Published May 1964. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

Carter, George E.

Oregon State University. Extension Service

Powelson, R. L.

Undetermined

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; AFS 77 i)September 1964 VUse of Soil Fumigation For Control ofVerticillium Wilt of PotatoesPrepared by R. L. POWELSON, Extension Plant Pathology Specialist and GEORGE E. CARTER, Assistant in Farm CropsOregon State University, CorvallisThe soil-borne fungus, V erticillium dahliae Kleb,incites an "early maturity disease" of potatoes, causingreductions in potato yields and quality. Disease severityis directly proportional to the fungus density in the soiland the number of root infections which occur.Soil fumigation reduces the fungus density in thesoil and the number of root infections. Trials conductedin Oregon since 1955 have shown that soil fumigationwill give economic yield increases on land where Verti-cillium wilt is the limiting factor in production.Considerations for successful soil fumigationHave potatoes been grown on the land more than 5years ? Yes NoIs "early maturity" caused by Verticillium wilt theprimary factor limiting production? Yes NoWas the land to be fumigated in a low residue crop,such as grain, last year? Yes NoIs the soil to be fumigated a light sandy loam with alow organic matter content? Yes NoIs control of root-knot nematodes, wire worms, sym-phylans, or quack grass required? Yes NoYes answers to questions 1 through 4 are importantfor successful soil fumigation. The pests listed in state-ment 5 are controlled by soil fumigation for Verticil-lium wilt, and a yes answer means additional benefits.Procedures for successful soil fumigationCrop residue. Minimize the previous crop residue byremoval or allowing time for decomposition.Moisture. Soil is usually at the proper moisture levelwhen it barely retains its shape after being squeezedin the palm of the hand. The moisture should be fa-vorable for germinating seed.Temperature. Most fall and spring soil temperaturesare adequate. A temperature range between 45° and60° F. six inches below the soil surface is desirable.0.9on Csmflosondthe U. S Deponraentof ApKwhvroCasper., 1)Tilth. Soil should be in seedbed condition, firm andrelatively free from clods.Application. Several types of applicators have beendesigned to apply soil fumigants ; however, the mosteffective for large-scale fumigation is the chisel ap-plicator. The chisels should be spaced 8 to 12 inchesapart with an injection depth of 6 to 8 inches. Referto the product label for specific application instruc-tions.Sealing. A "surface seal" should be established im-mediately after injection to maintain an effectiveconcentration of the fumigant. This is best accom-plished by the use of a "smooth-wheeled" cultipacker,Post fumigation treatment. Retain the "surface seal"for at least 7 to 10 days after treatment. Then till orplow 8 to 10 inches deep and allow 2 to 4 weeks be-fore planting. When fumigation is done in the fall,the soil should not be disturbed until spring.Other considerationsSoil fumigation should be considered for fields where"early maturity" caused by Verticillium wilt is re-sulting 'in yields under 300 cwt per acre.It is desirable to fumigate following a grain cropwhere the stubble has been burned. Avoid fumiga-tion after a potato crop or after crops which leave ahigh amount of residue, such as alfalfa, pasture, andcorn.Fall fumigation is recommended over spring fumi-gation.For the greatest economic return, potatoes 'should begrown two consecutive years following fumigation.Suggested fumigants and ratesD-D 40 to 60 gallons per acreTelone 30 to 50 gallons per acreVapam 30 to 40 gallons per acreVidden D 40 to 60 gallons per acreVorlex .. .. ..._20 'to 40 gallons per acreThis is one of a series of Fact Sheets reporting Cooperative Extension work in agriculture and home econom-ics, F. E. Price, director. Printed and distributed in furtherance of Acts of Congress of May 8 and June 30,1914. Oregon State University, Oregon counties, and U. S. Department of Agriculture cooperating.

Use of soil fumigation for control of Verticillium wilt of potatoes

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Use of soil fumigation for control of Verticillium wilt of potatoes

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