Location: Subtropical Insects and Horticulture Research
2017 Annual Report
Objectives
Objective 1: Investigate biological control and ecological interactions of whiteflies with their natural enemies using banker plant systems to promote environmentally sound control in vegetable and ornamental crops.
Sub-objective 1b: Determine the compatibility of insecticide regimes with beneficial insects and natural enemies used in banker plant systems.
Objective 2: Investigate structural, physiological, molecular and chemical aspects of the whitefly feeding process and identify inhibitor strategies/molecules such as but not limited to feeding disruptors and peptide inhibitors of disease transmission than can be used in the development of novel interdiction strategies envisioned to work either through production of transgenic plants or application of chemical treatments that block feeding/disease transmission.
Sub-objective 2a: Develop transgenic tobacco expressing enzymatic inhibitors of whitefly salivary sheath formation test for resistance to Bemisia tabaci feeding.
Sub-objective 2b: Test application of discovered small molecule inhibitors of sheath formation for their effect on whitefly feeding on tomato.
Sub-objective 2c: Conduct proteomic analysis of salivary exudates to identify salivary sheath structural and biosynthetic proteins.
Approach
Research will focus on constructing a nonflowering papaya banker plant through biotechnology that is resistant to both papaya ringspot virus and powdery mildew. Strategically timed insecticide applications including neonicotinoids in the rotation regimes will be evaluated against MED (Q-biotype whitefly) for whitefly efficacy and compatibility with two of the natural enemies used in our banker plant systems: the predatory mite, Amblyseius swirskii, and the whitefly parasitoid, Encarsia sophia. Development and testing molecular inhibitors of whitefly feeding processes with specific emphasis on the processes that must occur for the whitefly to develop a successful feeding event. Two main objectives include: 1) Continued characterization of the whitefly salivary sheath biosynthesis and composition. We already have basic compositional data and some knowledge on structural arrangement. Molecular, biochemical and structural analyses will continue to identify key biosynthetic enzymes and sheath structural components. 2) Evaluation of inhibitors of sheath formation as control agents. This evaluation will be performed using artificial diet assays and development of transgenic tobacco expressing inhibitors and conducting bioassays where the whitefly feed on the artificial diet or the transgenic plants.
Progress Report
Wrote and submitted a USDA, NIFA, Specialty Crop Research Initiative grant entitled “Building A Better Banker-Plant Strategy To Manage Invasive Whiteflies: Using Precision Breeding For Improved Efficacy And Expanded Use In Greenhouse Grown Vegetables and Ornamentals”. This was done through a collaboration with University of Florida scientists with expertise in plant pathology, economics and entomology extension.
The chilli thrips, Scirtothrips dorsalis, is a cryptic species complex (group of morphologically indistinguishable species) of at least nine distinct species, two (South Asia 1 and East Asia 1) of which exist in the United States. To determine their distribution range and find the dominant member of this thrips complex in the United States, a nationwide survey program is underway. To date, we received thrips samples from three counties in Florida (Hillsborough, Miami-Dade, and St. John), three counties in California (Los Angeles, Orange and Imperial), two counties in Texas (Harris, Brazos) and one county each in Georgia (McDuffie) and Massachusetts (Barnstable). Out of the 25 thrips samples received from different locations in the United States, 15 samples were confirmed as Scirtothrips dorsalis. The Scirtothrips dorsalis samples collected from Florida, Texas and California were South Asia 1 species suggesting this species is more prevalent (dominant species) in the United States compared to another counterpart of Scirtothrips dorsalis complex reported for the first time from the north eastern United States during 2012. East Asia 1 was only found in the samples collected from hydrangea in Massachusetts indicating movement of this species in the neighboring states on hydrangea. Cooperative Agricultural Pest Survey (CAPS) had previously indicated that chilli thrips would not pose a threat to northern states that experience hard freezes but apparently East Asia 1 is capable of surviving winters in both New York and now in Massachusetts. Identity of Scirtothirps dorsalis samples collected from roses in Riverside County, California, and Dallas County, Texas, areas still needs to be verified. Apart from Scirththips dorsalis, other thrips received during surveys were Frankliniella occidentalis, Frankliniella tritici and Leucothrips piercei. We expect to receive additional thrips samples from rose nurseries in Alabama, North Carolina, Louisiana and Texas during summer-fall 2017.
To determine the host range of the Scirtothips dorsalis, South Asia 1, we conducted seven greenhouse trials, where we evaluated 37 plant taxa (34 different species within 22 families and 16 plant orders) among vegetables, ornamentals, landscape plants, herbs and weeds as feeding and/or reproductive hosts of chilli thrips. Among all the tested plant taxa, 24 were true hosts (reproductive + feeding) and four were only feeding hosts (thrips will feed on these but avoid laying eggs). We also found nine new true hosts of chilli thrips which were not earlier reported as reproductive hosts of this pest in the literature.
