Texas A&M Entomology Research Network

Research

African horse sickness on Texas A&M, industry radar

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Potential insect vectors in Texas

by Kay Ledbetter, Texas A&M AgriLife Marketing and Communications

Horses would be at risk if African horse sickness makes it into the U.S. (Texas A&M AgriLife photo by Kay Ledbetter)
Horses would be at risk if African horse sickness makes it into the U.S. (Texas A&M AgriLife photo by Kay Ledbetter)

African horse sickness is not in the U.S., and it is important it stays that way.

Texas A&M AgriLife faculty, various state and federal agencies and the U.S. horse industry are already monitoring the situation, ensuring surveillance and determining practices to prevent the deadly horse disease from crossing our borders.

African horse sickness comes out of Africa and is common from Morocco down to the middle of the continent. But it has escaped the African continent several times, most recently into Thailand, where it is believed to have been introduced by importation of infected zebras. African horse sickness is caused by a virus, more specifically an Orbivirus, which is transmitted by certain insects.

“Equines including horses, mules, donkeys and zebras are moved all over the world for competitions, trade, breeding, zoologic and conservation purposes,” said Pete Teel, Ph.D., Texas A&M AgriLife Research entomologist with the Texas A&M Department of Entomology, College Station.

“There is a real risk that this foreign animal disease could be introduced to the Western Hemisphere, including North America, where we have insects that will likely serve as effective vectors of this virus,” Teel said.

“The U.S. is constantly threatened by introductions of foreign animal diseases,” he said. “Diligent surveillance, detection and planned responses at state and federal levels is essential, as is keeping an eye on what is happening globally. Having advanced knowledge and warnings is a huge advantage toward prevention before it gets into our country.”

Federal agencies, including the U.S. Department of Agriculture Animal and Plant Health Inspection Service, state agencies like the Texas Animal Health Commission, and concerned and vigilant equine industry stakeholders are all part of the first line of defense, Teel said.

“If African horse sickness does come to the U.S., do we have knowledge of insects that will likely transmit this virus? Yes,” Teel said. “Do we know everything we need to know about it? Probably not.”

He said depending on the serotype of the virus that were to be introduced, “it will be necessary to determine whether the insects we have are competent vectors in the laboratory and capable vectors in the field. And further, to improve practices to protect equines from vector transmission and infection.”

What is African horse sickness

The tiny biting midge, as seen here compared to a mosquito, right, is a vector for African horse sickness. (Courtesy photo)
The tiny biting midge, as seen here compared to a mosquito, right, is a vector for African horse sickness. (Courtesy photo)

African horse sickness is considered a Tier 3 disease by the National Bio and Agro-Defense Facility, NBAF, because of the potential negative impact on animal health.

African horse sickness symptoms are the same as those associated with respiratory and circulatory impairment. At the first signs of the disease, owners are advised to eliminate affected horses and vaccinate noninfected horses with polyvalent vaccine; then let them rest for two weeks.

The APHIS and the U.S. Fish and Wildlife Service have import requirements in place to reduce the likelihood of AHSV introduction. Per APHIS regulation, imported horses undergo inspection prior to export. Horses imported from AHS-affected countries are required to undergo a 60-day quarantine upon arrival in the U.S.

Horses are the most susceptible host with close to 90% mortality of those affected, followed by mules and donkeys. African donkeys and zebras very rarely display clinical symptoms, despite high virus titers in blood, and are thought to be the natural reservoir of the virus. Thus, it is thought the virus was transported to Thailand through asymptomatic zebras.

Texas A&M expertise on African horse sickness

“The primary vectors of African horse sickness are among species of biting midges, which are very small blood-feeding flying insects about 1/8th of an inch in length,” Teel said. “The immature stages of these insects complete their portion of the midge life cycle in association with wet habitats ranging from permanent and semi-permanent aquatic areas to very moist soils and decaying organic matter.”

He explained these are biological vectors meaning that the virus reproduces inside biting midges after blood meals are taken from infected animals; the resulting infected midges are then able to infect new animals.

