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Research Project: Production and Disease and Pest Management of Horticultural Crops

Location: Southern Horticultural Research

2018 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.

Progress Report
This is a bridging pending completion of NP 305 review. In 2018, an ARS entomologist at the Thad Cochran Southern Horticultural Laboratory, Poplarville, Mississippi, and an ARS chemist at the Southern Region Research Center, New Orleans, Louisiana discovered that two common and affordable sugar alcohols can be used in berry fields as an effective and environmentally-friendly (possibly organic) insecticide spray. The two compounds are synergistic against a new serious agricultural fruit pest, the spotted-wing Drosophila fruit fly (SWD fly). This research has garnered international and national interest with non-disclosure agreements being signed with Biologic Insecticide LLC (Canada/US) and Marrone Bio Innovations, Inc (U.S.). An ARS entomologist at the Thad Cochran Southern Horticultural Laboratory, Poplarville, Mississippi, and an ARS plant pathologist and chemist at the Natural Products Utilization Research Laboratory, Oxford, Mississippi have cooperated to screen natural plant products for potential insecticidal activity. Several species of Jatropha trees (belly plants) produce crude extracts that are as effective, or more effective, than commercial neem oil in controlling insect pests. Thirty-five species of belly plants occur in the Neotropics; their biology is largely unstudied, but this research confirms that complex secondary chemistries produce compounds with considerable agrichemical potential. In 2018, an ARS plant pathologist at the Thad Cochran Southern Horticultural Laboratory, Poplarville, Mississippi, in collaboration with researchers at Louisiana State University, Baton Rouge, Louisiana published a manuscript reporting that seven rabbiteye and one southern highbush blueberry cultivars, inoculated with Xylella (X.) fastidiosa isolated from rabbiteye blueberry, did not exhibit any signs of infection within nine months; however, rabbiteye blueberry likely harbors a genotype of X. fastidiosa pathogenic to southern highbush blueberry thus only clean rabbiteye blueberry plants should be planted into an orchard that contains susceptible southern highbush blueberry cultivars. Evaluated protocols for control of blackberry rosette disease in erect blackberry cultivars based on removal of rosette infected primocanes (the initial source of fungal inoculum). Mowing and disease control treatments were applied to two rosette susceptible erect blackberry cultivars established in replicated plots in Poplarville, Mississippi. No significant treatment difference has been measured through the progression from no rosette disease symptoms in 2015, to low rosette incidence in 2016, and moderate rosette incidence in 2017. Mowing and disease control treatments were applied to obtain an additional year’s data. In collaboration with a horticulturist at Mississippi State University, Starkville, Mississippi, a manuscript was published in HortTechnology about high incidences of white drupelet disorder observed in the rosette study planting. In 2018, ARS entomologists at the Thad Cochran Southern Horticultural Laboratory, Poplarville, Mississippi, have shown that an extremely fine (processed) mineral clay called kaolin can be tank mixed with insecticides to reduce attacks by ambrosia beetles on container grown trees in ornamental nurseries. Without such sprays, attacks by beetles weaken and kill trees soon after they introduce a symbiotic fungus that clogs the trees water-nutrient conducting system. In 2018, an ARS plant pathologist at the Thad Cochran Southern Horticultural Laboratory, Poplarville, Mississippi, evaluated nonlinear responses of Phytophthora nicotianae viability to disinfestant dose by rate exposure in irrigation water based on water quality parameters of ornamental plant nursery containment ponds. A systematic review and meta-analysis was performed to determine pathogen sensitivity to chlorine and quaternary ammonium. Efficacy, lethal dose curves, and phytotoxicity of disinfestants and copper were evaluated for the potential to eliminate epiphytic populations of Pseudomonas amygdali from Loropetalum stem-cuttings so pathogen-free plant stock can be commercially propagated. Whole genomic DNA sequencing was performed for 22 Passalora sequoiae cultures to develop a library of loci that can be used for primer development. In 2018, an ARS entomologists at the Thad Cochran Southern Horticultural Laboratory, Poplarville, Mississippi, in cooperation with researchers at the University of Texas, Kerrville, Texas, and the University of Florida, Gainesville, Florida, identified two wild solitary bee species with potential for management as commercial fruit pollinators, the “blueberry” orchard bee, a faithful blueberry pollinator, and the chimney bee, a potential pollinator of apple and cherry trees in the U.S. as well as rabbiteye blueberry in the southeast region. Orchard bees can be managed using reeds or paper/cardboard tubes as nesting materials. Sun-dried adobe mud blocks were used to raise chimney bees. In 2018, ARS entomology researchers at the Thad Cochran Southern Horticultural Laboratory, Poplarville, Mississippi, in cooperation with Mississippi State University researchers, in Starkville, Mississippi, discovered that many important bee pollinators, particularly solitary native bees that specialize on certain U.S. fruit and vegetable crops (blueberries, okra, squash, pumpkin, and sunflowers) are more vulnerable to persistent systemic insecticide exposure when compared with social bees such as honey bees under laboratory conditions. Bumble bees are social bee species that were the most sensitive to the ingestion of trace amounts of systemic insecticides. When undertaking pesticide risk assessments, honey bees are not proving to be good proxies for native bee species. As a result, native bee losses, including those of bumble bees, are currently unknown and may exceed the known global losses in honey bee populations.

