I. David Andow, 219 Hodson Hall, 1980 Folwell Ave., University of Minnesota, St. Paul, MN 55108, Phone: (612) 624-5323, FAX: (612) 625-5299, E-mail: dandow@tc.umn.edu

1) Project title: Parasitoid foraging for intermittently concealed hosts.

Investigators: Jennifer White and David Andow, Dept. Entomology, University of Minnesota

Contact: Jennifer White (whit0079@umn.edu)

Project description: Many insect herbivores feed in concealed locations and thus limit their susceptibility to foraging natural enemies. However, some herbivores move into and out of concealment many times over the course of their development, creating windows of greater vulnerability to attack. Parasitoids that specialize on such hosts face an interesting foraging decision: having located an inaccessible host, how long should the parasitoid wait for the host to become accessible? We previously developed a simple foraging model that predicted that the optimal strategy for M. grandii should vary with host density. At high host densities parasitoids should leave immediately upon discovering a host is inaccessible, whereas at low host densities parasitoids should persist for longer periods of time. To test this prediction, we compared the patch-leaving behavior of M. grandii that had been exposed previously either to conditions of high or low host density in field cages. Neither group left their patches immediately, but consistent with model predictions, we found that M. grandii that had experienced high host density persisted at their patches for half as long as M. grandii that had not experienced high host density. It is likely that the longer-than-predicted tenure of M. grandii from the high host density treatment resulted from the time it takes a wasp to assess the quality of a patch. Our model assumed instantaneous recognition of host accessibility upon arrival at a patch, whereas our empirical data suggests that M. grandii can take a substantial amount of time to find and parasitize a host, even when the host is accessible.

Investigators: Claudia Zwahlen and David A. Andow, Dept. of Entomology, University of Minnesota

Contact: Claudia Zwahlen (claudia.zwahlen@gmx.net)

Project description: Genetically modified (GM) crops that express toxins against various pests have the potential to alter the community structure of natural enemies. This may have a top-down effect on food-webs including pest populations. One group of natural enemies that acts as a biological control agent of pests in agricultural habitats is ground-beetles. Ground-beetles build an important link between the above- and below-ground ecosystem since they are predators of above- as well as below-ground organisms. Therefore, ground-beetles may act as indicator species that integrate direct and indirect effects of GM crops as a whole on the agricultural ecosystem. In our study we tested the hypotheses that 1) there are prey-mediated effects of Bt corn on the ground-beetle Pterostichus lucublandus; and 2) ground-beetles will be less abundant in Bacillus thuringiensis (Bt) corn than in non-Bt corn because they rapidly leave the areas with less food and accumulate in the areas with more food. To test our first hypothesis we carried out a tri-trophic laboratory experiment in which we fed the predator P. lucublandus with Bt corn-(expressing a toxin against the chrysomelid beetle Diabrotica virgifera) fed European Corn Borer (Ostrinia nubilalis) larvae. Our results indicate that there are no prey-mediated effect on survival, consumption, and weight of adult P. lucublandus. We tested our second hypothesis in a two-year study in 2003/2004 in a corn field planted with several Bt and non-Bt corn varieties in a randomized complete block design. So far only data from 2003 were assessed. Preliminary results indicate that there are substantial differences in the abundance of ground beetles in different corn varieties and it now needs to be established whether those are due to a Bt effect or not.

3) Project title: Does Bt corn expressing a coleopteran-specific toxin have a negative impact on non-target beneficial ladybird beetles?

Investigators: Claudia Zwahlen and David A. Andow, Dept. of Entomology, University of Minnesota

Contact: Claudia Zwahlen (claudia.zwahlen@gmx.net)

Project description: When assessing the risk of genetically modified (GM) crops on natural enemies, and hence the natural enemies’ ability to act as biological control agents, it is essential to investigate their exposure to GM crops and the toxicity of the crops. In spring 2003, a new generation of genetically modified Bacillus thuringiensis (Bt) corn plants was commercially released in the US. The coleopteran-specific Cry3Bb1 toxin expressed in those plants targets the corn rootworm larvae (Diabrotica virgifera). Does this toxin also have the potential to affect non-target beneficial ladybird beetles? To answer this question we first investigated which ladybird beetle species are exposed to the Bt toxin in corn fields. One of the species that showed to be exposed to the Cry3Bb1 toxin was the polyphagous coccinellid Coleomegilla maculata, an ubiquitous species in many agricultural habitats in the Midwest of the US. C. maculata is one of the most influential predators of the European corn borer. Additionally, C. maculata eat considerable amounts of pollen, which contains a high concentration of Cry3Bb1 toxin. In a laboratory study we currently investigate whether the exposure to Bt corn pollen has direct lethal or sublethal effects on C. maculata.

Biological Control Publications – Andow lab

Andow, D. A. and A. Hilbeck. 2004. Science-based risk assessment for non-target effects of transgenic crops. BioScience 54: 637-649.
Faria, M., J. G. Lundgren, E. Fontes, D. A. Andow, O. A. Fernandes, F. Schmidt and Nguyen V. T. 2005. Assessing the effects of Bt cotton on generalist arthropod predators. In Hilbeck, A., D.A. Andow and E.M.G. Fontes (eds.), Environmental Risk Assessment of Genetically Modified Organisms: A Case Study of Bt Cotton in Brazil. CAB International, Wallinford, UK. In press.
Harmon, J. and D.A. Andow. 2003. Alternative foods as a mechanism to enhance a generalist ladybird's predation of target prey, pp. 244-249. In R. van Dreissche (ed.), Proceedings of the International Symposium on Biological Control of Arthropods. Honolulu, Hawaii, 14-18 January 2002, United States Department of Agriculture, Forest Service, Morgantown, WV, FHTET-2003-05, 573p.
Harmon. J.P. and D.A. Andow. 2004. Indirect effects between shared prey: Predictions for biological control. BioControl, accepted.
Harmon. J.P. and D.A. Andow. 2004. Conditionally disrupted predator foraging for ant-tended aphids. Oecologia, submitted.
Olson, D.M. and D.A. Andow. 2004. Patch edges and insect populations in landscapes. Landscape Ecology, submitted.
Schellhorn, N.A. and D.A. Andow. 2005. Response of Coccinellids to their aphid prey at different spatial scales. Population Ecology 47: 71-76.
White, J. A. and D. A. Andow. 2005. Host-parasitoid interactions in a transgenic landscape: Spatial proximity effects of host density. Environmental Entomology, in press.
Zwahlen, C. and D. A. Andow. 2005. Field evidence for the exposure of ground beetles to Cry1Ab from transgenic corn. Environmental Biosafety Research, in press.

