Location: Invasive Plant Research Laboratory
Project Number: 6032-22000-013-153-I
Project Type: Interagency Reimbursable Agreement
Start Date: Oct 1, 2024
End Date: Jun 30, 2026
Objective:
Objective 1: Survey, colonize, and characterize by DNA sequencing cogongrass and key herbivores from China.
Approach:
The ABCL team will work with native range collaborators to colonize prioritized agents in local laboratories and greenhouses in Korea and Japan, and quarantine in Australia if useful for a particular herbivore. To optimize insect acceptance of rearing, plants will be grown with regular irrigation, fertilizer, and pruning. ABCL will share the methods and approaches that they have used to successfully rear one moth species and one fly species in Australia. Colonies will be shipped to the USDA-ARS quarantine in Ft Lauderdale, FL once rearing methods have been established. At the end of the project herbivores will be assessed and prioritized based on observations including literature records, impact, field specificity, abundance, regulation by natural enemies including by parasitoids, and life cycle information. Plants will be propagated either from rhizome or from whole plants collected from local populations. They will be aintained under optimal conditions to produce healthy robust growth. After rhizome or field collected plants reach eight weeks, they will be transplanted to pots (size as needed) and grown in an outside garden or glasshouse. Pesticides will be used if needed. Pesticide and fertilizer applications will be discontinued at least one week prior to the start of colonization, after which plants will only receive daily watering and hand-removal of pests. Appropriate plant stage and tissues will be provided to colonizing species depending on the insect life history and feeding preference. Seasonal surveys, once per quarter, will be conducted at field sites in Japan and South Korea to evaluate the abundance, impact, and plant genotype associations of the stem borers, and to gain information on their biology that will help to rear them (e.g., pupation location, preferred site conditions, etc.). Field sites will cover different plant genotypes, environment types, and soil conditions. At each site we will record the number of plants that are damaged by each stem borer species, impact on the plant, plant and herbivore life stage, and the presence of parasitoids and the data used to prioritize species for further evaluation. We will collect leaf material preserved in silica from colony plants and cogongrass plants at field sites and preserve stem boring insects in 95% ethanol. These specimens will be used for later molecular analysis. DNA will be extracted from leaf material and preserved insect specimens. Phylogenetic and population genetics analysis will be performed using the cogongrass DNA, and DNA barcoding will be performed for the stem borers. Through this analysis we will understand the specific association of the herbivores with native range plant genotypes (Nomura et al. 2022) as well as an understanding of the phylogenetic relationship between the host plants. Together with data from US collections of cogongrass we will determine whether our collections relate to C-type, E-type, or their hybrids (Nomura et al. 2022). The phylogenetic relationship between C-type, E-type, I. brevifolia, I. brasiliensis, and the US invasive cogongrass lineages will be assessed.