Location: Systematic Entomology Laboratory
Project Number: 8042-22000-316-001-A
Project Type: Cooperative Agreement
Start Date: Sep 1, 2020
End Date: Aug 31, 2021
Objective:
This agreement is established to investigate an invasive scale insect pest, the Roseau Cane Scale, recently established in Louisiana and determine its country of origin to aid in biocontrol measures. Roseau cane (common reed, Phragmites australis) is the dominant emergent vegetation and a critical species in the marshes of the Mississippi Delta. It grows at depths unsuitable for other marsh plants and the roots form dense mats that help build and maintain marsh sediment, hold the channels in place, protect inland areas from storm surge that accompany hurricanes, and provide important habitat for waterfowl and fish. By preventing erosion and soil deposition that would clog shipping channels and protecting the interior marshes and human structures (particularly oil and gas infrastructure) from storm surges, Phragmites provides an indispensable ecosystem service to this area.
In recent years, large areas of Phragmites cane have been dying in the lower Mississippi River Delta (MRD). Symptoms of the die-offs were first noted in the fall of 2016 by concerned landowners who noticed premature senescence, poor regrowth resulting in thinning stands, and stand retreat. Following these reports, analysis of the area using satellite imagery suggests that the die-backs had, in fact, been occurring for several years prior to discovery. The invasive Roseau cane scale, Nipponaclerda biwakoensis (Kuwana) (Hemiptera: Aclerdidae) (referred to here as RCS) has been implicated in die-offs. RCS is known from Asia, but this was the first record of RCS in the United States. Heavy infestations of P. australis in Louisiana reached over 2,000 scales per stem and as populations of the scales increased, there was a reduction in stem density of the Phragmites stands. Also, as the density of Roseau cane declines, scientists are seeing an increase in the incidence of invasive plants such as taro, water hyacinth, and giant salvinia. This leaves the underlying soil vulnerable to erosion from wave and storm action. Of the 110,000 acres of cane in the Gulf region, 80% are reportedly affected by the scale insect.
For a second year, Farm Bill funding has been awarded to an international team of researchers studying RCS, it’s impact and control. This sub-agreement uses a portion of the second round of funding to continue investigating population genetics of RCS across the native range in East Asia. The objective of this component is to identify the source of invasive RCS populations in Louisiana, which will direct efforts at its control.
Approach:
Field surveys of Phragmites australis were conducted in 2019 by cooperators from China, Hong Kong, Japan, Korea, Taiwan, and Vietnam; a second round of surveys is proceeding for summer 2020. Collections of RCS will be gathered from 2020 surveys and shipped to UMass PI’s for genetic analyses and preparation of vouchered museum collections, to be deposited in the United States National Museum of Natural History’s Entomology Collections (USNM).
Funding from this sub-agreement will be used to purchase supplies and hire a part-time undergraduate student technician for to prepare DNA extractions for genetic analyses and slide-mounted vouchers, and conduct PCR analyses. DNA extractions will be prepared using spin-column based protocols. Each preparation will consist of a single individual and will be labeled with a unique identifier used to link the DNA extraction, slide-mounted voucher, and associated research products. Following the initial digestion step, the insect skin will be removed from the lysis buffer and preserved for slide-mounting, which will be completed following the protocol of the Systematic Entomology Laboratory. Vouchers will be submitted to the ARS PI for inclusion in the USNM collections.
Genetic characterizations will be completed by sequencing a 928 basepair fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene. PCR amplification and sequencing will be accomplished using the following combination of primers, or additional published or novel primer sets: AcoF1 (5’-TATTCWACNAACCATAAAAAYATTAG-3’), Aco2568R (5’-GCAATTACATAAT AWGTRTCRTG-3’), C1-J-2183 (5’-CAACATTTATTTTGATTTTTTGG-3’ sequencing), NipbiwCo2045F (5’-GTATTAGCTAGAGGTATCAC-3’ sequencing), and HCO2198 (5’-TAAACTTCAGGGTGACCAAA AAATCA-3’ sequencing). Sequence editing and alignment can be completed using one or a combination of various software programs available, including Geneious, Sequencher, Mesquite, SeaView, etc.
A COI haplotype network will be constructed using statistical parsimony analysis in the program TCS. Extensive haplotype diversity has already been discovered from preliminary analyses using 2019 collections, with preliminary results suggesting RCS populations in Louisiana originated in or near China. Incorporation of specimens from additional sites will narrow down their origins. These results will be analyzed in combination with NGS data being generated as part of a separate sub-agreement funded through the Farm Bill.
