Bemisia tabaci MED (Q biotype) (Hemiptera: Aleyrodidae) in Florida is on the move to residential landscapes and may impact open-field agriculture.
Adults or immature stages of whiteflies collected were immediately placed in 95% ethanol for molecular analysis. If available, at least 12 whiteflies from each sample were used for species determination following the protocol developed by Shatters et al. (2009). DNA was extracted from individual whiteflies by placing a single whitefly in a 1.5 mL microcentrifuge tube, adding 50 [micro]l DNA lysis buffer, and grinding with a pestle. The pestle was rinsed with an additional 50 [micro]l DNA lysis buffer that was collected in the same tube. Tubes were placed in a metal boiling rack and boiled at 95 [degrees]C for 5 min and then placed in crushed ice for 5 min. Tubes were then centrifuged at 8,000 g for 30 s, and the supernatant (crude DNA lysate) was transferred to a new tube and stored at -80 [degrees]C for future processing.
We used species (biotype) specific polymerase chain reaction (PCR) primers that had been designed by Shatters et al. (2009) to recognize unique mtCOI gene regions within the MEAM1 (B biotype), NW biotype, and MED (Q biotype) species; these primers produce different-sized products depending on the source of the isolated template DNA and do not require DNA sequencing. The chosen mtCOI primer pairs amplified fragments of 303, 405, and 478 bp from DNA of the MED, NEW WORLD, and MEAM1 species, respectively. The 30 [micro]l final volume PCRs were run using a PTC-0200 DNA Engine[R] Peltier thermal cycler (MJ Research, Inc., Waltham, Massachusetts) under the conditions described by Shatters et al. (2009).
PCR amplifications for the mtCOI gene were also performed using the Btab-Uni primer set described by Shatters et al. (2009) for whiteflies determined to be B. tabaci NW biotype in any environment or B. tabaci MED in unique environments (residential landscapes and open field agriculture) by the species specific primer cocktail. An mtCOI sequence analysis was performed first by PCR amplifying an approximately 700 to 800 bp mtCOI DNA fragment and then sequencing the PCR amplified DNA. The 30 [micro]l PCRs were run using a T100 (TM) Thermal Cycler (BIO-RAD Laboratories, Inc., Hercules, California) under the conditions described by Shatters et al. (2009). Prior to sequencing, the amplified products were cleaned using Montage ([R]) PCR cleanup filters (Millipore, Billerica, Massachusetts). Fifty ng of total whitefly genomic DNA were used in BigDye[R] (Applied Biosystems, Foster City, California) sequencing reactions. All sequencing was performed bidirectionally with the amplification primers and BigDye ([R])Terminator v3.1 Cycle Sequencing Kits (Applied Biosystems, Foster City, California). Sequence reactions were analyzed on an Applied Biosystems[R] 3730XL DNA Analyzer (Applied Biosystems, Foster City, California) and were then compared and edited using Sequencher software (Gene Codes, Ann Arbor, Michigan). Biotype determination was based on direct sequence comparisons using the web based National Center for Biotechnology Information BLAST sequence comparison application (http://blast.ncbi.nlm.nih.gov/Blast.cgi), and sequences were deposited in GenBank.
Since the previous B. tabaci distribution surveys were done in Florida statewide (McKenzie et al. 2009) and in North America (McKenzie et al. 2012), B. tabaci MED was detected in Florida in 2011 (7 detections), 2013 (2), and 2014 (3) primarily on poinsettia (11) with a single detection on hibiscus. All B. tabaci MED detections were from nursery or greenhouse environments (McKenzie unpublished data). In 2016, landscapers and pest control operators in Palm Beach County, Florida, began experiencing problems controlling extremely high populations of Bemisia whiteflies on hibiscus plantings in multiple residential neighborhoods. In total, 10 residential landscapes were identified and subsequently determined to be infested by eastern B. tabaci MED (Table 1). Bemisia tabaci MED detected at 1 location was traced back to a wholesale nursery, and the infestation was the direct result of a new planting of hibiscus. Before it was contained, this infestation spread to lantana and a ficus hedge located on 2 neighboring properties. Bemisia tabaci MED was also detected on single family residences with established hibiscus (not new plantings), firecracker flower or mixed ficus hedges that did not have any apparent connection and were kilometers apart from one another. The original source of these infestations remains unknown. Bemisia tabaci MED was detected in Florida as far north as Tequesta, as far east as Palm Beach Island, as far south as Boca Raton, and as far west as Boynton Beach with a few detections in the center of Palm Beach County. In all of these residential landscape collections, B. tabaci MED comprised the entire sample. Three residential landscape collections resulted in 100% B. tabaci MEAM1 (data not shown). All residential detections were in very affluent well-manicured landscapes.
