Tick Expansion: Pest Control Strategies for Landscaping Professionals

The impact of climate change and human modification of the environment on tick-borne diseases emerged in September 2024 when a scientist at the Connecticut Agricultural Experiment Station (CAES) reported the first locally acquired human disease case of Rickettsia parkeri rickettsiosis in Connecticut. Transmitted by the Gulf Coast tick (Amblyomma maculatum), R. parkeri rickettsiosis is an emerging tick-borne disease similar to Rocky Mountain spotted fever, although with relatively milder symptoms.

“It is anticipated that warming temperatures related to climate change may lead to the continued range expansion and abundance of several tick species, increasing their importance as emerging threats to humans, domesticated animals and wildlife,” says Goudarz Molaei, Ph.D., who surveils tick disease vectors for CAES and is an associate professor at Yale School of Public Health, both in New Haven, Conn.

“Rising global temperatures, ecological changes, reforestation and increases in commerce and travel are important underlying factors influencing the rate and extent of range expansion of ticks and associated pathogens,” he says.

CAES: A history lesson

This latest discovery is nothing new for CAES, which long has been in the forefront of research on ticks and pathogens they carry. When several children and adults in and around the town of Lyme, Conn., contracted a strange form of arthritis in the fall of 1975, researchers at Yale University, a half hour’s drive to the west, figured out it was an illness they termed “Lyme disease.” From the get-go, researchers at CAES, its main campus located in a former estate near Yale, designated a National Landmark, have been defining the role of ticks in Lyme disease and today, the institution is arguably the center of research on the ecology of ticks that carry the Lyme pathogen as well as other tick-borne diseases.

Research on human disease vectors as well as organisms that give farmers fits makes the Connecticut station an important resource for pest control professionals nationwide. The CAES is a stand-alone state agency that was established in 1875 to study plants, soil, water, insects and pests. It was modeled on a German experiment station concept that a community of scientists would be free from the burden of academia for the purpose of serving the needs of agriculture and citizens at large.

What makes this facility unusual is that it is an agricultural experiment station but much different than those in other states because its science goes far beyond research that promotes food production and agribusiness. All other state agricultural experiment stations, absorbed by land grant universities and their cooperative extension programs, were established under the federal Hatch Act of 1887 to provide scientific support of agriculture. The extension programs then channeled the results of station research to the agricultural public. Each state has at least one station attached to a land grant university.

By the time the Hatch Act became law, the Connecticut Agricultural Experiment Station, a prototype for all others, was already a dozen years old and engaged in cutting-edge research on it six-acre campus. Unlike its counterparts in other states, the Connecticut station is independent of a university and its scientists work in fields far beyond agriculture, notably those impacting public health. It is a tad confusing, but the state also has an experiment station, similar to those in other states, with the University of Connecticut, called the Storrs station, after the community in which the university is located.

Wilbur’s ‘baby’

CAES was the baby of Wilbur Olin Atwater, a professor at Wesleyan University in Middletown, Conn., who was a leader introducing the science of agricultural chemistry in America.

While agricultural research remains a staple at the station, its researchers continue on the frontlines in the war against tick-borne pathogens.

Partly because the initial explosion of Lyme disease cases occurred in Connecticut, they were among the first to elucidate the ecology of the black-legged tick, its prime vector. Over the years since Lyme disease first came to the forefront, scientists at the station have been piecing together the complicated puzzle of black-legged tick ecology and how it transmits diseases.

Dr. Scott Williams, head of the station’s Department of Environmental Science and Forestry, and his colleagues have tromped through Connecticut’s forests and fields, probing the hidden aspects of what make ticks tick. Williams spearheaded the research that turned up a hitherto unknown habitat that amounts to tick heaven. Thickets of invasive Japanese barberry, they found, contain a dozen times more ticks than the same area without barberry.

“Tick and tick-borne pathogen management research continues to be a priority at the Connecticut Agricultural Experiment Station (CAES) in the interest of public health,” Williams says. “Currently we are evaluating host-targeted and seasonally-timed broadcast acaricide applications that utilize minimal volumes of pesticides to effectively target host-seeking and parasitizing ticks. This less-toxic approach is consistent with the mission of the CAES to reduce the amount of pesticides broadcast across the landscape.”

Recent developments

More recently, CAES scientists have pinpointed hotspots of backyard tick habitat more precisely than ever. They also demonstrated that one late-fall treatment works as well as conventional spraying in spring and, perhaps, then again in fall. Scientists at the station also were instrumental in developing antibody tests to identify patients infected with Lyme disease agent as well as other tick-borne illnesses.

CAES and Yale scientists in 1999 developed a new, simpler and more reliable blood test to detect a then-emerging disease called ehrlichiosis, which is carried by deer ticks. The diseases is caused by a rickettsial bacterium, Ehrlichia equi, carried by the same deer tick that carries the Lyme disease bacteria and, like Lyme disease, causes flu-like symptoms such as headache, fever and muscle cramps. But unlike Lyme disease, Ehrlichia equi does not produce a bull’s eye rash, which made it more difficult to diagnose until the new test became available.

