Location: Subtropical Insects and Horticulture Research
2022 Annual Report
Objectives
Objective 1: Investigate the interactions of subtropical invasive pests of vegetables and ornamental crops (e.g., tomato, pepper, floriculture) with their natural enemies and use this information to develop biocontrol-based banker plant systems for environmentally sound pest management. [NP304, C3, PS3A, 3B and 3C]
Sub-objective 1a: Expand the utility of the papaya banker plant system by incorporating predators and/or entomopathogenic fungi simultaneously or in combination with the parasitoid.
Sub-objective 1b: Build a better banker plant through biotechnology by genetically engineering papaya to contain attributes that make it more suitable for banker plant use: i.e. nonflowering, papaya ringspot virus and powdery mildew resistant.
Sub-objective 1c: Develop a mealybug banker plant system using ornamental muhly grass (Muhlenbergia capillaris), the native mealybug (Stemmatomerinx acircula), and predatory beetles (Diomus austrinus, Cryptolaemus montrouzieri) for control of pest mealybugs.
Objective 2: Investigate structural, physiological, molecular, and chemical aspects of whiteflies and identify inhibitor strategies/molecules such as but not limited to feeding disruptors and peptide inhibitors of disease transmission that 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. [NP304, C3, PS3A, 3B and 3C]
Sub-objective 2a: Identify interdiction molecules that can be expressed in transgenic or Plant-Host Activated-Cell Transplantation (PHACT) adapted plants for controlling hemipteran insects and their transmitted diseases.
Sub-objective 2b: Development of transgenic vegetables and ornamentals with increased resistance to hemipteran pest insects and/or their transmitted diseases
Sub-objective 2c: Plant-Host Activated-Cell Transplantation (PHACT) as a strategy to induce plant resistance to hemipteran insects and their transmitted diseases.
Approach
This project focuses on two control strategies for whitefly and subtropical invasive. The first approach will be the development of banker plant systems for whitefly and mealybug management that will be used to establish, augment and increase the numbers of natural enemies in vegetable and ornamental production. We will expand the utility of the papaya banker plant system to include general predators and/or entomopathogenic fungi to enhance the pest control capability of the system by increasing the number and diversity of pests controlled. We will construct a nonflowering papaya banker plant through biotechnology that is both Papaya ringspot virus and powdery mildew resistant to increase the utility of the banker plant system. Mealybug banker plant systems will be developed to provide viable biologically control alternatives for environmentally sound pest management for nursery, greenhouse ornamental and vegetable growers. The second approach focuses on the development of a biological interdiction strategy through identification of entomotoxic biomolecules (primarily peptides) that target the pest insect or the transmitted pathogen and delivering these molecules either through transgenic expression or through a novel Plant-Host Activated-Cell Transplantation (PHACT) organoid-biofactory strategy. The outcomes of this research range from development of improved and sustainable IPM strategies employing banker plant systems to identification of new biologically-based control strategies incorporating either resistant transgenic plants or deployment of an engineered plant organoid biofactory system for hemipteran pest insect control.
Progress Report
The pallidis predatory beetle used to control whitefly pest species was shown to avoid feeding on parasitized ficus whitefly nymphs of three parasitoid wasp species (Amitus bennetti and Baeoentedon balios, Encarsia protransvena). ARS scientists at Fort Pierce, Florida, findings indicate that beetle and parasitoid wasps could be used simultaneously in the banker plant system. Manuscript is in preparation.
Life table studies (including hatchability, development time, predation, longevity, and survivorship) of the predatory beetle, Delphastus pallidus beetle on papaya whitefly at four different temperatures (14°C, 24°C, 28°C, 35°C) have been completed. Research is ongoing to determine the fecundity and sex ratio of the beetle without having to dissect them to distinguish male and female.
