Deer Research Papers - Whole Articles



Development of a New Deer Repellent for the

Protection of Forest Resources



Bruce A. Kimball and Dale L. Nolte USDA/WS/NWRC, Fort Collins, CO 80521.

We have identified hydrolyzed casein as a promising repellent for minimizing damage to forest resources inflicted by browsing ungulates. Eight and twelve percent hydrolyzed casein formulations prepared in water with a latex-based agricultural sticker significantly reduced browse damage by captive black-tailed deer (Odocoileus hemionus columbianus) to western redcedar (Thuja plicata) saplings. These repellent formulations can be prepared by the user at significant cost savings versus commercial products. West. J. Appl. For. 21(2):108–111.


Largely because of deer management strategies and increased forage availability, deer populations have rapidly increased throughout North America throughout the past decades (Cote et al. 2004). Overabundance has contributed to significant economic losses in transportation, agriculture, and forestry, as well as to transmission of disease. Deer damage to agriculture has been recognized as a substantial economic problem for some time (Wywialowski 1998). In the Pacific northwestern United States, damage to forest resources by black-tailed deer is considered a significant impediment to reforestation efforts (Nolte and Dykzeul 2002). Increased agricultural losses because of deer browse have also been reported in Europe (Santilli et al. 2004). Browse damage can be lethal to plants, while also reducing the future value of crops via decreased yields and plant deformities (Nolte 1998). However, browse damage is not limited to commercial agriculture and reforestation efforts. Overabundant deer may have a significant impact on plant community structure and ecosystem properties (Cote et al. 2004). High rates of deer browsing suggest the possible extinction of valuable forest understory herbs (Mcgraw and Furedi 2005). A number of commercially available products are marketed to deter browsing of trees and shrubs by deer. These products contain a broad range of presumed active ingredients—some more effective than others (Nolte and Wagner 2000). The majority of these products are contact repellents that must be applied directly onto the plants to be effective. Among contact repellents, four different modes of action have been proposed: flavor aversion learning, taste modification, chemical irritation, and fear (Nolte and Wagner 2000). We recently demonstrated that a number of methionine containing proteins minimize browsing by making treated plants less palatable to deer (Kimball and Nolte 2005). Among these, casein has the potential for commercial use as a deer epellent. Here, we describe three experiments conducted to evaluate several protein sources as repellents for protecting conifers from deer browse damage. We sought to develop a new repellent formulation that effectively minimized browse damage, was easy to prepare in water, and was relatively inexpensive versus commercial repellent products.


Materials and Methods


Baker’s soy flour was provided by Archer Daniels Midland Co. (Decatur, IL). Egg Albumen was provided by Belovo, Inc. (Pinehurst, NC). Complete milk protein (CMP), edible acid casein (EAC), and hydrolyzed casein (HC) were purchased from American Casein Co. (Burlington, NJ). Methionine was purchased from Aldrich Chemical Co. (Milwaukee, WI) and hydrated lime (Kemilime) from Ash Grove Cement Co. (Overland Park, KS). Methionine was added to lime to yield a test treatment that was 5% methionine for experiment 1. Deer-Away Big Game Repellent powder (BGR-P; IntAgra, Inc., Minneapolis, MN) was used as a positive control in experiment 2. Ready-to-use premixed Plantskydd Deer Repellent (Tree World, Inc., Des Moines, IA) was used as the positive control in experiment NOTE: Bruce Kimball can be reached at (970) 266-6069; Fax: (970) 266-6063; Mention of specific products does not constitute endorsement by the US Department of Agriculture. A portion of this research was funded by USDA CSREES IFAFS Program Code 14.1: Alternative Natural Resource Management Practices for Private Lands (grant no. 2001-52103-11215). Copyright © 2006 by the Society of American Foresters. 108 WJAF 21(2) 2006 3. The agricultural sticker Tactic (Loveland Products, Greeley, CO) used to adhere treatments to the conifer seedlings in all experiments was provided by the manufacturer.