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II. George Heimpel, Dept. of Entomology, Univ. of Minnesota, St. Paul, MN 55108, tel. (612) 624-3480,FAX:(612) 625-5299, email: heimp001@tc.umn.edu

4) Project title: Impact of Flowering Buckwheat on Lepidopteran Cabbage Pests and their Parasitoids at Two Spatial Scales.

Investigators: Jana Lee, George Heimpel

Contact: Jana Lee (jctlee@ucdavis.edu)

Project description:We assessed the potential of buckwheat, Fagopyrum esculentum Moench, to lead to improved parasitism of lepidopteran cabbage pests over four years. Pest, parasitism and hyperparasitism rates were monitored in replicated cabbage plots (12 x 20 m) with or without 3 m wide buckwheat borders from 2000 to 2003. Floral borders did not increase egg, larval or pupal densities of cabbage looper, Trichoplusia ni (Hübner), imported cabbageworm, Pieris rapae (L.) or diamondback moth, Plutella xylostella (L.). Buckwheat increased parasitism rates by Voria ruralis (Fallen) on T. ni larvae and Cotesia rubecula (Marshall) on P. rapae larvae over four years. Parasitism by Diadegma insulare (Cresson) on P. xylostella larvae was higher in buckwheat than control plots in the first year, and parasitism by Euplectrus plathypenae (Howard) on T. ni larvae was lower in buckwheat than control plots in the second year. The hyperparasitoid Conura side (Walker) attacked D. insulare all four years, but buckwheat did not enhance hyperparasitism rates. The effect of spatial scale on pest densities and parasitism in 2001 was evaluated by comparing plots separated at least 67 m (nearby) versus 800 m apart (isolated). T. ni pupae and P. rapae eggs and pupae were more abundant in plots nearby each other, whereas, P. xylostella larvae were more abundant in isolated plots. Tachinids and Pteromalus puparum (L.) attacked more P. rapae in nearby plots. E. plathypenae responded to treatmentXscale interactions, parasitizing more in control than buckwheat when plots were isolated but not when plots were nearby. Reasons for differential responses to spatial scale are discussed.

5) Project title: Influence of floral resources on sugar feeding and nutrient dynamics of a parasitoid in the field

Investigators: Jana Lee, George Heimpel

Contact: Jana Lee (jctlee@ucdavis.edu)

Project description: To investigate how floral resources impact feeding and nutrient dynamics of parasitoids, the ichneumonid Diadegma insulare (Cresson) was monitored in cabbage fields with and without buckwheat Fagopyrum esculentum Moench borders. Biochemical analyses of field-collected wasps determined whether sugar feeding occurred, enhanced nutrient levels, and increased parasitism of diamondback larvae Plutella xylostella (L.) from 2000 to 2003. The effects of experimental spatial scale on sugar feeding dynamics were also evaluated in 2001.
A majority of D. insulare foraging in cabbage had fed upon sugar, but floral borders did not consistently increase the proportion of sugar-fed wasps or their levels of glycogen and lipid over all four years of the study. Floral borders increased sugar storage levels in females during one year. More females fed on sugar when experimental plots were separated at least 800 m apart rather than 67 m apart. Feeding on buckwheat nectar versus honeydew produced by the soybean aphid Aphis glycines Matsumura in surrounding fields was distinguished using the ratio of fructose to total sugars, which was higher in nectar- than honeydew-fed parasitoids. In some years, floral borders increased the probability that wasps collected from adjacent crops were nectar-fed, demonstrating that floral resources are utilized by foraging parasitoids. D. insulare that fed upon any sugar source had higher levels of sugar and glycogen stored than unfed wasps, and feeding on honeydew appeared to enhance nutrient storage. Over four years, the prevalence of sugar- or nectar-feeding by female D. insulare was not correlated with parasitism rates in the field.

6) Project title: Potential of a natural enemy to influence the evolution of resistance in European corn borer to Bt corn. and Effects of a natural enemy on the evolution of resistance of European corn borers to Bt corn.

Investigators: Cynthia (Simon) Hsu, George Heimpel

Contact: Cynthia Hsu (hsux0049@umn.edu)

Project description:Simon Hsu’s work is focused on understanding the dispersal behavior of a parasitoid, Macrocentus grandii, in relation to the spatial patterns of its host, the European corn borer, Ostrinia nubilalis. Current work includes a spatial pattern analysis of the distribution of corn borers and occurrence of parasitism by M. grandii. Results from these experiments will be used to determine whether identifying density dependent parasitism for this parasitoid depends on the spatial scale of analysis, and whether the ability to identify density dependent parasitism improves using a spatially explicit analysis compared with a spatially implicit analysis. The second project focuses on measuring the short-range dispersal of M. grandii within a corn field that has two host densities. In this experiment, 40-acre fields are split in half with one half of the field containing a low density of hosts while the other half has a high density of hosts. A strip of corn between the two halves is labeled using rubidium chloride (RbCl). Parasitoids emerging from this strip are labeled with RbCl and adult parasitoids are recaptured at different distances into the two halves. Results from this experiment will be used to determine whether the dispersal behavior of the parasitoid depends on host density, and to estimate the dispersal-distance relationship for M. grandii over short distances (i.e. within 50 meters) for each of the two halves. My final project makes use of the empirical data on parasitism and parasitoid dispersal to estimate the potential impact of M. grandii on the evolution of resistance in European corn borers to Bt corn.

7) Project title: Biological control of soybean aphid, Aphis glycines: host specificity testing of Binodoxys communis.

Current Investigators: George Heimpel, Zhishan Wu, Ruth Barta, Chris Kulhanek.

Contact: George Heimpel (heimp001@umn.edu)

Project description: Host specificity testing of Binodoxys communis strains from both China and Japan indicate an intermediate level of host specificity. Soybean aphid is the most suitable host, with Aphis monardae showing slightly lower suitability on vegetative growth of the native prairie plant Monarda fistulosa. Seven other species of aphids showed low suitability and a further 6 species were not used by B. communis at all.

8) Project title: Biological control of soybean aphid: Evaluating non-target risks of Binodoxys communis to Aphis monardae.

Investigators: Kris Wyckhuys, Bob Koch, George Heimpel

Contact: Kris Wyckhuys (wyckh001@umn.edu)

Project description: Aphis monardae is a native non-pest aphid that inhabits the native prairie flower Monarda fistulosa and therefore represents non-target species that may be at risk if B. communis is released. To evaluate this risk further, we have made observations of A. monardae in native prairie settings throughout Southern Minnesota. We found it relatively abundant in both undisturbed prairie remnants and parkland meadows. During these observations, we also noticed that (i) this aphid tends to cluster in flower heads of its host plant, and that (ii) many of these aphid colonies are tended by ants (Lasius sp.). Both of these factors may decrease the risk of introduced B. communis to the native A. monardae. Laboratory studies have shown that A. monardae gains significant and substantial protection from B. communis parasitism both by feeding within flowerheads of its host plants, and by being tended by ants.