“We have biting midges in the U.S.,” Teel said. “They are involved in the transmission of two similar viruses causing diseases known as blue tongue and epizootic hemorrhagic disease in livestock and wildlife.”

He said Texas has biting midges and both diseases. AgriLife Research entomologists have been involved in studying the taxonomy, ecology and management of biting midges associated with these and other pathogens, in part stimulated by the emergence of epizootic hemorrhagic disease in Texas deer farms.

“A recent study of biting midges in an urban area of Brazos County found eight species including the principle vector species associated with blue tongue and epizootic hemorrhagic disease,” Teel said. “This species has been studied under laboratory conditions and found to experimentally acquire and transmit the virus of African horse sickness.

“The discovery of African horse sickness in Thailand is another reminder that our global connectedness has risks and that state, national and global surveillance is the key to early warnings, to preparedness and to response.”

Teel reassured that were African horse sickness to threaten the U.S., AgriLife Research and AgriLife Extension has diverse expertise, facilities and services to assist in preparation and response, including basic and applied research.

“It is important for us moving forward to continue working with the equine industry and equine veterinarians here in the U.S. and with international organizations such as the World Organization for Animal Health, who recently did a series of webinars on this event and are the international standard setting body for how to safely move horses around the globe,” said Elizabeth Parker, DVM, AgriLife Research associate director for operations and strategic initiatives, College Station.

Prevention

Currently, vaccines for African horse sickness are effective but not optimal because they contain live pathogens that can sicken horses, especially if not administered correctly, or lead to the creation of new genetic variants of the disease.

In countries where African horse sickness is a problem, Teel said prevention is provided with vaccines to the serotype present in that region or the use of insecticides to keep the midges from biting.

With horses, it might mean keeping them stalled in areas where biting midges are a problem and using insecticides to keep the midges off them. But this might not be as possible with wild horses or horses in pastures that may not be able to be handled or stabled.

Moving forward

Teel said the investigation in Thailand should help scientists understand what happened and how the disease traveled – most likely infected animals moved to an area where there were native vectors.

“For the U.S., we need to be vigilant in understanding what this virus is, its cycle in nature as it is presently understood, and then to determine what vectors we have here and how they could potentially play a role in this,” he said. “With blue tongue and EHD, we might already have some insight on how efficient the midges might be as vectors.

“And then we have the other part of vector transmission and that is called vector capacity. Is the timing right for the vectors to work in the field, as opposed to the lab, looking at seasonal phenology? We have a lot to learn and we need to stay on top of it.”

Tick surveillance, control needed in U.S., study shows

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First nationwide survey of tick-management programs shows clear public health gap

by Olga Kuchment, Texas A&M AgriLife Marketing & Communications

Two Asian longhorned ticks atop a dime. Photo by CDC/James Gathany
Two Asian longhorned ticks atop a dime. Photo by CDC/James Gathany

The prevalence of Lyme disease and other tick-borne illnesses has steadily increased in the U.S. over the past 20 years. Now, an inaugural nationwide study of tick surveillance and control describes a clear need for more funding and coordination among programs across the country.

Among the coauthors is a Texas A&M AgriLife researcher, Pete Teel, Ph.D., a Regents professor in the Texas A&M Department of Entomology. Teel said that while Texas has monitored and controlled ticks since 1893, a nationwide database is needed.

The study’s authors surveyed 140 vector-borne disease professionals working at state, county and local agencies in fall 2018. Reaching even that many respondents proved challenging, the authors said. No central database of tick-management programs or contacts was available.

The survey’s aim was to learn about programs’ objectives and capabilities for tick surveillance and control. Respondents were also asked whether they tested ticks for disease-causing germs, and about barriers to success.

Nationwide, less than half of public health and vector-control agencies engage in active tick surveillance, according to the survey. Only 12% of the surveyed agencies directly conduct or otherwise support tick-control efforts.

