Summer of the Tick

Tick Population May Thrive in Summer 2016

The two major kinds of ticks that can be found in Midwestern states like Nebraska during spring and summer are the American dog tick and the lone star tick (pictured). (Photo by Benjamin Smith, CC BY 2.0)

OMAHA (DTN) -- Summer 2016 may turn out to be a great year for ticks, which may spell headaches for both humans and livestock in many areas of the U.S. Weather and temperature conditions are conducive to a thriving tick population this season, entomologists say.

Tick activity has been reported as high so far this spring, as ticks typically begin to emerge in May and June. However, this year, activity has been reported even earlier than usual, possibly because of the cool, wet spring weather that occurred in many areas.

According to Jeff Whitworth, Extension specialist in entomology for Kansas State University, ticks like weather that is humid and temperatures that are between 65 to 80 degrees Fahrenheit -- not too cold and not too hot. Most Midwestern crop- and livestock-producing areas had plenty of cool, humid conditions until the recent heat spell.

"Ticks like the kind of weather we like," Whitworth said. "That's when they're out looking for their hosts."

Tick activity has been reported as high in the U.S. and also in Canada. In fact, the York Institute for Health Research in Ontario reported in May 2015 the spread of blacklegged, or deer ticks into Canada and the potential for the growing incidence of Lyme disease in areas such as Toronto in the next 30 years. The spread of ticks northward was likely due to climate change and global warming, according to the York Institute.

TICK POPULATION DEPENDENT ON SUMMER WEATHER

Although conditions are sizing up for a significant tick population this summer, whether or not the tiny arachnids thrive will largely depend on the type of weather that ensues.

A large tick population is difficult to predict, according to Roberto Cortinas, veterinarian and assistant professor at the University of Nebraska-Lincoln's School Of Veterinary Medicine And Biomedical Sciences.

"If we have a really hot and dry summer, ticks are not going to be host-seeking like they would be if the temperatures were milder and it was more humid," Cortinas said.

Ticks have to expose themselves to the elements when they are looking for hosts. Cortinas explained that, each day, ticks climb from the protection of the litter on the ground and climb up plants, clinging to leaves or vegetation, waiting for a host to brush by that they can cling to. Because hot weather forces ticks to use more of their energy resources in order to regulate their temperature, they won't expose themselves as much during very hot, dry weather.

"The ticks may be there, but they're just not going to expose themselves," Cortinas said. "They're a little bit smarter than that."

Cortinas said he has experienced tick behavior firsthand when out trying to collect ticks in hot weather. They were difficult to find in the heat of the day, but more active early in the morning or late in the evenings, when temperatures were cooler and the air more humid.

Contrary to perceptions, ticks do not die at the end of the summer season. Many of the tick varieties that are in the Midwest actually live two years, Cortinas said. After a mild winter, they overwinter well, and as a result, more ticks appear in the spring and summer.

Whitworth added that those who live in areas that have been flooded this spring may find ticks in unusual places. Many times, ticks lay their eggs in low-lying areas along creeks and waterways. Since they are hard to drown, they tend to float around on water until they can crawl onto a log or vegetation.

"Floods just move them to higher ground, then when the water recedes, the ticks are left in someplace they are not normally found," Whitworth said.

TYPES OF TICKS

The two major kinds of ticks that can be found in Midwestern states like Nebraska during spring and summer are the American dog tick and the lone star tick, Cortinas said. Both kinds also have been reported in increasing numbers in northern states like Wisconsin and Michigan.

Other news sources also list the blacklegged tick, or deer tick, as another variety to watch out for. Deer tick activity has been reported as high as early as March by the University of Minnesota, as well as in New England and mid-Atlantic states, according to the University of Rhode Island TickEncounter Resource Center.

PASTURE CONDITIONS

Any pasture or rangeland that is wooded or contains trees or shrubs is more conducive to ticks. However, much tick exposure can be controlled by good management, Cortinas said.

"Some ranchers essentially manage for ticks behaviorally, and exclude cattle from areas that are wooded or partially wooded to minimize exposure to ticks," he said. "You can manage your pasture to try and minimize the exposure of cattle to tick bites."

Typically, ticks refrain from hot, dry pastures or cornfields. Cortinas said ticks rarely venture into fields of row crops, except sometimes at the end of the growing season when row crops are tall and provide more shade and humidity.

CATTLE TICK PREVENTION

Although dogs and possibly horses can get Lyme disease from ticks, cattle rarely get tick-borne diseases. Cortinas said there was a bad cattle tick fever outbreak in Nebraska at one time that was transmitted by the cattle tick, but that was eliminated, at least in Nebraska, around 1890-1900.

However, ticks can cause problems for cattle in other ways. With high tick infestations, cattle can get damage to hides, or even wounds that can fester and attract flies to the lesions. In calves, heavy infestations can decrease red cell counts. Also, ticks can result in reduced feed efficiency for producers.

"If you're feeding ticks instead of cattle, that's where your feed and your profit is going," Cortinas said.

Cortinas mentioned that certain cattle breeds are better suited to deal with ticks. All the south-Asian-origin Bos indicus-type cattle, such as Brahmas, tend to be much less susceptible to ticks than European breeds like Angus or Herefords. That is why in the Deep South, ranchers will have more Brahma crosses.

Bos indicus cattle have tougher hides, and even their immune systems seem better suited to deal with ticks. Cortinas said there have been studies that found those types of cattle have less ticks, and the female ticks, even if they do get blood, don't produce as many eggs.

FIGHTING BACK AGAINST TICKS

Cortinas said there are a number of options for chemicals that have activity against ticks, such as dips, sprays and even pour-ons and other insecticides.

He warned that producers need to be careful about what compounds they use, because not all will have activity against ticks.

He suggested that producers consult their veterinarians about what product to use and be very careful using them. For instance, some cannot be used on lactating dairy cows if their milk is to be sold or if they are nursing calves. Producers also need to be cautious of withdrawal times, as sometimes chemicals cannot be applied if cattle are to be slaughtered. Some chemicals are also dangerous to horses, Cortinas added. However, these are all things veterinarians would be well-versed in, he said.

In the end, Cortinas said that a lot of the success of tick control boils down to management.

"The most important thing is simply preventing tick bites. That's all it comes down to at the end of the day," Cortinas said. "Reducing the number of tick bites will alleviate the problems you have with ticks."

Cheryl Anderson can be reached at Cheryl.anderson@dtn.com

Follow Cheryl Anderson on Twitter @CherylADTN

(AG/BAS)