Don’t touch! How to identify and manage poison ivy in Christmas tree production – Part 2
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EmailManaging poison ivy early in Christmas tree rotation can help growers develop an effective control plan.
Poison ivy (Toxicodendron radicans L.) is one of the most common weeds in Christmas tree production (Photo 1). Poison ivy is known for creating contact dermatitis, a painful and itchy rash that most people who come into touch with it experience. Urushiol, a liquid component in the sap of the plant that is clear in color, causes the rash. Part 1 of this article series focused on the identifying characters and biology of this plant. Controlling poison ivy in their early stages is beneficial because it can compete strongly with the Christmas trees, especially during the establishment phase. Poison ivy growing is also a direct health issue for workers as well as customers. In this second part, we will be discussing the management strategies of poison ivy.
Non-chemical control
Mechanical removal of poison ivy should only be with proper precautions. Poison ivy seedlings that are small can be extracted while using gloves and protective clothes that block contact with skin. If the root system of poison ivy is well-established, manual removal is not a realistic method of control as any of the remaining roots can regenerate the plant. Proper scouting of poison ivy should be done in and around the Christmas tree field. Maintaining sanitation practices is also important to prevent movement of poison ivy seeds in the field.
Chemical control
Preemergence herbicides
Preemergence herbicides need to be applied prior to poison ivy emergence. This can provide effective weed control due to residual effects. These herbicides are effective when they are applied to the soil and later activated by either irrigation or rainwater. Indaziflam (Marengo 0.622 SC) and hexazinone (Velpar 2L) have shown to have fair preemergent control of poison ivy (Table 1).
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Table 1. Preemergence herbicides labeled for use in Christmas tree production that exhibited some effects in controlling poison ivy. (Adapted from “Weed Control in Christmas Trees” by Saha et al.) |
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|---|---|---|---|---|
|
Common name |
Trade name |
Rate of application (amount of product per year) |
Mode/site of action |
Efficacy |
|
indaziflam |
Marengo 0.622 SC |
7.5 to 15.5 fl oz/acre |
Inhibits the synthesis of cellulose |
Fair |
|
hexazinone |
Velpar 2L |
2 to 4 qt/acre |
Inhibitor of photosystem II |
Fair |
|
flazasulfuron |
Mission 25 WG |
2.14 to 2.85 oz/acre |
Inhibits acetolactase synthase (ALS) |
Poor |
Postemergence herbicides
The postemergence herbicides applied to control poison ivy may have adverse effects on Christmas trees, inducing phytotoxicity. These herbicides’ level of safety varies according to their chemical composition, the variety of trees they are used on and the seasonality of application. Therefore, it is essential that postemergence herbicides must be applied carefully and avoid contact with the tree foliage, especially during the growing season. Many postemergence herbicides have no control of poison ivy. Only triclopyr (Garlon 3 A) and glyphosate (Roundup Ultra 4L and many others) have good ratings (Table 2). Growers should read and follow the manufacturer’s label before applying any pesticide.
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Table 2. Postemergence herbicides labeled for use in Christmas tree production that exhibited some effects in controlling poison ivy. (Adapted from “Weed Control in Christmas Trees” by Saha et al.) |
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|---|---|---|---|---|
|
Common name |
Trade name |
Rate of application (amount of product per year) |
Mode/site of action |
Efficacy |
|
glyposhate |
Roundup Ultra 4L |
1 to 8 pint/acre |
Inhibits the shikimic acid pathway |
Good |
|
triclopyr |
Garlon 3A |
2 to 5 pint/acre |
A synthetic auxin |
Good |
|
2,4 – D |
Defy Amine 4 |
1 to 4 quartz/acre |
A synthetic auxin |
Fair |
For more Christmas tree weed control information, consider reviewing Michigan State University Extension bulletin E3237, “Weed Control in Christmas Trees.”