Four fungicides used to control powdery mildew on papaya were evaluated for mortality effects on papaya whitefly this year. This pathogen is the most limiting factor for the banker plant system because it reduces papaya whitefly (prey) and biocontrol agent (beetles and wasps) production. One residual followed by three contact sprays were demonstrated to be suitable fungicides for colony maintenance and banker plant development to control powdery mildew. Our data revealed no effect of fungicides on papaya whitefly populations or plant growth with very little or no phytotoxicity observed. Parasitoid wasps were present in the fungicide trials and were also unaffected. We selected the top 3 fungicides with the best efficacy for powdery mildew control from the total evaluated (9) to run mortality bioassays against predatory beetles. The results of our bioassays showed very little to no effect of fungicides on pallidus predatory beetles. Given no impact on whitefly, parasitoid or predatory beetles were observed, fungicide applications to the banker plant system, either preventative or curative are a viable alternative to development of a powdery mildew resistant transgenic papaya variety and are available and registered for use now to control powdery mildew. Studies are ongoing.
Completed greenhouse studies to test the host specificity of potential banker plant mealybug candidate, Stemmatomerinx acircula, on economically important cash crops and grasses that are taxonomically similar to its primary grass host, Muhlenbergia capillaris. Crops included pepper, tomato, hibiscus, and poinsettia, while taxonomically similar grasses included Tripsacum dactyloides, T. floridanum, M. schreberi and M. sericea. None of the cash crops evaluated were attacked and only one other taxonomically similar grass, M. schreberi, was suitable for reproduction. Manuscript is in preparation and banker plant development is ongoing.
Determined temperature-dependence of S. acircula life table parameters in laboratory trials to determine under what conditions a banker plant system may be most viable. Temperatures are being assessed at a range of 10-35°C and development from egg to adult determined. Successful development to adults has occurred from 15 to 30°C and 35°C is currently being tested to find the lethal temperature and optimal temperature for use. Data collection is ongoing.
Conducted greenhouse studies using a S. acircula/muhly grass banker plant system with the predatory beetle Diomus austrinus for managing pest populations of the highly invasive Madeira mealybug (Phenacoccus madeirensis) on Coleus as the ornamental cash crop. Mealybug control using banker plants was compared to the direct release of D. austrinus onto the crop and a predator-free untreated control. Successful establishment of beetles onto the crop using banker plants and via direct release of beetles was observed. Preliminary data suggests beetle treatments result in lower mealybug numbers, but it remains unclear whether a particular release strategy is superior or whether D. austrinus use is a viable economic management option for Madeira mealybug. Data analysis ongoing.
Ran laboratory trials to determine the functional response of a pantropical predatory thrips (Franklinothrips vespiformis) on whitefly (Bemisia tabaci) to assess its impact as a predator of whiteflies. The first and second larval stages as well as adult F. vespiformis were provided eggs, second to third instar nymphs, and adult whitefly in all possible predator/prey stage combinations at multiple densities of prey. Preliminary data suggest larval and adult F. vespiformis can consume upwards of 150 whitefly eggs and 30 nymphs per day. Only a few adult whitefly are consumed by adult F. vespiformis. Data collection ongoing.
Thrips parvispinus is a highly insecticide resistant invasive exotic quarantinable pest on ornamentals that was detected in central Florida in July of 2020 representing the first continental record for the United States. In May of 2022, pest control advisors, landscape companies and homeowners on Palm Beach Island were experiencing high thrips infestations on gardenia that were uncontrollable after many insecticide applications. Gardenia had extensive bud damage, leaf necrosis and the hedges appeared burnt. Positive T. parvispinus identification was confirmed and multiple releases were made of Franklinothrips vespiformis for biological control. Hedge improvement was noticeable in 3 weeks and by the fourth release (over two months) the gardenia hedge made a remarkable recovery with new flush green leaves and buds developing. Homeowners reported that their hedges had not looked this good in over a year when they first cut the hedge back. Studies with this highly invasive thrips pest and predatory thrips are ongoing.
Hibiscus mealybug, Nipaecoccus viridis, is an invasive, highly polyphagous pest that has recently been established in Florida. This pest is historically known to impact citrus production in other citrus-producing regions heavily and has negatively impacted citrus groves in several counties. We reviewed the known distribution and biology, including a description of life stages, host plants, and management options of hibiscus mealybug. We updated a field diagnostics guide to detect the pest early and prevent future introductions to new locations and plant hosts. We anticipate that the information shared here will help slow its spread in the USA. Manuscript submitted.
