Floriculture Industry Working To Solve The Whitefly Problem

Bemisia tabaci on Hibiscus
Bemisia tabaci on Hibiscus

This summer, the floriculture industry has been faced with a dangerous new development — the detection of the Q-Biotype whitefly (Bemisia tabaci) in outdoor landscapes. It’s the first time that the Q-Biotype has been found in the U.S., outside of a greenhouse or wholesale nursery, since the pest was first detected on an ornamental plant in an Arizona greenhouse in December 2004.

This year in Florida, there have been 47 detections of the Q since April, in retail nurseries and residential landscapes in 10 counties in Florida, from Miami-Dade to Duval County, primarily on hibiscus. Other hosts involved are crossandra, eggplant transplants, lantana, ficus, and porter weed. The detections have been in 17 retail nurseries, eight wholesale nurseries, 10 residential landscapes, and two agricultural fields. Other states have reported Q-Biotype detections this year, as well.

The discovery of Q-Biotype whitefly in the landscape is troubling for the entire ornamentals industry, as well as the vegetable and cotton industries, considering that the pest is an invasive that feeds on 600 crops and carries more than 100 viruses. Research on the Q-Biotype has also revealed that it is highly prone to developing resistance to insect growth regulators and other pesticides, that it maintains that resistance and doesn’t revert to susceptibility when pesticides are absent, and that it may be a better vector of pathogens than the B-Biotype whitefly.

However, due to the industry’s involvement in the National Whitefly Taskforce, which since its establishment in 2005 has developed a strong framework for control and management of Q-Biotype and B-Biotype whiteflies, the outlook for mitigating the whitefly problem is positive, though it’s still a problem.

“The introduction of the Q-Biotype whitefly has threatened to be a major crisis, but thanks to industry, government, and top entomologists’ cooperation, we have been able to deal with it,” says Dr. Joe Bischoff on behalf of the Society of American Florists (SAF).

Identifying Q-Biotype And Deciding On A Course Of Action

 

Initially detected at a retail nursery in Arizona in 2004, the Q-Biotype whitefly was found in 19 states in 2005, followed by two states in 2006 and 2007, and single-state detections in 2008 and 2010, according to Cindy McKenzie, Research Entomologist, USDA’s Agricultural Research Service (USDA-ARS). To date, Q-Biotype has been found in 26 states, with no new detections in additional states since 2010, though new samples continue to be submitted.

Cindy McKenzi, USDA-ARS
Cindy McKenzie, USDA-ARS

When the first Q-Biotype was traced back to poinsettias, the vegetable and cotton industries got involved, demanding that the USDA shut down imports of all poinsettia cuttings from offshore farms and limit the movement of ornamentals between states.

“When whitefly came in, it was threatening the industry at many levels, including infesting plants and putting a big bullseye on our backs,” says Dr. Lance Osborne, a Professor and Scientist of IPM-Biological Control of Insects and Mites with University of Florida’s Institute of Food and Agricultural Sciences (UF-IFAS). “Lin Schmale (of SAF) saw the writing on the wall, and with her ability to talk with people, she got the ear of Dr. Osama El-Lissy, a leading APHIS scientist who is now USDA’s Animal and Plant Health Inspection Service (USDA-APHIS) Deputy Administrator. They wanted to attack this whole issue with science, tasking industry and regulatory scientists with figuring out how to manage this.”

As a result of these discussions, in 2005, the USDA’s APHIS established an Ad Hoc National Whitefly Taskforce and technical working group to decide the best response and develop a coordinated response to the problem.

“APHIS determined that rather than taking a regulatory approach, an integrated pest management program should be used to control Q-biotypes,” says Dr. Mary Palm, Director of Pest Management, USDA APHIS.

The cross-functional taskforce is comprised of federal and state regulators, and university and industry representatives from the floriculture, nursery, cotton, and vegetable industries.

“The technical working group pulled together scientific and technical information to inform the task force, including virus transmission, distribution, susceptibility, and resistance issues, to determine chemical resistance and an appropriate treatment regime, since Q is resistant to many of the world’s pesticides and B may be developing resistance, as well,” Palm says.

