Location: Southern Horticultural Research2017 Annual Report
Objective 1: Develop integrated strategies to control invasive diseases and pests within the context of small fruit production systems of the Gulf Coast. Sub-objectives: 1.1: Determine the importance of wild fruit hosts to the ecology and life history traits of Spotted-wing Drosophila (SWD) and other vinegar fly pests of fruit crops of the U.S. Gulf Coast, with an emphasis on fly population dynamics in surrounding landscapes. 1.2: Develop and evaluate Integrated Pest Management (IPM) strategies involving selective chemical application. 1.3: Determine pathogen lifecycle events and spread patterns of bacterial leaf scorch, a new and emerging disease of blueberries in the Gulf South. 1.4: Develop disease screening assays using traditional and molecular screening techniques to identify disease resistant small fruit germplasm and characterize relevant host/pathogen relationships, the influence of cultural practices, and virulence levels of pathogens. 1.5: Develop disease control protocols based on cultural practices of removing rosette infected primocanes, which are a source of fungal inoculum, to reduce rosette disease severity in erect blackberry cultivars. Objective 2: Develop disease and pest control strategies that can be readily integrated with existing production practices used in container-grown ornamental plant nursery systems. Sub-objectives: 2.1: Develop a three-step ‘push-pull’ management strategy for protecting vulnerable nursery tree stock from ambrosia beetles. 2.2: Examine the effect of binding and leaching potential of soil-incorporated insecticides in alternative and standard soilless substrates in container-grown ornamental plants. 2.3: Determine optimal timing of disinfestant to restrict pathogen dispersal through irrigation water and limit plant disease. 2.4: Develop a comprehensive preventive and reactive disease management strategy to control Pseudomonas, Colletotrichum, and Rhizoctonia in plant propagation facilities. 2.5: Develop an integrated disease management strategy to control Leyland cypress blight in ornamental plant nursery production. 2.6: Identify changes in spray patterns across 100 foot blocks of container-grown plants using commercial sprayer equipment that correlate with reduction in disease intensity. Objective 3: Develop and improve pollination practices on berry and vegetable farms along the Gulf Coast and increase capability to use native bees.
Develop an updated pest management program to control the spotted-wing Drosophila fly from damaging fruits and vegetables. Develop cultural and chemical controls and tolerant cultivars of several small fruit diseases, with emphasis on Phytophthora root rot, a serious existing disease, and Xylella bacterial leaf scorch, a new disease of blueberry. Identify habitat sources of ambrosia beetle, and characterize repellant and attractant strategies that prevent ambrosia beetle movement into ornamental plant nurseries. Develop updated plant disease management practices to control existing and new pathogens in propagation, to time disinfestant treatments that prevent spread of Phytophthora in irrigation water, and to produce a risk-based fungicide timing model to control Passalora blight of Leyland cypress in the nursery. Nesting habitat for native pollinators will be promoted to expand bee management practices that are critical for achieving profitable fruit and vegetable yields.