The Lyme disease bacterium is spread through the bite of infected deer ticks, or blacklegged ticks. Photo courtesy of CDC
The Lyme disease bacterium is spread through the bite of infected deer ticks, or blacklegged ticks. Photo courtesy of CDC

The study appeared on June 17 in the Journal of Medical Entomology. In addition to Teel, the authors were from Cornell University; University of Florida, Gainesville; University of California, Davis; University of Illinois; and the Centers for Disease Control and Prevention Division of Vector-Borne Diseases. The authors are also affiliated with the CDC’s five Vector-Borne Disease Regional Centers of Excellence.

“Ticks are responsible for the majority of our vector-borne illnesses in the U.S., and our programming does not adequately meet the need in its current form, for both surveillance and control,” said Emily Mader, public health researcher, lead author on the study and program manager at the Northeast Regional Center for Excellence in Vector-Borne Diseases, led by Cornell University.

Texas has a long history of tick surveillance

In Texas, early detection and control have led to discoveries of exotic ticks, Teel said. These efforts kept the ticks from becoming established.

Dog ticks can transmit cattle fever and other animal and human diseases. Photo by CDC/James Gathany
Dog ticks can transmit cattle fever and other animal and human diseases. Photo by CDC/James Gathany

“These ticks could have introduced several devastating diseases with high risks for humans, livestock and wildlife,” he said. “National databases for the kinds of ticks that are present, and how those populations change with time and space, would be hugely informative for public health and animal health needs.”

Texas has engaged in tick surveillance and control activities since 1893. At that time, the 23rd Texas Legislature established the Livestock Sanitary Commission, which later became the Texas Animal Health Commission.

“I believe this to be the oldest and longest continuous tick surveillance program in North America,” said Teel. The commission’s aim was to protect livestock from dangerous diseases such as cattle fever.

The resulting state and federal cattle fever tick eradication program eliminated these ticks from 14 states by the 1940s. The program established a permanent quarantine zone along the Texas-Mexico border and has protected the U.S. cattle industry ever since. Statewide tick surveillance activities continue today.

“Today, the data from this program are becoming valuable and complimentary to public health needs,” Teel said. “Collaborations are growing in Texas to share information, improve surveillance and testing, train a new generation of vector biologists, and improve best practices for tick control and tick-borne disease prevention.”

One such collaboration is the Western Gulf Center of Excellence in Vector-Borne Diseases, where AgriLife is a partner. Other collaborators include academic institutions and public health and animal health agencies in Texas, Oklahoma, Arkansas and Louisiana. Led by the University of Texas Medical Branch, the center performs research to expand surveillance for ticks and tick-borne pathogens. The center also trains future scientists and public health practitioners.

Highlights from the nationwide survey of tick-management programs

Less than half of tick-management programs proactively collect ticks in their area

About two-thirds of respondents, 65%, said their programs engage in passive tick surveillance, such as accepting tick samples submitted by the public. However, only 46% said their programs engage in routine active tick surveillance, such as focused collection of tick samples within their community.

Only a quarter of tick-management programs test ticks for disease-causing germs

Survey respondents from Texas are among the 26% nationwide who said their jurisdiction conducts or financially supports testing of tick samples for disease-causing pathogens. Only 7% of respondents nationwide said their programs work to detect such pathogens in animal hosts, such as mice, that can pass the pathogens to ticks in their area.

“Pathogen testing is an essential component of surveillance and is needed in order to understand tick-borne disease risk to communities,” said Mader. “There appears to be a significant barrier for many tick-surveillance programs across the country to access pathogen-testing services.”

Capacity for public tick-control efforts is low

Texas provides financial support for tick control. Yet nationwide, only 12% of respondents said their jurisdiction conducts or financially supports tick control. Those efforts primarily focused on reducing tick presence on animal hosts such as deer and rodents.

Mader said limited resources mean tick-management programs need reliable, proven control methods.

“They are not going to invest in a strategy unless it has been investigated and shown to make a difference in reducing the burden of ticks and tickborne diseases,” she said. “Right now, supporting this research is a major need. These kinds of evaluations often take at least three years to complete and require a significant investment.”

