Tackle Whiteflies Head On

Tackle Whiteflies Head On

2016 Florida Ag Expo panel discussion on whiteflies

The emerging threat of the Q-biotype whitefly this past year earned it a prime time spot among the 2016 Florida Ag Expo educational session lineup. [From left] Lance Osborne, UF/IFAS MFREC; Cindy McKenzie, USDA (Ft. Pierce); and Hugh Smith, UF/IFAS GCREC discussed the hot topic. Osborne told the crowd: “It can be manageable. Just beware.” Photo by Paul Rusnak

A dangerous new development occurred this summer — the Q-Biotype whitefly (Bemisia tabaci) was detected in outdoor landscapes. This marks the first time 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 53 detections of the Q-Biotype since April, in retail nurseries and residential landscapes in 13 counties in Florida, from Miami-Dade to Duval County. Other states have reported detections this year, as well.

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The discovery of Q-Biotype whitefly in the landscape is troubling for the ornamentals and vegetable industries, considering that this is an invasive pest that feeds on 600 crops and carries more than 100 viruses. However, due to the collaboration of the industries within the National Whitefly Taskforce, which since its establishment in 2005 has developed a strong framework for control and management of both Q-Biotype and B-Biotype whiteflies, the outlook for mitigating the whitefly problem is positive.

Cindy McKenzie, Research Entomologist, USDA’s Agricultural Research Service, answers some questions on the current situation with the Q-Biotype, potential controls, and the next steps to mitigate the spread of this pest.

What is the current situation with Q-Biotype whitefly and where has it been found in the U.S. thus far?

McKenzie: Q-Biotype has been found in 26 states to date with no new state detections since 2010. This year in Florida, we have had detections primarily on hibiscus. Other hosts involved are crossandra, eggplant transplants, lantana, ficus, and porter weed.

What is the concern behind the finding of the Q-Biotype pest in the U.S.?

McKenzie: Q-Biotype develops resistance to insecticides faster (especially to the insect growth regulators), to a higher level and does not revert back to susceptible levels in the absence of insecticides (unlike the B-Biotype whitefly). Q-Biotype also is reported to be a more efficient vector of plant pathogenic viruses than B-Biotype.

What is the difference between Q- and B-Biotypes in the damage they do and the crops they affect?

Closeup of Q-biotype or B-biotype whitefly

Is this a Q-biotype or B-biotype whitefly? The two pests look identical. Photo courtesy of UF/IFAS

McKenzie: In terms of direct feeding damage, they are about equal. In extreme cases, both can kill a plant by sheer numbers alone. Biotype B is unique in that it causes plant disorders such as tomato irregular ripening and squash silverleaf disorder. Both are very good vectors of plant viruses, although Biotype Q has been reported to be more efficient at transmitting some of the vegetable viruses.

Are there any chemical or biological controls or methods currently in existence that will effectively control Q-Biotype whiteflies?

McKenzie: Both chemical and biological controls exist for control, but the best approach would be multi-pronged, where each is compatible and synergistic to the other. For vegetable growers, Hugh Smith at the University of Florida says the following insecticides have efficacy on both B- and Q-Biotype: Venom (Valent), Sivanto (Bayer CropScience), Movento (Bayer CropScience), and Verimark (DuPont).

What locations in the world have the Q-Biotypes been imported?

McKenzie: Q-Biotypes, also known as MED, originated from the Mediterranean regions of Europe. We have conducted microsatellite studies that have shown both the Eastern (Israel region) and Western (Spain region) MED are found throughout the continental U.S., and the Eastern MED is present in Hawaii. Our results suggest MED was introduced into the U.S. on at least three occasions and rapidly spread throughout the country.

How are the Q-Biotypes able to successfully pass by USDA-APHIS inspection to make it into the country?

McKenzie: Q-Biotypes are indistinguishable morphologically from B-Biotypes — they look identical and can only be differentiated molecularly. Regardless of the biotype, it can be difficult to detect whiteflies, especially eggs, and early immature stages and, thus, some go undetected by inspectors.

What can growers in the U.S. do to help mitigate the spread of Q-Biotype whitefly?

McKenzie: Scout, scout, and scout some more. Pay attention to detail, and, if you have a whitefly problem, get them identified early so you can make the best choice to control your specific whitefly population.

How will additional funds from Section 10-007 of the Farm Bill help you to continue with research to mitigate pests like Q-Biotype whitefly?

McKenzie: Continued funding will allow us to improve our management programs and develop an updated systems approach to managing this pest. We need to incorporate new chemistries into our proven management programs that are compatible with biological control agents. We also need to find ways of being less dependent on a single class of insecticides (neonicotinoids), which we may be in jeopardy of losing.

Neonicotinoids are already banned in some of the Pacific Northwestern states. And, of course, we need to continue biotyping grower samples anonymously and with no cost to the grower. This is paramount to successfully identifying the problem without regulatory repercussion and providing management tools to solve/mitigate the problem. AVG

Drotleff is Editor of Greenhouse Grower® magazine, a Meister Media publication.