Prioritizing regions for native range surveys: Imperata cylindrica (cogongrass)

Authors: BROOKES, DEAN - Commonwealth Scientific And Industrial Research Organisation (CSIRO); Wheeler, Gregory

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/14/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Cogongrass is one of the 10 worst weeds in the world impacting agriculture, forestry, and biodiversity in the southeastern US. There are few options to control cogongrass, only herbicides which provide temporary control and require frequent re-treatments. We are developing biological control agents to assist in the control of this weed. These agents will be safe, sustainable, and cost-effective control of cogongrass. We are searching for the best agents in the areas where cogongrass originated, the native range. These areas include Japan, South Korea, Australia, and Africa. We are prioritizing the most promising areas of the world based on the plant's similarity with the variety that invades the southeastern US. One of the closest matches to one of the invasive forms has been found in Japan and South Korea. We have found over 60 potential agents to study from these areas. These include insects that feed on different plant tissues including flowers, stems, shoot tips, and rhizomes. Three agents have been prioritized, a stem borer Emmalocera latilimbella, a shoot tip borer Atherigona sp., and a stem borer pos. Chilo sp. which have been colonized and are currently undergoing host range testing in quarantine at the USDA facility in Ft Lauderdale, FL. Preliminary tests indicate that Emmalocera and Atherigona are specific and may provide significant control of the target weed. Further testing will determine if these species can be used for safe and effective biological control of cogongrass.

Technical Abstract: Cogongrass, Imperata cylindrica, is one of the 10 worst weeds in the world impacting agriculture, forestry, and biodiversity. Options to control this invasive weed are limited to synthetic herbicidal compounds which provide only temporary relief requiring annual retreatments. We are developing ecologically safe, sustainable, and cost-effective control of cogongrass through the development of biological control agents. Our research seeks to identify the origin of the invasive lineages of I. cylindrica with molecular approaches and prioritize surveys for potential agents in the areas with the closest matches and where the weed originates. One of the invasive lineages invading the southeastern USA comes from Japan. Despite the traditional view that grasses have low herbivore diversity, we have recovered over 60 species of potential agents in Japan and Australia. These include a diverse assemblage of herbivores that feed on different plant tissues including flowers, stems, shoot tips, and rhizomes. Three agents have been prioritized, a stem borer Emmalocera latilimbella (Lepidoptera: Pyralidae), a shoot tip borer Atherigona sp. (Diptera: Muscidae), and a stem borer pos. Chilo sp. (Lepidoptera: Crambinae) which have been colonized and are currently undergoing host range testing in quarantine in the US. Preliminary tests indicate that both are specific and may provide significant control of the target weed. Further testing will determine if these species can be promoted for safe and effective biological control of I. cylindrica.