Together, the taskforce developed a functional plan to empower ornamental growers, so the Q-biotype would be managed by the industry through an integrated pest management program (IPM), to include sanitation, scouting, biotype identification, exclusion, educating workers, inspecting incoming plant material, etc.

“Because of the work of the National Whitefly Taskforce, and the vigilance of our growers in following the recommended spray protocols, the Q-Biotype has not become a serious problem here, as it has in the Mediterranean regions,” McKenzie says.

Based on the detection of Q-Biotype whitefly in the landscape, as well as increased whitefly pressure overall, Palm says APHIS is reinvigorating the cross-functional taskforce to collaborate on refocused outreach to growers and an updated IPM program.

“We are reaching out to scientists who work in other potentially impacted crops to determine how we might be able to help them,” Osborne says. “We probably have tools that they can’t use, and they may have a few tools that we have not evaluated for efficacy on the Q.”

Research Dollars Fund Biotyping And Integrated Pest Management Work

Through SAF’s role in working with USDA-ARS on the Floriculture and Nursery Research Initiative (FNRI), funding from FNRI has provided research grants to the National Whitefly Taskforce for the past decade.

Bemisia tabaci, Adult whitefly
Bemisia tabaci, Adult whitefly

“Initially, we needed some very quick evaluations of what could be used to control the Q-Biotype, so we made small subcontracts with Jim Bethke, Dan Gilrein, Scott Ludwig, Ron Oetting, and researchers all over the country, for help testing chemicals on whiteflies and chilli thrips and Q-Biotype,” Osborne says. “If you look at all the chemical registrations, they are the ones who developed the data. Cristi Palmer of USDA’s IR-4 was a very significant contributor to this effort, as well.”

Through the 2014 Farm Bill’s Section 10-007 Plant Pest and Disease Management and Disaster Prevention Program, APHIS has invested $787,769 over the last three years for research programs to enhance mitigation techniques for control of several exotic whitefly species at Florida Department of Agriculture and Consumer Services and UF-IFAS, according to Kenneth Bloem, Farm Bill Management Team, Plant Protection and Quarantine Science and Technology, USDA APHIS. In addition, Bloem says APHIS has had a cooperative agreement for the last two years with UF-IFAS ($110,000 in Farm Bill Section 10-007 funds) for the Neonic Stewardship Program for the Management of the Invasive Bemisia Whitefly Complex.

One major outcome of the investments by FNRI and APHIS is McKenzie’s development of molecular diagnostic tools for distinguishing different biotypes of Bemisia tabaci, and using these to more quickly determine the whitefly’s distribution.

“Universal primers and mtCOI PCR-primers specific for the B and Q biotypes of B. tabaci were designed that allow rapid discrimination among these biotypes, without sequencing. Sequencing is very time-consuming and can be costly,” McKenzie says. “We also determined two microsatellite markers that were also a cost-effective diagnostic alternative for biotype identification.”

These new primers allow national and international labs to determine biotype status without the cost, time, and equipment required to sequence primer products, according to McKenzie. Prior to her work, biotyping could cost $100 per whitefly and took up to two weeks for identification. Now, growers can send whiteflies to McKenzie’s lab to be biotyped for free, and get results within a week. The tools also help researchers identify best management strategies.

“These diagnostic tools are powerful genotyping methods that can be used to provide information for improved management decisions with respect to pesticide applications,” McKenzie says. “By coordinating mtCOI and microsatellite genotyping with insecticide resistance profiles, we can predict insecticide efficacy before the grower sprays.”

Further, the use of the molecular tools allows investigators to track the origins of whitefly biotypes, allowing offshore farms to improve management efforts, McKenzie says. Her research team was the first to report Q-Biotype whitefly in Guatemala, a distribution source for ornamental cuttings.

Crop Protection Changes Fuel Need For More Research On Integrated Pest Management Solutions

A significant challenge to the floriculture industry has been the rapid shift away from neonicotinoid pesticides, in large part due to mandates from retailers responding to consumer pressure and social media campaigns suggesting a potential impact on pollinators. The challenge has been particularly felt in attempts to deal with Q-Biotype whitefly, because neonicotinoids have been an important element in the whitefly management protocol.

