Matthew M Halldorson

Interests

No activities entered.

Courses

No activities entered.

Scholarly Contributions

Journals/Publications

• Halldorson, M. M. (2025).

  Integrated Pest Management for Powdery Mildew of Grapes

  . University of Arizona Cooperative Extension Fast Track.
• Halldorson, M. M., & Barnes, M. (2025).

  Recommended Fruit Varieties for the Arizona Central Highlands Series: Apples.

  . The University of Arizona Cooperative Extension Fast Track Publication, 21.
• Halldorson, M., & Keller, M. (2018). Grapevine leafroll disease alters leaf physiology but has little effect on plant cold hardiness. Planta, 248(5). doi:10.1007/s00425-018-2967-x
  More info

  Main conclusion: Foliar sugar accumulation in grapevines with leafroll disease was correlated with lower photosynthesis, likely due to feedback inhibition. However, cold acclimation of dormant tissues remained unaffected by the virus status. Grapevine leafroll-associated viruses (GLRaV) contribute to losses in fruit yield and quality worldwide. Visually, leafroll disease symptoms appear similar to those associated with an imbalance in source/sink relations and a concomitant feedback inhibition of photosynthesis, which is often caused by an impasse in sugar translocation. In order to test this potential relationship and related physiological responses, leaf water status, gas exchange, non-structural carbohydrates, and dormant tissue cold hardiness were examined over 2 years in healthy and GLRaV-3-infected, field-grown Merlot grapevines. Diurnal and seasonal changes in leaf water status and gas exchange were dominated by variations in water availability, temperature, and leaf age, while GLRaV-3 infection contributed less to the overall variation. By contrast, foliar carbohydrates increased markedly in infected plants, with starch accumulating early in the growing season, followed by soluble sugar accumulation, leaf reddening, and declining gas exchange. Photosynthesis correlated negatively with leaf sugar content. However, dormant-season cold hardiness of buds and cane vascular tissues was similar in healthy and infected vines. These findings support the idea that visible symptoms of grapevine leafroll disease are a consequence of carbohydrate accumulation which, in turn, may lead to feedback inhibition of photosynthesis. In addition, this study provided evidence that GLRaV-3 infection is unlikely to alter the susceptibility to moderate water deficit and winter damage in mature Merlot grapevines.

Presentations

• Halldorson, M. M. (2025, April).

  Sustainable Wine Growing in Arizona: Water Management, Cover Crops, and Amendments.

  . University of Arizona/ Natural Resource Conservation Service Climate Smart Workshop.. Page Springs Cellars, Cornville, AZ: NRCS.
  More info

  Spoke about water management and soil health and organic ammendments
• Halldorson, M. M. (2025, August).

  Wildflowers and Natural History of the Arizona Central Highlands

  . Prescott Wildflower Celebration. Prescott Community Nature Center, Prescott, AZ: City of Prescott.
• Halldorson, M. M. (2025, March).

  Integrated Weed Management.

  . Yavapai (and Gila) County Invasive Weed Workshop. Camp Verde Community Library: The University of Arizona.
• Halldorson, M. M. (2025, March).

  Upper Verde Watershed Historic Timeline and Story Map Project

  . Upper Verde Watershed Community Input Events 1 & 2. Prescott and Chino Valley, AZ: University of Arizona Water Research Resource Center & The Nature Conservancy.
  More info

  Presented to the community at 2 seperate events, telling them about the project and receiving input
• Halldorson, M. M. (2025, October).

  Yavapai County Cooperative Extension: Disseminating Local Knowledge fo rthe Benefit of the Community

  . Yavapai College Chino Valley Agribusiness Campus Harvest Fest. Chino Valley, AZ.
• Halldorson, M. M. (2024, August). Extension Work in Yavapai County. . “Dial the Dean”: Interview with Dean Burgess.. Zoom between Tucson and Prescott, AZ: College of Agriculture, Life & Veterinary Sciences & Cooperative Extension.
• Halldorson, M. M. (2024, July).

