Location: Invasive Plant Research Laboratory
Project Number: 6032-22000-013-131-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jun 1, 2024
End Date: May 31, 2025
Objective:
We propose to develop safe and sustainable biological control of the invasive weed, cogongrass (Imperata cylindrica, a common weed of disturbed areas of the southeastern US. During the one-year duration of this funding we propose to survey, collect, curate, and colonize select species from the native range of this weed. Depending upon the outcome, continuation of funding may be pursued. Cogongrass invasions in forests and grasslands constitute a significant challenge as resources are expended to control and restore invaded areas. Cogongrass is one of the ten worst weeds in the world, a US federally listed noxious weed, and one of the most problematic invasive weeds in the southeastern US. Cogongrass has broad impacts on native plant communities in terms of plant diversity and performance, it aggressively competes with other vegetation for soil nutrients, alters the rates of decomposition of native grasses, and increases vegetative fuel loads while tolerating controlled burns. Options to control this invasive weed are limited to two synthetic herbicidal compounds, glyphosate in natural areas and imazapyr in managed non-crop areas. This shortage of options raises concerns for the development of herbicide resistance. Further, the long-term success of control with these herbicides is highly variable, costly, and provide only temporary relief requiring annual repeat treatments. Additional causes for concern include human exposure to these pesticides and unintentional damage to non-target, valued plants. This proposal seeks funding to develop ecologically safe, sustainable, and cost-effective control of cogongrass for agriculture, forests and grasslands in the southeastern US through the development of biological control agents.
Cogongrass invades many subtropical and tropical areas and is estimated to infest over 500 million hectares world-wide. Asia is most likely the native range of cogongrass from where it was accidentally introduced to the US around 1912 in packing material from Japan. Cogongrass was later intentionally introduced for forage in Texas, Mississippi, Alabama, and Florida. Cogongrass is included in the federal noxious weed list and primarily invades the Gulf Coast states from Texas to Florida, Georgia, South Carolina, and Virginia. With climate change, this weed also has the potential to spread north to Oklahoma and Tennessee, and east to coastal North Carolina. Over 100,000 hectares are infested in Florida, Alabama, and Mississippi where cost of control may approach $ 400 per hectare. Cogongrass produces extensive rhizomes and seeds which allow it to spread, persist, and dominate invaded sites. The weed may reproduce vegetatively from rhizomes and is a prolific seed producer which allows wind dispersed invasion of new areas. Cogongrass leaves can grow to 1.2 to 1.5 meters in height and the plant can thrive in fire-based ecosystems.
Objective 1: Conduct biological control surveys for insects associated with cogongrass in Australia, Japan, and Indonesia
Objective 2: Curate collected insects from foreign surveys
Objective 3: Colonize and initiate suitability tests of potential biological control agents of cogongrass
Approach:
The primary purpose of this project is to discover, characterize and colonize potential agents in their native range. Further studies will be required in subsequent funding cycles to conduct host range testing and ultimately the release of approved biological control agents. This environmentally safe, cost-effective, and sustainable means of weed control will be accomplished with the mass production, distribution, and evaluation of the approved agents which will be discovered during this proposed research.
The proposed research described here will initiate and continue previous biological control efforts against this weed within the one-year time frame of the funding. If funded, we will provide a list of herbivore species associated with cogongrass from these areas of its native range. Further study will determine if the most promising agents will be safe for release. Objective 1, proposes to initiate surveys in Australia. Recent efforts have discovered a diversity of new species feeding on the target; return to Japan and Indonesia where previous work has discovered promising potential agents. Objective 2 will characterize the collections with both traditional morphological and molecular techniques to identify and determine if new species have been discovered feeding on cogongrass in the native range; Objective 3 will colonization and initiate testing of the collections on Florida cogongrass. As time allows, testing will be initiated on the most promising collections to obtain an impression of the agent safety for field release and justification for continued funding.
Genetic analysis confirmed that the sawfly colony established from ABCL collections in Thailand in December 2019 was merged with the existing IPRL quarantine colony. This combined colony will be used to conduct multigenerational tests of this species on the non-targets, L. oligostachyum and L. volubile.