Tick surveillance and control happen in a range of sectors

The most common employment sectors among respondents was public health, mosquito control, cooperative extension and agriculture. More than half of respondents, 57%, said their programs work with academic partners such as Texas A&M AgriLife to conduct tick surveillance.

Info and data sharing on ticks and public health is lagging

Less than a quarter of respondents, 23%, said their tick-management programs disseminate information to local health departments. Just 14% report data to the CDC.

Greater support for tick-management programs is critical. Respondents commonly cited the need for stable funding, training for personnel, and standardized, research-based guidance and protocols.

Recent national efforts begin to improve the tick situation

In December 2019, the Kay Hagan Tick Act authorized $150 million to strengthen the nation’s efforts on vector-borne disease. The act included funding the CDC’s Vector-Borne Disease Regional Centers of Excellence for an additional five years, through 2026. In the past two years, the CDC also issued guidance on the best practices for surveillance of several tick species.

These steps address several needs that survey responders had highlighted. The authors said the survey will serve as an important baseline from which to measure

Cattle fever tick numbers on the rise

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AgriLife experts warn of ticks’ potential negative economic impact

by Susan Himes, Texas A&M AgriLife Marketing and Communications

Quarantine Zone sign
A million acres beyond the permanent quarantine zone is now quarantined due to cattle fever. (AgriLife photo)

Texas A&M AgriLife Research and the Texas A&M AgriLife Extension Service are working to help thwart the spread of cattle fever.

An announcement from the Texas Animal Health Commission, TAHC, and the U.S. Department of Agriculture’s Cattle Fever Tick Eradication Program, USDA-CFTEP, that cattle fever tick infestations have spread outside the permanent quarantine zone prompted concern from AgriLife experts, who last dealt with a large outbreak in 2017.

“The discovery of more fever tick infestations, particularly outside of the permanent quarantine zone, is significant,” said Pete Teel, Ph.D., AgriLife Research entomologist, College Station. “At risk is the economy of the Texas cattle industry and the more than 400,000 cattle producers throughout the southern region of the U.S.”

Cattle fever ticks, known scientifically as Rhipicephalus annulatus and Rhipicephalus microplus, can carry the microscopic parasites that cause bovine babesiosis or cattle fever. These are the only two tick species that can transmit the disease. Once an animal is infected, these parasites attack red blood cells resulting in acute anemia, enlargement of the liver and spleen, and a high fever.

TAHC and USDA-CFTEP are currently working to determine the extent of the spread of the ticks and to trace the source.

Tracking tick locations

Cattle fever tick close up photo
Close up picture of a live cattle fever tick. (AgriLife Photo)

“When producers observe ticks on their livestock, it is imperative they contact their local TAHC livestock inspector or region office, USDA inspector, private veterinarian or local AgriLife Extension office to arrange for collection and submission of tick samples to the TAHC laboratory in Austin,” said Andy Schwartz, DVM, TAHC executive director, in a recent press release. “This extra surveillance protects the Texas cattle industry.”

So far, ticks have been found on cattle outside of the permanent quarantine zone in Cameron, Hidalgo, Jim Wells, Jim Hogg and Willacy counties. Traditionally, the southern counties of Texas bordering Mexico tend to have the biggest problem with fever tick disease. Both cattle fever ticks and bovine babesiosis are endemic in the neighboring states of Mexico.

An area of a half million acres, stretching from the Gulf of Mexico near Brownsville to north of Del Rio, makes up the permanent quarantine zone. There are now over a million acres quarantined outside of the permanent zone.

“One of the outcomes that often comes back to AgriLife from concerned citizens is the impact of trace-outs from these infestations and how that affects producers, livestock owners and land managers who may be temporarily quarantined until it can be determined that fever ticks have not spread,” said Teel.

AgriLife Research has a long history of dedicated joint research efforts in support of the U.S. cattle industry and the regulatory agencies responsible for the USDA-CFTEP. AgriLife researchers and specialists have formed a support group and all of the agency’s county agents in infected areas are up to date on the latest information.