  Insects of Arizona

  . MoYava 4-H Camp. James 4-H Camp at Mingus Springs, Yavapai County, AZ.
  More info

  Designed and delivered entomology programming to 4-H Campers (4 one-hour sessions) about the diversity of insects. Included presentation and hands-on insect collection at the camp riparian area.
• Halldorson, M. M. (2024, July). Principles of Integrative Pest Management. Sonoita Vineyard Integrative Pest Management Workshop.. Sonoita, AZ: University of Arizona Cooperative Extension.
• Halldorson, M. M. (2024, June). Vineyard Pest Prevention Concepts. Verde Valley Vineyard Integrative Pest Management Workshop.. Clarkdale, AZ: University of Arizona Cooperative Extension.
• Halldorson, M. M. (2024, June). Vineyard Scouting. Vineyard Scouting, and Sampling Workshop. Clarkdale,.
• Halldorson, M. M. (2024, September). Incorporating Pesticides into a Successful IPM Program. . Arizona Community Tree Council Annual Meeting (IPM Workshop).. Camp Verde, AZ: Arizona Community Tree Council.
• Halldorson, M. M. (2023, April). A Year in the Life of a Washington Vineyard. Emerging Winemaker's Symposium. Clarkdale, Arizona: Yavapai College.
• Halldorson, M. M. (2023, December). Irrigation Strategies for Arizona Vineyards. Arizona Viticulture Symposium. Controlled Environment Agriculture Center, Tucson, AZ: University of Arizona Cooperative Extension/ Arizona Wine Growers Association.
• Halldorson, M. M. (2023, June). Irrigation Strategies and Cover Crop Use in Arizona Vineyards. Arizona Climate Smart Agriculture Workshop. Cornville, Arizona: Natural Resource Conservation Service.
• Halldorson, M. M. (2023, March). Arizona Viticulture Needs Assessment Results. Arizona Viticulture Symposium. Biosphere II: University of Arizona Cooperative Extension.
• Halldorson, M. M. (2023, September). Grape Integrated Pest Management. Arizona Community Tree Council. Camp Verde, Arizona.
• Halldorson, M. M. (2023, September). Urban Agriculture: Home Grapevine Production. Urban Ag Field Day. Prescott: USDA/NRCS/UA.

Poster Presentations

• Halldorson, M. M., Gornish, E., Sanyal, D., Mcreynolds, K. H., & Weiss, J. L. (2025, March).

  Warm Season Cover Crops in Arizona Vineyard Systems

  . 2025 ENViSion Environmental Science Symposium. Tucson, AZ: The University of Arizona.
• Halldorson, M. M., Sherman, J. D., Weiss, J. L., & Rauluk, V. (2023, August). Arizona Statewide Commercial Viticulture Needs Assessment. University of Arizona Cooperative Extension Annual Conference. Tucson, Arizona: UA Cooperative Extension.

Other Teaching Materials

• Halldorson, M. M., & Schalau, J. W. (2023.

  Master Gardener Training Program Lecture Series: Botany, Soils, Climate, Composting, Nutrition, Water, Irrigation, Vineyard & Orchard Management, Vegetables & Annuals,  and Integrated Pest Management.

  . Yavapai County Cooperative Extension.
  More info

  Each topic is a 3 hour lecture that makes up the majority of the Yavapai County Master Gardener Training Program. Selecting, Planting, and Pruning is also taught by the agent, though not their original material. Native plants, pathology, weeds, wildlife and entomology are also part of the program, but were delivered by others in 2025
• Halldorson, M. M. (2023. Lecture Series: Botany, Climate, Irrigation, Soils, Veggies, Landscape Plants, Pest Management, Weeds and Disease. Yavapai County Home Horticulture Class (via Zoom).

Others

• Halldorson, M. M. (2022, October).

  Laboratories Conducting Soil, Plant, Feed or Water Testing

  . UA Extension Bulletin. https://extension.arizona.edu/pubs/laboratories-conducting-soil-plant-feed-or-water-testing
  More info

  This publication lists laboratories that provide soil, plant, feed, and water testing within the state of Arizona.
• Halldorson, M. M., & Pierce, M. (2025, August).

  Yavapai County Poultry Regulations by Community.

  . chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://extension.arizona.edu/sites/extension.arizona.edu/files/programs/PoultryRegulations.pdf
• Halldorson, M. M., DeGomez, T., & Celaya, R. (2025, August).

  The Pinon Ips Bark Beetle.

  . University of Arizona Cooperative Extension Publication az1394. https://extension.arizona.edu/publication/pinon-ips-bark-beetle
• Halldorson, M. M. (2023, June). Yavapai County Poultry Regulations by Community. Yavapai County Cooperative Extension.
• Halldorson, M. M., Trakas, A., Lesliee, G., Jeff, S., Kimberly, S., & T, W. (2023, June).

  Arizona Water Factsheet: Yavapai County

  . Water Resource Research Center Publication. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://wrrc.arizona.edu/sites/default/files/2025-11/Yavapai_8-page_Factsheet_11_2025.pdf