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What products can be used for organic weed control in walnut production?

M.J.CaliforniaAnswer: I am pleased to provide you with information on orchard floor management and flame weeding. Orchard Floor Management/Cover CropsThe orchard floor—the tree rows and alleyways—can be managed in a variety of ways, using tillage or mowing with cover crops, grazing, or mulching. A system that provides full ground-cover provides the best protection against erosion. Some fruit growers have practiced “clean cultivation,” eliminating vegetation throughout the orchard, but this system has many disadvantages, even if accomplished with allowed tillage practices instead of organically prohibited herbicides. A bare orchard floor is prone to erosion, gradual depletion of organic matter, increased soil compaction, and reduced water infiltration. It’s also difficult to move equipment through the orchard in wet weather. However, a ground cover that is actively growing in the summer uses up water. This is a severe disadvantage in irrigated orchards where water is limited and expensive.Orchard floor management can control erosion, improve the soil, and provide beneficial insect habitat.

  • Where they are adapted, orchard grass, fescue, and other cool-season grasses are practical because they go dormant during the heat of the summer, minimizing competition with the fruit crop for water. With proper fertility management, these grasses can also provide plentiful mulch. Likewise, grasses are a good choice in apple orchards, for example, where the excess nitrogen provided by legumes can actually reduce fruit yields.
  • Many warm-season legumes are deep-rooted and compete with the trees for water. Normally, they should not be allowed to grow under the tree canopy. However, leguminous ground covers can provide significant nitrogen to fruit trees or vines. Grass and legume ground covers alike promote water infiltration and hold the soil in place during the rainy season. Ground covers help maintain and increase soil organic matter, which increases the soil’s ability to retain moisture. Cool season legumes, such as fava or bell beans, vetches, and clovers, also can achieve these goals.
  • Planting subterranean clover into established orchards can provide mulch, fertilizer, between-row ground cover, and beneficial insect habitat. This clover reseeds itself in early summer and dies back during the hottest part of the growing season, leaving a relatively thick, weed-suppressive mulch. This system is used in apple and peach orchards in Arkansas and for a variety of orchard crops in California but not where winter temperatures regularly drop below 0? F. Subterranean clover can provide habitat for such beneficial insects as ladybeetles, syrphid flies, big-eyed bugs, soft-bodied flower beetles, and other predators.

A SARE report entitled An Evaluation of Interplanted Mulched Orchard Rows explains how interplanting of cover crops and vegetables can be an effective method of weed control, insect habitat management, and fertility management in orchards.Flame Weeders and Flame Weeding, Large and Small ScaleFlame weeding ? a type of thermal weed control ? was commonly used in row crops like cotton and sorghum from the late 1930s until the mid-1960s, when selective herbicides became widely available. In the 1980s and ’90s, flame weeding made a rapid comeback as a non-chemical weed control technique, especially among organic farmers. For information on flame weeding, consult the ATTRA publication Flame Weeding for Vegetable Crops.References and Resources: Orchard Floor Management/Cover Crops George Kuepper, Guy K. Ames, and Ann Baier. 2004. Tree Fruits: Organic Production Overview. Butte, MT: NCAT-ATTRA.David Sliwa. 2002. An Evaluation of Interplanted Mulched Orchard Rows. SARE Project Number FNC01-343, Final Report. References and Resources: Flame Weeding Anon. 1999. Flame weeding for weed management. The Practical Farmer [Practical Farmers of Iowa]. Winter. p. 17.Desvaux, R. and P. Ott. 1988. Introduction of thermic weed control in southeastern France. p. 479?482. In: Patricia Allen and Debra Van Dusen (eds.) Global Perspectives on Agroecology and Sustainable Agricultural Systems. Proceedings of the Sixth International Scientific Conference of IFOAM, UC-Santa Cruz, CA, Aug. 18?20, 1986.Daar, Sheila. 1987. Update: flame weeding on European farms. The IPM Practitioner. March. p. 1?4.Steve Meyer. March 2000. Personal communication.Bowman, Greg (ed.) 1997. Steel in the Field: A Farmer’s Guide to Weed Management Tools. Sustainable Agriculture Network, Handbook Series No. 2. Sustainable Agriculture Publications, University of Vermont. 