Source: N Y AGRICULTURAL EXPT STATION submitted to
PHEROMONE POLYMORPHISM IN A CRANBERRY PEST SPECIES
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
NRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
0204448
Grant No.
2005-35302-16217
Cumulative Award Amt.
(N/A)
Proposal No.
2005-01004
Multistate No.
(N/A)
Project Start Date
Sep 1, 2005
Project End Date
Feb 29, 2008
Grant Year
2005
Program Code
[51.2]- (N/A)
Recipient Organization
N Y AGRICULTURAL EXPT STATION
(N/A)
GENEVA,NY 14456
Performing Department
GENEVA - ENTOMOLOGY
Non Technical Summary
Phyllophaga anxia (LeConte) is a beetle species whose larval stages are severe root-feeding pests in cranberry bogs in Massachusetts and Wisconsin. My thesis work has revealed an unusual pattern of pheromone variation in this pest that includes three pheromone races. Two of the races are sympatric and synchronic at many sites. Our knowledge of small scale distributions of these races in cranberry growing areas is limited. Development of a means of managing P. anxia is crucial for growers because there are currently no viable control strategies. In order to monitor for this pest complex and to put disruption to work as a control strategy, a much closer look at local populations is required. Additionally, DNA sequence data from both nuclear and mitochondrial genes will be used to generate gene genealogies of trapped individuals to determine whether the three pheromone races are exclusive groups. If not exclusive, microsatellite markers will be used to characterize allele frequencies in different geographic and pheromone races to assess the degree of differentiation. These molecular studies will contribute to our understanding of the evolution of pheromone communication systems and speciation.
Animal Health Component
25%
Research Effort Categories
Basic
75%
Applied
25%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2113110113050%
3043110104050%
Knowledge Area
211 - Insects, Mites, and Other Arthropods Affecting Plants; 304 - Animal Genome;

Subject Of Investigation
3110 - Insects;

Field Of Science
1040 - Molecular biology; 1130 - Entomology and acarology;
Goals / Objectives
Objective 1. To determine on a micro-geographical scale what pheromone races exist in cranberry bogs in Wisconsin and Massachusetts, the two major cranberry production areas in the United States. The single site for which we have information in Wisconsin yielded a predominately valine responding population. However, at that location, P. anxia have also been captured with the two highest blends of isoleucine (65 males over two years), suggesting that other P. anxia pheromone strains may be present. In Massachusetts, trapping studies will be conducted over a wider area that encompasses the cranberry-growing region to determine the range limits of the blend responders. For management of pests whose pheromones are polymorphic, reliable information on local population responses is fundamental. Objective 2. To use DNA sequence data from both mitochondrial and nuclear genes to generate gene genealogies for the three pheromone races of P. anxia. The goal is to document genetic relationships within and among the three races in cranberry and non-cranberry locations across the US. Most importantly, we want to determine whether the pheromone races are exclusive groups (groups of individuals all of whom are more closely related to each other than to individuals outside the group). Exclusivity would imply that each pheromone race had a single origin, and that there is relatively little (if any) ongoing gene exchange. Absence of exclusivity could reflect multiple origins of pheromone types, a single origin but persistence of shared ancestral polymorphisms, or ongoing gene exchange among the races. Mitochondrial DNA (mtDNA) data are already available for a sample of P. anxia (see below), but more intensive sampling is necessary. Furthermore, because genomes are mosaics of different histories and because genetic isolation is a property of individual gene regions, it is essential to generate data from nuclear genes. Objective 3. To use highly variable microsatellite (simple sequence repeat) markers to characterize allele frequencies in natural populations. These data will be used to estimate the extent of gene exchange among different pheromone races where they occur together and between geographically isolated populations of single pheromone races.
Project Methods
Objective 1. Vane traps will be deployed at ca 20 sites in cranberry growing areas of Wisconsin and southeastern Massachusetts in 2006 and 2007. Three traps will be deployed at each site, containing lures that have 4 mg blends of 100/0, 50/50, and 0/100, valine/isoleucine. Traps will be checked and re-randomized three times each week. This data will provide information to characterize the P. anxia male populations at each location as valine responding, blend responding, or isoleucine responding. More information about Wisconsin sites is important because so little is known about the pheromonal responses of different populations. More information about Massachusetts and Rhode Island sites is important because enough information is now available to predict that the blend responders will be found in sympatry or in close proximity with the valine and/or isoleucine responders at some locations in the region. All this information is important for growers because the pheromone blends employed for management purposes must be appropriate for the location. Objective 2. The goal is to document genetic relationships within and among the three races in cranberry and non-cranberry locations across the US. Both nuclear DNA and mtDNA sequences will be employed to generate gene genealogies for the P. anxia complex. These genealogies will allow me to determine (1) whether the genitalic forms are distinct lineages and (2) whether the three pheromone races are exclusive groups. Using sequences identified from GenBank, degenerate PCR primers will be designed and used to amplify fragments from P. anxia genomic DNA. Because of the labor involved in cloning, the nuclear gene genealogies will involve a smaller sample of individuals than the mtDNA genealogy, but our choice of individual beetles will be informed by the mtDNA tree. For genealogical analysis, trees will be constructed by employing neighbor-joining and maximum parsimony methods using PAUP* and Bayesian approaches using MrBayes. Objective 3. To use highly variable microsatellite (simple sequence repeat) markers to estimate the extent of gene exchange among different pheromone races where they occur together and between geographically isolated populations of single pheromone races. If the pheromone races are not genetically exclusive groups as determined by gene trees, then to what degree are the various genitalic, geographic, and pheromone race populations differentiated? We will address this question through the use of microsatellite markers. Microsatellites are used in studies of this kind because they are highly polymorphic and a comparison of the allele frequencies from a sufficient number of individuals in candidate populations will provide estimates of population differentiation and gene flow. We propose to examine 10 polymorphic loci in 30-50 individuals from selected populations. Analysis of the multi-locus data will be done using a variety of approaches including pairwise Fst values, AMOVA, and STRUCTURE.

