S. Patricia Stock Lab

RESEARCH PROJECTS

• Nematode Biodiversity, Systematics, Phylogenetics
• • Species Inventory of Nematodes in Tropical Rain Forest of Costa Rica
• • Entomopathogenic Nematodes Diversity in Jordan: An Environmentally-Safe Alternative to Benefit Agriculture in Desert Systems
• • Entomopathogenic Nematode Diversity in Oak Woodlands in Southern Arizona
• Nematode-Bacteria Symbiotic Interactions
• • Development, Structure, and Function of the Bacterial Symbiont Colonization Site in Steinernematid Nematodes
• Biological Control
• • Assessment of exotic and native strains of entomopathogenic nematodes for the control of the citrus nematode, Tylenchulus semipenetrans
• • Assessment and Implementation of Native Insecticidal Nematodes: An Alternative for Control of Urban Pests
• • Evaluation of Arizona-Native Entomopathogenic Nematodes for Management of Lepidopteran Larvae in Lettuce

Research Projects: NEMATODE BIODIVERSITY, SYSTEMATICS, PHYLOGENETICS

Species Inventory of Nematodes in Tropical Rain Forest of Costa Rica

The proposed project will begin to answer the critical question, "Where is the biodiversity of nematodes in the tropics?" We hypothesize that most of the nematode diversity will be associated in intricate relationships with arboreal habitats and invertebrates found in tropical rain forests. We will collect nematode assemblages at four vertical positions (soil, litter, subcanopy, arboreal habitats) in the early wet season (July 2005) at each of three altitudes (500, 1000 and 2000 m). Sites will be chosen based on their complementation of other existing surveys in Costa Rica.

Four women (2 PIs from the U.S., 2 collaborators in Costa Rica) serve as senior scientists. We have partnered with Universidad Nacional and Universidad de Costa Rica. Vouchers of morphological specimens and molecular sequence data will be prepared, edited and integrated into i) the official INBio database in Costa Rica, ATTA, ii) web linkages at http://nematode.unl.edu and iii) NSF Tree of Life database for Nematoda (NemATOL, NSF-DEB) for global access and future systematic studies.

FUNDING: NSF- DEB (PIs Neher, Giblin-Davis, Powers, Stock), WISC-AAA (PI Stock)

Entomopathogenic Nematodes Diversity in Jordan: An Environmentally-Safe Alternative to Benefit Agriculture in Desert Systems

With the rapid worldwide degradation of soils, particularly in desert or semi-desert ecosystems, rational management urgently requires increased knowledge of the ecology of these soils, including knowledge of the diversity of the soil flora and fauna and their respective interactions. Nematodes and insects are among the most abundant faunal components of the soil. In this project we are isolating and identifying the diversity of insect parasitic nematodes (roundworms), particularly of soil-inhabiting insects and from cryptic habitats from arid and semi-arid ecosystems in Jordan. These nematodes have the potentially to provide an environmentally-safe alternative to control insect pests in agricultural and forestry systems and also for the control of insects pests of human and veterinary importance. In addition to developing a deeper understanding of the diversity, and biology of insect-pathogenic nematodes in Jordan, the present study will also provide new knowledge and tools for developing non-chemical and non-toxic pest control programs in desert and semi-desert habitats.

FUNDING: International Arid Land Consortium (IALC) (PI Stock)

Entomopathogenic Nematode Diversity in Oak Woodlands in Southern Arizona

Non-disturbed areas, such as Southern Arizona's oak woodlands are potential habitats for native nematode populations. Oak woodlands have recently taken on importance, since they provide one of the richest wildlife habitats with hundreds of vertebrates and thousands of invertebrate species. Oak diversity in Arizona is vast but with a scattered distribution in the different mountain ranges. This particular distribution of oak woodlands in the "sky-islands" of southeastern Arizona, provides an interesting framework to document the diversity and study the population structure of entomopathogenic nematodes associated to these habitats. In this study, an integrated approach, combining both traditional (morphological) and molecular methods, is being considered for examining the species diversity of insect-pathogenic nematodes.

