Increasing Ecological Insect Pest Management on Guam Through Building Agriculture Professionals' Understanding of Semiochemicals

Guam is the western most territory of the United States. It is located south of Japan and east of the Philippines at approximately 144? E and 13? N. Its climate is maritime tropical and it is seasonally subject to frequent passages of tropical low-pressure areas and occasional typhoons. Its population is ethnically diverse, consisting primarily of Chamorro, Filipinos, US mainland Americans, Koreans, Japanese, Chinese, Indians and Carolinian Islanders. Its economy is based on Asian tourism and the presence of US military facilities on the island (Osman, 1995).
Agriculture has played a relatively minor role in the island's economy since the drastic changes that took place at the end of the Second World War (WWII) and during the post-WWII military build-up of the island. More than 90 percent of the island's food supply is imported. By value, the major component of agriculture on Guam is the production of fresh produce for local markets. Fruits and vegetables accounted for 81.3 percent of the value of agricultural production on Guam.
In the past years, most banana produce found in the local markets were imported from other countries. Today, banana growing has become increasingly popular among local farmers in Guam and other neighboring islands. Banana plantations continue to be on the rise and can be seen throughout the island. The fact that the banana weevil is present on Guam and other Pacific Islands raises concern among local growers, consumers, and scientists alike. The weevils are causing yield reductions through the impeding of banana sucker establishment in newly planted crops resulting in loss of plant vigor and reduction in bunch size. It can cause a yield loss of up to 100% if left uncontrolled.
Guam (and the whole of Micronesia, for that matter) is in the midst of a decline of banana production. Thousands of trees are dying in this region due to the banana weevil, Cosmopolites sordidus (Coleoptera: Curculionidae). The banana root borer Cosmopolites sordidus, is considered one of the major pests in most banana growing regions of the world, particularly on dessert bananas, those that can be eaten only when fully ripe, and plantains, those generally known as cooking bananas (Sikora et al., 1989). While various control methods do exist, chemical application is both undesirable and expensive and biological control plays a limited role. Therefore, other means to control the banana weevil population must be further looked into. The existing pheromone-based trapping method using mahogany-brown ground traps 40 × 25 cm appears to be the most efficient at catching C. sordidus adults and has the greatest potential for use in mass trapping and programs for eradication of this pest (Reddy et al. 2008). Without taking appropriate effective control or implementing eradication methods, the banana borer is likely to cause huge or complete loss of banana production in Guam and other Micronesian Islands.
The New Guinea sugarcane weevil, Rhabdoscelus obscurus (Coleoptera: Curculionidae), originated in New Ireland, Papua New Guinea. It was reported that the original habitat of this weevil was New Guinea and the adjoining islands (Reddy et al. 2005). It has since spread to most islands in the Pacific, including Australia and Indonesia. Dispersal of the weevil was almost certainly associated with inter-island trading of sugarcane in earlier years, but in recent years, palms introduced for the ornamental horticultural industry have become the most favored host for this weevil. Especially evident on Guam, R. obscurus has become a major pest of ornamental palms, betel nut palm (Areca catechu), coconut palm (Cocos nucifera) and sugarcane (Saccharum officinarum). The most affected plants are coconut, betel nut, champagne palm (Hyophorbe lagenicaulis), pritchardia palm (Pritchardia pacifica), pygmy date palm (Phoenix roebelenii), Alexander palm (Archontophoenix alexandrae), royal palm (Roystonea regia) and date palm (Phoenix canariensis). Plant nurseries, hotels and gardens containing various ornamental palms are affected considerably by this pest weevil. The damage caused by the boring of this insect is evident on the trunks of the palms. If the damage becomes severe, it can ultimately cause death. More recently, local farmers on Guam have been complaining of noticeable damage occurring on coconut trees on their lands. While conducting a routine survey on R. obscurus throughout the island, our research team had stopped by a particular farmers home to find not only what appeared to be damage caused by R. obscurus on the trunk, but also damage beneath the fibrous sheaths, with adult weevils being found present as well. The coconut tree is extremely valuable to Guam and the Northern Marianas, as it has many different uses. With the recent introduction and attack of the rhinoceros beetle Xyloryctes jamaicensis (Coleoptera : Scarabaeidae) on the coconut tree, any secondary infestation, particularly that more recently seen on Guam by R. obscurus could prove fatal for coconut trees in this region. It is therefore vital that steps be taken to control or eradicate this weevil before it is too late. The chemical ecology laboratory in Guam has developed a trapping method to suppress the R. obscures (Muniappan et al. 2004; Reddy et al. 2005).
The major crop on Guam and the Commonwealth of the Northern Mariana Islands (CNMI) that experiences extensive insect damage is the sweet potato, Ipomoea batatas. Infestations of the sweet potato weevil are so severe on Guam and the Northern Mariana Islands (Saipan, Rota, and Tinian) that many local producers have considered giving up growing sweet potato, which for some may mean abandoning the crop entirely. In fact, there is not just one, but three different species (one which is so far unidentified) of sweet potato weevils already occurring on sweet potato crops in the Northern Mariana Islands. The extensive damage caused by the two sweet potato weevils, Cylas formicarius and West Indian sweet potato weevil Euscepes postfasciatus (Coleoptera: Curculionidae) upon these crops can be devastating to farmers and their workers alike, as it is clear by the numerous sweet potato stands seen alongside the road, that many depend exclusively on this crop for their livelihood. The situation in these regions is made worse by the lack of information and familiarity among growers concerning newer pesticide chemistries, such as imidacloprid and spinosid, and also semiochemical-based trapping methods and new bio-insecticides such as Bacillus thuringiensis. Less-toxic alternatives such as soaps and oils have likewise not been widely promoted on the islands. There is a dire need not only to control the sweet potato weevil but also to educate both farmers and the public alike, otherwise, both Guam and the CNMI will possibly lose another very important crop. The semiochemical-based trapping method has been very effective in reducing pest population and increasing the yield (Heath et al. 1986; Hwang et al. 1991; Yasuda, 1998).
Finally, there is a lack of local knowledge about the role of semiochemicals in pest management. Therefore, there is an urgent need to train the agricultural professionals on the semiochemical-based trapping method for the control of important weevil pests (C. sordidus, R. obscurus, C. formicarius and E. postfasciatus) on Guam.
The purpose of this project is to build agriculture professionals’ understanding of the role of semiochemicals in insect control and pest management and to assist agriculture professionals in passing their knowledge to growers. Guam’s agriculture professional are generally locally trained with minimal exposure to the finer nuances of semiochemicals. Guam College of Natural and Applied Sciences/Cooperative Extension currently has a chemical ecology laboratory that can provide information about various semiochemical availability and methods of use (Reddy and Guerrero, 2004). The laboratory has been very active in conducting research in the area of chemical ecology and has published several scientific papers (for example: Muniappan et al. 2004; Reddy et al. 2005; Reddy et al. 2008). These publications,along with many others, would serve as this project’s training material and would include discussions on semiochemicals of the banana weevil, Cosmopolites sordidus, the New Guinea sugarcane weevil, Rhabdoscelus obscures, and two sweet potato weevils, Cylas formicarius and West Indian sweet potato weevil, Euscepes postfasciatus (Coleoptera: Curculionidae) with accompanying photographs of trapping materials. The publications would also discuss the purchase and use of various traps and lures and general trapping method.