128 p.Janvanociski, Zlatko. 1999. Thermal infrared weed control. WA Bank Landcare Conference, “Where Community Counts,” Esperance, Australia.Kolberg, Robert L., and Lori J. Wiles. 2002. Effect of steam application on cropland weeds. Weed Technology. Vol. 16, No. 1. p. 43?49.Further ResourcesEquipment and SuppliesFlame Engineering, Inc.P.O. Box 577LaCrosse, KS 67548888-388-6724?Manufacturer of the famous Red Dragon handheld flamer as well as alfalfa flamers, row-crop flamers (2 to 8-row kits), and a grape vine berm flamer that can also be used in orchards. A major supplier of liquid propane accessories to the flame weeding industry. See their online book, Agricultural Flaming Guide.Thermal Weed Control Systems, Inc.Contact: Ron Jones N1940 State Hwy 95Neillsville, WI 54456715-743-4163715-743-2921 FAX ?Manufacturer of row crop flamers (flame kits and complete units) that combine flamers for in-row weed control and rolling cultivators for between-row cultivation. Row-crop flaming kits are available for 4, 6, and 8 rows. A flame hood setup is also available.LP Weed BurnerContact: Dennis Lutteke 56360 200th StreetWells, MN 56097507-553-5633?Manufacturer of row crop flamers (flame kits and complete units) adaptable to cultivators or toolbars.Peaceful Valley Farm SupplyP.O. Box 2209Grass Valley, CA 95945888-784-1722 (toll-free) 530-272-4769 (local)530-272-4794 FAX ?Organic farm equipment and supply dealer, carries: handheld flamers, backpack frames for propane tanks, row crop flame kit suitable for mounting on a toolbar and flaming 4 rows.Waipuna USAContact: Jeff Wingren 1050 W. LilycacheBowlingbrook, IL 60440630-514-0364630-759-8155 FAX ?Waipuna, from New Zealand, specializes in a hot foam system; the foam is derived from coconut sugar and corn sugar and is approved for organic production. A single-burner generator covers a width of 8 to 10 inches in the $22,000 price range. A double-burner generator covers a width of 24 to 32 inches in the $35,000 price range. Currently these are geared to municipalities, park departments, airports, and institutional settings. An agricultural unit is under development, with an aim toward orchards, vineyards, and similar agricultural applications.OESCO, Inc.P.O. Box 540, Route 116Conway, MA 01341800-634-5557 (toll-free)?Supplier of the Aquacide hot water weed control equipment system, in the price range of $9,000, geared to nursery production, landscapes, and park departments.VideosVegetable Farmers and Their Weed-Control Machines is a 75-minute educational video on mechanical cultivation and flame weeding equipment produced in 1996 by Vern Grubinger (University of Vermont) and Mary Jane Else (University of Massachusetts), with funding from USDA-SARE. Cost is $12.00 from:UVM Center for Sustainable Agriculture University of VermontAgricultural Engineering Building63 Carrigan DriveBurlington, VT 05405802-656-5459 Web ResourcesThermal Weed Control: Flame WeedingFlame Cultivation in Cotton Mississippi State University Extension Service, IS 1500?Flame weeding has a long history of use in the Mississippi Delta states. This fact sheet from Mississippi State University provides a brief introduction and summary on flame cultivation for cotton.Flame Engineering, Inc. OnLine Agricultural Flaming Guide?The Agricultural Flaming Guide provides a history of flame cultivation, with a summary of methods and flaming techniques for corn, soybeans, grain sorghum, cotton, potatoes, tomatoes, cole crops, alfalfa, and grape vineyards.Other Practices to Control Weeds: Flame Weeding Sustainable Practices for Vegetable Production in the South Dr. Mary Peet, NCSU?Dr. Mary Peet published one of the very first books on sustainable vegetable production. This section touches on flame weeding, with a couple of farmer profiles.Hot Tips For Flame Weeding From: Steel in the Field, SAN Publications?A section on flaming from Steel in the Field, a publication from SAN (Sustainable Agriculture Network). Steel in the Field is a practical handbook on non-chemical weed control, with very helpful diagrams and descriptions of 37 specialized cultivators used in mechanical weed control; highly recommended for the organic farmer’s bookshelf.Flame Weeding: Reducing Herbicide Usage on the Farm project, Agricultural Utilization Research Institute (AURI) and Sustainable Farming Association of Minnesota (SFA)?A report on flame weeding techniques and field trials on