by Candace Brassard
Public awareness of ticks and the pathogens they may carry has increased in the past 10 years. This article provides information specific to New England on tick species, their biology, and the pathogens they carry. Recommended integrated pest management (IPM) tactics are discussed including landscaping practices, the selection of plants to deter and resist deer browsing, and direct tick control recommendations.
Tick Presence and Tick-Borne Disease Prevalence
The four tick species reported in New England (Figure 1) include black-legged tick (Ixodes scapularis – also know as the deer tick), lone star tick (Amblyomma americanum), brown dog tick (Rhipicephalus sanguineus), and the American dog tick (Dermacentor variabilis).
Depending on species and pathogens, the following diseases could result from tick exposure: Lyme disease, babesiosis, ehrlichiosis, Rocky Mountain spotted fever, southern tick associated rash illness, and anaplasmosis. Of these, Lyme disease is the most noted in New England (Figure 2). Even within the region, the reported cases of Lyme disease varies widely by state (Figure 3).
Ticks prefer cool, humid arboreal and deciduous forests. Some species, however, can adapt to arid habitats (Goodman 2005). Tick development is tied to temperature as their developmental phases shorten with increasing temperatures (Ogden 2006). Cold temperatures impact them less than many people realize. It is surprising to many to learn that 99% of all ticks will seek hosts once temperatures exceed four (4) degrees centigrade (or 39 degrees Fahrenheit). A New York study indicated that, regardless of winter conditions, more than 80% of ticks survived and that winter conditions do not necessarily restrict tick populations or, correspondingly, the risk from tick-borne diseases (Brunner et al., 2012).
Brunner (2008) indicated that host competence varies by species with ticks demonstrating a preference for hosts in the following order: white-footed mouse, eastern chipmunk, white-tailed deer, raccoon, opossum, striped skunk, short-tailed shrew, and masked shrew.
Rabbits also serve as a host for ticks. Cooney (2005) examined ticks on eastern cottontail rabbits and found that of the nearly 4,000 ticks collected, 80% were Haemphysalis leporispalustris (rabbit tick), 9% Amblyomma americanum (lone star tick), 8% Ixodes dentatus (black-legged or deer tick), and 2% Dermacentor variabilis (American dog tick).
Birds also act as a host for Ixodes damini (now described as Ixodes scapularis). For example, Battaly and Fish (1993) surveyed Westchester County, NY, and reported that 9% of the 25 bird species collected were parasitized by ticks. Both the American robin and house wren are reservoir competent for the Lyme disease spirochete, Borrelia burgdorferi, and therefore may contribute to the risk of Lyme disease for humans.
Deer are not affected by Borrelia burgdorferi, and do not transmit disease, but are hosts that allow infected ticks to multiply. This results in more ticks within a given area to transmit the disease to future hosts.
It could be assumed that controlling deer populations in an area in which ticks carrying disease pathogens are endemic would
result in a reduction in risk for tick-borne diseases. However, other hosts may provide a means for ticks to migrate into an area with a depleted deer population. This theory was confirmed by a study conducted on Monhegan Island, ME. There, white-tailed deer were extirpated in 1999, but Ixodes scapularis ticks were discovered only three (3) years later, indicating a bird-derived reintroduction. (Elias, S.P., et al. 2011).
Tick Life Cycle
The life cycle of ticks is depicted in Figure 4. The immature tick (nymph) is the life stage of most concern because its small size (head of a pin) allows it to be easily overlooked during tick checks.
Recommended Landscape Management Practices
The following landscape practices are recommended as ways to reduce the exposure of you and your family to ticks. Figure 5 demonstrates how these practices can be integrated to create a backyard tick safe zone.
- Remove leaf litter, brush, and weeds at the edge of the lawn. Removal of leaf litter in wooded areas of a forested residential community significantly reduced the abundance of questing blacklegged tick (Ixodes scapularis) nymphs throughout their peak activity period. Removal of leaf litter in early spring (March) and early summer (June) resulted in reductions in nymphal tick density ranging from 73% to 100%. Subsequent sampling of the I. scapularis population during the summer revealed similar rates of suppression of larvae (Schulze 1995).
- Keep grass mowed (less than 3”).
