Emerging Issues in the Management of Silverleaf Whitefly

Hugh SmithVegetable Entomologist

Gulf Coast Research and Education CenterBalm, FL 33598

Whitefly Biotypes in Florida

Biotype Q: First detected in Florida 2005.Why are we concerned?

Biotype A: Up until late 1980s. Rarely caused damage.

Biotype B (silverleaf whitefly): Since late 1980s.TYLCV and irregular ripening.

I. Generalizations about the Q biotype

“Q biotype is resistant to neonicotinoids (MoA 4A).”

China, Israel, Spain:

Resistant to –imidacloprid (Admire)thiamethoxam (Platinum, Actara)acetamiprid (Assail)

However:

Insecticides with efficacy on Q (adults and nymphs):

● Venom/Scorpion (dinotefuran; MoA 4A)

● Sivanto (flupyradifurone; MoA 4D)

● Verimark/Exirel (cyazypyr; MoA 28)

II. Generalizations about the Q biotype

“Q biotype is resistant to insect growth regulators (IGRs)”

IGRs: prevent nymphs from becoming adults.

Israeli cotton: Q was resistant to pyriproxifen(Knack).

● China: Q not resistant to pyriproxifen

IGRs used in Florida tomato:

● Knack (pyriproxifen) – MoA 7C● Courier (buprofezin) – MoA 16

Courier (buprofezin)MoA 16

● reduces egg viability.

● interferes with molting.

● contact only.

● 2 applications at least 5 d apart.

● 1 day PHI.

Knack (pyriproxifen)MoA 7C

● reduces egg viability

● interferes with molting , adult emergence.

● translaminar: will reach underside of leaf.

● 2 applications at least 2wk apart.

● 1 day PHI

Other insecticides for controlling whitefly nymphs:

Movento (spirotetramat)

Oberon (spiromesifen)

● Lipid biosynthesis inhibitors

● Both are MoA 23 so choose one or the other.

● Movento works well on Q elsewhere.Ambimotile.

Biotype Q in Florida● April 2016: Q detected on hibiscus plants in residential landscape in Palm Beach County.

● First time Q has been detected in the landscape vs on potted plant in box store.

● Multiple detections in multiple counties since then.

● Glades Crop Care has been submitting samples from field vegetables since April: all have been B biotype.

● So far no evidence that Q has become established in field horticulture.

Current opinion: Whitefly biotypes are different species.

How much can we generalize about how an entire species reacts to insecticides?

Insecticide resistance: ● inherited (genetic)● determined by insecticide pressure● varies among populations of the same species.

Resistance Monitoring Biotype B: Oct 2013-Feb 2015.

● Whiteflies tested from 19 sites - Balm to Homestead.

● Susceptibility to Admire, Platinum, Venom and Sivanto.

● LC50 = “50% Kill” of test whiteflies. How much is needed to kill 50% of whiteflies from a given crop.

● The lower the LC50, the more effective the insecticide (less material needed to kill 50%).

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Sivanto

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Venom

VENOM (dinotefuran)

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VENOM (dinotefuran)

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Admire

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ADMIRE (imidacloprid)

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Platinum

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PLATINUM (thiamethoxam)

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Resistance Monitoring: Silverleaf Whitefly Biotype B in Florida

● Some populations generally susceptible to all four materials.

● Some populations generally tolerant to all four materials, including Sivanto, even though they had never been exposed to it.

● On the whole, populations responded in a similar way to Admire and Platinum, and in a similar way to Sivanto and Venom.

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Admire

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Smith, H. A., C. A. Nagle, C. M. MacVean, C. L. McKenzie. Susceptibility of Bemisia tabaci MEAM 1 (Hemiptera: Aleyrodidae) to imidacloprid, thiamethoxam, dinotefuran and flupyradifurone in South

Florida. Insects. In Revision.

● It is not possible to generalize about biotype B susceptibility to insecticides.

● The biotype Q populations in Florida are the result of multiple introductions from multiple sites.

● It is unlikely that we can accurately generalize about the impact Q will have on the state or how Q will respond to insecticide treatments without data.

III. Generalizations about the Q biotype“Biotype Q remains permanently resistant to insecticides.”

● This is biologically impossible.

Bioassay set-up: neonicotinoid tolerance

● How many generations does it take for susceptibility to return?

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Hillsborough1Admire

Hillsborough1Platinum

Hendry1Admire

Hendry1Platinum

LC50

ppm 2nd-3rd gen

6th-7th gen9th-10th gen

Biotype BTesting susceptibility to Admire and Platinum over multiple generations without exposure.

Funding from FDACS

Assessing the biotype Q threat to Florida agriculture.

1. Survey for biotype.

2. Test for tolerance.

1. Survey for biotype.

● Submit whitefly adults from your fields to Smith lab.

● Use my Fedex/UPS number.

● I will send to Cindy McKenzie for biotyping.

2. Test for tolerance● Establish colonies of Q at GCREC.

● Test for susceptibility to key insecticides.

● Develop guidelines for management.

Secure containment facility at GCREC for biotype Q resistance monitoring.

AcknowledgementsFunding

Florida Tomato CommitteeFlorida Department of Agriculture and Consumer ServicesBayer Crop Science.

Smith LabCurtis Nagle, Laurie Chambers, Justin Carter, Marc Santos, Pritika Pandey, Karla Medina-Ortega

Hugh Smithhughasmith@ufl.edu

813 633 4124

Questions?