Estimation of the population density of the sweetpotato weevils on the Mariana Islands

Abstract

The sweetpotato <em>Ipomoea batatas</em> L. (Convolvulaceae) has been one of the most important foods for Pacific islanders for centuries. However, the yield levels have been declining in the recent past due to the presence of sweetpotato weevils <em>Cylas formicarius</em> (Fabricius) (Coleoptera, Brentidae), <em>Euscepes postfasciatus</em> (Fairmaire) and <em>Daealus tuberosus</em> (Zimmer man) (Coleoptera, Curculionidae). Therefore, urgent management or eradication methods are sought in the Mariana Islands (Guam, Rota, Saipan, and Tinian). However, the management or eradication of these weevil pests requires accurate assessments of the target pest density. Currently, no advice is provided to growers on the best method for sampling sweetpotato for weevil pests, although pheromone-based traps or chemicals are being used. This study defines the results of field counts designed to adjust relative sampling techniques for three sweetpotato weevil pests by inspecting plants visually and at random in the field with an absolute measure of population density. Significant relationships were detected between the relative four sampling sites between the three weevil pests. In the dry and wet season, 90% and 35.5%, respectively, of population density of <em>C. formicarius</em> was noticed in Rota. This density of the population levels of this species is significantly lower in Saipan, Guam and Tinian. No incidence of <em>E. postfasciatus</em> and <em>D. tuberosus</em> was observed on Guam. However, <em>E. postfasciatus </em>is identified as the second most destructive pest in Rota, Tinian and Saipan in both the dry and wet seasons. Likewise, <em>D. tuberosus </em>is the third major pest as the recorded population density ranged from 12.5% to 2.5%. Also, it is evident from the sampling study that the population densities of all three weevils are significantly higher in the dry season than the wet season

Invertebrate pests and diseases of sweetpotato (Ipomoea batatas): a review and identification of research priorities for smallholder production

“…This eradication programme is expected to take a long time due to the long generation time and problems that have occurring during the mass rearing (Sato et al, 2010). The general utility of this approach is limited by the fact that weevils, even C. formicarius which is capable of flight, mostly move by crawling (Reddy et al, 2012b(Reddy et al, , 2014a. The sterile insect technique requires resources for the technological infrastructure to rear and sterilise large numbers of insects for release.…”

Laboratory adaptation reduces female mating resistance in the sweet potato weevil

“…(Convolvulaceae). Cylas formicarius originated in the Indian subcontinent (Wolfe, 1991) and invaded the South Pacific, Caribbean Basin, Mariana Islands, some countries of Central and South America, and islands of south-western Japan (Chalfant et al, 1990;Yasuda & Kohama, 1990;Jansson & Raman, 1991;Yasuda, 1993;Reddy et al, 2012). In 1994, an eradication program targeting C. formicarius by using SIT was initiated on Kume Island in Japan (Moriya, 1997).…”

Perbandingan Metode Aplikasi Jamur Entomopatogen Beauveria Bassiana Untuk Pengendalian Cylas Formicarius (Coleoptera: Curculionidae)

“…Salah satu hama utama ubi jalar adalah penggerek umbi yang disebabkan oleh Cylas formicarius (Jackai et al, 2006;Reddy et al, 2012b). Kerugian hasil yang disebabkan oleh hama ini mencapai 100%.…”