9)Project title: Biological control of soybean aphid: Foreign exploration I

Investigators: George Heimpel, Keith Hopper

Contact: George Heimpel (heimp001@umn.edu)

Project description: We visited the Lang Fang Agricultural Experiment station near Beijing, China in August of 2005. The trip was very instructive in demonstrating (i) low aphid densities along with (ii) high parasitoid densities. Predators were also seen, but at relatively low densities. This pattern is consistent with suppression of aphids by parasitoids. In contrast, soybean aphids in North America are virtually entirely free from parasitoid attack and are present in high densities (in some cases despite high densities of predators). We also assessed the extent to which Binodoxys vs. Aphelinus mummies were preyed upon in the field. The reason for this is that predators are often abundant in soybean fields in North America, and any parasitoids that we release may be fed upon in mummy or larval stages post-release. We therefore are interested in determining which parasitoids are most compatible with predatory insects. As the predator complex in China and North America is similar, these observations can be readily made in China, where both parasitoid species, and a diverse predator complex are present. We assessed predation by collecting mummies and assessing whether or not they had been consumed by predators (predated mummies have characteristic signs that indicate extensive chewing). Predation on B. communis was approximately half that on Aphelinus sp. Since the mummy state of Aphelinus is approximately twice as long of that of B. communis, this is consistent with a similar rate of predation on both species. From the standpoint of compatibility with predators though, these data suggest that B. communis escapes predation better by virtue of its shorter development time.

10) Project title: Biological control of soybean aphid: Foreign exploration II

Investigators: Keith Hopper, George Heimpel

Contact: Keith Hopper (khopper@udel.edu)

Project description: To begin evaluating field host range, we collected parasitoids from three aphid species on three host plant species: cotton aphid (Aphis gossypii) on cotton, corn leaf aphid (Rhopalosiphum maidis) on corn, and soybean aphid (A. glycines) on soybean. We are rearing out the braconids and aphelinids from these collections. If they appear to be the same species, we will compare their host use, molecular markers, and reproductive compatibility to confirm this. From the material collected in China, we established cultures of Binodoxys sp. from soybean aphid, an Aphidius sp. from corn leaf aphid, and Aphelinus sp. from both species of aphids.

11) Project title: Biological control of soybean aphid: Intra-guild predation among coccinellid species

Investigators: Annie-Eve Gagnon, Jacques Brodeur, George Heimpel

Contact: Annie-Eve Gagnon (annie-eve.gagnon.1@ulaval.ca)

Project description: Understanding guild interactions between natural enemies of herbivorous pests is of great interest for ecologists and biological control practitioners. The presence of intraguild predators may either enhance or impede biological control. This type of interaction can be difficult to assess under field conditions by focal observations, however, because insects are small and cryptic. In addition, the interactions can be relatively rare. Here we describe a method for the development of DNA markers for the detection of intraguild prey in predator gut-contents. Specific primers for regions of the internal transcribed spacer of the ribosomial gene complex (ITS-1) and the mitochondrial cytochrome oxidase I gene (COI) were designed for four coccinellid species: Coccinella septempunctata (105-bp), Propylea quatuordecimpuntata (115-bp), Harmonia axyridis (120-bp) and Coleomegilla maculata (137-bp). Primer specificity and the duration of the detection period following a meal were determined for all coccinellid species. We used these primers to evaluate the incidence of intraguild predation between coccinellids collected in soybean fields in Quebec during the 2004 growing season. Each interspecific combination of coccinellid species was tested. PCR analyses of whole coccinellid larvae revealed the presence of intraguild prey remains (irrespective of species) in 38.4% of all samples (N=365). The interactions were symmetric (mutual intraguild predation) as each species may become prey or feed on each other. Also, in a few instances, two (4.7%) and three (0.6%) intraguild prey species were detected in a single predator. This technique is a powerful tool to disentangle and quantify poorly understood interactions among natural enemies.

12) Project title: Biological control of soybean aphid: Effects of a winter cover crop on soybean aphid suppression.

Investigators: Bob Koch, George Heimpel, Paul Porter, David Ragsdale, Bruce Potter, Karrie Koch, Matt Harbor

Contact: Bob Koch (koch0125@tc.umn.edu)

Project description: This research evaluates the use of a fall-seeded rye cover crop for suppression of an economically significant pest of soybeans, the soybean aphid (Aphis glycines ). Results from the first year’s field trials suggest that winter rye does lead to lower soybean aphid densities, particularly early in the season.

13) Project title: Biological control of soybean aphid: Intra-guild predation between coccinellids and parasitoids

Investigators: Jeremy Chacon, George Heimpel, Doug Landis

Contact: Jeremy Chacon (annie_chaco001@UMN.EDU)

Project description: This research is based upon the effects of Asymmetrical Intraguild Predation on soybean aphid populations. Intraguild Predation (IGP) is when two or more species share a host/prey species, and also engage in a trophic interaction with each other. Asymmetrical Intraguild Predation is a type of IGP in which only one of the species (the IG-Predator) feeds or parasitizes the other species (the IG-Prey), while both species share a single host/prey. In this study, I am trying to determine if either (i) the natural enemies present in the field (the IG-Predators, such as Coccinellids), (ii) a released parasitoid wasp, Aphidius colemani (the IG-Prey), or (iii) both together are the most effective controllers of the soybean aphid. Results from a field study in summer 2005 indicate that (i) A. colemani is able to suppress SBA within field cages, and (ii) predators disrupt this control. In the lab, I am working on sequencing the Internal Transcribed Spacer 1 (ITS-1) region of the 16S gene of multiple parasitoid wasps. After finishing this, I will develop species-specific primers within that region for subsequent use in molecular gut-content analysis of predators collected from my field study. My hope is that I will be able to determine the frequency with which certain predators will eat parasitized aphids, thus engaging in IGP. The combination of this knowledge plus the knowledge gained from the field study will help give a better understanding of Asymmetrical IGP of soybean aphid biocontrol agents, and thus a better understanding of the most efficient way to control the soybean aphid.