FUNDING: University of Arizona Small Faculty Grant, USDA-Hatch

Research Projects: NEMATODE-BACTERIA SYMBIOTIC INTERACTIONS

Development, Structure, and Function of the Bacterial Symbiont Colonization Site in Steinernematid Nematodes

The more common natural relationship between animals and microbes are mutually beneficial (mutualistic) since microbes are absolutely necessary for normal animal development, nutrition, and immunity. In these associations microbes typically colonize discrete locations on or within the animal. Little is as yet understood regarding the distinct physical nature of such colonization sites, or how beneficial animal-microbe associations are formed and maintained. It is known that these processes rely on animal-microbe communication that can involve chemical signals exchanged from a distance, as well as signaling through direct physical contact. Still lacking is a fundamental understanding of the identities of signals, how and where they are produced, how they are recognized, and the effects they mediate in each partner. To begin to address these questions, the proposed research focuses on an emerging model of animal-microbe mutualism between a small, soil-dwelling nematode (roundworm) and the beneficial bacterium with which it associates. The bacterial symbiot lives in a specific vesicle (receptacle) within the intestine of the nematode, and is the only microbe capable of residing at this location and establishing a relationship with the nematode; in other words, it is the only microbe that can correctly communicate with the nematode to achieve a mutually beneficial relationship. In this study the morphological and developmental features of the nematode intestinal vesicle will be analyzed to better understand the colonization process. The proposed research will also explore new hypotheses regarding the chemical signals and the physical interactions that occur between the nematode and the symbiont and how these interactions might affect the physiology of each organism. Furthermore, the proposed research will address questions of how such intimate animal-microbe associations evolve. The three labs involved in this collaborative research are each contributing distinct expertise required for the proposed studies.

Research Projects: BIOLOGICAL CONTROL

Assessment of exotic and native strains of entomopathogenic nematodes for the control of the citrus nematode, Tylenchulus semipenetrans

Assessment and Implementation of Native Insecticidal Nematodes: An Alternative for Control of Urban Pests

The overall goal of this project is to develop an alternative tool for use in urban integrated pest management systems. Use of native entomopathogenic nematodes (EPNs) as a substitute for chemical pesticides for control of pests is not a novel idea, but many urban pest species have at best anecdotal information with regard to efficacy. In this project we will: 1) determine the optimum nematode species/strain (in relation to pest species,) and dosage for the management of selected urban pests in Arizona (concentrating on subterranean termite and ant species); 2) evaluate the effect of environmental parameters (e.g. temperature, soil moisture, UV tolerance) on nematode efficacy (i.e. virulence and reproductive potential); 3) evaluate EPN efficacy with or without synergistic chemical/biological insecticides; 4) assess compatibility of nematodes with other IPM tactics. The accomplishment of the proposed objectives will help selection of the most efficacious native EPN strains and the identification of factors influencing their success against the targeted pests. We will also develop statewide multi-location demonstration trials on effectiveness of nematodes against selected pests, and develop extension materials and conduct training workshops on the optimal use of insecticidal nematodes.

FUNDING: USDA-Western IMP (PIs Gouge and Stock)

Evaluation of Arizona-Native Entomopathogenic Nematodes for Management of Lepidopteran Larvae in Lettuce

Lepidopterous pests are probably the most important group of insect pests affecting lettuce production. Among them, the beet armyworm, cabbage looper, Heliothinae and cutworms are currently known as the major species affecting lettuce production in desert growing areas of Arizona. Management and control of lepidopteran pests in Arizona currently considers a combination of approaches. Cultural practices, insect monitoring, as well as chemical and biological (Bt) pesticides have been considered both separately and/or combined for the control of these insect pests. One of the most promising choices to help minimize usage of chemical pesticides is the implementation of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae). In this project, we are testing a selection of native EPN isolates for the control of lettuce lepidopterous pests (i.e. dose-response, exposure time, nematode penetration efficiency, nematode progeny production). Morever, we are comparing the efficacy of the most effective EPN strains with commercially available formulation of EPN (i.e. S. riobrave and H. bacteriophora)
Upon completion of these objectives, future goals will consider evaluation of combined effect of the best fitted EPN species/strains with a currently used chemical pesticide (i.e. methomyl or thiocarb, among others) and field application of successful EPN species/isolates to control the targeted insect pests in lettuce.

FUNDING: Arizona Iceberg Lettuce Research Council (PI Stock)