Newsletter of 1996 Events and Research of
NCR-148 Migration & Dispersal of Insects & Other Biotic Agents
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Chippendale New Administrative Advisor

Dr. Michael Chippendale, Acting Associate Director, Missouri Agricultural Experiment Station, has been assigned as the new Administrative Advisor to NCR-148, replacing Dr. George Ham of the Agricultural Experiment Station at Kansas State University. The reassignment of administrative advisors was due to changes among the North Central Directors and we will surely miss George Ham's excellent guidance and encouragement (see letter from NCR-148 ). Meanwhile, we welcome Mike Chippendale and look forward to seeing him at our meeting in Chicago on October 24-25, 1996.

Corn Earworm Migration Studies

The USDA/ARS Areawide Pest Management Research Unit (APMRU) at College Station, Texas, has scheduled corn earworm (Helicoverpa zea [Boddie]) migration field projects in the Lower Rio Grande Valley (LRGV) for mid-March when adult H. zea feed on citrus nectar, and for mid-June when peak populations of H. zea emigrate from mature corn fields. Entomological radars will be deployed in March along the Rio Grande River from Weslaco, Texas, to Del Rio, Texas, to monitor the flux of migrant insects from interior Mexico into the south-central U.S. The entomological radars will be deployed in the LRGV and at downwind locations to monitor H. zea migration from a large irrigated area of mature corn in June; however, a prevailing drought in the LRGV may significantly reduce the area of corn production (from 200,000 ha) and lead to sparse H. zea populations.

Much of the research effort will focus on verification of migrant insects. One method of verification will be by entomological surveys and night vision observations in the LRGV. A second method of verification will be by aerial capture of insects using insects traps attached to tethered balloons, tetroons and aircraft. A third method of verification will be to mark insects in the LRGV and identify marked specimens captured in traps downwind.

Insect Monitoring Radar APMRU welcomes Dr. V. Alistair Drake and Mr. Ian T. Harman of the University of New South Wales, Australia, who will collaborate in H. zea migration field projects in Texas in 1996. Dr. Drake has brought an Insect Monitoring Radar (IMR) that he developed in Australia. The IMR will complement ARS meteorological and entomological radar measurements by continuously monitoring concentrations and physical characteristics of individual radar targets such as speed, displacement direction, orientation, length-to-width ratio and mass. In addition to migration field projects, the ARS entomological radars and the IMR will operate in May near the NEXRAD doppler radar at New Braunfels, Texas, to compare radar detection of insect concentrations and flight characteristics using these radars.

Bat Predation of Noctuids

APMRU scientists are collaborating with scientists from the Univ. of Tennessee - Knoxville (UTK), Bat Conservation Intl. (BCI), and Boston University (BU) in studies of bat predation of noctuids. Dr. Gary McCracken of UTK will install acoustic detectors on a tethered balloon in the LRGV and on drifting tetroons to monitor the feeding behavior of Mexican free-tail bats during northward migrations from Mexico to central Texas. APMRU scientists will install insect traps on the tethered balloon in the LRGV that will also carry acoustic detectors. Dr. McCracken is also exploring DNA analysis of bat diets, which he believes are largely composed of noctuids during early-morning feeding. Brian Keeley of BCI cooperates with Dr. McCracken and will conduct surveys of Mexican free-tail bat colonies under bridges in south-central Texas. Dr. Tom Kuntz of BU will investigate fatty acid characteristics of noctuid species to identify differences of bat diets.

Please contact meteorologist John Westbrook or agricultural engineer Wayne Wolf for more information about the APMRU noctuid migration research projects.

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	Beached Insects on the Eastern Shore of Lake Michigan: Exploring Hypotheses for Migration of a Multi-Order Taxa William D. Hutchison Department of Entomology University of Minnesota, St. Paul, MN
Collection techniques demonstrated by Dr. Bill Hutchison to Research Assistants, Luke and Ellie Hutchison.

During late June, 1995, while surveying the sand dune beaches near Luddington, Michigan, I observed an interesting influx of a diversity of insects suddenly beached, following severe thunderstorm activity. On 27 June, arthropod activity was virtually non-existent, with the exception of a few sand spiders. However, by 29 June, the beach was active with a variety of stunned, yet living (most species) insects, representing at least 6 orders. Most individuals were limited to a 1.5 m band adjacent to the shoreline, with no significant insect activity beyond this zone, further into the sand dunes. The extent of this migration was confirmed along at least 6 km of shoreline, confirming that the migration was not limited to the initial section of beach where the insects were first discovered.