Florida vegetable fields have been heavily sampled to determine B. tabaci species composition for well over a decade and especially in tomato (McKenzie et al. 2004, 2009, 2012; Schuster et al. 2010; Caballero et al. 2014; Smith et al. 2016) with only B. tabaci MEAM1 being detected. In 2016, we processed 551 whiteflies from 28 vegetable field samples including tomato (9), cucumber (2), potato (1), watermelon (6), eggplant (3), and sweet potato (7); all were B. tabaci MEAM1. In Aug 2016, B. tabaci MED was detected in a field of sweet potato in Elkton, St. John County (Table 1), at a very low ratio (15:1 MEAM1: MED). This collection was totally comprised of immature nymphs removed from a sweet potato leaf from an isolated open field planted 90 d prior indicating that, because whitefly immatures are not mobile after the 1st instar, B. tabaci MED had oviposited on sweet potato in the field. However, approximately 1 wk after the initial collection, additional whitefly samples were taken from the same field, and only B. tabaci MEAM1 was detected (138:0 MEAM1: MED). Bemisia tabaci MED was also detected (1:16 MEAM1: MED) on morning glory weeds growing on the border of a fallow vegetable field ready to go into production in Palm Beach County and was confirmed 3 wk later with another sample (2:3 MEAM1: MED). This field was 800 m west of a wholesale nursery known to have B. tabaci MED.
In addition to the residential and open field detections, B. tabaci MED has been detected in 8 wholesale nurseries from 4 counties and 17 retail nurseries from 8 counties in Florida (Table 2). Bemisia tabaci MED was detected on multiple sampling dates from several of the nurseries. Hibiscus was the driving host plant in nursery (wholesale and retail) infestations and accounted for 78% of B. tabaci MED detections followed by firecracker flower and eggplant each with 9% and a single lantana detection. Sixty-five percent of the B. tabaci MED positive samples (21) were 100% B. tabaci MED and 35% (11) were mixed populations of B. tabaci MEAM1 and MED. One hundred samples from retail and wholesale nurseries were 100% B. tabaci MEAM1 and 1 sample from a retail nursery sampled from mint was 5:1 MEAM1:NW (National Center for Biotechnology Information accession number: KY131961) and represents the first detection of B. tabaci NW in Florida since it was displaced by B. tabaci MEAM1 in the mid-1980s (McKenzie et al. 2004, 2009, 2012).
We do not know why B. tabaci MED (Q biotype) emerged as a pest in Florida landscapes in 2016. Bemisia tabaci is not usually a problem in the landscape due to the multiple host plants and the presence of a complex of natural enemies that keep whiteflies in check. In addition, commercial producers of ornamental plants have successfully managed B. tabaci MED since its first detection in Florida years ago.
Several factors may explain the detection of B. tabaci MED in Florida landscapes in 2016. First, environmental conditions may have been favorable for the buildup of B. tabaci in the landscape. It is also possible that growers have gotten complacent and less vigilant in implementing solid whitefly management strategies. In addition, due to recent publicity about potential impacts on pollinators, some large retail garden centers have been pressuring ornamental producers to stop using neonicotinoid insecticides. Certain neonicotinoids are among the few insecticides that are highly effective against B. tabaci MED. As a result, some growers may have relied on older, less effective chemistries to which B. tabaci MED is resistant. These include pyrethroids, organo-phosphates, carbamates, insect growth regulators, and some neonicotinoids (Nauen et al. 2002, Horowitz et al. 2005, Nauen & Denholm, 2005).
