title: Neonicotinoid-induced resurgence of rice leaffolder, Cnaphalocrocis medinalis (Guénee).
abstract: BACKGROUND
  Among the neonicotinoids, imidacloprid and thiamethoxam have been frequently used in planthopper endemic areas. Wherever leaffolder incidence occurs along with planthoppers in rice fields, use of neonicotinoids has resulted in increase in leaffolder population. The present study was carried out to verify and confirm the resurgence, as well as to identify factors contributing to resurgence.
  
  
  RESULTS
  In imidacloprid- and thiamethoxam-applied plots, a 17.5-217.5% increase in leaffolder population over the untreated control was observed. Neonicotinoids showed moderate toxicity to eggs with <50% hatching, and less toxicity to first instars with >60% survival, while 37-60% of larvae reached adult stage. The larval duration was also reduced. Fecundity was stimulated, with a 6.2-37.21% increase over the untreated control. A significant positive correlation was observed between larval population and total soluble sugars in thiamethoxam treatment (r = 0.9984, P ≤ 0.01).
  
  
  CONCLUSIONS
  Stimulated fecundity on neonicotinoid-sprayed plants, coupled with reduced larval duration and low egg toxicity, could be the major factors contributing to the upsurge of leaffolder. This study aids in cautioning farmers to be more vigilant while using imidacloprid and thiamethoxam, particularly in rice fields where leaffolder exists alongside planthoppers.
authors: Entomology Section, Directorate of Rice Research, Rajendranagar, Hyderabad, India.
authors: Padmavathi
authors: P
authors: Chintalapati
authors: Entomology Section, Directorate of Rice Research, Rajendranagar, Hyderabad, India.
authors: Gururaj
authors: G
authors: Katti
authors: Plant Physiology Section, Directorate of Rice Research, Rajendranagar, Hyderabad, India.
authors: Raghuveer Rao
authors: RR
authors: Puskur
authors: Entomology Section, Directorate of Rice Research, Rajendranagar, Hyderabad, India.
authors: Krishnaiah
authors: K
authors: Nagella Venkata
mesh_terms: D000818:Animals; D005298:Fertility / Q000187:drug effects; D007093:Imidazoles / Q000378:metabolism*; D007194:India; D007306:Insecticides / Q000378:metabolism*; D009036:Moths / Q000187:drug effects* / Q000502:physiology; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000378:metabolism*; D010078:Oxazines / Q000378:metabolism*; D011158:Population Growth; D000077922:Thiamethoxam; D013844:Thiazoles / Q000378:metabolism*
chemical_list: D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010078:Oxazines; D013844:Thiazoles; C082359:imidacloprid; D000077922:Thiamethoxam
keywords: Cnaphalocrocis medinalis; host plant factors; imidacloprid; insect factors; resurgence; thiamethoxam