14) Project title: Sex determination in parasitoid wasps

Investigators: George Heimpel, Jetske De Boer

Contact: Jetske De Boer (deboe039@umn.edu)

Project description: Parasitoid wasps are haplodiploid, males normally being haploid and females diploid. This means that they cannot have true sex chromosomes. In the 1940’s, Whiting showed that in the parasitoid Bracon hebetor sex is determined at a single highly polymorphic sex locus and not just by fertilization of the egg. Individuals that are heterozygous at this locus develop into diploid females, whereas homozygotes develop into diploid males. Unfertilized eggs are always hemizygous and develop into haploid males. This complementary sex determination (CSD) has since been found in more than 40 hymenopteran species, including honeybees, wasps, and ants. CSD is now thought to be the ancestral mode of sex determination in the Hymenoptera. Diploid males that are produced under CSD usually have low viability, are sterile or they may produce triploid daughters. They are produced instead of fertile diploid females so they represent a strong cost to a population, and potentially reduce the efficiency of biological control. The cost of CSD is especially high under inbreeding conditions because the frequency of diploid males is much higher under inbreeding than under random mating. My project aims to determine whether in a range of Cotesia species sex is determined by CSD or not. I will study both solitary and gregarious Cotesia species. We expect to find CSD in solitary but not in gregarious species because under natural conditions, the level of inbreeding is thought to be much higher in gregarious species. We therefore expect these species to have evolved away from CSD to another mechanism of sex determination in which diploid males are not formed. Current results suggest that the solitary parasitoid C. pluttellae, does exhibit CSD, but a variant where 2 or more sex loci need to be homozygous to produce diploid males (multiple-locus CSD). Besides studying sex determination at the population level, we are currently starting to investigate the molecular basis of CSD in parasitoid wasps. A single gene for CSD has been cloned in honeybees and we are using this recent development to search for homologous genes in parasitoid wasps.

Biological Control Publications since 2004– Heimpel lab

Carrillo, M. A., G. E. Heimpel, R. D. Moon, C. A. Cannon, and W. D. Hutchinson. 2005. Cold hardiness of Habrobracon hebetor (Say) (Hymenoptera: Braconidae), a parasitoid of pyralid moths. Journal of Insect Physiology 51:759-768.
Heimpel, G. E., and M. A. Jervis. 2005. Does floral nectar improve biological control by parasitoids?, Pages 267-304 in F. Waeckers, P. van Rijn, and J. Bruin, eds. Plant-provided food and plant-carnivore mutualism. Cambridge, UK, Cambridge University Press.
Heimpel, G. E., and T. E. Shelly. 2004. The soybean aphid: a review of its biology and management. Annals of the Entomological Society of America 97:203.
Heimpel, G. E., J. C. Lee, Z. Wu, L. Weiser, F. Wackers, and M. A. Jervis. 2004. Gut sugar analysis in field-caught parasitoids: adapting methods originally developed for biting flies. International Journal of Pest Management 50:193-198.
Heimpel, G.E., D.W. Ragsdale, R. Venette, K.R. Hopper, R.J. O’Neil, C. Rutledge & Z. Wu. 2004. Prospects for importation biological control of the soybean aphid: anticipating potential costs and benefits. Annals of the American Entomological Society 97: 249-258.
Heimpel, G. E., C. Neuhauser, and D. A. Andow. 2005. Natural enemies and the evolution of resistance to transgenic insecticidal crops by pest insects: the role of egg mortality. Environmental Entomology 34:512-526.
Heimpel, G. E., P. M. Porter, D. W. Ragsdale, R. L. Koch, and B. Potter. 2005, The potential role of insect suppression in increasing the adoption of cover crops. M. S. Hoddle, ed. Second International Symposium on Biological Control of Arthropods:185-191.
Hoogendoorn, M. & G.E. Heimpel. 2004. Competitive interactions between an exotic and a native ladybeetle: a field cage study. Entomologia Experimentalis et Applicata 111: 19-28.
Jervis, M.A. & G.E. Heimpel. 2005. Phytophagy. In Jervis, M.A. & N.A.C. Kidd (eds.): Insect Natural Enemies: Practical Approaches to their study and evaluation, 2nd ed. Kluwer Press.
Jervis, M. A., J. C. Lee, and G. E. Heimpel. 2004. Use of behavioural and life-history studies to understand the effects of habitat manipulation, Pages 65-100 in G. M. Gurr, and S. D. Wratten, eds. Ecological Engineering for Pest Management. Collingwood, Victoria, Australia, CSIRO.
Lee, J. C., and G. E. Heimpel. 2004. Dynamics of parasitoids and nectar sources. M. S. Hoddle, ed. California Conference on Biological Control 4:40-44.
Lee, J. C., and G. E. Heimpel. 2005. Impact of flowering buckwheat on lepidopteran cabbage pests and their parasitoids at two spatial scales. Biological Control 34:290-301.
Lee, J. C., and G. E. Heimpel. 2005, Impact of sugar feeding on parasitoid behavior in the field. M. S. Hoddle, ed. Second International Symposium on Biological Control of Arthropods:398-408.
Lee, J.C., G.E. Heimpel & G. Leibee. 2004. Comparing floral nectar and aphid honeydew diets on the longevity and nutrient levels of a parasitoid wasp. Entomologia Experimentalis et Applicata 111: 189-199.
Weiser, L., M. F. Antolin, Z. Wu, and G. E. Heimpel. 2004. Does temperature affect diploid male production in Habrobracon hebetor (Say)(Hymenoptera: Braconidae)? Journal of Hymenoptera Research 13:103-109.
Wold-Burkness, S. J., W. D. Hutchison, J. C. Lee, R. L. Hines, P. C. Bolin, and G. E. Heimpel. 2005. A long-term survey of parasitoid species composition and parasitism of Trichoplusia ni (Lepidoptera : Noctuidae), Plutella xylostella (Lepidoptera : Plutellidae), and Pieris rapae (Lepidoptera : Pieridae) in Minnesota cabbage. Journal of Entomological Science 40:211-221.
Wu, Z., K. R. Hopper, R. J. O'Neil, D. J. Voegtlin, D. R. Prokrym, and G. E. Heimpel. 2004. Reproductive compatibility and genetic variation between two strains of Aphelinus albipodus (Hymenoptera: Aphelinidae), a parasitoid of the soybean aphid, Aphis glycines (Homoptera: Aphididae). Biological Control 31:311-319.
Wu, Z., Schenk-Hamlin, D., Zhan, W., Ragsdale, D.W. & G.E. Heimpel. 2004. The soybean aphid in China – a historical review. Annals of the American Entomological Society 97: 209-218.
Wu, Z., K. R. Hopper, P. J. Ode, R. Fuester, M. Tuda, and G. E. Heimpel. 2005. Single-locus complementary sex determination absent in Heterospilus prosopidis (Hymenoptera: Braconidae). Heredity 95:228-234.