Deer and Facilities

Forty-eight captive 1- to 3-year old, black-tailed deer (Odocoileus hemionus columbianus) were used for the bioassays conducted in 0.2 ha outdoor pens. The same 24 deer were used in experiments 1 and 2; whereas 24 different deer were used in experiment 3. Shelter and ad libitum pelleted basal ration (USDA Deer Pellet; X-Cel Feeds, Tacoma, WA), water, and mineral block were provided throughout each experiment. Naturally occurring forage in the pens was limited to an assortment of cool season grasses. The experiments were conducted February 2004 to February 2005 and approved by the Institutional Animal Care and Use Committee of the USDA National Wildlife Research Center.


Experiment 1

In each of eight 0.2-ha pens, western redcedar (Thuja plicata) saplings (_60 cm) were planted in five unique plots consisting of 12 trees per plot arranged in a 3 _ 4 arrangement with 1 meter spacing. To assure independence of treatments, plots were separated by at least 3 meters and treatments were randomly assigned (each treatment represented by one plot in each pen). Treatments were applied by spraying individual saplings uniformly with 0.054% (v/v) Tactic solution in tap water with a tank-type garden sprayer. The wetted saplings were immediately dusted by hand with the appropriate powdered treatment. The four methioninecontaining treatments were: egg albumen, CMP, 5% methionine in lime, and Baker’s soy flour. Lime was included in the experiment as a control. Three deer were confined to each pen for the duration of the experiment and provided ad libitum access to test trees for 22 days. The number of bites on each tree were recorded on days 1, 2, 3, 4, 5, 7, 8, 12, 16, 19, and 22, or until the individual tree was completely consumed (defined as 25 cumulative bites) according to previously established procedures  (Nolte 1998). Severe browse damage was defined as 10 cumulative bites to an individual tree. Experiment 1was conducted from Feb. 2 to 27, 2004.


Experiment 2

Experiment 2 was similarly conducted with five plots replicated in eight pens except that each plot consisted of nine western redcedar saplings in a 3 _ 3 array. The five treatments consisted of three casein-related sources: CMP, EAC, and HC, a positive control (BGR-P), and a control [0.054% (v/v) Tactic spray only]. Three deer were confined to each of eight pens for the 16 days of the experiment. The number of bites on each tree were recorded on days 1, 2, 3, 6, 9, 13, and 16, or until the individual tree was completely consumed. Experiment 2 was conducted from May 26 to June 11, 2004.


Experiment 3

The final experiment was similarly conducted with six plots (12 western redcedar saplings per plot in 3 _ 4 array) in each of eight 0.2-ha pens. The six treatments used in experiment 3 consisted of four HC solutions, Plantskydd, and a control (Tactic only). For this experiment, the sticker was mixed with tap water at a concentration of 0.26% (v/v). The four HC solutions were prepared by adding the powder to the sticker solution to yield HC concentrations of 2, 4, 8, and 12% (w/v). Treatments were applied to the saplings by handheld spray bottle. During application, occasional shaking of the container was required to keep HC suspended in the 8 and 12% solutions. Three deer were confined to each pen for the duration of the experiment and provided ad libitum access to test trees for 21 days. The number of bites on each tree were recorded on days 1, 2, 3, 4, 7, 9, 14, and 21, or until the individual tree was completely consumed. Experiment 3 was conducted from Jan. 27 to Feb. 16, 2005.


Statistical Analyses

For each experiment, a Kaplan-Meier survival analysis was performed to compare survivability distribution functions among treatments, using the Wilcoxon test of equality (PROC LIFETEST; SAS/STAT 2002, SAS/STAT version 9.1; SAS Institute Inc., Cary, NC). Failure day was defined as the first experimental day when severe browse (10 cumulative bites) was measured on an individual tree. Trees that survived to the end of the experiment (did not meet definition of failure) were assigned a failure day of 25 and censored according to the standard application of survival analysis. Failure data were also analyzed by ranking failure day among treatments in each pen (1 _ shortest failure day) and subjecting the rank data to Kruskal-Wallis analysis (Iman 1982). Rank was the rsponse for the nonparametric analysis with treatment the fixed effect. Multiple comparisons of mean ranks were made using Fisher’s least significant difference (LSD option; SAS/STAT 2002). A separate analysis was conducted for each of the three experiments.



