Estimated Hatching Period of the Carpenter Moth, Cossus insularis (Lepidoptera: Cossidae), in Tokushima Prefecture

The larvae of the carpenter moth, Cossus insularis (Staudinger), bore deeply into branches and trunks after hatching under the bark of Japanese pear trees. For estimation of the optimum timing for pest control against the hatching period, the effect of temperature on hatching and developmental time of eggs was examined by rearing experiments at constant temperatures. Eggs were incubated at the following temperatures: 15, 20, 23, 25, 28, 30 and 35°C. Hatching was observed from 20-30°C. Hatching rates at 25, 28 and 30°C were higher than those at 20 and 23°C. Duration of egg stage decreased with increasing temperature. Since the developmental zero and effective cumulative temperature for duration of egg stage were 16.2°C and 169 degree-days, respectively, the duration of egg stage was estimated at 13-17 days in a field in Tokushima Prefecture, Japan. Subsequently, the optimal timing for chemical control against hatching period was estimated to range from mid-July to mid-August. However, the observed dates of the optimal timing in the field were late-July to late-August. The difference between the estimated and observed dates of the optimal timing was corrected approximately, taking into consideration that the duration of the 1st instar larval stage was 6-14 days.