Looking for Red Palm Weevil in Indonesia

By Mark Hoddle |

The discovery of red palm weevil (RPW) in Laguna Beach Orange County, California USA has generated considerable interest amongst University of California Riverside research scientists and County, State, and Federal regulatory agencies. There are two color forms of the red palm weevil, the orange form (known as Rhynchophorus ferrugineus) and the black form with the red stripe (formerly known as Rhynchophorus vulneratus). Both color forms are found in Southeast Asia (e.g., Thailand, Indonesia, Malaysia and Papua New Guinea). In 2004, a research team from Simon Fraser University in Canada, decided that the red and orange forms of RPW are probably the same species. This decision was based on several lines of supporting evidence: (1) Both forms of the weevil respond to the same aggregation pheromone, (2) There are no significant differences in mitochondrial DNA between the two color morphs, (3) Both color morphs are capable of interbreeding and producing offspring, and (4) Morphological differences used to separate the two color forms are not significantly different. The combined weight of this evidence led Hallet et al. (2004) to combine the red stripe form (R. vulneratus) and the orange form (R. ferrugineus) under one name, R. ferrugineus.

The orange form of RPW has been accidentally introduced to many countries (e.g., Saudi Arabia, Egypt, Israel, France, Spain, Portugal, Italy, Greece, Turkey, Aruba, and Curacao) most likely via the movement of infested palm trees. Curiously, California appears to have been invaded by the red stripe form of RPW. This is very odd, because unlike the orange form of RPW, the red stripe form of RPW has not invaded any other areas of the world. It is only known to inhabit its native range in Southeast Asia. So two questions of great interest for California are: (1) Where did the red stripe form of RPW come from, and (2) How did it come to Laguna Beach?

In an attempt to answer this question, researchers from the Department of Entomology, University of California are collecting specimens of the red stripe form of RPW from various sites throughout the home range of this color morph. Extraction and analysis of DNA from these specimens may indicate where the California population of RPW originated. If this area can be identified within the very large native range of the red stripe form of RPW it may be provide insight into how this pest was introduced into California. Identification of this invasion pathway could be very important as it may allow additional pests to enter California if it is not monitored.