砕土によるサトウキビ害虫ケブカアカチャコガネ幼虫の物理的防除

概要

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White grub Dasylepida ishigakiensis (Coleoptera: Scarabaeidae) is an important pest that infests the roots and underground stems of sugarcane. Thus, the establishment of an effective control method for this pest is urgently required. Changes in the vertical distribution of third stadium larvae of D. ishigakiensis in the soil were surveyed in a post-harvest sugarcane field on Miyako Island, Okinawa, in 2005. Although 73.8% of third stadium larvae were captured within 30 cm soil depth on March 17, the rate decreased to 38.1% on April 5 and to 25.0% on April 17, suggesting that most larvae move to deeper soil from the end of March to mid-April. The possibility of physical control by rotary tillage while the larvae are in shallow soil (0 to 30 cm) was examined in another field on March 16, 2005, with three treatments: 1) control, 2) tilling once and 3) tilling twice. The number of living larvae per sugarcane stool with tilling once or twice was much lower than in the control. Furthermore, the difference between the control and tilling twice six days after treatment was significant. These results indicate that tilling sugarcane fields by mid-March after the harvest can effectively control D. ishigakiensis larvae.