1. Dealing with Deer Impacts and Damage to Crops in NYS
Suburban Damage in New York
Dr. Paul D. Curtis
Department of Natural Resources
Cornell University, Ithaca, NY
Collaborative Deer Management Outreach Initiative

2. Problems Caused by Deer Overpopulation
Deer cause several negative impacts in suburban areas including deer-vehicle accidents, damage to ornamentals, damage to crops and gardens, influences on tick abundance and diseases, and impacts to forest regeneration and wildflowers in woodlots and parks. Vegetation damage also impacts biodiversity and the abundance of songbirds and other wildlife.

3. Deer-related vehicle accidents (DRVAs) are an important safety concern
Deer-related vehicle accidents (DRVAs) are an important safety concern. Motorists may hit 100,000 or more deer on NYS highways each year. It is difficult to find reliable data because of the different ways DRVAs are recorded by a variety of law enforcement agencies and highway departments.

4. 150+ Human Fatalities per year
We do know that people lose their lives in DRVAs each year in the US. It is common for larger states like NY or PA to have two or three fatal DRVAs each year, and many other drivers are injured. National statistics show about 4% of DRVAs result in a human injury that is reported. Insurance data show that each reported DRVA results in >$4,000 in vehicle repair costs.

5. Ways to Reduce DRVAs Education for motorists is important
Use extra caution while driving during Oct., Nov., and Dec.
Be careful when driving at dawn or dusk
Note areas with deer crossing signs and places where deer cross roads
Scan the roadsides for eye reflections
Manage herd density where possible
Education is important for motorists. People need to know when deer are most likely to cross roads, such as during the rut (Oct. to Dec.), and near dusk or dawn. Also learn how to identify deer eye-shine in headlights and note areas where deer often cross roads. Data clearly show that significantly reducing deer numbers in an area will also lower the number of DRVAs.

6. Seasonal Trends in DVCs
Old DRVA records from NYSDEC clearly show that deer-related vehicle accidents peak during November, the peak of the deer breeding season. There is also a smaller increase in DRVAs during May and early June as yearling deer (mostly bucks) disperse out of their birth home ranges before the new crop of fawns is born. These records don’t show this early summer dispersal that we see with tagged and collared deer.

7. Bells and Whistles …Don’t Work!
Many types of devices are supposed to emit sounds that scare deer from roadways. There is no research evidence that these devices actually work. Most produce sounds in the ultrasonic range that people can’t hear. However, ultrasound transmits poorly, and there is no behavioral reason deer should pay any attention to these sounds.

8. Black-legged (‘Deer’) Tick Ixodes scapularis
Nymph
Male and female
There are two main tick species targeted by the 4-Poster technology. Both utilize various wildlife as hosts, but deer are considered the most important. Blacklegged, also called deer tick, are shown here. The adult male is at left of the larger female. Both adults and nymphs can transmit the pathogen causing Lyme disease. Although nymphs carry the pathogen at much lower rates than adults, they are less easily detected. There is one smaller stage, the larvae, which are about the size of a period at the end of a sentence and they do not carry the pathogen. The white-footed mouse is the primary reservoir of the Lyme pathogen.
Iowa State Univ.
Larva 8

9. Lone Star Tick Amblyomma americanum
1st documented Long Is (Montauk) 1971 (Good 1973)
1st documented Fire Is.1988 (Ginsburg et al. 2002)
• Birds
• Mammals
Female
The lone star tick, so-named for the white dot on the back of the adult female, is a relative newcomer to NYS, having been reported from Montauk in 1971 (1st LI occurrence, breeding population) & Fire Island in It has since become the dominant species, quite common. This slide shows the adult female and male, as well as the small nymph at center surrounded by numerous larvae. All stages have a particularly irritating bite, causing an itching welt that lasts for weeks. The larvae, which are most common from mid- to late summer, are the reason some believe they have been bitten by chiggers, which are not known to occur around Long Island. Often hundreds of lone star larvae will crawl onto and bite their host, making for a very annoying and painful experience!
Male
Nymph & larvae 9