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III. William Hutchison, 219 Hodson Hall, 1980 Folwell Ave, University of Minnesota, St. Paul, MN 55108, phone: (612) 624-9272, fax: (612) 625-5299, E-mail: hutch002@tc.umn.edu

15) Project title: Cold hardiness of the multicolored Asian lady beetle (Coleoptera: Coccinellidae)

Investigators: R.L. Koch, M.A. Carrillo, R.C. Venette, C.A. Cannon and W.D. Hutchison

Contact: Robert Koch (koch0125@tc.umn.edu)

Project description: A classical biological control agent, Harmonia axyridis (Pallas), is having both beneficial and detrimental impacts in North America. The objective of this study was to evaluate the cold hardiness of H. axyridis in North America. Supercooling points and survival at subzero temperatures of field-collected and insectary-reared H. axyridis were examined. The mean (±SE) supercooling points for eggs and pupae (i.e., non-feeding stages) were -27.0±0.18°C and -21.3±0.52°C, respectively. The mean supercooling points for larvae and adults (i.e., feeding stages) were -14.17±0.33 and -11.9±0.53°C, respectively. Sex and color morph (i.e., red: f. succinea versus black: f. spectabilis) had no effect on the supercooling point of H. axyridis adults. Mean supercooling points of H. axyridis adults from Minnesota and Georgia were significantly lower during winter months than summer months. The mortality of H. axyridis increased significantly after individuals were exposed to temperatures below the mean supercooling point of the population. Supercooling point was a good predictor of cold hardiness. However, the cold hardiness of H. axyridis appears to be a poor predictor of its northern distribution.

16) Project title: Phytophagous preferences of the multicolored Asian lady beetle (Coleoptera: Coccinellidae) to autumn ripening fruit

Investigators: R.L. Koch, E.C. Burkness, S.J. Wold Burkness and W.D. Hutchison

Contact: Robert Koch (koch0125@tc.umn.edu)

Project description: The objective of these studies was to assess the potential pest status of Harmonia axyridis (Pallas) on autumn ripening fruit. In autumn, H. axyridis has been observed feeding on pumpkins, apples, grapes and raspberries in Minnesota. To determine if H. axyridis can inflict primary feeding damage to fruit (i.e., breaking the skin of the fruit), we conducted laboratory feeding studies with undamaged pumpkins, apples, grapes, and raspberries. The only fruit that H. axyridis was able to damage directly was raspberry. Laboratory choice test studies were conducted to determine if H. axyridis exhibits a preference between damaged and undamaged fruit, between varieties of fruit, and between sugar water and water alone. For all fruits tested, H. axyridis showed a preference for damaged fruits over undamaged fruits. Harmonia axyridis also exhibited a strong preference for sugar water over water alone. However, few differences were exhibited in preference between varieties of fruit. In autumn, it appears that H. axyridis is an opportunist, taking advantage of previously damaged fruit, caused by other agents.

17) Project title: Influence of alternate prey on predation of monarch butterflies (Lepidoptera: Nymphalidae) by the multicolored Asian lady beetle (Coleoptera: Coccinellidae)

Investigators: R.L. Koch, R.C. Venette and W.D. Hutchison

Contact: Robert Koch (koch0125@tc.umn.edu)

Project description: An invasive, exotic coccinellid, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), was recently identified as a potential hazard to immature monarch butterflies, Danaus plexippus (L.) (Lepidoptera: Nymphalidae). To further evaluate the risk of H. axyridis impacting D. plexippus, we evaluated the influence of an alternate prey, Aphis nerii Boyer de Fonscolombe (Homoptera: Aphididae), on the predation rate of D. plexippus by H. axyridis. When D. plexippus were placed in Petri dish arenas with H. axyridis and varying densities of A. nerii, D. plexippus survival after 24 h increased significantly from 0% with 0 A. nerii present to 73% with 30 A. nerii present. Least squares linear regression suggested that H. axyridis consumed fewer D. plexippus, in the presence of A. nerii, than would be expected if predation was at random. In predation studies conducted in field cages, survival of D. plexippus larvae decreased with increasing densities of H. axyridis larvae. In addition, a logistic regression analysis of the survival data from the cage studies showed a mitigating effect of A. nerii on the predation of D. plexippus by H. axyridis. For example, the model predicted that D. plexippus survival on plants with 4 H. axyridis would decrease from 86.2 to 25.5% if A. nerii densities were decreased from 1000 to 0 per plant. However, an effect of A. nerii on D. plexippus survival was not detected in open-field predation studies. Results of these studies suggest that the abundance of alternate prey should be considered when assessing the risk of an exotic predator affecting a non-target species.

18) Project title: Compatibility of commonly used insecticides in sweet corn and soybeans to the multicolored Asian lady beetle (Coleoptera: Coccinellidae)

Investigators: T.L. Galvan, R.L. Koch and W.D. Hutchison

Contact: Ted Galvan (tedersonlg@msn.com)

Project description: The success of conservation biological control, particularly in agricultural systems, may depend on the selectivity of insecticides to natural enemies. Insecticides with new modes of action and narrow spectrums of activity, such as spinosad and indoxacarb, may be valuable for use in conjunction with biological control. The Multicolored Asian Lady Beetle, Harmonia axyridis (Coleoptera: Coccinellidae), has recently become a dominant natural enemy in Minnesota corn and soybean. Toxicity of insecticides to H. axyridis was evaluated under field and laboratory conditions. In an in-field sweet corn trial, the abundance of H. axyridis was recorded following multiple applications of spinosad, indoxacarb, carbaryl, chlorpyrifos, bifenthrin, and lambda-cyhalothrin at labeled field rates. In general, larvae were more abundant than adults across all treatments. Adults and larvae were more abundant in plots treated with spinosad than in plots treated with other insecticides. In a laboratory topical assay, the acute toxicity of the same insecticides was evaluated for eggs, first and third instars, pupae, and adults. Spinosad and indoxacarb were less toxic than carbaryl, bifenthrin, lambda-cyhalothrin, and chlorpyrifos to eggs, third instars, and adults. All of the insecticides, except spinosad, were highly toxic to first instars. Spinosad, indoxacarb, and carbaryl were not toxic to pupae. Although spinosad and indoxacarb showed a reduction in the negative impacts on the beetle in field and topical assays, both insecticides conferred sublethal effects. The indoxacarb treatment resulted in fewer females ovipositing and fewer eggs laid per ovipositing female. In addition, percent egg hatch was significantly reduced in eggs laid by females treated with spinosad.