The primary step for pest management is to know what pests can be found on the crop. Hemp, Cannabis sativa cultivation has begun in Florida, and hemp attracts one of the most diverse pest complexes globally. ARS scientists at Fort Pierce, Florida, compiled a thorough list all arthropod and Mollusk species reported from hemp in Florida to date. We identified 144 arthropod and Mollusk species reported from hemp in Florida from the following insect orders: Hemiptera (65), Lepidoptera (26), Coleoptera (17), Thysanoptera (9), Orthoptera (6), Hymenoptera (5), Diptera (4), Dermaptera (1), and from following two non-insect orders: Trombidiformes (Arthropoda) (9) and Stylommatophora (Mollusca) (2). There were 77 species already reported in published literature, and 67 were reported for the first time. Even though there are 144 species in Florida that are/were reported from hemp, not all can reproduce, complete the life cycle, and cause damage to hemp. Therefore, we divided them into three categories based on their pest potential based on the criteria developed in this study. Scientists assembled representative images of 31 families from nine orders of insects and non-insects. ARS scientists at Fort Pierce, Florida, identified future challenges related to hemp pest diagnostics and provided easy-to-follow field diagnostics keys. Pictorial identification keys will help extension agents, growers, regulators, and researchers scout and inspect hemp regardless of their background by familiarizing hemp pest species commonly found in Florida. Hemp management plan was developed for pest species in Florida combined with our list of arthropods reported and diagnostics keys for easy identification will help manage hemp pests in the field and regulate incoming pests in Florida.
ARS scientists at Fort Pierce, Florida, discovered that the plant cells within Agrobacterium induced galls on tomato and papaya plants producing a broad array of defensive proteins. Initial trials showed that tomato and papaya plants with such galls reduced whitefly development in caged no-choice experiments.
A method of In vitro culturing of tomato Agrobacterium-induced gall tissue was developed where a diverse array of plant defensive proteins are produced and secreted into the liquid medium and can be continuously harvested. ARS scientists at Fort Pierce, Florida, are collaborating on the potential use of this as a treatment for plant diseases.
Accomplishments
1. Pest status, survey of natural enemies, and a management plan for ficus whitefly in the USA. The ficus whitefly, Singhiella simplex, has been causing damage to Ficus hedges and trees globally for the last 15 years. Heavy infestation of the ficus whitefly can cause defoliation and plant death could occur after several defoliation episodes. Ficus hedges are part of the longstanding landscape in south Florida and have been there for several decades. It is vital to prevent the ficus whitefly infestation or control it early to preserve the integrity of these hedges. ARS scientists at Fort Pierce, Florida, developed diagnostic keys and scouting techniques, surveyed distributions, screened host plants, prepared species assemblage, studied population dynamics, biology, surveyed natural enemies, including parasitoids and predators, and prepared a management plan for the ficus whitefly. Research was shared through national media by Entomology Today, ARS-USDA Twitter, and the University of Florida Institute of Food and Agriculture Facebook and published in refereed journals and extension publications. The ficus whitefly management plan is aiding extension agents, master gardeners, homeowners, and pest control operators to manage ficus whitefly in the landscape by making correct and timely control decisions based on scouting and overall pest pressure.
2. Pragmatic applications and universality of DNA barcoding for substantial organisms at species level: a review to explore a way forward. DNA barcoding has numerous inventive traits that have undertaken continuous improvements in its wide array of applications in life science. DNA barcoding in different organisms ranging from unicellular to multicellular is not yet 100% reliable. Future efforts should be made to develop nuclear barcodes to augment DNA barcodes. The DNA barcodes are at the beginning of their application in species discovery but can turn into a standard identification protocol for all living organisms. ARS scientists at Fort Pierce, Florida, reviewed DNA barcoding technology, its application to different organisms, its universality, applicability, and innovative approach to handling DNA-based species identification. We concluded that the taxon coverage of reference sequences is far from complete for genus or species-level identification. We suggested applying the next-generation sequencing approach to the parallel acquisition of DNA barcode sequences could greatly expand the potential for library preparation or accurate identification in biodiversity research.
3. New records of whiteflies and their host plants from Colombia. More than half of all whitefly species are distributed in the tropics and very little is known about the whitefly fauna of Colombia. This situation causes limitations on the study of basic and applied entomology of whitefly, which are of considerable importance in agriculture as they affect many cultivated and wild plants. ARS scientists helped in identifying whitefly species in a nationwide survey of Columbia. Many species recorded in this study were previously known from Brazil and several other countries bordering Colombia, such as Venezuela, Panama, and Ecuador. ARS scientists at Fort Pierce, Florida, predict that the number of species in Colombia could increase due to the high dispersal capacity of whitefly. Knowledge on the global distribution of whitefly pests represents important data used to evaluate risks of pest incursions into the USA through human activities.