vegetable farms in Minnesota.Flame Weeding for Weed Control and Renovation with Strawberries Greenbook 2000 (PDF 476KB), Energy and Sustainable Agriculture Program, Minnesota Department of Agriculture Flame Weeding for Weed Control and Renovation with Strawberries Greenbook 2001 (PDF 372KB), Energy and Sustainable Agriculture Program, Minnesota Department of Agriculture?These two research reports summarize field trials on flame weeding for strawberries in Minnesota, with relevant details on weed control techniques and tips for flame weeding.A Review of Non-Chemical Weed Control TechniquesS. Parish, Biological Agriculture and Horticulture, Vol. 7?A reprint of a classic article in the journal Biological Agriculture and Horticulture, from one of the European researchers.Comparison of Three Weed Control Methods: Chemical, Flame and Hot Water University of Queensland (Australia)?Hot water was as effective as glyphosate herbicide. Flaming was less effective, but acceptable weed kill was obtained on juvenile weeds.Great Balls of Fire! Ecological Farmers Association of Ontario?A brief report on field trials regarding flame weeding in potato production.Controlling Weeds in Organic Crops Through the Use of Flame Weeders (PDF 313KB) Ronnie W. Heiniger. Organic Farming Research Foundation. No. 6. Summer. p. 17?19.?A research report from the Organic Farming Research Foundation. The project took place in North Carolina and investigated the use of flame equipment in organic popcorn, soybeans, and cotton. The complete 11-page report is available from OFRF and includes tables with economic cost, gas usage figures based on pressure and tractor speed, and weed biomass and yield figures for popcorn.Thermal Weed Control: Infra-Red, Steam, Hot Water, International Companies & TechnologyThe Use of Steam as an Alternative Herbicide Sandra Robinson, Virginia Tech?Reviews the use of the Aqua Heat hot-water weed control system, with a summary of the advantages and disadvantages.Hot Water Weed Control in Carrboro, NC (PDF 807KB)?The Waipuna hot-water weed control system is being used by the Town of Carrboro, North Carolina, as part of its Least Toxic Integrated Pest Management (IPM) policy and pesticide reduction program that seeks least-toxic alternatives.Hot Water: A “Cool” New Weed Control Method Journal of Pesticide Reform. Vol. 15, No. 1.?Reprint of a brief article introducing the hot-water weed control method, featuring the Waipuna system from New Zealand.Effect of Steam Application on Cropland Weeds Kolbert, Robert L. and Lori J. Wiles. 2002. Weed Technology. Vol. 16, No. 1. pp. 43?49.?Journal article in Weed Technology, summarizing research on a custom-built, prototype steam generator-applicator machine with combined tillage implements for use in row crop weed control and no-till agriculture.Hot Water Technology EPA Methyl Bromide Alternatives?A case study on field trials with the Aqua Heat system in Florida, aiming to control nematodes and soil-borne pathogens. Custom applicator costs are estimated at $1,000 to $1,500 per acre for hot water, which is comparable to $1,200 to $1,500 per acre for methyl bromide.Nursery Soil Fumigation Dick Karsky, National Proceedings: Forest and Conservation Nursery Associations, 1997 (PDF 2.94 M) ?A paper on steam for soil fumigation in field-grown nursery production. This item is included for the notes, photos, and comments on steam technology and equipment in general.Eco-Weeder (Puzzy Boy) The Nature Conservancy newsletter ?A newsletter about the Swiss-made infrared eco-weeder from Forevergreen, also known in Europe as the Puzzy Boy.Atarus Thermal Weed Control (Australia) ?The Atarus Stinger features a technology known as water-quenched combustion?a generator that converts combusting fuel and water into a high-velocity, high-temperature, moist air flow. It is geared to orchards, vineyards, and row crops. The Atarus Ranger is a handheld flame torch for use on farms, parks, and other landscapes.Weed Control HOAF Group InfraRed Technology (The Netherlands)The Greenburner (UK) ISHS Acta Horticulturae 372: Symposium on Engineering as a Tool to Reduce Pesticide Consumption and Operator Hazards in Horticulture?Symposium abstracts, including a number of papers on thermal weed control.Puzzy Boy Unkrautvernichter?Web page for a German company selling the Puzzy Boy line of infra-red weeders. The pictures are a fast way to grasp what the different models look like.UV Weed Control Kaj Jensen and Electro Light ApS?Weed Control by ultraviolet (UV) light using high-powered electronic ballasts.