10. Pathogens, Hosts, Vectors, Reservoirs
Disease
Tick
Vector
Reservoir
E. chaffeensis
HME
(Erlichiosis)
Lone star
deer
A. phagocytophilum
HGE
(Anaplasmosis)
BL, Am. dog
deer, small mammals (w-f mouse)
B. burgdorferi
Lyme
(Borreliosis) BL
rodents
B. microti
Babesiosis
w-f mouse, rodents
Bartonella spp.
Bartonella
BL?
rodents, cats, cattle, dogs
Black-legged ticks can carry the pathogens causing babesiosis and anaplasmosis, along with the bacterial spirochete responsible for Lyme disease. Lone star ticks can carry the pathogens causing erlichiosis, which can cause flu-like symptoms and be quite debilitating, or even fatal. Deer are the main reservoir for this pathogen.
Clin Microbiol Rev Jul;13(3):428-38
Emerging Inf. Diseases CDC Mar (3)
J Clin Microbiol ,Aug.1992,p
BL = blacklegged (deer) tick 10

11. The chart shows reported Lyme disease incidence in NY to 2009
The chart shows reported Lyme disease incidence in NY to Suffolk County and the lower Hudson Valley are the ‘hotbed’ areas for Lyme disease in NYS. We don’t have good data for therapy, such as numbers of prescriptions for control of diagnosed disease or for preventive treatment.
Source: 11

12. Managing Lyme Disease Direct reductions in deer densities (??)
Fencing to exclude deer from sensitive areas (parks, playgrounds, etc.)
Self-application of acaricides to deer via 4-Poster Device (only on LI)
Landscaping changes
From a few past island studies, it was shown that deer densities need to be <10 deer per square mile in order for tick populations to decline. This is probably not feasible in most suburban areas, especially those closed to hunting. Fencing should be used to exclude deer from sensitive areas such as playgrounds and parks where children may play in lawns or natural areas. The 4-Poster Device applies a pesticide (permethrin) to deer to kill ticks. Currently this is only registered for use on Long Island, and is intended for application at the community scale (not individual properties). Homeowners can make some landscaping changes to reduce exposure to black-legged ticks.

13. Create a Tick-Safe Zone
It is recommended to create a barrier (wood chips or stone) between wooded areas and mown lawns. Black-legged ticks desiccate easily in full sun, and are less likely to cross an open barrier. Also, gardens and children’s play sets should be more than 3 yards from the barrier in areas with full sun.

14. Deer Management Toolbox
No Population Control
Hands-off
Damage control
repellents
fencing
Feeding illegal
Population Control
Lethal methods
Predator introduction
Capture and kill
Bait and shoot
Traditional hunting
Controlled hunting
Commercial hunting??
Non-lethal methods
Habitat alteration
Capture and relocation
Fertility control
transient
permanent
There are several potential deer management tools, however, usually only a few are cost-effective and feasible. Repellents or fencing can reduce deer damage to gardens and ornamental plants. Relocation is not recommended because of cost and poor deer survivorship. Fertility control can only be used in NYS with a research permit from NYSDEC. It is still considered experimental as research is ongoing. Lethal control of deer may be the most practical option. Hunting should be encouraged where it can be legally used. However, hunting alone may not reduce impacts caused by high-density suburban deer herds. Sometimes bait and shooting of deer with a DEC Damage Permit may be needed to supplement hunting. Some wildlife agencies are discussing the commercial sale of venison. This would require several changes in state and federal laws, and is currently not feasible. 14

15. Deer Population Reductions
Recreational hunting
Deer Damage Permits
DMAP Permits
Special urban deer permits
The most common and cost-effective way to reduce deer numbers is with recreational hunting. If management goals can’t be achieved by conventional hunting, DEC may authorize Deer Management Assistance Program permits, which allow landowners or their agents to take additional antlerless deer during open hunting seasons. Sometimes deer are causing damage in areas that can’t be hunted (e.g., corporate parks, college campuses, etc.). DEC may authorize Deer Damage Permits to take deer from these areas with skilled or professional shooters using special equipment and bait. In addition, DEC may authorize special permits to study new approaches for deer management (e.g., fertility control) in suburban areas.

