Maturity-Dependent Mortality of Colorado Potato Beetle Eggs Treated with Novaluron

Abstract

Novaluron is a chitin synthesis inhibitor (a benzoylphenyl urea) that kills larval stages and causes reversible cessation of laying viable eggs in adults of the Colorado potato beetle, Leptinotarsa decemlineata (Say). Previous studies also suggest that it has ovicidal properties, but not on all tested egg masses. We investigated if egg maturity at the time of exposure affects its susceptibility to novaluron. Novaluron application significantly reduced the hatch of eggs that were 0-24 h old at the moment of treatment, but had no effect on the eggs that were 96-120 h old. Novaluron also interfered with the development of the hatched larvae regardless of the egg age at the time of treatment, probably due to chorion feeding by neonates. Ovicidal properties of novaluron may contribute to Colorado potato beetle control, but their effect will be limited to newly laid eggs. If that window of susceptibility is missed, hatching larvae will be exposed to a fairly old novaluron residue that might be weathered down to sublethal levels. This supports the current recommendations to apply novaluron as a larvicide.Resumen Novaluron es un inhibidor de la síntesis de quitina (un benzoylphenyl urea) que mata estados larvales y causa cese reversible de la deposición de huevos viables en adultos del escarabajo de Colorado, Leptinotarsa decemlineata (Say). Estudios previos también sugieren que tiene propiedades ovicidas, pero no en todas las masas de huevos probadas. Investigamos si la madurez del huevo al tiempo de la exposición afecta su susceptibilidad al novaluron. Su aplicación redujo significativamente la eclosión de los huevos de 0 a 24 hs de edad al momento del tratamiento, pero no tuvo efecto en los de 96 a 120 hs de edad. Novaluron también interfirió con el desarrollo de la larva emergida, independientemente de la edad del huevo al momento del tratamiento, probablemente debido a la ingestión de la cubierta externa del huevo por los neonatos. Las propiedades ovicidas de novaluron pueden contribuir al control del escarabajo de Colorado, pero su efecto estará limitado a la oviposición nueva. Si se pierde esa ventana de susceptibilidad, la larva resultante estará expuesta a un residuo de novaluron bastante viejo que pudiera ser disminuido a niveles subletales por el ambiente. Esto respalda las recomendaciones actuales de aplicar novaluron como un larvicida.

Toxicity and Some Biological Effects of Emamectin Benzoate, Novaluron and Diflubenzuron against Cotton Leafworm

“…Applications of novaluron or diflubenzuron may result in mortality by disrupting the molting process through inhibiting the formation of chitin. Additionally, reduced egg hatch has been documented from eggs treated with benzyl ureas as well as sublethal effects on the treated insects (Alyokhin andChoban, 2010, Elliot andAnderson, 1982), which was confirmed in this study. Novaluron and diflubenzuron negatively affect most of the growth and development parameters that tested when the 2 nd instar larvae of S. littoralis were treated by two sublethal concentrations.…”

Difficulties in Potato Pest Control: The Case of Pyrethroids on Colorado Potato Beetle

“…In these areas, CPB generally brings up two generations per year, but in mild climate zones, three or even four generations may grow up [70]. During the spring or early summer, adult beetles colonize potato fields, they are attracted to volatile compounds of the Solanum species and immediately start to reproduce [71,72]. CPBs have high fecundity: female beetles may lay up to 800 eggs in their life [67].…”