- Clear ground cover and vegetation around stonewalls and wood piles. The ground cover pachysandra is deer resistant but is also known to harbor ticks. Trim tree branches and shrubs around the lawn edge to let in more sunlight. Clear and widen woodland trails to avoid exposure to questing ticks.
- Adopt hardscape and xeriscape landscaping techniques with gravel pathways and mulches. These dryer or less water demanding landscapes are environmentally friendly and reduce tick exposure. Create a 3-foot or wider wood chip, mulch, or gravel pathway surrounding landscaped areas.
Plants Resistant and Susceptible to Deer Feeding
The selection of plants for a landscape can directly impact the attractiveness to deer. Deer demonstrate preferences and dislikes for certain plants just as humans prefer some foods over others. Those living near deer habitat can take advantage of this fact by using deer-resistant plants in their landscapes.
The following plants, identified as being resistant to deer browse damage (Ward 2000), can be grown where moderate browse damage would be expected.
Annuals and Perennials Grown as Annuals: Spiderflower (Cleome), Marigold (Tagetes), Forget-me-not (Myosotis), Vinca (Catharanthus), Alyssum (Lobularia), and Dusty miller (Senecio)
Groundcovers: Myrtle (Vinca), Dead nettle (Lamium), Pachysandra (Pachysandra), Bugleweed (Ajuga), Sweet woodruff (Galium), and Wild ginger (Asarum)
Bulbs and Corms: Hen & chicks (Sempervivum), Star of Bethlehem (Ornithogalum), Snowdrop (Galanthus) Ornamental chives (Allium), Daffodil (Narcissus)
Herbaceous Perennials: Lily of the valley (Convallaria), Lamb’s ears (Stachys), Lavender (Lavandula),Yarrow (Achillea), Foxglove (Digitalis), Mint (Mentha), Russian sage (Perovskia), Oregano (Origanum), Silvermound (Artemisia), Lady’s mantle (Alchemilla), Thyme (Thymus), Poppy (Papaver), Catmint (Nepeta), Goldenrod (Solidago), Rubarb (Rheum), Monkshood (Aconitum), and Mayapple (Podophyllum).
Vines: Wisteria (Wisteria) and Virginia creeper (Parthenocissus)
Shrubs and Trees: Leucothoe (Leucothoe), flowering quince (Chaenomeles), weigela (Weigela), butterfly bush (Buddleia), deutzia (Deutzia), spruce (Picea), cotoneaster (Cotoneaster) boxwood (Buxus), and spirea (Spiraea), honeysuckle (Lonicera), heather (Calluna), goldenbells (Forsythia), and andromeda (Pieris).
Recent research indicates that invasive honeysuckle (Figure 6) eradication reduces tick-borne disease risk by altering host dynamics (Allan, B. et al., 2010). The data suggest that management of biological invasions may help ameliorate the burden of vector-borne diseases on human health. This study removal of honeysuckle and measured tick survival rates in invaded and restored habitats and it was reported there was a greater ten times greater chance for exposure to E. chaffeensis (pathogen carried by ticks) in honeysuckle plots compared to native vegetation.
Plants Susceptible to Deer Browsing
The converse of plants that are not palatable to deer are those to which deer show a preference. The following plants were identified as being susceptible to deer browsing in a survey of Connecticut gardeners (Ward 2000).
Annuals and Perennials Grown as Annuals: Impatiens (Impatiens), sunflower (Helianthus), English daisy (Bellis), dahlia (Dahlia), and fibrous begonia (Begonia)
Bulbs and Corms: Tulip (Tulipa), daylily (Hemerocallis), lilies (Lilium), and spring-flowering crocus (Crocus)
Herbaceous Perennials: Hosta (Hosta), garden phlox (P. paniculata), hollyhock (Alcea), daisy (Chrysanthenum), black-eyed susan (Rudbeckia), Jerusalem artichoke (Helianthus), candytuft (Iberis), shasta daisy (Leucanthemum), coneflower (Echinacea), cardinal flower (Lobelia), hibiscus (Hibiscus), and rose mallow (Malva)
Shrubs and Trees: Yew (Taxus), euonymus (Euonymus), arborvitae (Thuja), deciduous azalea (Rhododendron), rhododendron (Rhododendron) evergreen azalea (Rhododendron), rose (Rosa), hydrangea (Hydrangea), American holly (Ilex), evergreen holly (Ilex), yucca (Yucca), eastern red cedar (Juniperus), juniper (Juniperus), mountain laurel (Kalmia), and hemlock (Tsuga).
