THE APPLIED INSECT GENETIC LABORATORY (AIGL): DNA TECHNOLOGY ILLUMINATES THE BIOLOGY OF INSECT PESTS

Summary

The Applied Insect Genetics Laboratory (AIGL) in the Department of Entomology on the UGA Griffin campus uses DNA technology to study insect pests of interest to stakeholders representing billions of dollars. Genetic evaluation of DNA data has been used to track invasive species to their country or state of origin, predict pest dispersal patterns across Georgia based on genetic diversity and endosymbiont type, uncover breeding structure for insights into control and verify the efficacy of management strategies in insect pests from four orders: Isoptera, Hymenoptera, Coleoptera, and Hemiptera.

Situation

The Applied Insect Genetics Laboratory (AIGL) is part of the applied insect genetics program under the aegis of Dr. Tracie M. Jenkins and located in the Entomology Department on the UGA Griffin Campus. DNA data collected, processed and evaluated through AIGL affected structural, horticultural, and agricultural stakeholders representing billions of dollars. Genetic insights from AIGL DNA analyses follow and includes the very recent invasive Megacopta cribraria (Fabricius) (Hemiptera: Plataspidae) commonly known as the bean plataspid, globular stinkbug or lablab bug, which has the potential of being a soybean pest. (1) Megacopta cribraria (Fabricius) (Hemiptera: Plataspidae): bean plataspid, globular stinkbug or lablab bug In November 2009 Dr. Dan R. Suiter, an extension entomologist who studies structural and household pests on the UGA Griffin Campus and Lisa M. Ames, director of the Homeowner Insect and Weed Diagnostics laboratory, showed Dr. Joe Eger, a research entomologist with Dow AgroSciences, insects submitted to them by county extension agents and pest control operators. Dr. Eger and others tentatively identified the insect as the bean plataspid or lablab bug, Megacopta cribraria (Fabricius) (Hemiptera: Plataspidae). It is an indigenous kudzu and soybean pest in Asia, but has never been seen on this continent. Soybean production in 2008 in the U.S. was worth $27 billion (http://www.ers.usda.gov/Briefing/soybeansoilcrops/) and in Georgia it was estimated to be worth $65-70 million in 2007 (November Soybean Newsletter, UGA Soybean Extension Team). In order to understand this insects' biology, a working team was quickly assembled from entomologist on the Griffin Campus. It consisted of Dr. Tracie Jenkins and the AIGL lab, Dr. D. Suiter, and Dr. D. Buntin. Dr. Jenkins and the AIGL lab analyzed DNA sequence data which appears to confirm Dr. Joe Eger's identification. Other DNA fingerprint data appears to verify that a unique endosymbiont was present in all samples studied. This result is significant because a recent Japanese study suggests that if the endosymbiont is present in M. cribraria it is more likely to be a pest. The AIGL lab has begun to collect DNA from Asian samples in an effort to determine the origin and mode of entry of this pest into Georgia. Subsamples from collections logged into Dr. Suiter's lab representing sites across Georgia are being processed through AIGL to verify species, determine genetic variation and presence of the endosymbiont. As money becomes available studies regarding the management importance of the endosymbiont will begin. (2) Camponotus pennsylvanicus (Hymenoptera: Formicidae), Black carpenter ant A longitudinal study on the black carpenter ant, Camponotus pennsylvanicus, in Georgia continues in collaboration with Dr. Dan Suiter, UGA Griffin Campus. The purpose of the research is to evaluate site-specific treatments with an eye toward long term IPM strategies. Camponotus pennsylvanicus is the largest, most difficult ant to control, and one of the most costly. Individual DNA fingerprints and maternal-specific DNA markers are being used to monitor ant population structure, including changes in social structure over time that may alter a colony's genetics as well as to track patterns of dispersal including long range alate flights. Several sites, which have been genetically characterized, are then chemically treated by Dr. Suiter. These sites are monitored for multiple years to determine if ants return; and if so, to evaluate whether the ants are from the treated colony or a new one. Genetic verification of field data will aid in developing successful, environmentally friendly, and cost effective IPM protocols. (3) Coptotermes formosanus (Isoptera: Rhinotermitidae), Formosan Subterranean Termite The urban population already represents more than 51% of the Georgia population and by 2030 it is predicted to represent more than 58% of the total population in the state. The Formosan subterranean termite, Coptotermes formosanus, is of Asian origin and has been established as an urban pest in Georgia, particularly around the metropolitan Atlanta area. Work done in the AIGL lab in collaboration with Dan Suiter and Brian Forschler illuminated not only the origin of the infestation, but the method and mode of entry into Georgia. Genetic data indicated that railroad ties infested with termites were likely taken off grade in New Orleans, LA and/or Charleston, SC and loaded onto trucks bound for Georgia. Insects were passively spread by human activity because infested ties were unloaded in Atlanta and then used for landscaping in metropolitan area subdivisions. Steps, due to this work, have been taken to be sure that railroad ties are termite free. (4) Altica species (Coleoptera: Chrysomelidae: Galerucinae), Flea beetle Flea beetles in the genus Altica are horticultural pests on woody ornamentals as well as agricultural crops. In collaboration with Dr. S. Kris Braman who specializes in pests of turfgrass and woody ornamentals, a two year study was conducted designed to genetically verify beetle species in the genus Altica, which are difficult to identify from external morphology. DNA data was correlated with type specimen morphology verified from scanning electron microscope images by Dr. Laurent LeSage in Canada, an expert on Altica morphology. It was discovered that there were two major Altica species, not one, feeding on the above mentioned horticultural plants. Understanding species-plant interactions are important to understanding the insect biology and pest status. Furthermore, two other species were verified in Georgia. Since these insects all have species-specific DNA fingerprints, it is reasonable to suggest that they have species-specific IPM protocols. Beetle-specific DNA fingerprints will also facilitate using Altica beetles as model organisms for Envirotron mediated studies on the effects of global warming on insects in Georgia. These insights are needed if we are to understand how insects will respond to temperature changes.