Survivability functions differed significantly among treatments in all experiments (P _ 0.0001; Figures 1, 2, and Figure 1. Survivability functions for western redcedar (Thuja plicata) saplings treated with three different protein sources, 5% free methionine in lime, and a control (lime only) in experiment  1. Deer had ad libitum access to the treated saplings for 22 days. . . . . . . , complete milk protein; , albumen; _ _ _ , soy; _ _ . . , free methionine; _ . _ , lime (control). WJAF 21(2) 2006 109 3). In experiment 1, all trees treated with Baker’s soy flour, 5% methionine, or lime were severely browsed (defined as

10 bites) by day 16 of the experiment (Figure 1). Forty percent of trees treated with CMP and 26% of trees treated with albumen were not severely browsed by the end of the experiment. Kruskal-Wallis analysis of the ranked data in experiment 1 demonstrated a significant treatment effect (P _ 0.0001) with multiple comparisons of the means indicating that failure day rank followed the order: CMP _ albumen _ soy _ 5% methionine _ lime. Kruskal-Wallis analysis of the ranked data from experiment 2 demonstrated that CMP, EAC, HC, and BGR-P were each effective in minimizing browse with respect to the control (P _ 0.0001). One hundred percent of trees treated with the casein sources or BGR-P were protected from browse damage (Figure 2). Conversely, 71% of control trees were severely browsed by the end of the 16-day experiment. The results of experiment 3 established that deer avoidance of HC-treated trees was concentration-dependent (Figure 3). Kruskal-Wallis analysis of the ranked data demonstrated a significant treatment effect (P _ 0.0001) with multiple comparisons of the means indicating failure day rank followed the order: Plantskydd _ 12% HC _ 8% HC _ 4% HC _ 2% HC _ control.



In each experiment, treatments were visibly apparent as white- or cream-colored powder adhering to unbrowsed foliage throughout the tests. There was no indication that plot assignment, or proximity of a treatment plot to another, impacted relative preference for the treatments. This is consistent with the observation that deer repellents such as BGR-P and Plantskydd have “aversive distances” of less than 1 meter (Nolte and Wagner 2000). This is the distance from a repellent-treated food source that deer will avoid an untreated test food. In practice, the aversive distance of contact repellents is typically 0 meters, wich is why reapplication is frequently necessary to protect new growth. Therefore, 3 meters was considered sufficient distance between plots to avoid confounding effects of treatment interaction in these experiments. The treatments used in experiment 1 were chosen because they each contain methionine. Many proteins do not contain methionine or are methionine-limited (Friedman 1996). For example, porcine collagen (gelatin) contains  litthionine and was not avoided by deer (Kimball and Nolte 2005). Among experiment 1 treatments, CMP and albumen contain approximately six times more protein bound. methionine than Baker’s soy. Previous chemical analyses demonstrated that methionine was protein-bound (i.e., not present as the free amino acid) in these sources (Kimball and Nolte 2005). The proteins used in these experiments all contained less than 5% methionine. Experiment 1 confirmed that CMP and albumen were more effective repellents than soy flour, which has low methionine content. More importantly, results of experiment 1 suggest that proteins with protein-bound methionine were more effective than the free amino acid. Although Kruskal-Wallis analysis established that the 5% methionine treatment was more effective than the control (lime only), it was no more effective in reducing browse damage than the soy treatment that has low levels of protein-bound methionine. Additionally, consumption of the lime control in experiment 1 indicated that avoidance of protein treatments did not result from simple tactile or visual cues. Experiment 2 was designed to compare the repellency of three casein sources versus a positive control. CMP contains all protein fractions present in skim milk (whey and casein). EAC is the casein fraction of skim milk. HC is the enzymatic digest of casein. Enzymatic hydrolysis yields small peptides and free amino acids from the intact proteins. BGR-P was chosen as the positive control for this experiment because it is a powder that could be delivered in the same manner as the casein treatments. Furthermore, it is a contact repellent with proven efficacy in bioassays with  captive deer (Nolte and Wagner 2000). Activity of BGR-P is attributed to short-chained aliphatic aldehydes produced by auto-oxidation of egg lipids (Oita et al. 1977). The results of experiment 2 demonstrated that CMP, EAC, and HC were each as effective as the positive control. The results of experiments 1 and 2 indicated that methionine-containing proteins as well as hydrolysates of methionine-containing proteins are potentially effective deer repellents that warrant further investigation. They further suggest that of the numerous products of casein hydrolysis, the active ingredient(s) are probably small peptides containing methionine—not methionine present as the free amino acid. The decision to focus on HC for the development of a new repellent was based on the assumption that its water solubility would be greater than intact proteins as a consequence of the hydrolysis process. The choice of HC was further justified when it was demonstrated that white-tailed deer (Odocoileus virginianus) avoided HC-treated food, but not EAC-treated food in one-choice feeding trials after food deprivation (Kimball et al. 2005).


