BLACK LOCUST CONTROL

Wisconsin Department of Natural Resources State Natural Aarea crew July 2006

The following is a summary of black locust control successes and failures from the WI-DNR South Central Region State Natural Areas Crew (a winner of the 2006 Invader Crusader Award!). Ryan Magana, Crew Leader, emphasizes that results are often unpredictable between sites, seasons and chemicals. This is not THE definitive answer to black locust control, but an insightful and experienced account that should provide helpful info and a stimulus for discussion.

Following Ryan’s summary is an interesting chain of emails that came in response to the summary.

* Before using any herbicide, be sure to read and follow all labeled instructions. This document is not intended to replace proper labeling guidelines. These are field notes taken from personal experience and experimentation.

Failures

• Krenite (Fosamine Ammonium) stump treatment – mixed 1:1 with water. In some areas, this worked fair – in others it was a complete disaster. Not worth the follow-up.
• Krenite foliar – 2.5 oz/gallon water. We did not get good results with this either.
• Garlon 3A (Triclopyr) 1:1 with water; Tahoe 4e 1:3 with Diluent Blue – both as stump treatments. Complete failures for both treatments.

Successes

1. Foliar

• Transline (Clopyralid). Mix at a rate of 1 oz/gallon water + surfactant (we used Preference). Use on trees up to 8 feet tall. Apply solution to at least 70% of the foliage, during full leaf out, mid summer. Do not apply too late in the fall, when the trees are beginning to senesce. This method is fairly cheap – one 3 gal backpack of spray costs under $9. We have seen 100% kill at the above mix rate. Transline is mostly legume and aster specific (we have seen it affect sumac), therefore not affecting a number of native plant families.

• Escort (Metsulfuron Methyl). Mix at a rate of 1.5 grams/gallon water + surfactant (we used Preference or crop oil). We have been informed that using 2 ounces of ammonia per backpack helps dissolve Escort into solution better, but we have not tried this yet. Use on trees up to 8 feet tall. Apply solution to at least 70% of the foliage, during full leaf out, mid summer. Do not apply too late in the fall, when the trees are beginning to senesce. This method is fairly cheap – one 3 gallon backpack of solution costs under $7. We have seen 100% kill at the above mix rate. For foliar application, we prefer Escort over Transline for a few reasons. First, it is slightly cheaper. Escort can be purchased by the ounce, and costs $25/oz ($21/oz when you buy a lb), which makes about 18 gallons of solution. Also, it comes as a granulated powder, with a measuring device that is super easy to use, and nearly impossible to spill. Third, Escort is deadly to a number of other species, such as honeysuckle, while not impacting native prairie grasses. It does harm some prairie forbs.

2. Basal Bark

• Tahoe 4e (Triclopyr). Mix at 1:3 with Bark oil blue LT + Bas oil blue dye. Apply when temp is below 80F. We did most of these treatments in September and October, when the trees had at least 25% of leaves remaining. We did not attempt to treat any trees over about 4 inch dbh (diameter at breast height), as the bark begins to become extremely corky, and it seems that the chemical does not absorb as effectively. Any trees under that size were treated with a band starting at ground level, up to about 15 in, around the entire trunk. Using the above techniques, we have seen upwards of 90% kill, with resprouting only where trunks were missed, or insufficiently treated. You will probably see a dead spot around the base of the treated trees, which is a result of the oil. While Bark Oil Blue LT is more expensive than diesel (some folks use diesel as a carrier in basal bark treatments), we have seen far better results with BOB, especially in higher temps.

3. Chainsaw girdle

• Transline (Clopyralid). Mix at 10% Tline, 90% Bark Oil Blue EC + Bas Oil blue. This method is great for trees over 4 inch dbh. Cut with saw around entire circumference of the tree, just deep enough to expose the vascular cambium. Treat the entire girdle with the above formulation. If the tree is under 4 in dbh, just drop it, and stump treat. Do not use anything but Bark Oil Blue EC. We used Diluent blue once, and the mixture turned into a thick slurry. Bark Oil Blue LT does not mix well with Tline. BOB EC is only available in 15 gal drums. We used this method on trees up to about 18 in dbh, and it killed 100% of them. The following summer, we started to see small, very weak looking resprouts around the treated area, but even some of those eventually withered. Some may balk at the price of the mixture ($9/ gal for oil, ~$300/gal for T-line), but we have found that a successful treatment is infinitely cheaper than repeated failures.

• Transline + Water. Mix at 10% Tline, 90% water + surfactant+dye. We tried this as a cheaper alternative to the Tline/BOB EC. The site it was used on was a dry upland with gravely-glacial till soils. This was a huge stand – well over 100 trees with some individuals approaching 24" dbh. The result was equal, if not more effective than using the Bark Oil. The stand was treated last fall, and as of July 1, we have not seen any leaf-out, or resprouts/root suckers. Having said that, we will not declare this a complete success until the end of the growing season.

Management Tool Guidelines

Trees under 8' tall – Foliar spray

Trees over 8' tall, and all trees under 4" dbh – Basal Bark treat

Trees over 8' tall and over 4" dbh – chainsaw girdle/treat or cut/treat for small trees

Chemical sources:

UAP Great Lakes (Deforest) – Rick Schulte (608) 770-4041
• We have found Rick to be the most knowledgeable salesman in the area, providing advice on usage and technique. As far as we know, UAP is the only place in the area to get Bas oil blue, Bark Oil Blue, and Tahoe 4e. We also buy Escort at UAP.

From Rick Schulte- UAP Timberland:

Just a little FYI for all, The Krenite can take up to 1.5 years to work. I have sprayed some in the summer of 02 and the next year, 03, it did not look like it was sprayed. I was informed by David Spatcher the area DuPont rep, that Krenite sometimes has a delayed effect and can take awhile. The following year 04, all the black locust were dead. So, if you are using or have used Krenite, be patient.

From John Van Altena:

In July, 2005 I sprayed about 2 acres of locust 3-6 feet high with Transline and got a 100% kill. This summer there is no re-sprouting. I'm impressed. I used 1/2 oz. Transline / gal water with 1/2 oz of Activator 90/ gal. water, as per Rick Schulte. That stuff is dynamite and I had almost no collateral damage on native plants.

More images and information about black locust from UW Herbarium

and Wisconsin DNR