Response

(1) Invasive bean plataspid or globular stinkbug, Megacopta cribraria (Fabricius) DNA evidence has been collected and analyzed which confirms M. cribraria has been introduced into Georgia. The endosymbiont, which appears to make the bean plataspid more fit and, therefore, likely a crop pest has been shown to be present. The genetic diversity is being determined from samples collected from infected Georgia counties so that environmental adaptation and dispersal can be predicted. DNA from pinned museum specimens of M. cribraria from indigenous areas, Taiwan, India, Japan, and Thailand, is being studied with recently collected samples in Georgia in order to determine the country of origin. DNA data continues to be collected as samples are brought in. (2) Camponotus pennsylvanicus (Hymenoptera: Formicidae), Black carpenter ant Over forty colony sites have been identified by Dr. D. Suiter. Twenty-two of these sites have been genetically characterized and the rest are in the process of being characterized. Sites are being monitored. Data will be processed at the end of a year, then two years in order to answer two questions: Will the same colony return, and if not what will return? The best treatment strategies or strategy will then be published. (3) Coptotermes formosanus (Isoptera: Rhinotermitidae), Formosan Subterranean Termite It was determined that the Formosan subterranean termite, Coptotermes formosaus, likely came into Georgia in railroad ties taken off grade in New Orleans, loaded onto trucks and transported into Atlanta via I-75 and I-85 and off loaded to be used in home landscaping. Recent DNA evidence has also shown that the same maternal line found in New Orleans and Atlanta is also in Charleston, SC, specifically at sites at the Citadel Military College. Thus these insects may have come into Atlanta from two states. As a result of this work, railroad ties are monitored by the state and the company which shipped them more closely. (4) Altica species (Coleoptera: Chrysomelidae: Galerucinae), Flea beetle Genetic evidence from DNA sequence data has showed that there are at least three species in the genus Altica in Georgia. This was a significant finding because the literature suggests that A. litigata adults fly to woody ornamentals in the spring from primroses to the detriment of the woody ornamental. This does not seem to be the general case since primroses were found to be infested with a different Altica species. A DNA marker, therefore, has been developed that can easily identify pests in the genus Altica to species. IPM strategies can now be species-specific.

Impact

The growing urbanization in the southeastern United States and ecological changes due to warming trends will exacerbate infestations of ants and termites. It may also change the dynamics between insect herbivores important to urban agriculture such as flea beetles and new invasive such as the bean plataspid, Megacopta cribraria. This is why it is imperative that insect pests be studied from an interdisciplinary, collaborative perspective that includes DNA technology. Dr. Tracie Jenkins and the AIGL laboratory combined state of the art genetics equipment with bioinformatic tools to complement the expertise of other applied entomologist representing urban, horticultural, and agricultural stakeholders. Results and impacts include the following. (1) Megacopta cribraria (Fabricius) (Hemiptera: Plataspidae): bean plataspid, globular stinkbug or lablab bug. In an effort to help urban and agricultural stakeholders make informed decisions in an expatiated manner, DNA information has been collected and processed as fast as possible since 11/3/09, when the first sample was received. Next year may be critical in terms of dispersion, so it is imperative that a genetic baseline be establish now before the weather turns cold and collections become difficult. So far: (a) Megacopta cribraria, collected 11/3/09, has been confirmed from DNA fingerprints. (b) A unique endosymbiont that may contribute to M. cribraria fitness has been verified by DNA sequence to be in all samples analyzed to date as well as in a museum sample from India. Further DNA data is being collected as follows. (c) DNA continues to be collected and analyzed from museum specimens representing four other indigenous countries in an effort to determine the country of origin and the possible mode of entry into Georgia. (d) DNA fingerprints continue to be collected from individuals representing all collections as they come in. (2) Camponotus pennsylvanicus (Hymenoptera: Formicidae), Black carpenter ant Twelve microsatellite markers have been developed specific to black carpenter ants. DNA fingerprints from individuals sampled from 22 colonies are, therefore, being collected in order to establish a genetic baseline for these insects. Another 20 colonies will likely be added later. Five colonies have been eliminated and are being monitored to determine if the sites are reinfested; and if so by what. The study will help in developing IPM programs to control these urban pests. (3) Coptotermes formosanus (Isoptera: Rhinotermitidae), Formosan Subterranean Termite. Formosan termite DNA fingerprints from individuals collected from New Orleans, The Citadel Military School, and Atlanta have been processed for maternal lineages. DNA evidence shows that infestations are the result of few female lineages. DNA data shows that the insects do exhibit surprising DNA diversity, which indicates that they will adapt and more likely continue to disperse. The efficacy of treatment strategies is high and indicates that these insects will respond to targeted treatments just as indigenous termites do. (4) Altica species (Coleoptera: Chrysomelidae: Galerucinae), Flea beetle. Georgia appears to have at least three species in the genus Altica that are capable of attacking woody ornamentals instead of just Altica litigata. To make it easier on researchers a simple DNA marker has been used to validate species. This has a quick turn around and provides an exact test for a taxonomic difficult species.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2009
• Geographic Scope: State
• County: Spalding
• Program Areas:
  • Agriculture & Natural Resources