
a forester for further advice to help increase your odds of answering
this question favorably.
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20. What role do white-tailed deer
play in the successful establishment of forest regeneration?
Large numbers of white-tailed deer have a profound negative impact (through excessive browsing) on the
establishment of desirable tree regeneration in much of Pennsylvania.
In most cases, deer population levels should be reduced (through
increased hunting) to a level of 10 to 15 deer per square mile before,
during and after the regeneration harvest. If hunting is impractical or
if the heard cannot be effectively controlled, then deer deterrent
fences may become necessary to exclude deer from the regeneration site.
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21. How much do forest herbicide applications
cost?
This will vary depending on herbicide(s) used, species being controlled,
terrain, etc. Please CALL FOR QUOTE.
If you have additional questions, please
feel free to call:
Barry S. Rose, Certified Forester
PO Box 319 • Lawn, PA 17041-0319
Phone/Fax: 717-964-2264
Note to Forest Stewardship Plan Writers:
Permission is granted to reproduce and include this FAQ’s sheet
in the appendix of your stewardship plans if appropriate.
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Revised
February, 2003