Because we have detected B. tabaci MED in open field crops in the United States for the first time, and this pest is known to attack vegetables and cotton in other countries, there is a risk that unmanaged populations of B. tabaci MED could move from protected ornamental greenhouse production to open agriculture. In some cases, vegetable transplants and an array of ornamental plants are grown together in a greenhouse, which further increases the risk of introducing B. tabaci MED to field plantings of vegetables. There is also a concern that increased pesticide resistance will evolve in B. tabaci MEAM1.
To decrease the risk of B. tabaci MED and insecticide resistant B. tabaci MEAM1 spreading from ornamentals to field-grown vegetables and cotton, it is critical for producers and managers of ornamental plants to practice sound integrated pest management. This includes the use of cultural control, biopesticides, natural products (oils, soaps), and biological control. These management practices can provide some control of whiteflies under low pest pressure. However, under higher pest pressure, it is critical for growers to select targeted chemistry with known activity against B. tabaci MED and, if necessary, destroy infested crops.
This research was partially funded by the Floriculture and Nursery Research Initiative of the United States Department of Agriculture, Agricultural Research Service.
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Cindy L. McKenzie (1,*) and Lance S. Osborne (2)
(1) United States Department of Agriculture, Agricultural Research Service, United States Horticultural Research Laboratory, Fort Pierce, FL 34945, USA; E-mail: firstname.lastname@example.org (C. L. M.)
(2) University of Florida, Entomology and Nematology Department, Mid-Florida Research & Education Center, Apopka, FL 32703, USA; E-mail: email@example.com (L. S. O.)
Please Note: Illustration(s) are not available due to copyright restrictions.
Table 1. Sample date, location by city and zip code, host plant, electrophoresis and sequencing results, and National Center for Biotechnology Information (NCBI) accession number for residential landscape and open field detections of Bemisia tabaci Mediterranean (MED). Sample date Location by city Host plant and zip code 25 Apr 2016 North Palm Beach, FL 33408 Hibiscus 4 May 2016 North Palm Beach, FL 33408 Hibiscus 4 May 2016 North Palm Beach, FL 33408 Lantana 4 May 2016 North Palm Beach, FL 33408 Ficus / Hibiscus 12 May 2016 Palm Beach, FL 33480 Hibiscus 13 May 2016 Boca Raton, FL 33496 Hibiscus 20 May 2016 Boynton Beach, FL 33437 Hibiscus 24 May 2016 Palm Beach, FL 33480 Hibiscus 7 Jun 2016 Boca Raton, FL 33496 Firecracker flower 25 Jul 2016 Tequesta, FL 33469 Porterweed 25 Jul 2016 Tequesta, FL 33469 Hibiscus Field Detections 17 Aug 2016 Elkton, FL 32033 Sweet Potato 23 Aug 2016 Elkton, FL 32033 Sweet Potato 25 Aug 2016 Boynton Beach, FL 33472 Morning glory on fallow vegetable field border 16 Sept 2016 Boynton Beach, FL 33472 Morning glory on fallow vegetable field border Electrophoresis Uni-tab MED NCBI results sequence accession Sample date MEAM1:MED (a) results number 25 Apr 2016 0:44 Eastern MED KY073617 4 May 2016 0:4 Eastern MED