A New Method of Soil Application of Aldicarb

Abstract

Only 5 to 20% of in-furrow, soil-applied aldicarb (2-methyl -2-(methylthio)propionaldehyde 0(methylcarbamoy1) oxime) is absorbed by crop plants, with up to 80% degrading in the soil. The objective of this research was to determine if aldicarb could be applied directly to potato (Solanum tuberosum L.) seedpieces at planting using in-furrow rates without a reduction of potato beetle (Leptinotarsa decemlineata Say) control, thus reducing the amount of aldicarb that falls between the seedpieces. Field tests were conducted for 2 yr to determine the effectiveness of two methods of soil applications of aldicarb for control of Colorado potato beetle on white potato. Aldicarb applied at planting time as in-furrow seedpiece treatments, or as in-furrow banded applications, at rates of 1.0, 2.0, 3.0 lb a.i./acre were effective for early season reduction of Colorado potato beetle larvae. Rates of 1.0 and 2.0 lb a.i./acre of aldicarb with either application method effectively reduced plant defoliation caused by Colorado potato beetle until early June, while the 3.0 lb a.i./acre rate reduced plant defoliation through July. Research Question The Colorado potato beetle is the most important pest of white potatoes throughout the eastern coast of the USA. Aldicarb was used on potatoes from 1969 through the 1970s as a banded in-furrow application at a rate of 3.0 lb a.i./acre. Because of concerns of groundwater contamination, the rate was reduced to 2.0 lb a.i./acre in 1985, then changed to a topdress postemergence application at 2.0 lb a.i./acre in 1988, and finally the label was suspended after 1989. Would aldicarb application directly to the seedpiece at planting time effectively control Colorado potato beetle and reduce environmental concerns? Literature Summary Residues of aldicarb persist longest in the more acidic, sandy soils. These soils are found throughout the potato-production areas of the eastern USA. Aldicarb behavior is influenced by pH, soil moisture, soil temperature, clay content, and organic matter. Only 5 to 20% of soil applied aldicarb is absorbed by crop plants. Study Description A field test was conducted over 2 yr to compare the standard in-furrow application method of aldicarb on white potatoes with an experimental seedpiece application. Rates of 1.0, 2.0, and 3.0 lb a.i./acre were applied either in the furrow or with the seedpiece at planting time. Percentage of plant defoliation over time, numbers of Colorado potato beetle larvae, and tuber yields at harvest were compared to evaluate the effectiveness of the treatments. Applied Question Is there an alternative application method of aldicarb granules to the standard in-furrow method that can potentially decrease the amount of aldicarb placed between the seedpieces? Aldicarb applied as an in-furrow seedpiece treatment, using a modified Bio-Serv seedpiece applicator, was as effective as the standard in-furrow application method for early season reduction of Colorado potato beetle. Rates of 1.0, 2.0, 3.0 lb a.i./acre, significantly reduced the number of early season beetle larvae, compared with larval number in untreated plots. Application rate did not significantly influence larval number. Rates of 1.0 and 2.0 lb a.i./acre with either application method effectively reduced the defoliation caused by beetle feeding until early June, while the high rate reduced plant defoliation through July. Aldicarb application rate, within application method, did not influence tuber yield. The seedpiece application method of aldicarb is as effective as in-furrow application for Colorado potato beetle control. The seedpiece application method concentrates aldicarb granules directly over and around the seedpieces and may improve absorption by the plant and reduce environmental concerns.