Industrial hemp, derived from the Cannabis sativa L. plant, has seen a significant increase in cultivation across the United States. This crop is grown for its fiber, seed, and cannabinoid content. However, the expansion of hemp fields has introduced the plant as a novel forage source for local wildlife. Deer interaction has quickly emerged as a serious concern for growers, leading to substantial crop loss and economic damage. Understanding how deer interact with this crop, the effects consumption has on the animals, and implementing effective protection strategies are necessary for successful hemp cultivation.
Deer Palatability and Crop Damage
Deer readily consume industrial hemp, especially during its vegetative growth stages when the plant material is tender and palatable. Young hemp plants are attractive due to their nutritional profile, which includes a high protein content that deer seek for growth and maintenance. The plant’s natural defense mechanisms, such as pungent terpenes and cannabinoids, are not fully developed in these early stages, making the young growth an easy target.
The specific parts of the plant targeted are the tender leaves and the growing tips, a behavior known as browsing. This preferential feeding on the terminal buds causes the most damage, as it halts the plant’s vertical growth and forces it to bush out, significantly reducing the final yield. Beyond consumption, deer also inflict damage through trampling, which crushes plants, and through antler rubbing on mature, fibrous stalks, which can destroy the plant structure entirely.
Biological Effects of Hemp Consumption on Deer
Industrial hemp, by legal definition, contains less than 0.3% of the psychoactive compound delta-9-tetrahydrocannabinol (THC). This low concentration means that consumption does not result in the intoxicating effects associated with high-THC cannabis varieties. The risk of psychoactive intoxication in deer from consuming industrial hemp is negligible.
The primary cannabinoid is cannabidiol (CBD), which is not psychoactive but interacts with the endocannabinoid systems found in mammals. Cannabinoids influence various physiological processes, including appetite and inflammation. Deer appear to tolerate the consumption of hemp, often only seeking alternative forage after initial browsing. The high protein content remains the primary attractant, outweighing any potential minor digestive upset or aversive taste from the naturally occurring compounds.
Physical Exclusion Methods for Crop Protection
Physical barriers are the most reliable method for preventing deer damage to high-value hemp crops. A robust deer fence is the standard for exclusion, creating a permanent barrier that deer cannot easily breach. For white-tailed deer, a woven-wire fence must be a minimum of eight feet tall to be effective at preventing them from jumping over the barrier.
Alternatively, a double-strand electric fence uses the animal’s aversion to electrical shock as a psychological deterrent. This method typically involves two parallel fences: a three-to-four-foot perimeter fence with a single electric wire, and a taller, non-electric fence behind it. For larger fields, a high-tensile electric fence with multiple wires, energized to a minimum of 4,000 to 6,000 volts, is necessary. The bottom wire should be placed 10 to 12 inches above the ground to prevent crawling, and subsequent wires spaced progressively wider toward the top.
Individual Plant Protection
For smaller, high-value hemp plots, individual plant protection methods offer a focused defense. Cages constructed from welded wire mesh or hardware cloth can be placed around single plants to prevent browsing on the terminal buds. Trellis netting can also be used vertically to protect rows or horizontally to create a physical cover over young plants. These smaller-scale tactics are best suited for mother plants or breeding stock where the loss of a single specimen is a significant economic setback.
Chemical Deterrents and Cultural Practices
Sensory deterrents, commonly known as repellents, offer a non-physical approach to managing deer by making the hemp plants unpalatable or the area feel unsafe. These products fall into two categories: taste repellents, which contain foul-tasting compounds, and odor repellents, which emit strong, alarming smells. Common active ingredients include putrescent egg solids, which create a rotten smell, and capsaicin, which produces a burning taste on contact.
Repellents must be applied directly to the plant material and require frequent reapplication, typically every two to four weeks, or immediately after heavy rainfall. Deer can become accustomed to a single repellent over time, so rotating between two or three different products with distinct active ingredients is necessary to maintain effectiveness. Applying a sticker or anti-transpirant agent can also help the repellent adhere to the plant surface and resist weathering.
Cultural Practices
Cultural practices focus on altering the environment and plant management to reduce the likelihood of deer feeding. Avoiding the placement of hemp fields near known deer bedding areas or established travel corridors, such as wooded edges or stream banks, can reduce pressure. Modifying the habitat by clearing dense brush and cover near the field edge makes the area less appealing to deer, as they prefer to feed under cover of darkness or where quick escape is possible. Some growers utilize border crops, such as sunn hemp, planted early around the perimeter of the main crop to act as a lure, drawing deer away from the industrial hemp inside the boundary.