Fumigants,rates, and application methods affecting Verticillium wilt incidence and potato yields

A three year comparison was made among fumigants, rates and placement for control ofVerticillium albo-atrum (microsclerotial type). Fumigants were placed in the soil by (i) row method one shank with duck-foot tool attached to give two bands of fumigant 9 inches (22.8 cm) deep and 9 inches apart (4.5 inches = 11.4 cm from center of a 36-inch row = 91.44 cm)], (ii) deep shank method one shank in center of a 36-inch row, 18–20 inches (45.7–50.8 cm) deep], (iii) and by the standard broadcast method (four shanks spaced 9 inches deep and 9 inches apart per 36-inch row). The row and deep shank methods were no more effective than the broadcast method when the fumigant rate was equal (calculated on an acre basis and not on the actual portion of the row treated by the method of application). Fewer wilted plants and increased yields (120–160 hundredweight per acre = 134–179 quintals per hectare) were found in plots treated with (i) DD + Picfume (4:1), (ii) Telone + Picfume (4:1), (iii) Telone C, (iv) Terr-o-cide 30, (v) Terr-o-cide 30D and (vi) Vorlex at 25 gal per acre (233.8 liters per hectare) for all years tested. Yield was increased in plots treated at 12.5 gal per acre (116.9 liters per hectare) in 1968 and 1970, but not in 1969. Rates below 12.5 gal per acre were not effective in increasing yield and there was no advantage to applying fumigants above 25 gal per acre. All the six fumigants were equally effective in their control.