title: Development of a rapid resistance monitoring bioassay for codling moth larvae.
abstract: BACKGROUND
  The codling moth, Cydia pomonella (L.), is one of the most important pests of apple worldwide. Use of insecticides for management of this insect has been extensive and has resulted in resistance development. There are a number of different bioassay methods to monitor for codling moth resistance; however, many are not applicable to new insecticides and most are time consuming. A novel 16-well plasticware bioassay plate containing lyophilized diet was developed for rapid resistance monitoring of codling moth.
  
  
  RESULTS
  The contact insecticides acetamiprid and azinphosmethyl were significantly more toxic to neonates than to fourth instars. However, there was no significant difference in LC(50) values between neonates and fourth instars to the ingestion insecticides chlorantraniliprole, methoxyfenozide, novaluron and spinetoram. Field colonies of codling moth were significantly more resistant to methoxyfenozide than susceptible populations. A diagnostic dose of 20 µg mL(-1) (LC(99) ) was established to monitor for codling moth resistance to methoxyfenozide.
  
  
  CONCLUSIONS
  The results presented here demonstrate that a novel and rapid bioassay can be used to monitor for codling moth resistance to methoxyfenozide. The bioassay method is relevant to both ingestion and contact insecticides, but a single diagnostic dose, regardless of larval age, is only relevant to ingestion insecticides. Age-dependent diagnostic doses are likely necessary for contact insecticides.
authors.affiliation: Department of Entomology, North Carolina State University, Raleigh, NC 28759, USA.
authors.forename: Leonardo C
authors.initials: LC
authors.lastname: Magalhaes
authors.forename: Jaap B
authors.initials: JB
authors.lastname: Van Kretschmar
authors.forename: Vonny M
authors.initials: VM
authors.lastname: Barlow
authors.forename: R Michael
authors.initials: RM
authors.lastname: Roe
authors.forename: James F
authors.initials: JF
authors.lastname: Walgenbach
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001413:Bacillus thuringiensis; D001427:Bacterial Toxins; D001681:Biological Assay / Q000379:methods*; D018556:Crops, Agricultural; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D003368:Gossypium; D007306:Insecticides; D007814:Larva / Q000502:physiology; D007915:Lepidoptera / Q000502:physiology*; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D001427:Bacterial Toxins; D007306:Insecticides