Experiment 3 was conducted to determine the effective HC concentration required to minimize deer browsing. Ready-to-use, premixed Plantskydd was used as the positive control for this experiment because the liquid could be applied to the test trees in identical manner as the HC formulations. Plantskydd (active ingredient dried blood) has also exhibited proven efficacy as a contact repellent in bioassays with captive deer (Nolte and Wagner 2000). The efficacy of the HC treatments was directly proportional to HC concentration. Plantskydd, 8% HC, and 12% HC all effectively reduced deer browsing of a preferred conifer species throughout the 3-week period of the experiment. Browse damage to saplings treated with Plantskydd, BGR-P, and various casein sources varied among the three experiments. For example, not a single tree treated with CMP was severely browsed in experiment 2. Conversely, 60% of trees treated with CMP were severely browsed in experiment 1. The motivation of herbivores to use a particular resource is subject to many variables, including experience with the food, nutritional state, and food alternatives (Provenza 1995). This is true for deer browsing of agricultural resources in natural systems as well as the experiments described here. It is unlikely that the deer’s motivation to browse test trees was consistent among experiments. Accordingly, the results from each experiment must be considered independently. Any comparisons among the three experiments can only be made with respect to the control treatments. These experiments indicate that HC is an effective repellent for reducing browse damage to forest resources. Specifically, a liquid formulation consisting of 8% or 12% HC with 0.26% latex-based sticker shows great promise for operational use. Although this formulation offers no advantages versus commercially available products with respect to labor investments (it must be delivered to seedlings in the same manner as the commercial products), potential savings in material costs are significant. At the time of publication, a 12% HC formulation would cost approximately $6 USD per 4.0 L in total material costs. Four liters would be capable of treating _500 30-cm seedlings. This price is based on the current retail price for the latex sticker and the cost of HC when purchased in bulk (e.g., 900 Kg pallet). The price per equivalent volume when HC is purchased in smaller quantities (e.g., 22 Kg bags) would be approximately $8 USD. The cost of an HC repellent formulation could be significantly reduced by using an 8% HC formulation, which was found to be as effective as the 12% formulation in these bioassays. However, because the price of HC is subject to worldwide milk stores and economics, the price of a HC repellent formulation could fluctuate proportionally. By comparison, commercial deer repellent products purchased in bulk or concentrate typically cost between $15 and $25 USD per equivalent coverage.


Literature Cited

COTE, S.D., T.P. ROONEY, J.P. TREMBLAY, C. DUSSAULT, AND D.M. WALLER. 2004. Ecological impacts of deer overabundance. Annu. Rev.Ecol. Evol. Syst. 35:113–147.

FRIEDMAN, M. 1996. Nutritional value of proteins from different food sources. A review. J. Agric. Food Chem. 44:6 –29.

IMAN, R.L. 1982. Some aspects of the rank transform in analysis of variance problems. P. 676–680 in Proc. of the Seventh Annual SAS Users Group International. SAS, Cary, NC.