16. Fertility Control Experimental Theoretically possible
Rose petal hypothesis
Unproven in the field
Biologically feasible?
Economically practical?
Females only
Limited scale
Maintenance required
In NYS deer fertility control is still considered experimental. DEC requires a research license (LCP) to study different methods in free-ranging deer. Although computer models show deer fertility control might be feasible, field data collected to date have not been encouraging. Even with more than 90% of the female deer in one herd being surgically sterilized, deer abundance remained stable after 6 years. Immigration was sufficient to offset mortality from vehicles and hunting. It only makes biological sense to treat female deer given deer breeding and dispersal behavior. Annual treatment would be required to capture and sterilize any new immigrant female deer. 16

17. IPM Management Options Plant selection Population management Fencing
Repellents
Deer and other wildlife damage should be handled with an Integrated Pest Management approach. Growers should determine the best combination of methods to reduce or prevent damage to their crops in a cost-effective way. For most farm situations, usually a combination of fencing and/or reducing deer numbers will help manage negative deer impacts.

18. Factors Influencing Deer Feeding Pressure
Deer population density
Food and cover sources
Travel corridors
Alternative foods
Season and weather
Deer nutrition
Plant palatability and nutrients
Previous experience
Many factors influence deer feeding pressure and damage during any given season or year. Farm areas with good brush or forest cover nearby may suffer higher levels of deer damage. Also, damage may increase to fruit trees or nursery stock during severe winters when deep snow makes natural plant foods less available. Each adult deer will consume 6-8 pounds of plant parts daily.

19. Reducing Plant Damage
Repellents may work when deer pressure and damage is light
Fencing provides reliable control when deer damage is moderate to heavy
Manage herd density
Choose plants that are less attractive to deer if possible
Deer repellents work best when deer feeding pressure is light, and the damage is short term (a month or two each year). When deer damage to plants is moderate to heavy, or occurs most of the year, physical barriers (e.g., fencing or netting) provide the only reliable control of deer damage. Reducing deer numbers may reduce plant damage, as each adult deer consumes 6 to 8 pounds of forage per day. Although limited, there are some plants that tend to be resistant to deer damage. There are many published lists of deer-resistant plants but none is completely reliable.

20. Commercial Deer Repellents
BGR Deer-Away
Hinder
Deer-Off
Chew-Not
Bonide Rabbit/Deer Repellent
Hot Sauce Repellent
Tree Guard
Spotrete-F
There are several deer repellents that have been tested under research conditions. Read the labels carefully as they contain different active ingredients, and follow all label directions for application. Most deer repellents can only be used on ornamentals, or fruit trees during the dormant season without fruit. No deer repellent is 100% effective, but some do perform much better than others.

21. We have tested several deer repellents on Japanese yews, a favorite plant frequently eaten by deer during the winter. Testing repellents during winter when deer are most hungry provides the best evaluation of relative efficacy. We have photographed plants weekly during winter to examine deer feeding pressure.

22. Untreated (control) yews are usually heavily damaged by deer in suburban areas in a few weeks when there is snow cover on the ground. This untreated yew had more than half of the plant surface area removed by deer in less than a month. The deer tracks are evident in the snow.

23. All the repellents we tested failed after 8 weeks during winter
All the repellents we tested failed after 8 weeks during winter. The best deer repellents were all egg-based (putrescent egg solids as an active ingredient), and provided 4 to 5 weeks of protection on average. This means that plants would need to be re-sprayed monthly, which is not feasible when they are covered with snow or ice during mid-winter.

24. Deer Exclusion Alternatives
8-foot barrier fences
Individual plant protection
Electric fences
Fencing or netting provides the only reliable protection for plants from deer damage year-round. There are many different fence types that can be effective depending on the types of plants and area which requires protection from deer feeding.

