The impact of Cecidochares connexa on Chromolaena odorata in Guam.
Chromolaena odorata (L.) King & Robinson (Asteraceae) is one of the most serious invasive weeds in Guam and on other Micronesian Islands. For biological control of this weed, a moth, Pareuchaetes pseudoinsulata Rego Barros (Lepidoptera: Arctiidae) from India and Trinidad and a gall fly, Cecidochares connexa (Macquart) (Diptera: Tephritidae) from Indonesia were introduced into Guam and other Micronesian islands in 1985 and 1998, respectively. To assess the impact of these established natural enemies, eight field sites in northern, central and southern Guam, each with well-established stands of C. odorata, were assessed in 2009. Measurements of various growth parameters of C. odorata indicated steady decline in the number of stems and leaves, and height of plants at the sites from October 2009 to September 2010. This gives a snapshot picture of the decline of C. odorata on Guam, likely due to the introduced natural enemies.