19) Project title: Management of the multicolored Asian lady beetle (Coleoptera: Coccinellidae) in Minnesota vineyards

Investigators: T.L. Galvan, R.L. Koch, E.C. Burkness and W.D. Hutchison

Contact: Ted Galvan (tedersonlg@msn.com)

Project description: The Multicolored Asian Lady beetle, Harmonia axyridis (Pallas), has become a contaminant pest in vineyards where grapes are grown for wine production, throughout the eastern and midwestern U.S. The beetle appears to have an ability to locate ripening fruit, with infestations in grapes increasing just before harvest. There are presently no published IPM strategies, effective biological control agents, or insecticides labeled for this new economic pest of grapes. In 2004, we initiated a multifaceted research effort to better understand the phenology and spatial spread of vineyard colonization by H. axyridis adults, and evaluated several insecticides for possible management of the beetle in vineyards. Using a field assay, we measured the direct impact on beetle kill, repellency effects, the degree to which the insecticides effect juice quality (i.e., soluble solids, acidity, pH), and effects on the sensory properties of the final wine product. Treatments included: bifentrhin, malathion, carbaryl, a pyrethrum containing, and floating row covers. Bifenthrin was the most effective insecticide overall, providing a high level of initial control, but also exhibiting an apparent, significant residual (repellency) effect for 7 days after treatment. Carbaryl was also effective, but showed less residual activity. Studies of effects of insecticides on juice quality and wine are in progress. In addition, we monitored beetle populations in two vineyards from veraison of the grapes to harvest. The phenology and spread data continue to be analyzed, but should prove useful for developing sampling methods and an early-warning system for growers. We also have two additional studies in progress, including experiments to better understand the relationship between wasps and H. axyridis damage to grapes. The second study included feeding choice tests to assess the preference of H. axyridis for damaged grapes of 4 grape varieties common to Minnesota (Frontenac, Saint Croix, LeCrescent, and Marechal Foch; data still being analyzed). A companion feeding study, indicated that for these same varieties, the adults were not able to break the fruit skin or cause direct feeding damage. The results of this work will be beneficial for developing an effective IPM program.

20) Project title: Cold hardiness of Habrobracon hebetor (Say) (Hymenoptera: Braconidae), a parasitoid of pyralid moths

Investigators: M.A. Carrillo, G.E. Heimpel, R.D. Moon, C.A. Cannon, and W.D. Hutchison

Contact: Mario Carrillo (macarrillo13@yahoo.com)

Project description: The parasitoid Habrobracon hebetor (Say) attacks stored-grain infesting pyralid moths that are able to overwinter under extremely cold conditions. Whether H. hebetor can withstand these conditions is not known, but has important implications for the ability of H. hebetor to provide continuous suppression of these pests in temperate climates. Basic aspects of the cold hardiness of H. hebetor from a mutant eye-color strain are being investigated. Preliminary data indicate that food in the alimentary canal significantly increases the supercooling point (SCP) (i.e., the temperature at which spontaneous freezing occurs) of H. hebetor. In addition, we have found that mortality for pupae and adults increases significantly whenever the temperature dropped below the mean SCP, indicating that H. hebetor does not tolerate freezing. Furthermore, we have observed a high percentage of pre-freeze mortality for pupae and adults at relatively high subzero temperatures (e.g., -12 and -5ºC). Although it appears that H. hebetor could not be able to withstand temperatures during the winter in northern states, data reported in the literature suggest that this parasitoid may be able to acclimate to low temperatures considerably increasing its chances for survival. A better understanding of how well this parasitoid tolerates low temperatures will be useful in evaluating its possible role as a biological control agent of stored-product moths in temperate regions.

Biological Control Publications since 2004– Hutchison lab

Koch, R.L., M.A. Carrillo, R.C. Venette, C.A. Cannon and W.D. Hutchison. 2004. Cold hardiness of the multicolored Asian lady beetle (Coleoptera: Coccinellidae). Environmental Entomology 33(4): 815-822.
Koch, R.L., E.C. Burkness, S.J. Wold Burkness and W.D. Hutchison. 2004. Phytophagous preferences of the multicolored Asian lady beetle (Coleoptera: Coccinellidae) to autumn ripening fruit. Journal of Economic Entomology 97(2): 539-544.
Koch, R.L., W.D. Hutchison and R.C. Venette. 2004. Non-target effects of the multicolored Asian lady beetle (Coleoptera: Coccinellidae): Case study with the monarch butterfly (Lepidoptera: Nymphalidae). American Entomologist 50(3): 163-164.
M.A. Carrillo, Koch, R.L., R.C. Venette, C.A. Cannon and W.D. Hutchison. 2004. Response of the multicolored Asian lady beetle (Coleoptera: Coccinellidae) to low temperatures: Implications for overwintering. American Entomologist 50(3): 165-166.
Koch, R.L., R.C. Venette and W.D. Hutchison. Influence of alternate prey on predation of monarch butterflies (Lepidoptera: Nymphalidae) by the multicolored Asian lady beetle (Coleoptera: Coccinellidae). Entomologia Experimentalis et Applicata (in review).

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IV. Timothy J. Kurtti, 219 Hodson (office), University of Minnesota, 1980 Folwell Avenue, St. Paul, MN, 55108, Phone: (612) 624-4740, Email: kurtt001@umn.edu

21) Project title: Interaction of Entomopathogenic Fungi and Black Legged Ticks, Ixodes Scapularis (Acari: Ixodidae)

Investigators: Lina B. Flor, Timothy J. Kurtti

Contact: Lina Flor (flor0119@umn.edu)

Project description: This project is focused on the mitosporic fungi that infect black legged ticks in Minnestoa. In nature, ticks are attacked by a number of fungi, most of them under Class Deuteronomycetes. We are currently working on the morphological and molecular characterization of the fungus we collected infecting black legged ticks. These experiments will ascertain us the identity of the fungus and how is it related to some other fungal strains of the same species infecting other organisms. The second study we are working is on the pathogenesis of the fungi on I. scapularis. This is to compare the pathogenic activity of the fungus on ticks to determine which is more susceptible to fungal infection, when they are fed or unfed? A part of the study will also look on the pathogenesis, focusing on the adherence, point of entry, penetration and proliferation of the fungus on ticks. The third study will be on the physiological test of the fungal isolate infecting I. scapularis. This is to determine the ability of the fungal isolate from ticks to grow at different temperature range and its tolerance to UV.

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V. David Ragsdale, 219 Hodson Hall, 1980 Folwell Ave.,University of Minnesota, St. Paul, MN 55108, phone: (612) 624-6771, FAX: (612) 625-5299, E-mail: ragsd001@maroon.tc.umn.edu

22) Project title: Development and application of phenological models for Aphthona lacertosa and A. nigriscutis, two leafy spurge, Euphorbia esula L., biological control agents in Minnesota.

