1987 Volume 31 Issue 2 Pages 125-133
Control effect of the communication disruption technique with sex pheromone component(s) in Chilo suppressalis was evaluated in paddy fields in Okayama Pref. from 1981 to 1985. Disruption treatment against the adults of the overwintering generation (=first flight period), in which a significant disruptive effect was observed in monitoring tests, was not effective for the control presumably because most of the moths in the paddy had emerged, mated and migrated from outside. On the other hand, effective control by the treatment was obtained in the first generation adults (=second flight period) when the release rate of the compound(s) was adequate. The appropriate release rate varied with the population density of the moths, being approximately 50mg/10a/day for a low population density and >100mg/10a/day for a high population density. Release rate of the compounds could be well controlled for a longer period (>1 month) of time by using a polyethylene capillary tube with a thicker wall as a dispenser. No apparent differences in the control effect between a single component (Z-11-hexadecenal) and a 3-component mixture (natural ratio) as a disruptant have so far been revealed. The treatment area necessary for effective control was found to be greater than 50 a, unless the moth population density was unusually high. Also, to obtain a highly effective control, it may be important to reach both nearly 100% attraction inhibition in the pheromone trap and a mating suppression rate higher than 90% in the tethered females in the monitoring tests during the treatment. Correlation for the degree of damage by larvae before and after the treatment in the treated areas was lower as compared to that in the control areas. This phenomenon may be due to the effect of the disruption treatment in relation to the mating frequency of the tethered females and estimated number of egg masses.
