Frequently Asked Questions

Forest Herbicides
Disclaimer: The information contained in this FAQ's Sheet does not in any way replace or supercede the information on the pesticide product label or other regulatory requirements. Please refer to the herbicide product labeling for complete directions for use, safety, and handling. This information relates specifically to herbicide spray applications conducted by Forest Regeneration Services, Inc. and Barry S. Rose, Certified Forester, PO Box 1260, Gouldsboro, PA 18424 and may not be appropriate for a particular use.

  1. When is an herbicide spray application warranted?
  2. What types of vegetation can be controlled?
  3. What chemicals are used most frequently in forest herbicide applications performed in Pennsylvania?
  4. When to apply ACCORD® and OUST® in combination?
  5. Are the chemicals safe?
  6. What is the best way to control-striped maple?
  7. Can planted conifers be released from competing hardwood and herbaceous vegetation by using herbicides?
  8. When is the best time to spray herbicide?
  9. Is it better to spray before or after a timber harvest?
  10. How long must the spray site remain undisturbed before and after the actual herbicide spray date?
  11. What special precautions must be taken immediately after the herbicide spray application?
  12. How late in the season can you spray?
  13. When can I expect to see results after the herbicide spray application?
  14. How much vegetation control is enough?
  15. How long will the herbicide treatment remain effective?
  16. Have my goals been met by the forest herbicide spray application?
  17. How much does it cost?
  1. When is an herbicide spray application warranted?

    Herbicide spray applications are associated with timber harvests designed to promote forest tree regeneration. The application of herbicide may be necessary to remove existing understory vegetation that competes for light, water and nutrients needed to establish tree seedlings. Generally speaking, if more than 30% of the total area contains competitive understory vegetation, then herbicide control may be warranted. Spray applications may also be appropriate for timber harvests designed to salvage timber from a recent insect or disease outbreak, particularly if stand density is reduced to a point where conditions become favorable for the establishment of advanced regeneration.

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  2. What types of vegetation can be controlled?

    The three most common types of interfering understory vegetation found in Pennsylvania are ferns, beech brush, and striped maple. Other species such as mile-a-minute vine, honeysuckle, bittersweet, mountain laurel, multiflora rose, poison ivy, grasses and others present problems for forest regeneration in certain parts of the state.

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  3. What chemicals are used most frequently in forest herbicide applications performed in Pennsylvania?

    DuPont manufactures OUST®, a preemergent and postemergent herbicide. Preemergence treatments control or suppress weeds through root uptake during seed germination. Postemergence herbicides control through root and foliar uptake. OUST® will provide a diminishing residual effect for a period of 9 to 12 months. OUST® cannot be applied to surface water or wetland areas that include surface water. Generally, use OUST® when ferns are present. OUST® has better control on young ferns earlier in season. OUST® is best applied alone when a) the target species is light to moderate fern cover b) significant amounts of advanced regeneration are present. OUST® will kill some existing regeneration. OUST® will not kill some species of established grasses. Monsanto manufactures ACCORD®, a postemergent herbicide that controls or suppresses vegetation through foliar uptake. Unlike OUST®, ACCORD® exhibits no residual action to control vegetation. ACCORD® is best applied alone when the target species are primarily beech brush and striped maple.

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  4. When to apply ACCORD® and OUST® in combination?

    ACCORD® and OUST® will be most effective at controlling mixed understory vegetation. Heavy fern cover also requires a mixture of OUST® and ACCORD®.

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  5. Are the chemicals safe?

    ACCORD® and OUST® provide the greatest levels of control and the lowest levels of toxicity of all herbicides suitable for forest application in Pennsylvania.

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  6. 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 it may be necessary to a) cut all the stems greater than twenty feet in height, then herbicide the site the following spray season, b) herbicide the stand, then cut and 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 two seasons following the harvest. Option C is probably most cost effective.

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  7. Can planted conifers be released from competing hardwood and herbaceous vegetation by using herbicides?

    Yes, ACCORD® 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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  8. 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 in combination spray at the time best suited for striped maple. Spray beech brush anytime. If given a choice, the herbicide spray application should be timed to take advantage of a good overstory seed crop.

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  9. 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 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, and likelihood of abundant seed crops within 6 years of herbicide application.

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  10. 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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  11. What special precautions must be taken immediately after the herbicide spray application?

    Stay out of the spray site for at least 12 to 24 hours after the spray application.

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  12. 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. All spraying must end after the first hard frost.

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  13. When can I expect to see results after the herbicide spray application?

    Brownout should occur within 2 to 3 weeks for fern, grasses, and beech brush. Overall understory control can be determined near the end of the first growing season following the herbicide spray operation. It will be 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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  14. 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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  15. 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 be extended to 6 to 10 years if used in conjunction with other measures such as deer fencing. During this time advanced regeneration must become firmly established.

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  16. 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 as discussed in Question 14, above. 2) Did we achieve an adequate level of regeneration after the herbicide application? Your actual regeneration success will depend on a number of different factors including, but not limited to, seed crops, deer browsing, 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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  17. How much does it cost?

    Cost varies depending on herbicide(s) used, species being controlled, terrain, etc. Please call for quote.

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Frequently asked questions about deer fencing are coming soon!
If you have other questions or concerns, feel free to contact us. We are located in Gouldsboro Pennsylvania and service all of the Pennsylvania area!