KY073618 4 May 2016 0:20 Eastern MED KY073619 4 May 2016 0:12 Eastern MED KY073620 12 May 2016 0:20 Eastern MED KY073621 13 May 2016 0:20 Eastern MED KY073622 20 May 2016 0:20 Eastern MED KY073623 24 May 2016 0:1 Eastern MED KY073624 7 Jun 2016 0:14 Eastern MED KY073625 25 Jul 2016 0:18 Eastern MED KY073626 25 Jul 2016 0:18 Eastern MED KY073627 17 Aug 2016 15:1 Eastern MED KY073628 23 Aug 2016 138:0 no MED data Not applicable 25 Aug 2016 1:16 Eastern MED KY073629 16 Sept 2016 2:3 Eastern MED KY131960 (a) MEAM1 = Middle Eastern Asia Minor 1. Table 2. Sample date, host plant, nursery environment, Florida county, and biotype specific primer results for wholesale and retail nursery detections of Bemisia tabaci Middle Eastern Asia Minor 1 (MEAM1; biotype B) and Mediterranean (MED; biotype Q). Date received Host plant Nursery environment Florida county 11 May 2016 Hibiscus Wholesale (1) Palm Beach 1 Jun 2016 Hibiscus Wholesale (2) Highlands 12 Jun 2016 Hibiscus Retail (1) Martin 13 Jun 2016 Hibiscus Wholesale (2) Highlands 13 Jun 2016 Hibiscus Wholesale (3) Palm Beach 14 Jun 2016 Hibiscus Retail (2) Seminole 14 Jun 2016 Hibiscus Retail (2) Seminole 17 Jun 2016 Hibiscus Retail (3) Palm Beach 17 Jun 2016 Hibiscus Retail (3) Palm Beach 17 Jun 2016 Hibiscus Retail (4) Duval 22 Jun 2016 Hibiscus Retail (5) Broward 22 Jun 2016 Firecracker flower Retail (6) Pinellas 23 Jun 2016 Hibiscus Retail (7) Palm Beach 23 Jun 2016 Hibiscus Retail (8) Martin 27 Jun 2016 Eggplant Retail (9) Hillsborough 27 Jun 2016 Hibiscus Retail (10) Palm Beach 6 Jul 2016 Eggplant Retail (11) Seminole 6 Jul 2016 Hibiscus Wholesale (4) Miami-Dade 6 Jul 2016 Hibiscus Retail (12) Palm Beach 18 Jul 2016 Hibiscus Wholesale (5) Palm Beach 18 Jul 2016 Hibiscus Retail (13) Palm Beach 18 Jul 2016 Lantana Wholesale (6) Hillsborough 18 Jul 2016 Hibiscus Wholesale (1) Palm Beach 18 Jul 2016 Hibiscus Wholesale (1) Palm Beach 22 Jul 2016 Hibiscus Retail (14) Palm Beach 27 Jul 2016 Firecracker flower Wholesale (7) Hillsborough 27 Jul 2016 Hibiscus Wholesale (8) Miami-Dade 29 Jul 2016 Firecracker flower Wholesale (7) Hillsborough 12 Aug 2016 Eggplant Retail (15) St. Lucie 22 Aug 2016 Hibiscus Retail (16) Martin 8 Sept 2016 Hibiscus Retail (17) Palm Beach 8 Sept 2016 Hibiscus Wholesale (8) Miami Dade Biotype specific primer Date received MEAM1 (B) MED (Q) 11 May 2016 0 16 1 Jun 2016 0 23 12 Jun 2016 1 1 13 Jun 2016 1 7 13 Jun 2016 0 1 14 Jun 2016 0 5 14 Jun 2016 0 16 17 Jun 2016 0 20 17 Jun 2016 1 8 17 Jun 2016 0 20 22 Jun 2016 0 2 22 Jun 2016 0 6 23 Jun 2016 0 1 23 Jun 2016 0 2 27 Jun 2016 14 1 27 Jun 2016 0 1 6 Jul 2016 10 1 6 Jul 2016 6 1 6 Jul 2016 0 18 18 Jul 2016 0 6 18 Jul 2016 0 4 18 Jul 2016 15 2 18 Jul 2016 0 13 18 Jul 2016 1 3 22 Jul 2016 0 7 27 Jul 2016 13 3 27 Jul 2016 0 16 29 Jul 2016 0 8 12 Aug 2016 15 1 22 Aug 2016 0 3 8 Sept 2016 0 3 8 Sept 2016 6 10 (a) Samples under nursery environment with the same superscript number are confirmatory (2 or more collections at the same wholesale or retail nursery from different sampling dates).
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|Author:||McKenzie, Cindy L.; Osborne, Lance S.|
|Date:||Jun 1, 2017|
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