Anyone with questions or concerns may reach out to their local AgriLife Extension office. The TAMU TickApp for smartphones is also an informative tool.

“More than one-third of the U.S. fed cattle are produced in this region of Texas,” Teel said. “U.S. cattle are naive to bovine babesiosis and mortality is estimated to exceed 70% in naive cattle. There are no protective vaccines or approved drugs. Our focus is to prevent the only vector, cattle fever ticks, from spreading further across Texas.”

Cattle fever eradication efforts began in the U.S. in 1906 and were declared successful in the 1940s. Periodic incursions have been occurring in Texas since the 1970s. Teel said the expansion of native and exotic game, diversification of animal enterprises, changes in land-use, brush encroachment and variation in climatic cycles have all contributed to the challenge of warding off incursions.

“We ask that livestock producers help us in protecting the nation from fever ticks by being proactive when purchasing cattle from counties with known fever tick infestations,” said Schwartz. “The TAHC and USDA-CFTEP operate public dipping vats along the Texas-Mexico border and in a few South Texas counties where producers can voluntarily take their cattle to be treated before returning home.”

Horses, deer and exotic livestock may also host cattle fever ticks. Transportation of any of these hosts can spread cattle fever ticks. Once the ticks are discovered on a location, it is quarantined. Once under quarantine, the cattle and other susceptible animals are prescribed a treatment program until the ticks can be eradicated from the area.

“AgriLife is fully engaged in research projects directly focused on improving technologies, tactics and strategies to prevent these ticks from becoming re-established in the U.S. and thus preventing outbreaks of bovine babesiosis,” said Teel.

AgriLife Research, 4Ry and the USDA’s Agricultural Research Service are also currently working on collaborative research projects to develop additional means to more efficiently and effectively kill cattle fever ticks on cattle, other livestock and wildlife.

Kaufman named head of Department of Entomology, effective July 1

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Phillip Kaufman joins Texas A&M as the head of the Department of Entomology in the College of Agriculture and Life Sciences.
Phillip Kaufman joins Texas A&M as the head of the Department of Entomology in the College of Agriculture and Life Sciences.

Phillip Kaufman, Ph.D., will begin his appointment as head of the Department of Entomology at Texas A&M University, starting July 1.

Kaufman joins Texas A&M from the University of Florida where he served as a professor in the Entomology and Nematology Department in the Institute of Food and Agricultural Sciences. During his 15 years at the university, he helped develop and implement research programs to support Florida livestock producers, taught courses on medical and veterinary entomology and forensic entomology, as well as provided support to Florida Extension faculty and livestock and companion animal stakeholders.

Kaufman’s appointment will include responsibilities in both administration and research. He aims to foster success in both basic and applied research with a plan to continue his own research in addressing current threats and evaluating potential threats to livestock.

“I am very excited to be joining the department’s world-class faculty,” he said. “I believe that it is a department head’s charge to foster faculty and staff professional development, and I look forward to working with everyone in our department to ensure that they feel they are appreciated and have every opportunity to be successful.”

With facilitating an environment where faculty may explore new, cutting-edge research avenues that improve the lives of Texans, Kaufman will also be seeking opportunities for global reach, he explained.

“I want faculty to feel confident in looking in new directions, experimenting with new techniques and areas of interest, so that they can offer the students that we are teaching at Texas A&M the opportunity to be at the forefront of scientific discovery,” he said.

“Dr. Kaufman’s background and experience in research, teaching and Extension will benefit the Department of Entomology and the College of Agriculture and Life Sciences,” said Patrick J. Stover, Ph.D., vice chancellor of Texas A&M AgriLife, dean of the College of Agriculture and Life Sciences and director of Texas A&M AgriLife Research. “I look forward to his leadership of the department and the contributions he will make in this new role. I would also like to thank Dr. Pete Teel for his service as interim department head during the last year.”