With the overall goal to improve existing management strategies for Bemisia tabaci (MEDiterranean or biotype Q whitefly) and stewardship of the neonicotinoid class of insecticide (dinotefuran - grower standard), seven greenhouse chemical efficacy trials were conducted on salvia. In these trials, the compatibility of insecticides used in rotation programs to control Bemisia tabaci with the predatory mite, Amblyseius swirskii used in biological control programs was evaluated. Experiments testing cyantraniliprole and flupyradifurone as a drench application was compatible with the predatory mite, and were found to significantly reduce whitefly populations during the majority of the study period. Foliar application of spinetoram, pyrifluquinazon and flupyradifurone was effective against whitefly, however among these only flupyradifurone was found benign on the mite population. Although foliar application of pymetrozine was compatible with the predaceous mite, it was not effective against MED whitefly by itself.
To complement the previous study, additional studies were conducted where the compatibility of insecticides used to control Bemisia tabaci with the parasitic wasp, Eretmocerus eremicus, used in biological control programs was evaluated on mint in the greenhouse. Eretmocerus eremicus is among the parasitoids which utilize their prey for both food and sites of reproduction resulting in suppression of the pest population on the plant. In this study, whitefly parasitization by wasps was insignificant, and thus parasitized immatures and emerged wasps were not observed. Results showed that the drench application of cyantraniliprole and flupyradifurone, and the parasitic wasps applied alone or in combination can suppress whitefly population more than 5 weeks.
In order to integrate biocontrol agents in the management program of Bemisia tabaci, predation potential of two naturally occurring predatory beetles (Delphastus catalinae and Delphastus pallidus) was evaluated against the two most notorious members (Mediterranean or MED, biotype Q and Middle Eastern Asia Minor 1 or MEAM1, biotype B) of Bemisia tabaci species complex. Under laboratory conditions, each of the two beetles was found to consume an average of 50-65 whitefly eggs per day, and feeding potential of Delphastus cataliane was higher than Delphastus pallidus. While comparing prey developmental stage preference between whitefly eggs and early immatures, both the beetle species preferred eggs over nymphs.
Native to the Neotropical region, Aleurotrachelus trachoides commonly known as the solanum whitefly, is an emerging pest of pepper and many other horticultural crops in the United States. Lab bioassay trials are underway to evaluate the biocontrol potential of two generalist predatory beetles Delphatus catalinae and Delphastus pallidus against solanum whitefly on pepper as a host. For the studies, separate colonies of the two beetles and whitefly have been initiated.
The pathogenicity of a naturally occurring entomopathogenic fungus, Isaria fumosorosea (PFR 97®) was evaluated under laboratory conditions against solanum whitefly on tomato as a host. In the preliminary studies, Isaria fumosorosea was found ineffective (mortality <50%) against the whitefly pest. Similar studies with another major whitefly plant host (pepper) is underway to determine the effect of plant hosts on the activity of entomopathogenic fungus for controlling this whitefly.
In the wake of the potential threat of solanum whitefly to Florida tomato production, which is one of the important hosts of this pest, a greenhouse study is being conducted to assess the ability of solanum whitefly to vector Tomato Yellow Leaf Curl Virus disease. For the studies, whitefly colony on tomato has been initiated.
Work on salivary sheath inhibition as a method of blocking Bemisa tabaci feeding was advanced. We have continued evaluations of topical application strategies for initial analysis instead of transgenic plant development. This decision was justified because of: 1) breakthroughs we have had in development of new topical applications strategies for the control of Asian citrus psyllid (ACP) sheath formation/sheath production; 2) our earlier demonstration that sheath inhibitors that work on ACP sheaths also work on Bemisia tabaci sheaths; and 3) completion of filing for patent to cover this technique that has resulted in initiation of a CRADA with a private company to advance this to a commercial product.
Because isolation and analysis of psyllid salivary sheaths was easier than that for the whitefly and because we previously demonstrated that the same sheath inhibitors worked for both insects, ARS scientists used the psyllid system as a surrogate for the whitefly. We have conducted initial salivary sheath proteome analysis using the Asian citrus psyllid as a surrogate. This work was done in collaboration with a research molecular biologist, USDA-ARS, BioIPM Research Unit, Ithaca, New York, and resulted in the identification of two proteins presumed to be involved in sheath biosynthesis. This discovery has led to development of a research program to identify inhibitors of one of these proteins/enzymes.
Accomplishments
1. Urban invasion by serious whitefly pest spurs regulatory action. Bemisia tabaci MEDiterranean (Q biotype) is on the move in Florida to residential landscapes and may impact open field agriculture. For the first time in the United States, researchers from ARS in Fort Pierce, Florida and the University of Florida in Apopka, Florida have detected MED outside of greenhouse or nursery environments when it was collected from ten residential landscapes and two open field environments in Florida. MED was also detected in 11 wholesale nurseries from five counties and 19 retail nurseries from 8 counties in Florida resulting in stop sale actions of facilities with high whitefly populations. Hibiscus was the host plant driver for MED whitefly infestations in both retail and wholesale nurseries and in Florida residential landscapes. This situation has the potential to become a major agricultural problem if this whitefly known to be resistant to insect growth regulators and neonicotinoid insecticides spreads to vegetable field production.
