Resistance, movement and rotation distance in the Colorado potato beetle, Leptinotarsa decemlineata (Say)

Insecticide resistance offers a contemporary opportunity to observe evolution in action. The primary method proposed for slowing the evolution of resistance is the use of refuge crops, and the primary methods used by potato growers, are rotation of fields, and rotation of treatments within fields. Both refuge crops and crop rotation depend critically on movement (or restriction of movement) for their success.

Monitoring of rotated and non-rotated potato fields, Solanum tuberosum L., for 3 growers was conducted in 2008 and 2009 in Long Island, NY for the Colorado potato beetle, Leptinotarsa decemlineata (Say). In 2008 I found that colonists of rotated fields on Long Island NY were more resistant that those continuously planted in potato. I am analyzing the 2009 data now.

A second study also conducted in 2008 and 2009 compares flyers and walkers emerging from diapause. In 2008 one overwintering site from one grower was used. In 2009 two overwintering sites and two growers were used. Flyers might be more resistant than those captured while walking. These ‘Walkers’ might be capable of flight, but just not flying at the time of capture. This would skew the ‘walker’ population resistance levels clouding the true measure.

This lack of resistance costs might reflect a positive correlation between movement and resistance. It may also result from uniform exposure of the population to insecticide, leaving only the most resistant in sufficient condition to fly.