ARS entomologist evaluated virulence of Paenibacillus popilliae, the cause of Milky Spore Disease, as a biological control agent of spotted wing dorsophila (SWD) larvae. The ARS entomologist and an ARS chemist at New Orleans, Louisiana are developing insecticidal compounds using different sugar alcohols based on erythritol. Sugar alcohols and ethanol are important stressors of SWD in their environment. ARS plant pathologist in collaboration with researchers at Louisiana State University determined that seven rabbiteye blueberry cultivars and one southern highbush blueberry cultivar inoculated with a Xylella (X.) fastidiosa isolate from rabbiteye blueberry did not exhibit any symptoms of infection within nine months; however, rabbiteye blueberry likely harbors a genotype of X. fastidiosa pathogenic to southern highbush blueberry, so growers should use clean planting material when introducing rabbiteye blueberry plants into an orchard with susceptible southern highbush blueberry cultivars. Isolates of the root rot pathogen Phytophthora cinnamomi were collected from soil samples near symptomatic blueberry plants grown in the Gulf South. These isolates will be identified and their virulence evaluated by growing susceptible blueberry cultivars in soil infested with each isolate. Protocols for control of blackberry rosette disease were evaluated in erect blackberry cultivars based on removal of rosette infected primocanes (the initial source of fungal inoculum) (1.5). Mowing and disease control treatments were applied to two rosette susceptible erect blackberry cultivars established in replicated plots in Poplarville, Mississippi. In 2016 these two-year-old plants produced plentiful fruit on both cultivars; however, rosette incidence was still very low on these young plants and no significant differences were found among treatments. ARS plant pathologist is generating rate tables whereby disinfestant rates can be adjusted based on actual water quality of individual nursery ponds. Critical to that goal, water quality ranges were published from irrigation ponds on ornamental nurseries in mid-Atlantic and gulf coast regions. Virulent Phytophthora species are required to initiate a field-based epidemiological in-ground tank study to determine seasonal timing of irrigation water treatments. Isolates of Phytophthora (P.) cinnamomi, P. nicotianae and P. tropicalis were collected and pathogenicity tested on azalea, boxwood, Pieris, and Cleyera, but none proved to be aggressive. New isolates are being collected for further testing. Efficacy, lethal dose curves, and phytotoxicity of disinfestants and cooper supplements were tested for the potential to eliminate epiphytic populations of Pseudomonas savastanoi from Loropetalum stem cuttings so pathogen-free plant stock can be commercially propagated. Protocol and greenhouse systems are in place to evaluate integrated control strategies of Rhizoctonia species on propagation of azalea stem cuttings, but the study is delayed until time is available to perform it. Conidia manipulation techniques and optimal culturing conditions were determined to facilitate recovery of Passalora sequoiae, a cause of Leyland Cypress blight, because it is a very slow growing fungus. Development of primers to quantitatively detect P. sequoiae spores was initiated for developing a weather-based predictive model. A simple descriptive model was accepted for publication describing weather conditions that favor conidia dispersal of P. sequoiae. ARS entomologist sampled Osmia bee artificial nests in Austin and Kerrville Texas, but most nests were destroyed by arboreal Crematogaster ants. Ant proof shelters are being built, furthermore nests will be deployed in areas where acrobat ants are not plentiful. Bioassays were initiated to assess sublethal and lethal effects of neonicotinoid insecticides on horticulturally important native bee species. In cooperation with University collaborators, bee sensitivities to imidacloprid insecticide were assessed, with the endemic digger bees, Anthophora abrupta, being further investigated as a new manageable pollinator of southern blueberries.
1. The sugar alcohol, Meso-Erythritol, as a new potent ingestible insecticide of Spotted Wing Drosophila (SWD). Currently, no effective insecticides are available for SWD control for organic berry production. An ARS entomologist in Poplarville, Mississippi, discovered that food grade meso-erythritol, an artificial sweetener in Truvia®, is a potent organic insecticide that kills 75% - 99% adult and larval SWD under field and lab conditions. The entomologist and an ARS chemist in New Orleans, Louisiana, began testing more affordable erythritol-based compounds. ARS researchers have been approached by the Manager of the Biopesticide and Organic Support Program of the Interregional Research (IR)-4 Project at Rutgers University; Director of Business Strategy with Biologic Insecticide Inc.; and berry producers in Georgia, Michigan and Ohio to aid in testing and development.
2. Efficacy of fungicides for control of rosette, fruit, foliar, and cane diseases of ‘Kiowa’ and ‘Chickasaw’ erect blackberries. Rosette and fruit rot diseases are often limiting factors in the production of blackberries in the southeastern U.S. Fungicides will usually control these diseases if applied at the proper time. ARS researchers in Poplarville, Mississippi, identified the optimum timing of fungicide applications for control of rosette and determined that three fungicides used to control rosette also controlled the fruit rot diseases, Botrytis gray mold and ripe rot. These same fungicides also reduced common foliar diseases including Septoria leaf spot and leaf and cane rust. This information will benefit blackberry growers particularly in the southeastern U.S. and should result in a more plentiful supply of quality blackberries for the American public.