Progress 09/01/07 to 02/29/08

Outputs
OUTPUTS: Two microsatellite loci have been identified that will aid in determining the degree of gene exchange and relatedness of the three pheromone morphs of Phyllophaga anxia (LeConte). We continue our research to identify additional loci. The results will contribute to our understanding of speciation and hybrid zones. The second year of sex pheromone trapping has been completed at ten cranberry growing sites in Wisconsin. PARTICIPANTS: Tim Dittl, Ocean Spray Cranberries, Babcock, Wisconsin, 54413 Jayne Soyka, Lady Bug IPM, 10107 Hwy 54, Pittsville, WI 54466 Tim and Jayne managed the pheromone trapping program in Wisconsin. They identified ten cranberry growers distributed among the four cranberry growing areas of Wisconsin who were willing to make a two-year commitment to the 6-8 week study period each year. Growers checked and randomized traps 2-3 times each week and put the collected beetles in their freezers in bags marked by date and the blend the beetles were caught by. Tim and Jayne later collected the frozen beetles from each grower and shipped them to Geneva, NY, for species identification. TARGET AUDIENCES: Target audiences include cranberry growers and those academic, governmental, and industry professionals who assist and advise them on best practices regarding pest control. It is hoped that information resulting from this research will yield tactics that can be used to manage white grub populations in an environmentally sound and practical manner.

Impacts
Root-feeding P. anxia white grubs damage cranberry plantings by both directly reducing yield as well as reducing vine density, thus pre-disposing the plantings to subsequent weed invasion. Perennial weeds are of particular concern since the cranberry plants themselves are perennials. Robbins et al. (2006) identified three pheromone morphs of the cranberry pest, P. anxia. The trapping project in Wisconsin in the 2006 and 2007 field seasons has revealed that at least two of the morphs are found there. This has highlighted the necessity of identifying which pheromone morphs of P. anxia occur at a particular cranberry site. Both the L -valine methyl ester producing and responding populations and the L -isoleucine methyl ester producing and responding populations have been found at locations in both sympatry and allopatry. Monitoring or management options using sex pheromones will prove fruitless if traps using the wrong blend are deployed. The remaining options for cranberry growers to manage damaging grub populations are last-ditch, desperate measures. There are no registered chemical pesticides registered or biological materials available that provide any level of control. The two options that can be used are summer flooding and bog renovation. The summer flood involves re-flooding the cranberry bog from mid-May until mid-July. This may kill a large number of grubs, but results in the loss of the current year's crop. Bog renovation involves scraping off the top 12 inches of soil, plants, and grubs, and hauling it away for disposal. The bog must then be re-planted and will not be harvested again for 3-5 years. Mass trapping of males or mating disruption may provide the most efficient method of managing a pest population whose economic threshold is not zero.

