Pasture Weed Control with Juglone (Black Walnut) Spray

The first goal of the project was to successfully extract Juglone from the walnut hulls.  Walnuts gathered in October 2014 had recently fallen to the ground, and most retained some green hull.  The walnuts were run through a corn sheller to loosen and remove some of the hull.  Five gallon food grade buckets were filled with 10 pounds of hulls each and filled 3 inches below the top with the liquids.  Three buckets were filled with water and two buckets with a 5% acidity white vinegar.  Due to weather constraints, the water buckets were soaked indoors for 10 days and the vinegar buckets for 15 days.  Contents were stirred daily.  Hulls were removed from the liquid by straining through a jersey cotton cloth. The water buckets produced 10 gallons and the vinegar 5 gallons of Juglone liquid. Samples were stored in one quart glass jars and dropped off for analysis on November 25, 2014. Remaining Juglone liquid was stored indoors at no less than 60F and no more than 70F.  

Since my initial research into Juglone, I have found several people who used green unripe walnuts soaked whole to extract Juglone.  In the fall of 2015, unripe walnuts were collected and soaked in water.  Collecting from the tree would increase labor, however,  it should even out since the hulls were not be removed.

Laboratory analysis using Mass spectrometry found that neither the water walnut nor the vinegar walnut solution contained Juglone in levels above 0.4 parts per million.  It was decided to continue with the tests to see if even at a level of Concentration rates were as follows:
Water/Walnut Solution #1
3:1
2:1
1:1
0:1
Water/Immature Walnut Solution #2
0:1
Vinegar/Walnut Solution
3:1
2:1
1:1
0:1
5% Vinegar Only
0:1
Application was done by hand-held sprayers with all foliage being covered while avoiding contact with the soil.  Bush Honeysuckle and Multiflora rose were also cut to soil level and brushed with the solutions.  
Test plants
Primary, 20 each: cocklebur, multiflora rose, nightshades, and thistle
Secondary, 10 each: nettles, bush honeysuckle, poison ivy.
Due to an unusual amount of rain this year, all plants were sprayed at the mature stage.

RESULTS
The Water/Walnut solutions at all concentration levels had no effect on any test plants.
The Vinegar/Walnut solution caused slight burns/wilting at the 2:1 concentration after 7 applications and severe burns/wilting at the 0:1 concentration after 7 applications on all primary and secondary test plants.  At 3:1 there was no significant change to plant size, color, or growth.   At 0:1, only poison ivy, nightshades, nettles, and cockleburs died after daily applications for 14 days.  Both the bush honeysuckle and Multiflora rose stumps showed no regrowth after 3 applications of 0:1 solution. All stumps are still flagged for evaluation next spring.  While the results of the 0:1 Water/Vinegar solution seemed promising, after creating a Vinegar Only sample, the same results were obtained as the Vinegar/Walnut sample.

With all concentrations there was no collateral damage to surrounding plants.  Total rainfall for the 3 month test period was 8.56”, max temperature 95F, min temperature 77F.
While the application of the Juglone solution may not be appropriate for foliar application, further testing with vinegar to control invasives such as bush honeysuckle and multiflora rose could be promising. Furthermore, a vinegar application at a less mature plant stage may be more effective as well.