3. Susceptibility of blackberry cultivars adapted to the Southeastern U.S. to post-harvest fruit diseases. Extensive losses suffered by blackberry farmers each year due to fruit rot and other diseases could be greatly reduced if cultivars with greater disease resistance were available. ARS researchers in Poplarville, Mississippi, evaluated blackberry cultivars adapted to the southeastern US for resistance to post-harvest fruit diseases and identified pathogens causing these losses. Berry quality data were used to determine the correlation between fruit rot disease severity and fruit quality. Cultivars were also evaluated for susceptibility to rosette. Disease and quality evaluation data from five trials showed that berries from the two cultivars that were most resistant to post-harvest berry diseases also received higher scores for fruit quality. Thorny cultivars were more susceptible to rosette disease than thornless cultivars. This study identified cultivars with good post-harvest disease resistance that can be used by growers and extension agents selecting cultivars to plant and by plant breeders selecting parental lines for their breeding programs.
4. Kaolin for protecting nursery trees from ambrosia beetle attack. Ambrosia beetles (ABs) are difficult to control with short-residual, broad-spectrum insecticides because of their nearly year round activity and unpredictable emergence schedules. ARS entomologists in Poplarville, Mississippi and Wooster, Ohio, as well as researchers from Tennessee State University spent two years testing mineralized kaolin clay as a long-lasting physical barrier to prevent female ABs from constructing brood galleries in vulnerable tree stock. Kaolin clay was further tested as a synergist with bifenthrin, a pyrethroid insecticide commonly applied against ABs. Kaolin clay by itself reduced gallery excavation when female beetle populations were high (e.g at the Tennessee site). Kaolin doubled and tripled bifenthrin effectiveness and the two compounds together reduced beetle attacks 90%-95%.
5. An improved method of raising spotted wing drosophila flies (SWD) identified vulnerabilities in this global fruit pest. SWD is a major global pest of berry crops, and in the U.S., the fly has no effective natural enemies or any other ecological vulnerability other than desiccation. Moreover, this Drosophila species is difficult to mass rear. ARS researchers in Poplarville, Mississippi, colleagues at Tennessee State University, and at the University of Florida developed a suitable rearing protocol for SWD using a vial and test-tube rearing system. Diet formula included by weight, 1 part sterile berry tissue for oviposition, 1.5 parts dry diet media for carbohydrate, 7 parts clean water for moisture, and ~5 grains (0.8 mg) of dry yeast for protein. During culturing, flies displayed high sensitivity to triethylamine anesthetic and to ethanol used for fruit sterilization, which indicated that a trapping system baited with these compounds might be useful for SWD control.
6. The health of honey bee hives is dependent on the type of habitat in the landscape. ARS researchers in Poplarville, Mississippi, along with collaborators at the University of Tennessee observed that honey bee hives located in areas of predominantly high amounts of southern row crop agriculture were the stronger and healthier than colonies located in areas of low agriculture as well as urban areas. This study concluded that there was a trade-off between colonies obtaining food sources from agriculture and potentially coming in contact with harmful pesticides.
Sampson, B.J., Mallette, T., Addesso, K., Liburd, O., Iglesias, L., Stringer, S.J., Werle, C.T., Marshall-Shaw, D.A., Adamczyk Jr, J.J. 2016. A practical method for culturing and novel biology of the spotted wing Drosophila (Diptera: Drosophilidae). Florida Entomologist. 99(4):774-780.
Werle, C.T., Addesso, K.M., Sampson, B.J., Oliver, J.B., Adamczyk Jr, J.J. 2017. Integrating kaolin clay for ambrosia beetle (Coleoptera: Curculionidae: Scolytinae) management in ornamental tree nurseries. Journal of Insect Science. 52(1):94-98.