4. Rapid species-level hemolymph color test for all life stages of hibiscus mealybug, an invasive and regulatory pest in the United States. Hibiscus mealybug is a polyphagous pest that has been reported from over 50 host plant families, including several citrus species, from at least 63 countries worldwide. Its feeding damage includes distorted fruit and leaves, branch dieback, and even tree death in young and recently planted trees. Premature fruit drop has been documented to cause up to 50% of crop losses in citrus orchards. At low populations, this pest can be easily misidentified to species based on eggs, first instars, and other immature stages because they are hard to distinguish from those of other mealybugs. Slide-mounting is a mandatory step in accurate species-level identification of mealybugs; unfortunately, the typical slide-mounting protocol is a resource- and time-consuming process and the chemicals used can be corrosive, flammable, and carcinogenic or can produce toxic fumes. ARS scientists at Fort Pierce, Florida, developed a hemolymph color metrics test for the first time in mealybugs providing a rapid and relatively safe tool for species-level identification of hibiscus mealybug. We discuss implementing this test in the field to help growers, researchers, and regulators make preliminary identifications.
Review Publications
Guo, C., Ahmed, M.Z., Ou, D., Zhang, L., Lu, Z., Sang, W., Mckenzie, C.L., Shatters, R.G., Qiu, B. 2021. A parasitoid vectors a plant pathogen, potentially diminishing the benefits it confers as a biological control agent. Communications Biology. https://doi.org/10.1038/s42003-021-02851-2.
Urbina, H., Ahmed, M.Z. 2022. Characterization of the entomopathogenic fungal species conoideocrella luteorostrata on 17 the scale insect pest fiorinia externa infesting the christmas tree abies fraseri in the USA. Florida Entomologist. 105(1). https://journals.flvc.org/flaent/article/view/128966
Ahmed, M.Z., Moore, M.R., Liu, D., Feng, J., Normark, B., Miller, D.R., Mckenzie, C.L., Rohrig, E.A. 2021. Taxonomic and identification review of adventive fiorinia targioni tozzetti (hemiptera: coccomorpha: diaspididae) of the United States. ZooKeys. https://doi.org/10.3897/zookeys.1065.69171.
Ahmed, M.Z., Mckenzie, C.L., Revynthi, A.M., Evans, G.A., Mottern, J.L., Mannion, C., Osborne, L. 2022. Pest status, survey of natural enemies, and a management plan for whitefly singhiella simplex (hemiptera: aleyrodidae) in the United States. Journal of Integrated Pest Management. 13(1):11;1-14. https://doi.org/10.1093/jipm/pmac007.
Ahmed, M.Z., Deter, L.A. 2022. Rapid species-level hemolymph color test for all life stages of Nipaecoccus viridis (Newstead) (Hemiptera: Pseudococcidae), an invasive and regulatory pest in the United Sates. Journal of Applied Entomology. 2022;00:1-7. https://doi.org/10.1111/jen.12985.
Ahmed, S., Ibrahim, M., Nantasenamat, C., Nisar, M.H., Malik, A., Waheed, R., Ahmed, M.Z., Alam, M.E., Ojha, S. 2022. Pragmatic applications and universality of DNA barcoding for substantial organisms at species level: A review to explore a way forward. BioMed Research International. 2022:1846485. https://doi.org/10.1155/2022/1846485.
Schoeller, E.N., Mckenzie, C.L., Osborne, L.S. 2022. Control of Echinothrips americanus on lima bean by Franklinothrips vespiformis crawford using supplemental food. Biocontrol. https://doi.org/10.1007/s10526-022-10151-9.
Ahmed, M.Z., Miller, D.R., Rohrig, E., Roda, A., Mckenzie, C.L., Osborne, L. 2021. Field report and survey of fiorinia phantasma (hemiptera: diaspididae), potential pest of palms, and ornamental plants in the United States. Journal of Integrated Pest Management. 12(1):33. https://doi.org/10.1093/jipm/pmab032.