2. Susceptibility of Bemisia tabaci to nicotinic insecticides in South Florida Tomato. Researchers from the University of Florida, Wimauma, Florida in collaboration with Saint Francis University, Loretto, Pennsylvania and ARS researchers at Fort Pierce, Florida, determined the insecticide susceptibility of populations of whitefly in vegetable fields in south Florida. Populations of Bemisia tabaci MEAM1 (Middle Eastern Asia Minor 1, biotype B) were established from nineteen locations in south Florida, primarily from commercial tomato fields, and were tested using a cotton leaf petiole systemic uptake method for susceptibility to the nicotinic acetylcholine agonist insecticides imidacloprid, thiamethoxam, dinotefuran and flupyradifurone. Eleven populations produced lethal concentration for 50% of the tested population (LC50s) for one or more chemicals that were not significantly different from the susceptible laboratory colony based on overlapping fiducial limits, indicating some degree of susceptibility. LC50s more than a 100-fold in the laboratory colony were measured in at least one population for each material tested, indicating tolerance. Based on overlapping fiducial limits, there were no significant differences in relative mean potency estimates for flupyradifurone and dinotefuran in relation to imidacloprid and thiamethoxam. Monitoring tolerance of Bemisia tabaci to neonicotinoid insecticides and establishing baseline information for new insecticides such as flupyradifurone are essential for the sustainable stewardship of crucial crop protection tools.
3. Identified proteins used by plant-feeding Hemipteran pest insects to develop a successful feeding event on host plants. ARS researchers at Ft. Pierce, Florida, in collaboration with ARS researchers at, USDA-ARS, BioIPM Research Unit, Ithaca, New York, identified proteins secreted during establishment of a successful feeding event by Hemipteran insects. Using psyllids as a surrogate for whiteflies because of their more prolific feeding and ease of salivary sheath isolation, we identified two proteins as major components of their saliva that is secreted during the piercing process that is used to establish a plant vascular tissue feeding event. These proteins are now being used to screen for inhibitors of their activity as a means of preventing salivary sheath formation and thus inhibiting the insect’s ability to feed on plants. Development of a commercially available feeding inhibitor of this process would offer a sustainable strategy to prevent crop damage resulting from feeding by this class of insects.
Review Publications
Smith, H.A., Nagle, C.A., MacVean, C.A., McKenzie, C.L. 2016. Susceptibility of Bemisia tabaci MEAM1 (Hemiptera: Aleyrodidae) to imidacloprid, thiamethoxam, dinotefuran and flupyradifurone in south Florida. Insects. 7(57). doi:10.3390/I.2016-7040057.
Barr, N., Ruiz-Arce, R., Obregon, O., Shatters, R.G., Norrbom, A.L., Nolazco, A., Thomas, D.B. 2017. Diagnostic characters within ITS2 DNA support molecular identification of Anastrepha suspensa. Florida Entomologist. 100:182-185.
Kumar, V., Xiao, Y., McKenzie, C.L., Osborne, L.S. 2015. Early establishment of the phytoseiid mite Amblyseius swirskii (Acari: Phytoseiidae) on pepper seedlings in a Predator-In-First approach. Experimental and Applied Acarology. 65(1):465-481.
Taravati, S., Mannion, C., Osborne, L., McKenzie, C.L. 2016. Feeding and development of Nephaspis oculata (Coleoptera: Coccinellidae) on rugose spiraling whitefly. Florida Entomologist. 99(3):516-521.
Dickey, A.M., Stocks, I.C., Smith, T., Osborne, L.S., McKenzie, C.L. 2015. DNA barcode development for three recent exotic whitefly (Hemiptera: Aleyrodidae) invaders in Florida. Florida Entomologist. 98(2):473-478.
Dickey, A., Kumar, V., Morgan, J.K., Jara-Cavieres, A., Shatters, R.G., McKenzie, C.L., Osborne, L. 2015. A novel mitochondrial genome architecture in thrips (Insecta: Thysanoptera): extreme size asymmetry among chromosomes and possible recent control region duplication. BMC Genomics. 16:439. doi:10.1186/s12864-015-1672-4.
Dickey, A.M., Trease, A.J., Jara-Cavieres, A., Kumar, V., Christenson, M.K., Potluri, L.P., Morgan, J.K., Shatters, R.G., McKenzie, C.L., Davis, P.H., Osborne, L. 2014. Estimating bacterial diversity in Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) via next generation sequencing. Florida Entomologist. 97(2):362-366.
Dickey, A.M., Kumar, V., Hoddle, M.S., Funderburk, J.E., Morgan, J.K., Jara-Cavieres, A., Shatters, R.G., Osborne, L.S., McKenzie, C.L. 2015. The Scirtothrips dorsalis species complex: Endemism and invasion in a global pest. PLoS One. https://doi.org/10.1371/journal.pone. 0123747
McKenzie, C.L., Osborne, L.S. 2017. Bemisia tabaci MED (Q biotype)(Hemiptera: Aleyrodidae) is on the move in Florida to residential landscapes and may impact open field agriculture. Florida Entomologist. 100(2):481-484.