Investigators: Luke C. Skinner¹, Monika Chandler^1,2, Dharma Sreenivasam², David Ragsdale^1,2
1Department of Entomology, University of Minnesota
²Minnesota Department of Agriculture

Contact: D. Ragsdale (ragsd001@umn.edu)

Project description: Two flea beetles, Aphthona lacertosa Foudras and A. nigriscutis Fourdas, are biological control agents introduced to control leafy spurge, Euphorbia esula L., in North America. Understanding the phenological patterns, in particular predicting peak abundance, provides researchers and land managers information on when to collect agents for redistribution. To develop this model three steps were required: 1) determine lower developmental threshold for each species, 2) estimate peak emergence for each species using accumulated degree-days (ADD), and 3) develop maps of the state that spatially represents predicted occurrence of peak abundance. Lower developmental thresholds (LDT) were determined through controlled growth chamber experiments where field collected soil cores containing diapausing beetle larvae were held at 15,18, 21, 24, and 27º C. Average days to adult emergence were determined for each temperature and applied to a linear regression model to predict the lower developmental threshold. The LDT for Aphthona lacertosa and A. nigriscutis is 7.5 and 9.3º C, respectively. Twenty-six field sites were sampled for flea beetle abundance weekly during June and July in 2000 and 2001. A third order polynomial was used to approximate seasonal abundance and predict peak abundance for each species as a function of ADD (based on previously determined LDT). Peak adult abundance for Aphthona lacertosa and A. nigriscutis occurred at 594 ADD and 670 ADD, respectively. Using 30 year adjusted normal temperature data from 172 weather stations in Minnesota, a contour map of estimated peak emergence dates was developed.

23) Project Title: Purple loosestrife and buckthorn biological control

Investigators: David Ragsdale, Michele Van Veldhuisen, Luke C. Skinner, and MIchele Yoder

Project Description: Buckthorn biological control (Rhamnus cathartica L.):

Continuing research from 2004, buckthorn stances were sampled for insect fauna as possible biological control agents or possible biotic resistance for a biological control program. Six sites located in southern Minnesota were divided into three landscape categories (Mississippi River basin, urban forest, and agriculture) were surveyed twice monthly. At each site, 50 buckthorn trees were selected for sampling; 25 consecutive trees along a roadside or path which received direct sunlight and 25 consecutive trees located in the shaded under-story which received shade or filtered sunlight. Records are maintained on each insect relating to the location and date collected. Over 450 insect specimens have been collected on buckthorn in 2005. We also conducted the first sampling of buckthorn site characteristics to better categorize and compare habitats. Data collected in each plot includes: percent shade coverage, diameter of surrounding trees within 1m radius of plot, diameter of buckthorn trees, percent buckthorn coverage, percent native vegetation coverage and native vegetation abundance/diversity. This information will help us understand the diversity and abundance of insects collected in the buckthorn survey.

Purple loosestrife biological control (Lythrum salicaria L.):

Two leaf-feeding beetles, Galerucella calmariensis L. and Galerucella pusilla Duft (Coleoptera: Chyrsomelidae), were released in 1992 as biological control agents for purple loosestrife in several states including Minnesota. Post-release monitoring in Minnesotan wetlands may provide insight into factors that effect the establishment of each Galerucella spp. In 2004 and 2005, approximately 60 and 70 wetlands were sampled for G. calmariensis and G. pusilla, respectively. Species were determined by dissection of male genitalia. Multiple sampling techniques, such as random walk-through sampling and pheromone traps, were used to collect insects within each wetland. Factors such as location, year of initial release, years a site was defoliated by beetles, wetland type, density of purple loosestrife, size of purple loosestrife infested area, and water level were used in a categorical analysis to determine if any of these factors are predictive of species composition. To help determine how water level and initial species composition affects the observed species composition, laboratory experiments were set up in child swimming pools. Each individually netted purple loosestrife plant was assigned an initial species composition and water level. Newly emerged beetles were collected every other day for identification to determine if species composition changed over time. These post-release monitoring efforts can provide valuable information that can lead to improved efficiency and effectiveness of subsequent Galerucella spp. releases for controlling purple loosestrife.

24) Project title: Biological Control of Garlic Mustard: Host Specificity of Ceutorynchus spp. on native mustards.

Investigators: Jeanie Katovich, Roger Becker, Brian P. McCornack, Luke C. Skinner, and David Ragsdale

Contact: D. Ragsdale (ragsd001@umn.edu)

Project description: The objectives of this newly funded project (started in October 2003) was to determine if several weevils, Ceutorynchus spp., identified by colleagues at CABI as garlic mustard specialists, will feed and reproduce on selected native plant speciesincluding native mustards(Brassicaceae). The plant species to be tested are unique to the North Central region of the United States and will expand the list of species included in current host specificity testing of Ceutorynchus spp. conducted in at the CABI facility in Switzerland and at the University of Minnesota.

Three hundred Ceutorhynchus scrobicollis adults were received in mid-November from the CABI facility in Delemont, Switzerland. The weevils arrived in excellent shape and were placed under quarantine conditions in the High Containment Security Facility on the University of Minnesota campus.

In mid December, 2003, sequential no-choice and single choice host range studies were conducted with mating pairs of C. scrobicollis (Gerber et al., 2003) on the plant species, Anemone canadensis and Carex laxiflora. Six valid replications of the sequential no-choice test and 12 valid replications of the single choice test were completed for both plant species. No feeding or oviposition was observed on either Anemone canadensis or Carex laxiflora plants. Collaborators from IL, IN, MI, MN and WI have collected and shipped a number of test plant species for C. scrobicollis host range screening at the University of Minnesota. We currently have in cultivation hogpeaut (Amphicarpaea bracteata), yellow trout lily (Erythronium americanum), white trout lily (Erythronium albidum), cut-leaved toothwort (Dentaria laciniata), northern blue monkshood (Aconitum noveboracense), swamp buttercup, (Ranunculus septentrionalis), Cardamine heterophylla, Cardamine bulbosa, and Arabis canadensis.

Newly emerged C. scrobicollis weevils have been collected from garlic mustard plants on which the original weevils were placed. This indicates that C. scrobicollis may complete their life cycle in quarantine conditions. The C. scrobicollis adults are now in an aestivation period. We are currently determining the best method to manipulate the length of aestivation required by C. scrobicollis prior to ovipostion so we can begin to conduct additional host range tests on our native non-target plant species later this fall and winter. Four hundred Ceutorhynchus roberti were received in late April from CABI. A colony was started with these founding insects and host range testing will begin as plants become available in the fall.