“At some point in the process of analyzing the benefits and risks of using any pesticide, some common sense should be used,” Osborne says. “When we’re dealing with invasive species, if we start removing tools like neonicotinoids, it becomes much more difficult to keep these things in check.”

Whitefly adult infected by a fungal pathogen, courtesy of Dr. Lance Osborne, University of Florida IFAS.
Whitefly adult infected by a fungal pathogen, courtesy of Dr. Lance Osborne, University of Florida IFAS.

These new challenges require additional research dollars, to allow the taskforce to develop whitefly management programs that are not totally dependent on the use of at-risk pesticides like neonicotinoids. The taskforce recently applied for third-year funding from the USDA’s 10-007 program for continued work in this area.

Currently, Osborne and McKenzie and their teams are evaluating three new chemistries — Rycar, Mainspring, and Xxpire, as well as pesticide rotations with and without neonicotinoids, and multiple unregistered materials.

“We have no silver bullets, but I feel we have the ability to manage this pest by using a systems approach, and stringing a number of control tactics together in an overall management plan,” Osborne says.

This approach incorporates new chemistries that are compatible with certain biological control agents showing efficacy on Q-Biotype whitefly, including three beetles, two wasps, one predatory thrips and two mites.

Next Steps For Whitefly Management Must Include Cooperation Among Regulators, Scientists, And Growers

What could actually harm the battle against Q-Biotype whitefly, the taskforce agrees, is for states to make it a regulated, actionable pest and quarantine greenhouse operations until no Q-Biotype whiteflies are found in the crops, as growers will then use all means to try to obtain 100% whitefly-free plant material, irrespective of the species or biotype.

“We need continued cooperation from everyone involved,” Osborne says. “Growers must be able to have their whitefly populations biotyped without fear of being quarantined. Otherwise, we could have a serious problem on our hands.”_mg_9004-wcf

Going forward, APHIS recommends that growers mitigate Q-Biotype whitefly with IPM practices, including scouting, exclusion, sanitation, isolating and inspecting young plants, and using the appropriate controls. Follow the Q-Biotype whitefly management recommendations at http://goo.gl/E5w4mC.

Communication with other growers, customers, and scientists is crucial, to understand the problems at hand, what controls are working and what is not. This is especially important during high-pressure production times like poinsettia season.

“Whiteflies are particularly fond of poinsettia, so growers must be especially vigilant and if they are having problems controlling whiteflies, send samples to me for identification,” McKenzie says. “Both B and Q are controlled best if you know which type you are dealing with. But you do not want to develop a population of Q that could survive in your greenhouse or nursery from one season to another, or that could move to vegetable transplants.”

USDA-APHIS To Introduce Certification Program For Offshore Producers In 2017

The USDA’s Animal and Plant Health Inspection Service (APHIS) is partnering with the floriculture and nursery industry to develop an offshore cuttings greenhouse certification program. The voluntary program will ensure that participating producers are following specific facility requirements and growing standards that address plant pests and pathogens, according to Andrea Simao, Director of Preclearance and Offshore Programs, USDA-APHIS. APHIS and the industry hope to pilot this program in fiscal year 2017.

“APHIS works collaboratively with many industries domestically and abroad to develop operationally practical solutions that mitigate against quarantine pests entering the U.S. via various plant import pathways,” Simao says.

Currently, APHIS is working with the major offshore ornamental cutting producers to develop production and sanitation standards for implementation offshore that control a range of pests, including insect pests and plant pathogens.

“While further analysis and planning are necessary, creating an industry-APHIS cooperative greenhouse certification program for vegetative cuttings produced offshore could result in detection and management of pests at the point of origin, thereby improving protection of American agriculture through reduced interceptions at U.S. ports of entry,” Simao says. “These standards rely on data generated as part of the Q-Biotype Working Group and data generated by scientists in the U.S. as the result of Farm Bill funding.”

Look for additional details on the certification program soon, on GreenhouseGrower.com.

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