Alburaki, M., Steckel, S.J., Chen, D., McDermott, E., Adamczyk Jr., J.J., Weiss, M., Skinner, J.A., Kelly, H., Lorenz, G., Tarpy, D.R., Meikle, W.G., Stewart, S.D. 2017. Landscape and pesticide effects on honey bees: forager survival and expression of acetylcholinesterase and brain oxidative genes. Apidologie. doi:10.1007/s13592-017-0497-3.
Gregorc, A., Knight, P.R., Adamczyk Jr, J.J. 2017. Powdered sugar shake to monitor and oxalic acid treatments to control varroa mites (Parasitiformes: Varroidae) in honey bee (Hymenoptera: Apidae) colonies. Journal of Apicultural Research. 56:71-75.
Stafne, E.T., Carroll, B.L., Marshall-Shaw, D.A. 2017. Effect of precocious grapevine fruiting on subsequent year’s growth and yield. Journal of American Pomological Society. 71(1):47-54.
Hussender, C., Park, J., Werle, C.T., Adamczyk Jr, J.J. 2017. Development of microsatellites for population genetic analyses of the granulate ambrosia beetle. Journal of Economic Entomology. 110:1107-1112.
Meikle, W.G., Adamczyk, J.J., Weiss, M., Gregorc, A., Johnson, D.R., Stewart, S.D., Zawislak, J., Carroll, M.J., Lorenz, G.M. 2016. Sublethal effects of Imidacloprid on honey bee colony growth and activity at three sites in the U.S. PLoS One. 11(12):e0168603. doi:10.1371/journal.pone.0168603.
Zhu, Y., Yao, J., Adamczyk Jr, J.J., Luttrell, R.G. 2017. Synergistic toxicity and physiological impact of imidacloprid alone and binary mixtures with seven representative pesticides on honey bee (Apis mellifera). PLoS One. 12(5):e0176837. doi:10.1371/journal.pone.0176837.
Zhu, Y., Yao, J., Adamczyk Jr, J.J., Luttrell, R.G. 2017. Feeding toxicity and impact of imidacloprid formulation and mixtures with six representative pesticides at residue concentrations on honey bee (Apis mellifera). PLoS One. 12(6):e0178421. doi:10.1371/journal.pone.0178421.
Sampson, B.J., Marshall-Shaw, D.A., Smith, B.J., Stringer, S.J., Werle, C.T., Magee, D., Adamczyk Jr, J.J. 2017. Erythritol and Lufenuron detrimentally alter age structure of Wild Spotted Wing Drosophila (SWD) Drosophila suzukii (Diptera: Drosophilidae) populations in blueberry and blackberry. Journal of Economic Entomology. 110(2):530-534.
Gregoorc, A., Adamczyk Jr, J.J., Kapun, S., Planinc, I. 2016. Integrated varroa control in honey bee colonies (Apis mellifera carnica) with or without brood. Journal of Apicultural Research. 55:253-258.
Sampson, B.J., Werle, C.T., Stringer, S.J., Adamczyk Jr, J.J. 2016. Novel ingestible insecticides for spotted wing Drosophila control: a polyol, Erythritol, and an insect growth regulator, Lufenuron. Journal of Applied Entomology. 141(1-2):8-18.
Williams-Woodward, J.L., Copes, W.E. 2017. Environmental factors impact Passalora sequoiae conidia counts from Leyland Cypress. Journal of Phytopathology. 165:538-546.
Copes, W.E., Zhang, H., Richardson, P.A., Belayneh, B.E., Ristvey, A., Lea-Cox, J., Hong, C. 2017. Nutrient, pH, alkalinity, and ionic property levels in run-off containment basins in Alabama, Louisiana, Maryland, Mississippi and Virginia ornamental plant nurseries. HortScience. 52:461–468.