Ovicidal effect of primary insecticides on Cnaphalocrocis medinalis in paddy field
Author of the article:GUO Jia-Wen;HE Xiao-Chan; CHENG Yi-Sha; AUNG Thura; LU Yan-Hui;LI Wen-Qiang;XU Hong-Xing;HUNG Jian-L
Author's Workplace:State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China; Jinhua Academy of Agricultural Sciences, Jinhua 321000, China
Key Words:Cnaphalocrocis medinalis; egg development; insecticides; toxicity; egg dipping method
Abstract:
[Objectives] To clarify the ovicidal effect of primary insecticides on
the rice leaf folder, Cnaphalocrocis medinalis, in paddy fields and
thereby provide a scientific basis for the safe and efficient control of this
pest. [Methods] The toxicity of
eight primary insecticides (chlorantraniliprole,
abamectin, chlorpyrifos, indoxacarb, imidacloprid, pymetrozine, thiamethoxam and thiazide) commonly used in rice
fields was determined in a laboratory. The toxicity of these insecticides on C. medinalis eggs of different
ages, and their effects on the survival of newly hatched larvae, were measured,
and the effect of insecticides on the subsequent development of eggs was
observed. [Results] Chlorantraniliprole
had a corrected egg hatching inhibition rate of 10.42%-100.00%, and had
stronger ovicidal activity than abamectin, chlorpyrifos or indoxacarb.
Chlorantraniliprole was most toxic to 1 and 3-day-old (LC50 2.123 and 1.904 mg/L, respectively).
Treatment soon after eggs are laid can cause them to fail to develop normally
and the age at which eggs were treated significantly affected the mortality of
newly hatched larvae, indicating that it is better to treat eggs as soon as
possible. The corrected hatching inhibition rate for imidacloprid ranged from
20.00% and 91.67%. Imidacloprid had stronger ovicidal effect than pymetrozine
and thiamethoxam. Thiazide had the least ovicidal effect. Treating 3 to
4-day-old eggs with imidacloprid resulted in larvae
developing normally but inhibited hatching. Treating eggs at this time achieved
both the best ovicidal effect and the highest mortality among newly hatched
larvae, indicating that imidacloprid should be applied 2 days after eggs have
been laid. [Conclusion] Of the eight insecticides, chlorantraniliprole had the strongest
ovicidal activity to the rice leaf folder, and its ovicidal effect was higher
when applied to newly laid eggs. Imidacloprid and thiamethoxam had a lower
ovicidal effect, but, of these imidacloprid had the stronger effect and can
achieve good results when applied to eggs 3 to 4 days after laying.