KIMBALL, B.A., AND D.L. NOLTE. Animal tissue-based herbivore repellents: Scary odors or altered palatabilty? In Advances in vertebrate pest management: Proc. of the Fourth European Vertebrate Pest Conference, Feare, C., and D.P. Cowan (eds.). Filander, Furth, Germany. In press.

KIMBALL, B.A., D.L. NOLTE, AND K.B. PERRY. 2005. Hydrolyzed casein reduces browsing of trees and shrubs by white-tailed deer. HortScience 40:1810 –1814.

MCGRAW, J.B., AND M.A. FUREDI. 2005. Deer browsing and population viability of a forest understory plant. Science 307:920 –922.

NOLTE, D.L. 1998. Efficacy of selected repellents to deter deer browsing on conifer seedlings. Int. Biodeterior. Biodegrad. 42:101–107.

NOLTE D.L., AND M. DYKZEUL. 2002. Wildlife impacts on forest resources. Human conflicts with wildlife: Economic considerations. P. 163–168 in

Proc. of the Third NWRC Special Symposium, Clark, L. (ed.). National Wildlife Research Center, Fort Collins, CO.

NOLTE, D.L., AND K.K. WAGNER. 2000. Comparing the efficacy of delivery

systems and active ingredients of deer repellents. P. 93–100 in Proc. Of the Nineteenth Vertebrate Pest Conference, Salmon, T.P., and A.C. Crabb (eds.). University of California, Davis, CA.


Method for using a ruminant repellent comprising aliphatic aldehydes. US Patent no. 4065577.

PROVENZA, F.D. 1995. Postingestive feedback as an elementary determinant of food preference and intake in ruminants. J. Range Manage. 48:2–17.

SANTILLI, F., L. MORI, AND L. GALARDI. 2004. Evaluation of three repellents for the prevention of damage to olive seedlings by deer. Eur.J. Wildl. Res. 50:85– 89.

WYWIALOWSKI, A.P. 1998. Are wildlife-caused losses of agriculture increasing? P. 363–370 in Proc. of the 18th Vertebrate Pest Conference, Baker, R.O., and A.C. Crabb (eds.). University of California, Davis, CA. WJAF 21(2) 2006 111


Comparison of Commercial Deer Repellents

The Olympia Field Station of the USDA Animal and Plant

Health Inspection Service,
Wildlife Services, National Wildlife Research Center has conducted numerous studies to identify trends that could help predict the efficacy of repellents. A recent test evaluated 20 commercially available repellents representing a variety of active ingredients (Wagner and Nolte 2001).

How Repellents Work
Deer repellents generally rely on fear, conditioned avoidance, pain, or taste. Fear-inducing repellents contain compounds that emit sulfurous odors (such as predator urine, meat proteins, or garlic). We interpret the avoidance of these odors as a fear response, suggesting herbivores perceive sulfurous odors as indicators of predator activity. Conditioned avoidance occurs when ingestion of a food is paired with nausea or gastrointestinal distress. Animals generally don’t eat as much of a food if it is associated with illness. Active ingredients, such as capsaicin, allyl isothiocyanate, and ammonia, cause pain or irritation when they contact trigeminal receptors in the mucous membranes of the mouth, eyes, nose, and gut. An inherent problem of using pain repellents is that they are universally aversive to all mammals. Bad taste can also induce avoidance.Bittering agents are often used to induce a bad taste. Unfortunately, while omnivores normally avoid bitter tastes, herbivores are generally indifferent, at least at the concentrations used in most repellents.

Delivering Repellents

Repellents may be incorporated into the plant (systemic delivery), spread throughout an area (area delivery), or applied to the plant (contact delivery). Systemic repellents are compounds absorbed and translocated by the plant, endering the foliage less desirable. Systemic delivery is ideal. The repellents are contained within the plant. They cannot be washed off, and the aversive agents are moved to new foliage as it grows. Few, if any, products have effectively incorporated repellents into a plant at concentrations that did not harm the plant.

Table 1—Product names, sources, active ingredients, and modes of action for repellents evaluated as a means of reducing black-tailed deer damage to western red cedar seedlings during deer repellent tests from October 1998 to July 1999 at Olympia, WA.