Kaufman was awarded the Lifetime Achievement Award in Veterinary Entomology in 2014 at the 58th Annual Livestock Insect Workers’ Conference, and the Illinois 4-H Alumni of the Year award in 2013 by the Illinois 4-H Foundation. He earned his bachelor’s degree in animal sciences from the University of Illinois, his master’s degree in entomology from the University of Wisconsin and his doctorate in plant, soil and insect sciences at the University of Wyoming.

Research looks to beneficial insects for pest control

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by Adam Russell, Texas A&M AgriLife Communications

Predator insects could reduce pesticide use in commercial production

Erfan Vafaie, Texas A&M AgriLife Extension Service entomologist, Overton, holds a vile filled with whiteflies captured during a trial focused on the use of beneficial insects to control whitefly populations. (Texas A&M AgriLife Extension Service photo by Adam Russell)
Erfan Vafaie, Texas A&M AgriLife Extension Service entomologist, Overton, holds a vial filled with whiteflies captured during a trial focused on the use of beneficial insects to control whitefly populations. (Texas A&M AgriLife Extension Service photo by Adam Russell)

A Texas A&M AgriLife Extension Service entomologist is studying how a combination of beneficial insects can help control the pests in greenhouses.

Erfan Vafaie, AgriLife Extension program specialist in Integrated Pest Management, Overton, just wrapped up the second year of a three-year study looking at the use of predatory beneficial insects – mites and wasps – to control sweet potato whiteflies in commercial settings.

Vafaie’s study is for his doctorate dissertation under the supervision of Kevin Heinz, Ph.D., a senior professor in Texas A&M University’s Department of Entomology at College Station.

Whiteflies are sucking insect pests, similar to aphids, and can feed on hundreds of different ornamental, field and vegetable crops. Adults are winged while young whiteflies lie flat against leaves and can be difficult to see with the naked eye.

They reduce plant growth by consuming plant nutrients, he said. Whiteflies also excrete honeydew, which can lead to sooty mold. Sooty mold will not directly hurt the plant but can reduce plant aesthetics; the most important characteristic for retailing ornamental plants. Left unchecked, whitefly populations can overwhelm and cause mortality to many plants, including poinsettias.

Vafaie said ornamental crops, like poinsettias, are especially vulnerable to decreased marketability and ultimately loss in value from appearance of whiteflies and their feeding. Growers are often aggressively proactive with chemical spray treatments to ensure their poinsettias will meet market demands.

“They’re protective of their crop,” he said. “But the potential for using a combination of biological controls to address a suite of harmful insects instead of conventional chemical controls is something growers are interested in and want to learn more about. I think there are a number of potential benefits to using beneficial insects in commercial settings.”

Fighting pests with predators

An adult sweet potato whitefly on the underside of a poinsettia leaf with her recently produced group of eggs. (Texas A&M AgriLife Extension photo by Erfan Vafaie)
An adult sweet potato whitefly on the underside of a poinsettia leaf with her recently produced group of eggs. (Texas A&M AgriLife Extension photo by Erfan Vafaie)

Vafaie said there are many questions about pesticide efficacy, pest resistance to certain chemicals, increased pesticide applicator regulations and the overall cost of using pesticides. Consumer trends also show they want ornamentals to have limited-to-no exposure to pesticides.

Using beneficial insects to control pests and minimize damage to crops could be an important aspect of sustainable production, he said. There are numerous studies showing the effectiveness of using beneficial insects in commercial settings in more temperate climates, especially in fruit and vegetable production, but very little information about how they manage pests of ornamentals in hot, humid areas like East Texas.

Previous studies have tended to focus on the use of a single beneficial insect, such as a parasitic wasp, he said.

“The goal is to determine whether the combination of two beneficial insect species to manage whiteflies can work better than just one for poinsettias in a greenhouse environment,” he said. “I want to know how the wasp and mite work together to suppress whiteflies.”