The following recommendations are for use by those in the landscape community:
Initiate personal protection by wearing long pants, long shirt, hat, gloves, and boots (covering lacings). CDC (2013) recommends the use of a repellent with DEET (N, N-diethyl-m-toluamide) on skin. Repellents containing 20% or more DEET can protect up to several hours. Always follow product label instructions when applying any repellent. The US Environmental Protection Agency provides approved protection times for skin applied insect repellents at http://cfpub.epa.gov/oppref/insect/.
Products containing permethrin kill ticks. Permethrin can be used to treat boots, clothing, and camping gear; it remains protective through several washings. (CDC 2013)
Landscape Worker Exposure
Ticks are usually more active in the months of April through October and peak in the summer months of June through August. The time of year when ticks are active may vary with the geographic region and climate. Outdoor workers should take care to protect themselves in the late spring and summer when immature ticks are most active (http://www.cdc.gov/niosh/topics/tick-borne).
Area Wide Treatment
A single springtime application of an acaracide (tick pesticide) can greatly reduce the number of ticks in your yard (CDC 2013). If you are considering applying an acaracide or having one applied to your property:
- Check with local health officials about the best time to apply an acaricide in your area.
- Identify rules and regulations related to pesticide application on residential properties (EPA and your state determine the availability of pesticides).
- Consider having a professional pest management company make the application to your property.
As noted by Sir Francis Bacon in his work Meditationes Sacrae, knowledge is power. This is particularly salient when it comes to mitigating exposure to tick-borne diseases. The provided information can help empower both landscape professionals and citizens to identify tick species as well as control variables often associated with tick propagation. With that, may citizens be emboldened to enjoy outdoor environments – wherever the path may lead.
Allan B, Dutrac HP, Goessling LS, Barnett K, Chasea JM, Marquisc RJ, Pang G, Storch GA, Thach RE, and JL Orrock. 2010. Invasive honeysuckle eradication reduces tick-borne disease risk by altering host dynamics. PNAS. October 26, 2010, Vol. 107, No. 43, pages 18523–18527.
Battaly GR, Fish D. 1993. Relative importance of bird species as hosts for immature Ixodes dammini (Acari: Ixodidae) in a suburban residential landscape of southern New York State. J Med Entomol. Jul; 30(4):740-7.
Brunner JL, Killilea M, Ostfeld RS. 2012. Overwintering survival of nymphal Ixodes scapularis (Acari: Ixodidae) under natural conditions. J Med Entomol. 2012 Sep;49(5):981-7.
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Ogden NH, Lindsay LR, Beauchamp G, Charron D, Maarouf A, O’Callaghan CJ, Waltner-Toews D, Barker IK. 2004. Investigation of relationships between temperature and developmental rates of tick Ixodes scapularis (Acari: Ixodidae) in the laboratory and field. J Med Entomol. Jul;41(4):622-33.
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Stafford III, K. C. 2007. Tick Management Handbook. Connecticut Agricultural Experiment Station, New Haven, CT. Bulletin No. 1010.
Ward, J. 2000. Limiting Deer Browse Damage to Landscape Plants. Connecticut Experiment Station, New Haven, CT. Bulletin No. 968.
University of Texas at Austin. 2013. Native Plant Database. Austin, TX. [Online]. Available: http://www.wildflower.org/plants/result.php?id_plant=DILO
US Environmental Protection Agency. 2013. Insect Repellents: Use and Effectiveness. Washington, DC 20460. [Online]. Available: http://cfpub.epa.gov/oppref/insect.
About the Author
Candace Brassard is a as Senior Biologist with the U.S. Environmental Protection Agency’s Office of Pesticide where she is responsible for tick Integrated Pest Management efforts. Ms. Brassard has a bachelor’s degree in Animal Science with a minor in Zoology from UMass Amherst and a master’s degree in Environmental Public Policy from George Washington University. The past 10 years of her 25+ year career with EPA has focused on tick IPM and the evaluation of efficacy data for tick control methods. She may be reached at 703-305-6598 or firstname.lastname@example.org.