Publications

  • No publications reported this period


Progress 09/01/05 to 02/29/08

Outputs
OUTPUTS: Seven microsatellite loci have been identified that will aid in determining the degree of gene exchange and relatedness of the three pheromone morphs of Phyllophaga anxia (LeConte). We continue our research to identify additional loci. The results will contribute to our understanding of speciation and hybrid zones. The second year of sex pheromone trapping has been completed at ten cranberry growing sites in Wisconsin and a manuscript describing and discussing the work is in preparation. PARTICIPANTS: Tim Dittl, Ocean Spray Cranberries, Babcock, Wisconsin, 54413 Jayne Soyka, Lady Bug IPM, 10107 Hwy 54, Pittsville, WI 54466 Tim and Jayne managed the pheromone trapping program in Wisconsin. They identified ten cranberry growers distributed among the four cranberry growing areas of Wisconsin who were willing to make a two-year commitment to the 6-8 week study period each year. Growers checked and randomized traps 2-3 times each week and put the collected beetles in their freezers in bags marked by date and the blend the beetles were caught by. Tim and Jayne later collected the frozen beetles from each grower and shipped them to Geneva, NY, for species identification. TARGET AUDIENCES: Target audiences include cranberry growers and those academic, governmental, and industry professionals who assist and advise them on best practices regarding pest control. It is hoped that information resulting from this research will yield tactics that can be used to manage white grub populations in an environmentally sound and practical manner.

Impacts
Root-feeding P. anxia white grubs damage cranberry plantings by both directly reducing yield as well as reducing vine density, thus pre-disposing the plantings to subsequent weed invasion. Perennial weeds are of particular concern since the cranberry plants themselves are perennials. Robbins et al. (2006) identified three pheromone morphs of the cranberry pest, P. anxia. The trapping project in Wisconsin in the 2006 and 2007 field seasons has revealed that at least two of the morphs are found there. This has highlighted the necessity of identifying which pheromone morphs of P. anxia occur at a particular cranberry site. Both the L -valine methyl ester producing and responding populations and the L -isoleucine methyl ester producing and responding populations have been found at locations in both sympatry and allopatry. Monitoring or management options using sex pheromones will prove fruitless if traps using the wrong blend are deployed. The remaining options for cranberry growers to manage damaging grub populations are last-ditch, desperate measures. There are no registered chemical pesticides registered or biological materials available that provide any level of control. The two options that can be used are summer flooding and bog renovation. The summer flood involves re-flooding the cranberry bog from mid-May until mid-July. This may kill a large number of grubs, but results in the loss of the current year's crop. Bog renovation involves scraping off the top 12 inches of soil, plants, and grubs, and hauling it away for disposal. The bog must then be re-planted and will not be harvested again for 3-5 years. Mass trapping of males or mating disruption may provide the most efficient method of managing a pest population whose economic threshold is not zero.

Publications

  • No publications reported this period


Progress 09/01/06 to 08/31/07

Outputs
We have sequenced a portion of COI from mtDNA from greater than 20 individuals from each of five populations from four geographical regions responding to different pheromone blends. Gene trees constructed from these sequences provide incomplete resolution within and between populations. Six polymorphic microsatellite loci have been isolated. Work continues to use these loci to assess population differentiation and gene flow within and between the various groups. A large pheromone trapping study was conducted in Wisconsin in 2006 that included three trapping sites in each of the four cranberry growing regions in Wisconsin. These results will provide a very accurate assessment of the pheromone signatures of the P. anxia populations occurring in Wisconsin.

Impacts
We hope that this study will lead to management tactics tailored for local populations of this pest occurring in the two major cranberry growing areas of the United States, Massachusetts and Wisconsin. At present, there are no viable control strategies. Using sex pheromones for disruption may be a workable option since the economic threshold for grub populations is not zero.

Publications

  • No publications reported this period


Progress 09/01/05 to 08/31/06

Outputs
We are currently extracting genomic DNA from large numbers of individual beetles representing the various sex pheromone morphs and geographical locations. We are sequencing a portion of COI from mtDNA from these individuals for haplotyping and are identifying microsatellite sequences of interest that can be used to assess relatedness and degree of genetic exchange within and among populations. Preliminary analysis of these results will allow us to determine key locations where additional sex pheromone trapping can add to the resolution of our understanding of the interactions, distribution, and evolutionary history of this species.

Impacts
We hope that this study will lead to management tactics tailored for local populations of this pest occurring in the two major cranberry growing areas of the United States, Massachusetts and Wisconsin. At present, there are no viable control strategies. Using sex pheromones for disruption may be a workable option since the economic threshold for grub populations is not zero.

Publications

  • No publications reported this period