Parasitic wasps are distributed by hanging cards containing more than 60 wasp pupae per card, and slowly emerge and disperse within the greenhouse. The predatory mites are dispersed using a custom-made blower that distributes the mites on carrier material (wood chip-like material seen on the leaves). (Texas A&M AgriLife Extension photo by Erfan Vafaie)
Parasitic wasps are distributed by hanging cards containing more than 60 wasp pupae per card, and slowly emerge and disperse within the greenhouse. The predatory mites are dispersed using a custom-made blower that distributes the mites on carrier material (wood chip-like material seen on the leaves). (Texas A&M AgriLife Extension photo by Erfan Vafaie)

Vafaie is looking to determine how introducing beneficial predatory mites and parasitic wasps affect the need for pesticide spray treatments. His study started with determining initial whitefly populations on poinsettia cuttings at the grower facilities over two years, whitefly retailer thresholds for two years, and small-scale studies to determine if the combination of the two beneficial insects works better than either one alone.

In the most recent year, Vafaie has focused on commercial trials to manage whitefly populations using beneficial insects in three locations where poinsettias are being grown – two local commercial growers’ greenhouses and Texas A&M AgriLife Research  greenhouses holding poinsettia trials in Overton.

The mites, which are tiny spiders, and wasps, which are smaller than fruit flies and do not sting humans, are natural whitefly predators. The mites feed on small soft-bodied insect nymphs and eggs, including eggs and young nymphs of whiteflies and thrips. The wasps lay eggs under middle-aged nymphs, and the young wasps ultimately feed on the whitefly nymphs.

Wasps have a better ability to move around and often encounter dense populations of whiteflies, whereas mites’ dispersal is much more limited, Vafaie said.

Vafaie and his assistant scouted for whiteflies in both greenhouses managed under conventional insecticide rotations and greenhouses that relied mainly on the wasps and mites for whitefly control.

So far, so good

A predatory mite feeding on a whitefly nymph on the underside of a poinsettia leaf. (Texas A&M AgriLife Extension photo by Erfan Vafaie)
A predatory mite feeding on a whitefly nymph on the underside of a poinsettia leaf. (Texas A&M AgriLife Extension photo by Erfan Vafaie)

At Location 1, Vafaie said spot sprays were required in addition to the beneficial insects in sections of the greenhouses after whitefly populations moved in. At Location 2, no pesticide applications for whiteflies were necessary in the beneficial insect-managed greenhouse, but fire ant bait was needed to manage the fire ants, which were consuming the beneficial insects.

In Overton, two broadcast applications were needed to bring whitefly populations back down to manageable levels for the beneficial insects.

In small-scale trials, Vafaie said the combination of wasps and mites worked as well as either predator alone. Scouting for whiteflies and spot-spraying alone helped decrease the use of pesticides during the study.

Pesticides that do not kill the wasps and mites are typically used, or a spray that will not leave residuals that will harm the beneficial insects following a treatment, he said.

“Throughout the small-scale study, the combination of mites and wasps were more reliable in handling simulated whitefly migrations into the greenhouses,” he said. “Mites are thought to wait and intercept incoming whiteflies, while wasps actively move around and encounter new populations of whiteflies.”

Wasps were released every week while mites were released every four weeks, Vafaie said.

Vafaie said applications of beneficial insects took less time and labor than spray applications. Although the cost of beneficial insects was roughly equivalent to the typical cost of pesticide inputs, a full cost comparison between conventional insecticide rotations and the beneficial insect strategy is still pending.

“The key to this strategy is to use the beneficial insects to maintain whiteflies below the retailer threshold,” he said. “Unlike pesticide applications, biological control is a numbers game; each beneficial insect can only eat or lay eggs under so many whiteflies for a given period of time. If whiteflies are reproducing at a faster rate than the beneficial insects can consume, then it’s time to knock down whitefly population with some selective pesticides to levels manageable by the beneficial insects again.”

Vafaie hopes to extend the study further and incorporate an economist to analyze the cost benefits of using beneficial insects compared to conventional preventative insecticide rotations for commercial poinsettia production.