36th International Carrot Conference Abstract

Can insecticide seed treatments protect carrots from damage by carrot weevil and carrot rust fly?

Mary Ruth McDonald¹, Kevin Vander Kooi¹ and Alan Taylor²

¹Department of Plant Agriculture, University of Guelph, Muck Crops Research Station, King Ontario, L7B 0E9, Canada

²Cornell University, Department of Horticultural Science, New York State Agriculture Experiment Station, Geneva New York, USA

Carrot rust fly (Psila rosea (Fabricius)) and carrot weevil (Listronotus oregonensis (LeConte)) are major insect pests of carrots grown on muck soils in eastern Canada. The carrot rust fly has two generations per year; adults emerge at 329 and 1399 day degrees at base 3 C. Carrot weevils have one generation per year; they overwinter as adults and begin depositing eggs at 138 day degrees at base 7 C. Both pests deposit eggs on the soil at the base of carrot plants and the larvae feed on the roots. Populations of both insects are monitored as part of the local integrated pest management program. Foliar insecticide sprays are registered for both pests, but control of carrot rust fly can be erratic. Limited effective foliar insecticides have turned focus to alternative methods for controlling these pests. Insecticide seed treatments could be an efficient method of reducing the damage caused by the larvae. Insecticide seed treatments spinosad, thiamethoxam, cyantraniliprole and clothianidin were evaluated in field trials in the Holland Marsh, Ontario, from 2010-2012. Each year trials were seeded in late May and harvested in October. Carrot were washed and assessed for insect damage following harvest. Carrot rust fly damage varied greatly from year to year (6.0%, 20% and 0.2% in 2010, 2011 and 2012, respectively). Foliar applications of Cyazapyr and Ripcord reduced carrot rust fly damage by 50% in 2011. In 2012 the seed treatment of Cyazapyr had significantly lower carrot weevil damage than the check. Carrot weevil damage was low in 2010 (0.6 %) and high in 2011 (24%) and 2012 (21%). The insecticide Cyazapyr shows promise for suppression of both pests as a seed treatment and foliar spray.

Last updated Thursday, 25-Jul-2013 11:53:59 CDT