1. Agricultural landscape and pesticide effects on honey bees. ARS researchers at Poplarville, Mississippi, along with University of Tennessee and Mississippi State University partners, examined how the effects of pesticides (including neonicotinoid) impact colony health of honey bee hives in apiaries across intensive southern row crops’ production areas. No direct or acute health problems, such as colony collapse disorder, effected honey bee health from hives located in these agricultural areas. In fact, hives located in areas of row crop agriculture thrived due to abundant sources of pollen and nectar, while some hives on low agricultural areas starved. However, there were trade-offs. Hives in areas of high agriculture had more varroa mites than hives in areas of low production agriculture, and some of the bees around urban centers were healthier than we originally thought due to abundance of plant diversity (food sources) and lower pesticide use. The information increases our understanding of bee health and what challenges honey bees face in each of the two habitats. This gives us better direction for future research efforts.

Review Publications
Smith, B.J. and Miller-Butler, M.A. 2016. Botryosphaeria stem blight on blueberries: effect of Vaccinium cultivar, Botryosphaeriaceae species and temperature. Abstract Book XI International Vaccinium Symposium, University of Florida Gainesville, FL. Page 177.
Smith, B.J., Miller Butler, M.A. 2017. Effect of nitrogen fertilization and fungicides on Botryosphaeria stem blight lesion development on detached stems. Acta Horticulturae. 1180/61-70.
Smith, B.J., Miller Butler, M.A. 2017. Effect of cultural practices and fungicide treatments on the severity of Phytophthora root rot of blueberries grown in Mississippi. Acta Horticulturae. 10.17660/ActaHortic.2017.1180.8.
Smith, B.J., Miller Butler, M.A., Curry, K.J., Sakhanokho, H.F. 2017. Effects of Phytophthora cinnamomi isolate, inoculum delivery method, flood, and drought on vigor, disease severity and mortality of blueberry plants. Acta Horticulturae. 1180/93-104.
Copes, W.E., Zhang, H., Richardson, P.A., Belayneh, B.E., Ristvey, A., Lea-Cox, J., Hong, C. 2018. Monthly levels and criteria considerations of nutrient, pH, slkalinity and ionic Variables in runoff containment basins in ornamental plant nurseries. HortScience. 53(3):360–372.
Gregorc, A., Alburaki, M., Werle, C.T., Knight, P.R., Adamczyk Jr, J.J. 2017. Brood removal or queen caging combined with oxalic acid treatment to control varroa mites (Varroa destructor) in honey bee colonies (Apis mellifera). Apidologie. 48(6):821-832.
Alburaki, M., Steckel, S., William, M., Skinner, J., Tarpy, D., Meikle, W.G., Adamczyk Jr, J.J., Stewart, S. 2017. Agricultural landscape and pesticide effects on honey bee (Hymenoptera: Apidae) biological traits. Journal of Economic Entomology. 110(3):835-847. https://doi:10.1093/jee/tox111.
Yao, J., Zhu, Y., Adamczyk Jr, J.J. 2018. Responses of honey bees to lethal and sublethal doses of formulated clothianidin alone and mixtures. Journal of Economic Entomology. 1-9.
Yao, J., Zhu, Y., Adamczyk Jr, J.J., Luttrell, R.G. 2018. Influences of acephate and mixtures with other commonly used pesticides on honey bee (Apis mellifera) survival and detoxification enzyme activities. Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology. 209:9-17.