Mode Product and Manufacturer Active Ingredient

1CA Detour (Sudbury Consumer Products Co., Phoenix, AZ) 7% thiram

Fear Deerbuster’s Coyote Urine Sachet (Trident Enterprises, Frederick, MD) 50% coyote urine

Fear Wolfin (Pro Cell Bioteknik, Hornefors, Sweden) Di (N-alkyl) sulfides

Fear Deerbuster’s Deer and Insect Repellent (Trident Enterprises, Frederick, MD) 99.3% garlic juice

Fear Deer Away Big Game Repellent Powder (IntAgra, Inc., Minneapolis, MN) 36% putrescent whole egg solids

Fear Deer Away Big Game Repellent Spray (IntAgra, Inc., Minneapolis, MN) 4.93% putrescent whole egg solids

Fear Bye Deer (Security Products Co., Phoenix, AZ) 85% sodium salts of mixed fatty acids

Fear Hinder (Pace International LP, Kirkland, WA) 0.66% ammonium soaps of higher fatty acids

Fear Plantskydd (Tree World, Lackawanna, NY) 87% edible animal protein (in concentrate)

Pain Hot Sauce (Miller Chemical and Fertilizer Corp., Hanover, PA) 0.53% capsaicin and related compounds

Pain Get Away Deer and Rabbit Repellent (DRR), IntAgra, Inc., Minneapolis, MN) 0.625% capsaicin and related compounds, 0.21% isothiocyanate

Taste Ropel (Burlington Scientific Corp., Farmington, NY) 0.065% denatonium benzoate, 0.35% thymol

Taste Tree Guard (Nortech Forest Technologies, Inc., St. Paul, MN) 0.2% denatonium benzoate

Taste Orange TKO (TKO Industries, Calgary, Alberta, Canada) d-limonene

Multiple Deer Stopper (Landscape Plus, Chester, NJ) 3.8% thiram, 0.05% capsaicin, 1.17% egg solids

Multiple Not Tonight Deer (Not Tonight Deer, Mendocino, CA) 88% dehydrated whole egg solids, 12% Montok pepper (in concentrate)

Multiple Plant Pro-Tec (Plant Pro-tec, LLC, Palo Cedro, CA) 10% oil of garlic, 3% capsaicin and related compounds

Multiple Dr. T’s Deer Blocker (Dr. T’s Nature Products, Inc., Pelham, GA) 3.12% putrescent whole eggs, 0.0006% capsaicin, 0.0006% garlic

Multiple Deerbuster’s Deer Repellent Sachets (Trident Enterprises, Frederick, MD) 99% meat meal, 1% red pepper

Multiple N.I.M.B.Y. (DMX Industries, St. Louis, MO) 0.027% capsaicin and capsaicinoid product, 4.3% castor oil

Area repellents are products that create a chemical barrier animals will not cross, or products that permeate an area with an odor that cause animals to avoid the area. Little evidence suggests animals will abandon areas treated with area repellents except when highly palatable alternative foods are readily available elsewhere. Contact repellents are products that are topically applied or attached directly to a plant. If the goal is to reduce consumption of plants, available evidence suggests that chemical repellents are most effective when they are applied directly to the plants.

