Cordell C.E., Anderson R.L., Hoffard W.H., Landis T.D., Smith R.S. Jr., Toko H.V., 1989. Forest Nursery Pests. USDA Forest Service, Agriculture Handbook No. 680, 184 pp.
| Soil Fumigation Factors |
Guidelines and Precautions |
| Soil preparation |
Work into fine, loose, friable condition to minimum depth of 8 to 10 inches.
Soil should be as free of clods as possible.
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| Organic matter |
Do not use nondecayed organic matter. Organic matter can render fumigant ineffective and harbor fungi and nematodes.
Cut or chop green organic matter into the soil a minimum of 3 to 4 weeks prior to fumigation.
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| Soil moisture |
Coarse-textured sandy soils -- 75 percent field capacity.
Fine textured sandy soils -- 25 to 50 percent field capacity. |
| Soil temperature |
Soil temperature above 50 0F at 6-inch depth.
Air and soil temperatures not usually correlated. |
| Soil fumigants and target pests |
Mixtures of 98% methyl bromide/2% chloropicrin fumigant; broad spectrum for nematodes, weeds, insects, and most soilborne fungi.
Mixtures of 67% methyl bromide/33% chloropicrin fumigant; particularly effective against soilborne fungi with tough resistant stages.
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| Calibrating and monitoring soil fumigation equipment |
Fumigant dosage = concentration X time. Dosage determined by injector nozzle size, fumigant pressure, and tractor speed. Inject fumigant at minimum 8-inch soil depth.
Inject deeper for deeper-rooted species.
Maintain constant pressure, tractor speed, and fumigant flow through all nozzles for uniform, effective coverage.
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| Soil tarping |
Apply clear polyethylene tarp with adequate strength and thickness immediately after fumigation for maximum effectiveness.
Alternate strips require longer fumigation and time intervals and afford opportunity for contamination from adjacent nonfumigated soil strips.
Solid tarping requires shorter fumigation time interval and minimizes opportunity for soil contamination.
Repair and seal any holes or opened glue joint immediately.
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| Fumigation exposure period |
Consult fumigant label for recommendations.
Minimum of 48 hours at soil temperature above 60 0F at 6-inch depth. At lower temperatures and during wet weather (following fumigation), double the exposure period.
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| Fumigation aeration period |
Consult fumigant label for recommendation.
Minimum of 48-72 hours; varies with fumigant, soil, temperature, moisture, and crop to be planted.
Double aeration period in wet weather or at temperatures below 60 0F.
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| Extended aeration for seedbeds receiving artificial inoculations of ectomycorrhizal fungi. |
Aerate soil at least 3 weeks following fumigation with mixture of 67% methyl bromide/33% chloropicrin. This strong fumigant has extended residual toxicity to all soil fungi, including those which form mycorrhizae. |
| Contamination of fumigated soils |
Avoid possible contamination by movement of soil, plants, mulches, etc., into fumigated areas. Clean, by steam or equivalent, all equipment: plows, bed shapers, tractor tires, etc.
Avoid transplanting from nonfumigated soils. |
| Fumigation of mulch materials |
Prefumigate mulch materials such as pine needles, straw, and bark with mixture of 67% methyl bromide/33% chloropicrin or mixture of 98% methyl bromide/2% chloropicrin formulations at a dosage rate of 1.0 lb/yd3.
Tightly compacted or baled materials should be a maximum of 18 inches deep. Loose pine needles, straw, etc., may be 36 to 48 inches deep.
Fumigation procedures and precautions (tarping, temperature, moisture, exposure, aeration periods, etc.) are same as for soil fumigation.
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| Soil nutrient alterations |
Level of soluble salts and ammonia nitrogen may be increased due to decreased populations of nitrifying bacteria.
Do not use ammonia fertilizers on plants requiring nitrates or those sensitive to ammonia. Apply only nitrate fertilizers until seedlings are established and soil temperature is above 68 0F.
Base your fertilizer applications on soil tests made after fumigation.
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| Water requirements |
Water requirements per unit of plant production are generally less.
Water requirements per acre are increased due to generally larger plants and increased production.
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| Safety |
The methyl bromide/chloropicrin formulations are highly toxic to animals (including humans) and plants. Fumigants must be handled with care and applied only by trained, certified personnel.
Always read fumigant label prior to use and follow all directions and precautions closely.
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