title: Milling effect on the control efficacy of spray-dried Bacillus  thuringiensis technical powder against diamondback moths.
abstract: BACKGROUND
  The relationship between the particle size of spray-dried Bacillus thuringiensis NT0423 technical powder and its insecticidal activity against diamondbackmoth was investigated in laboratory and glasshouse conditions. A variety of sizes of Bt particles were made by homogenisation, followed by pilot-scale milling to optimise further the current Bt formulation process.
  
  
  RESULTS
  In laboratory conditions, homogenised Bt suspension with smaller particles had higher control efficacy against diamondback moth. However, in glasshouse conditions, the smallest particle treatment did not follow the size-dependent insecticidal activity, rather showing decreased control efficacy. Secondly, air-jet-milled Bt powder (16.9 μm) had higher control efficacy than hammer-milled Bt powder (35.1 μm) in glasshouse conditions. However, double air-jet milling (5.3 μm) had lower control efficacy compared with one-time milling.
  
  
  CONCLUSIONS
  These results suggest that NT0423 technical powder with smaller particles is better in controlling diamondback moths, but excessively small particles (<10 μm) possibly reduce the insecticidal activity.
authors.affiliation: Entomology Research Laboratory, University of Vermont, Burlington, VT, USA.
authors.forename: Jae Su
authors.initials: JS
authors.lastname: Kim
authors.forename: Yeon Ho
authors.initials: YH
authors.lastname: Je
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry* / Q000502:physiology; D007300:Insect Control; D007306:Insecticides / Q000737:chemistry / Q000494:pharmacology*; D009036:Moths / Q000187:drug effects*; D010316:Particle Size; D010572:Pest Control, Biological; D011208:Powders / Q000737:chemistry
chemical_list: D007306:Insecticides; D011208:Powders