Test of Commercial Repellents

A study directly compared 20 commercially available deer repellents. These products relied on fear, conditioned avoidance, pain, and taste. Fifteen products were contact repellents. The others were area repellants. All products were applied according to the manufacturer’s recommendations. An initial test to screen all 20 repellents was conducted during the winter while seedlings were dormant. Tests were conducted in five pastures containing five or six captive blacktailed deer (Odocoileus hemionus columbianus). Pastures varied from 2 to 5 acres with natural habitat consisting of Douglas-fir, alder, and associated understory vegetation (figure 1). Trees were planted in 21 plots scattered evenly across each pasture. A separate plot was used for each repellent with one plot of untreated seedlings serving as a control. Plots consisted of three rows of three western red cedar (Thuja plicata) seedlings planted at about 3 Figure 2—Olympia Field Station personnel planting western red cedar for the deer repellent tests. The 20-inch seedlings were planted at 3-foot intervals in three rows. 3-foot intervals. At planting, seedlings were about 20 inches high with many lateral branches (figure 2). All seedlings were planted immediately before treatment. Seedlings were examined for browse damage at 24 hours, 48 hours, and 1 week after planting, and then at 1-week intervals for 18 weeks. Damage was determined by counting the number of bites taken from each seedling. No more than 25 bites were recorded because seedlings were generally defoliated by then. Seedlings pulled from the ground were considered destroyed and recorded as having 25 bites. Efficacy of repellents may vary depending on several factors, including available resources and seasonal changes in plant palatability. Red cedar seedlings are generally more palatable after winter dormancy has broken. Therefore, repellents that worked during the winter were tested again during the spring when seedlings were actively growing.


Figure 3 shows the results of the winter test. None of the repellents eliminated deer browsing throughout the 18-week test. However, there were distinct differences among the repellents. In general, topical repellants performed better than area repellents. Fear-inducing repellents performed better than the other types of repellents. Eight of the nine repellants considered most effective for the first 11 weeks emitted sulfurous odors. Repellents containing decaying 4 animal proteins, such as egg or slaughterhouse waste, appeared to be the most effective. These repellents include Deer Away Big Game Repellent Powder (and liquid), Bye Deer Sachets, Deerbuster’s Sachet, and Plantskydd.Results were similar for the test conducted during spring 1999 (figure 4). None of the repellents provided complete protection throughout the 11-week test. Deer Away Big Game Repellent Powder was the most effective repellent tested, followed by Plantskydd, Deerbuster’s Sachets, and Bye Deer Sachets. Get Away Deer and Rabbit Repellent failed to protect seedlings during this test.


During trials comparing the efficacy of repellents, those emitting sulfurous odors are generally the most effective. Deer Away Big Game Repellent Powder has been effective in several trials conducted by the Olympia Field Station, as well as in trials conducted by others. Browsing generally is eliminated for 4 weeks. The repellent provides good protection for 8 to 12 weeks, sometimes longer. Efficacy can be expected to decline significantly after 12 to 16 weeks. Surprisingly few commercial repellents have effectively incorporated trigeminal irritants as active ingredients. Most likely, current repellents that depend on pain to induce avoidance are ineffective because concentrations are too low. Taste repellents, such as bittering agents, have proven ineffective in most trials. Efficacy of repellents based on conditioned avoidance is generally limited because animals must be trained to avoid these materials. Damage inflicted on seedlings during training or subsequent sampling can be extensive. Repellents based on training are not likely to be effective for a transitory or migratory species (such as elk moving from winter to summer range). Repellency is always susceptible to failure (Mason 1998). Many factors other than aversive properties affect a repellent’s efficacy. Ultimately, avoidance of the protected plant is affected by: . Number and density of the animals inflicting problems. . Mobility of the problem animals.. Prior experience of animals with foods and their familiarity with the surroundings. . Accessibility of alternative sites.. Availability of alternative foods. . Palatability of the treated plants. . Weather conditions. Repellents that protect highly palatable plants from dense animal populations with few alternative foods will probably be effective under more favorable conditions. However, repellents that are successful under favorable conditions are not necessarily likely to be successful under less favorable conditions. It is difficult for someone to predict the efficacy of repellents in the field by extrapolating from empirical data. Anecdotal or testimonial evidence is even less reliable.

Source Material

This Tech Tip summarizes two manuscripts produced by the Olympia Field Station:

Nolte, D. L.; Wagner, K. K. 2000. Comparing the efficacy of delivery systems and active ingredients of deer repellents. In: Proceedings of the 19th Vertebrate Pest Conference. 19: 93–100. Wagner, K. K.; Nolte, D. L. 2001. Comparison of active ingredients and delivery systems in deer repellents.Wildlife Society Bulletin. 29: 322–330. Another report with information on this subject is:Mason, J. R. 1998. Mammal repellents:options and considerations for development. In: Proceedings of the Vertebrate Pest Conference. 18: 325–329. Repellents emitting sulfurous odors were the most effective. Deer Away Big Game Repellent Powder virtually eliminated browsing for 4 weeks. It provided good protection for 8 to 12 weeks, sometimes longer.