25) Project title: Impacts of natural enemies on soybean aphid population growth and development

Investigators: David Ragsdale, Brian P. McCornack, and Karrie Koch

Contact: D. Ragsdale (ragsd001@umn.edu)

Project description: The effect of fungicides likely to be used if soybean rust becomes established in North America was evaluated for their impact on soybean aphid population growth. In 2005, we estimated the prevalence of entomopathogenic fungi on soybean aphid populations in Lamberton, MN using combinations of various fungicide treatments (e.g., Headline, Folicur, Bravo, Stratego, and Quilt). From 19 August to 5 September, a soybean aphid epizootic occurred and infection prevalence was recorded using laboratory bioassays of field collected aphids. Ten leaves were collected from each fungicide treated plot (40 leaves per treatment). One-hundred apparently healthy apterae (i.e., mobile, non-infected) from each treatment were then transferred to sterile, excised soybean leaflets grown under greenhouse conditions. Aphids and leaves were placed in Petri dishes (100 x 15 mm) and were monitored for 72 h. Prevalence of infection in each treatment was recorded. The epizootic consisted of three species: Pandora neoaphidis, Conidiobolus thromboides, and Zoopthora radicans. Over the epizootic, 90% of the infections were Pandora neoaphidis, 9% of the infections were Conidiobolus thromboides, and 1% of the infections were Zoopthora radicans. The epizootic peaked on 30 August with 31% prevalence in the untreated plots, 6% prevalence in plots treated with Headline, Folicur, and Bravo, 5% in plots treated with Quilt, 2% prevalence in plots treated with Stratego, and 1% in plots treated with Headline and Folicur.

In a separate set of studies, we measured the impact of planting date on soybean aphid and predator abundance in replicated field plots. Time series data for soybean aphid and key aphid predators found in soybean were collected weekly using sweep net samples (i.e., 20 sweeps per plot) and destructive plant counts (i.e., 5 plants per plot). Aphid pressure was low across all planting dates (i.e., <250 aphids per plant) and peaked at the beginning of August. In destructive plant counts, abundant predators included Coccinella septempunctata, Harmonia axyridis, Coleomegilla maculata, Nabidae spp., Orius spp., chrysopids, and predatory thrips. Sweep net data is currently being processed, entered, and analyzed. In the laboratory, functional responses for C. septempunctata, H. axyridis, and C. maculata at constant 25ºC were also measured. Consequently, functional responses for various life stages of H. axyridis at different temperatures and prey size (i.e., 1st-2nd, 3rd-4th, and adult apterae) will also be assessed.

Biological Control Publications since 2004– Ragsdale lab

McCornack, B., D. W. Ragsdale, and R. C. Venette. 2004. Demography of Soybean Aphid (Homoptera: Aphididae) at Summer Temperatures. J. Econ. Entomol. 97(3): 854-861.
Skinner, L. C., D. W. Ragsdale, R.W. Hansen, M.A. Chandler and R.D. Moon. 2004. Temperature-dependent development of overwintering Aphthona lacertosa and A. nigriscutis (Coleoptera: Chrysomelidae), two flea beetles introduced for the biological control of leafy spurge, Euphorbia esula. Environ. Entomol. 33: 147-154.
Ragsdale, D. W., D. V. Voegtlin and R. J. O’Neil. 2004. Soybean Aphid Biology in North America. Annals Entomol. Soc. Amer. 97: 204-208.
Heimpel G. E., D. W. Ragsdale, R. C. Venette, K. Hopper, R. J. O’Neil, C. Rutledge, and Z. Wu. 2004. Prospects for importation biological control of the soybean aphid: anticipating potential costs and benefits, Ann. Entomol. Soc. Amer. 97: 249-258.
Wu, Z., D. Schenk-Hamlin, Zhan, D. W. Ragsdale and G. E. Heimpel. 2004. The soybean aphid in China – an historical review. Ann. Entomol. Soc. Amer. 97: 209-218
Venette, R. C and D. W. Ragsdale. 2004. Assessing the invasion by soybean aphid (Homoptera: Aphididae): where will it end? Ann. Entomol. Soc. Amer. 97: 219-226.

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VI. Ray Newman, Department of Fisheries and Wildlife, University of Minnesota, St. Paul, MN 55108, Phone: 612-625-5704, Internet:rmn@fw.umn.edu

26) Project title: Research on the Biological Control of Myriophyllum spicatum

Investigators: Ray Newman, University of Minnesota Dept. of Fisheries and wildlife

Contact: R. Newman (RNewman@umn.edu)

Project description: Our main focus is to determine and attempt to ameliorate factors limiting populations of milfoil herbivores (the milfoil weevil and aquatic Lepidoptera) and assess the role of plant community response and competition in successful biological control of Eurasian watermilfoil. We have shown that herbivores can cause sustained declines of Eurasian watermilfoil when milfoil weevil populations remain high, but predation by sunfish appears to limit herbivore populations in many lakes. Sunfish density explains 50-70% of the variation in herbivore densities among lakes. We are also examining the role of wide spread milfoil harvesting and shoreline habitat on milfoil weevil densities. Laboratory experiments show that although milfoil weevil performance is better on the exotic Eurasian watermilfoil than the native northern watermilfoil, performance on the exotic X native hybrid is not poorer, as had been predicted by Moody and Les. We have also isolated and identified two water soluble chemicals released by Eurasian watermilfoil that are used by the milfoil weevil to locate its hostplant. Detailed information is available at the following web site:
http://www.fw.umn.edu/research/milfoil/milfoilbc/ . Reports (including our completion report for 2001-2004) are available at: http://www.fw.umn.edu/research/milfoil/milfoilbc/currentresearch.html#reportsavail_in_pdf

Biological Control Publications since 2004– Newman lab

Newman, R.M. 2004. Invited Review – Biological control of Eurasian watermilfoil by aquatic insects: basic insights from an applied problem. Archiv für Hydrobiologie 159 (2): 145 - 184

VII. Diane Larson, Department of Ecology, Evolution and Behavior,USGS, Northern Prairie Wildlife Research Center 100 Ecology Building, 1987 Upper Buford Circle, St. Paul, MN, 55108 (dlarson@biosci.cbs.umn.edu) Phone: (612) 625-9271; Fax: (612) 624-6777

27) Project title: Canada thistle biological control agents on two South Dakota Wildlife Refuges

Investigators: Catherine C. Reed, Diane L. Larson and Jennifer L. Larson

Contact: Diane Larson (dlarson@biosci.cbs.umn.edu)

Project desription: We monitored populations of Canada thistle biocontrol agents Cassida rubiginosa, Ceutorhynchus litura, Larinus (= Hadroplantus) planus, Urophora cardui, Orellia (= Terellia) ruficauda, and Rhinocyllus conicus on Canada thistle (Cirsium arvense) at two national wildlife refuges in South Dakota from 1999 through 2003. C. litura, U. cardui, O. ruficauda, and R. conicus were present on both refuges. Agent populations were low except for C. litura, which was present in up to 90% of stems in some plots. C. litura infestation did not reduce thistle flowering, stem length, or overwinter survival. There was no change in thistle stem numbers over the study period and no diference in stem numbers in areas of high C. litura populations compared to areas of low C. litura populations. Our results suggest that insect biological control agents are inadequate for reduction of Canada thistle in southern South Dakota.

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