The identification of Rickettsia parkeri rickettsiosis in Connecticut last year put public health authorities on high alert. Although cases of this disease have been reported in the southeastern part of the country, the presence of this disease in the Northeast, an area already plagued by tick-borne diseases, suggests it could continue to spread. The distribution of the Gulf Coast tick was considered restricted predominantly to coastal regions of states bordering the Gulf of Mexico and the southern Atlantic coast. However, in recent decades, its range has expanded northward into the Mid-Atlantic states, with new populations reported from Delaware and Maryland.

According to Molaei, the first established population of the Gulf Coast tick was reported in Fairfield County, in the southwestern corner of the state, in 2021. Additional populations of this tick species with higher infections were later reported in New York and New Jersey in 2022 and 2024, respectively. It is believed that migratory grassland birds serve a crucial role in the spread of Gulf Coast ticks to locations in central and northern states that possess favorable environmental conditions for their survival.

“Because of morphological similarities between Gulf Coast ticks and American dog ticks — the principal vector of RMSF in the Northeast — these two species can be misidentified,” Molaei says. “Since most tick species are associated with a unique suite of pathogens, it is important to improve regional capacity for accurate detection and identification of ticks and the pathogens they transmit in the Northeast, an area already endemic for Lyme disease, Rocky Mountain spotted fever, ehrlichiosis, anaplasmosis, babesiosis and Powassan virus disease.”

With tick-related diseases monopolizing the spotlight today, some of the other major discoveries by CAES scientists many years past have been overshadowed despite their significance. In 1909, scientists from the station and Yale verified that essential amino acids were those that the body cannot synthesize but had to be consumed. A few years later the same team reported an “unknown substance is essential to growth and that this unknown substance is present in milk.” The substance was Vitamin A. Together with research at the University of Wisconsin, this work led to the discovery of vitamins.

CAES today

Today, the station’s 100 scientists work in laboratories housed with a complex of a half dozen buildings in New Haven and three satellite locations in other parts of the state — a research center, research farm and an additional laboratory. The first commercial hybrid corn, which revolutionized corn production because of higher yields, was developed at satellite farms during the 1920s.

Emblematic of the way in which station scientists use agricultural applications as a basis for research that impacts society is their work on where and how small contaminants called engineered nanomaterials (ENMs) from manufacturing impact the environment. Sized between one and 100 nanometers — a sheet of paper is 100,000 nanometer thick — ENMs such as titanium oxide or zinc oxide are employed in electronics, pharmaceuticals and medicine, often as sensors and transduces. Many are extremely reactive and toxic.

CAES research has evolved into focusing on using many nanoparticles to protect crops and organisms in the soils that support them. It includes investigating the beneficial as well as negative impacts of nano-scale chemistry, using tiny particles of substances to improve plant nutrition, yield and, importantly for the pest control industry, suppress plant diseases.

“It is anticipated that warming temperatures related to climate change may lead to the continued range expansion and abundance of several tick species, increasing their importance as emerging threats to humans, domesticated animals and wildlife.” Goudarz Molaei, Ph.D., Department of Entomology, CAES; associate professor at Yale School of Public Health.

One area of research has investigated the use of nano-scale treatment to protect crops from fungal diseases like verticillium wilt. Scientists sprayed seedlings of eggplant and watermelon with a solution containing copper nanoparticles. They found copper was incorporated readily into the plants, which ended up healthier than plants treated with large-scale doses of the metal. The miniscule size of the copper particles, researchers found, facilitated their movement through plant tissues.

Certain pesticides can be delivered as nanomaterials to plants, says Dr. Christian Dimkpa, who heads analytical chemistry at the station.

Perhaps of greater interest to the general public is the station’s entomology department. Its Connecticut Insect Inquiry Office, headed by a concert pianist turned entomologist, handles thousands of inquires yearly from residents curious about insects and other arthropods. The office, says Dr. Gale Ridge, is there to answer questions about “animals with more than four legs.” Its mission is to diagnose and assist citizens of Connecticut with insect problems. The inquiry office serves homeowners, medical professions, health departments, pest management professionals, municipalities, the nursery industries, arborists, law enforcement, schools, universities and native American tribes.

When it comes to public health, CAES is the state agency responsible for trapping, identifying and testing mosquitoes for encephalitis viruses. More than 25 scientists and support staff conduct the statewide surveillance program annually.

The station’s research on mosquito- related illnesses, however, has impact far beyond state boundaries. Station scientists in 1999 were the first to culture and characterize West Nile encephalitis virus from mosquitoes collected in North America.

They found that the American robin is a favorite host for some mosquitoes and is an important carrier of the virus. Other findings revealed that Culex salinarius, a mosquito that breeds in brackish and fresh water, is the probable “bridge vector” moving the virus from birds to mammals, including humans.

The author is a journalist, author and naturalist who has been writing for more than a half century.