This isn't a "research" paper but good practical testing is still good to read. If you want to know more abou these repellents and several others, then check out our Repellent pages.

Combination Deer Repellent
Taste Repellent
Odor Repellent

Are you frustrated with deer defoliating your prized plants overnight? Are you ready to learn about some products that others have used that really do work ?

This summer we have tested some products that our local garden center and some catalogs offered to see which deer resistant products worked and which ones didn't. The following are the deer deterrents that we tried and the results.

The first product we used was Liquid Fence. This is a natural deer and rabbit repellent. It is true what the cover states... "It really works." Clark Kaskie , the inventor of Liquid Fence, developed this product out of frustration of having his plants eaten by all types of critters. After trying many different kinds of homemade remedies and expensive over the counter products, he decided to make his own repellent. Being a chemical engineer for over 60 years gave him a good idea of where to start. He knew he wanted it to be both environmentally safe and safe for the animals. After a few years of experimenting, he came up with this solution. His friends and wife tried it and told him that it worked "just like a liquid fence," so that's what he named it. All you do is spray the liquid liberally onto plants and their perimeter during a dry period. Repeat the process 1 week later and then approximately once per month thereafter. If areas where feeding pressure from deer and rabbits is intense, he suggests spraying it once a week for 3 weeks and then about once per month after that. You are really "training" the deer and rabbits to stay away. We found that this product smells pretty bad when you first apply it, but it really does work. We had some coneflowers that the rabbits where nipping at the stems. After applying this as directed, the nibbling stopped. We also had success with using it on our hibiscus trees and other annuals, perennials, as well as our gourds.

The second product we tested was The Wireless Deer Fence. It works like a baited electric fence but without the wires. Instead, it contains individual posts, 19 inches tall and weighing 6 ounces, that are positioned around plants that deer like and on deer paths into your yard or garden. The deer in your yard are attracted by a sweet smell to touch a post, then the post will deliver a harmless shock which frightens them from the area. It is recommended to use this product along with a deer resistant spray while you are "training" the deer. The idea is to put the post between 5 and 25+ feet apart where the deer will find them. The distance varies widely depending on terrain existing barriers, landscaping, etc.

We used this product mainly to keep the deer away from my new Pinky-Winkie hydrangeas. We still had a little damage while the deer were being trained, but I hadn't used a deer detterent spray on them at the time. The directions suggest this just while you are "training" the deer. With this product it helps to read all of the directions! I liked The Wireless Deer Fence. My Pinky-Winkies still haven't been eaten. It gives an added protection to using the Liquid Fence.

We tested these products in our 5 acre garden with a variety of deer resistant perennials, such as coneflowers, grasses, and hellebores. Plant as many of these types of plants as possible. That is your first tactic when gardening with deer. For more information on plants that deer don't like, visit Even after you have planted several deer proof plants, you will still need to protect your other vegetation with some type of product.

As reported in the book Deerproofing Your Yard and Garden, by Rhonda Hart, if you take a look at state agricultural reports, you will see that deer do millions of dollars of damage each year. It's not surprising when you realize that one acre of a healthy environment can support 18-24 deer per square mile. These deer can consume 6 to 10 pounds of greenery per day. This equates to about half a ton of plants over the growing season. So, there goes your yard!

With Liquid Fence and The Wireless Deer Fence, along with planting deer resistant plants, you can at least learn to coexist with the deer and make the damage minimal. Both of these products have a money back guarantee.

By: Julia Stewart

About the Author:
Julia is a Master Gardener, floral designer, and garden crafter. Married to a landscape contractor, they enjoy gardening on their 5 acre flower farm and sharing it with others. Visit their web site at

Check out these products at the links listed above. For something that will end up being cheaper in the long run, check out our page Mechanical Deer Control to read about some new mechanical controls that will save you having to spray at all unless you have a very big area.