Conventional and Alternative Placement of Soil Insecticides to Control Sugarbeet Root Maggot (Diptera: Ulidiidae) Larvae

Abstract

This field study was carried out in northeastern North Dakota from 1999 to 2002 to compare an alternative device, the spoon, with conventional band and modified in-furrow equipment for applying aldicarb, chlorpyrifos, and terbufos insecticides to control sugarbeet root maggot, Tetanops myopaefonnis (Roder), larvae. Insecticides differed consider­ ably in placement effects on performance, although yield dif­ ferences were rare. Effects ofpostapplication rainfall on effi­ cacy were insecticide- and placement-specific. Placement method had the greatest impact on performance of terbufos and chlorpyrifos, the least water-soluble insecticides tested. Spoon-applied terbufos reduced root maggot feeding injury more than conventional banded and modified in-furrow applications in two of five environments. Plots treated with spoon-applied chlorpyrifos yielded 30.8% more recoverable sucrose than those that received the insecticide as a banded application in 1999, the year of least postapplication rainfall. Aldicarb, the most water-soluble insecticide tested, was gen­ erally unaffected by placement. However, spoon-treated aIdicarb plots produced 19.2% less recoverable sucrose than those receiving the material via modified in-furrow place­ ment in 2001, the year of highest postapplication rainfall. Contrasts of root injury across ail insecticides suggested that, of ail placement methods tested, the spoon technique has the greatest potential to optimize granular soil insecticide effica­ cy for management of sugar beet root maggot larvae.