25. Baited Electric Deer Fence
A simple, low-cost (approx. $1 per linear foot) electric fence baited with attractants (peanut butter tabs) or repellents (sprayed on cloth strips) can reduce damage during summer for fruit and vegetable crops, or home gardens. These fence designs usually work well on areas <5 acres in size. They work best in small home gardens or small fields.

26. Northeastern Woody Ornamentals Rarely Damaged by Deer
Paper Birch
Common Boxwood
Russian Olive
American Holly
Drooping Leucothoe
Colorado Blue Spruce
Japanese Pieris
Few woody ornamentals are deer resistant with high deer densities in suburban areas. Plants like blue spruce or boxwood are starvation foods for deer, and such plants are usually damaged only under extreme conditions or very high deer densities.

27. Northeastern Woody Ornamentals Frequently Severely Damaged
Balsam fir Rhododendrons
Frasier fir Evergreen azaleas
English ivy Pinxterbloom azalea
Norway maple European mountain ash
Eastern Redbud Yews
Atlantic white cedar American arborvitae
Clematis Hybrid tea rose
Cornelian dogwood Winter creeper
Winged Euonymus Cherries
Apples Plums
Many common ornamentals are preferred by deer, and deer may search for these plants in the landscape. In areas with relatively moderate deer densities and damage, these plants may require protection (fencing or netting). Deer tend to damage fruit trees and plants that are evergreen during the winter.

28. We have also evaluated the resistance of >30 varieties of flowering bulbs to deer foraging damage. Bulbs were grown indoors in pots, then placed in yards where deer frequented. The pots were placed in long rows so deer could pick and choose the flowers they wanted to consume.

29. Bulb Varieties in the Trial
Narcissus- Carlton, Ice Follies, Tete a Tete, Minnow
Hyacinth- Pink Pearl, Carnegie
Crocus- Pickwick
Allium- Caruleum, Christophi, Sphaerocephalon, Ivory Queen, Purple Sensation, Neapolitanum
Iris- Buchaica, Blue Diamond, Reticulata JS Dyt and Pauline
Fritillaria- Imperalis Rubra Max, Persica
Colchicum- The Giant
Chionodoxa- Forbesii
Galanthus- Nivalis Single
Camassia- Leigh Coer
Arum- Italicum
Muscari- Armeniacum
Scilla- Siberica
Tulips- Turkestanica, Tarda Dasystemon, Apeldoorm, Monte Carlo
Tulips were used as “control” bulbs as we know that deer love to consume tulips. A relative damage score was recorded for each bulb genus in the experiment.

30. Deer Damage by Bulb Genus
Hyacinth
Tulip
Narcissus
Crocus
Iris “Blue D”
Allium
Arum
Camassia
Chionodoxa
Colchicum
Fritillaria
Galanthus
Iris
Muscari
Scilla
Not surprisingly, tulips had the highest damage score. Deer also liked to eat crocus and chionodoxa flowers. Most of the other spring bulbs were rarely eaten and tended to be very resistant to deer damage, Flowers from hyacinth, daffodil, and iris bulbs were almost never eaten by deer, along with several other bulb types.

31. Urban Deer Management Summary
Exclusion provides the best long-term deer control
Repellents provide limited short-term control
Choose ornamental plants carefully to reduce damage
Scare devices are usually ineffective
Hunting of female deer should be encouraged where possible to lower impacts
Protecting plants with fencing or netting provides the best long-term deer control. It is possible to choose more deer resistant plants for landscaping so that deer management is not needed. Repellents are not completely effective, and the best deer repellents only last for a month before reapplication is needed. Deer usually pay little attention to scare devices and quickly learn to avoid real danger. Hunting or removal of female deer should be encouraged where possible to lower deer damage and negative impacts.

32. For PDF files and fact sheets
For More Information
For PDF files and fact sheets
Cornell Cooperative Extension has free fact sheets and PDF files available at the web site. Click on the “Publications” tabs to find and download the files.