Though species identification continues, it is interesting to note that representatives from the Orthoptera (a few katydids), Coleoptera (mostly lady beetles, weevils, and the largest group), Lepidoptera (2 moths), Hymenoptera (ichneumonids, paper wasps, bees), Homoptera (leafhoppers), and Thysanoptera, have been documented. One of the more interesting finds, (5-10/30 ft), was the Colorado potato beetle, not normally known for its long-distance transport (Grafius 1995: Amer. Entomol. [Summer Issue]). All specimens, recorded to date, are typically found in midwestern agricultural or forested systems.

Although other accounts of insect taxa on beaches have been reported, particularly for lady beetles on midwestern lakes (e.g., near Duluth and Lake Superior), and Colorado Potato Beetle on Eastern shore lakes (G. Zhender, pers. comm.), I am not (yet) aware of similarly reported findings of the diversity observed here. Family, and species identification of all specimens collected is still underway. Backtrack synoptic weather patterns will be analyzed this fall in an effort to determine where this fauna may have originated during the 2-day time period. Any observations that NC-148 representatives, or their colleagues, might have in assisting with this analysis would be appreciated.

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A Greenhouse Wind Tunnel to Study the Ascent Phase of Aphid Migration and Dispersal

Scott A. Isard, Mark Belding, Michael E. Irwin, Gail E. Kampmeier.

University of Illinois at Urbana-Champaign; Illinois State Water Survey; University of Illinois; Illinois Natural History Survey.

We have completed the third year of a research program to study the ascent phase of flight. Our research objective is to determine the biological and environmental factors that govern the ascent phase of aphid flight. We hypothesize that the relative strength of buoyant and mechanical forces in the surface layer and the aphids' flight aptitude combine to govern the trajectories of alatae during the ascent phase of flight.

We constructed a large wind tunnel in a greenhouse room provided by the Illinois Natural History Survey for our experiment. The wind tunnel is 12.2 m (40 ft) long, 3.7 m (12 ft) wide, and 2.2 m (7 ft) in height. The structure of the airflow within the tunnel is controlled with a bank of 28 electric fans and eight, fin-tube heating/cooling elements. The fans and heating/cooling elements are arranged in four, independently controlled, horizontal tiers.

The speeds of the fans may be adjusted using 28 rheostats, while the water circulating through each tier of fin-tubes may be either heated or cooled in an ice bath. Forty-eight (3, 4 by 4 grids) thin wire thermocouples connected to a bank of three Campbell microloggers provide a continuous, three-dimensional air temperature monitoring capability. The vertical wind velocity field may be monitored with four, mobile, hot wire anemometers.

Artificial lighting may be provided by two, mobile, metal halide lights suspended on tracks above the tunnel ceiling. Because the open ends of the greenhouse wind tunnel allow air to circulate and also let in sunlight, experimental runs thus far have been conducted at night so that the light source within the tunnel is controlled. Ultraviolet light acts as a stimulus, causing alatae, once airborne, to fly upward when the atmospheric structure and wind permit (Moericke 1962). Light from overhead attracts aphids and thus maximizes the vertical component of their flight trajectories.

A small vial is used to hold test aphids. During an experiment it is positioned approximately 7 m downwind of the fans and with its orifice at the top of the plant canopy. Because both species of aphids we tested (Rhopalosiphum padi and Rhopalosiphum maidis) tend to climb to the top of plant parts before attempting to initiate flight, this system allows many aphids to take off from the same general area (vial orifice area is 0.0007 sq. m).

Light reflecting off their rapidly beating wings illuminates aphids in flight, making them easy to view and track against the black felt background. A grid of colored strings stretched across the tunnel 1.5 m downwind from the release vial is currently used to quantify the flight trajectories of the aphids. The vertical resolution of the flight trajectory grid is 0.3 m and the horizontal resolution is 1 m. This technique assumes a linear flight trajectory, and only roughly characterizes the aphids' true flight paths. For example, the low trajectories were often made by aphids that briefly flew upward at relatively steep angles after take-off and then assumed a horizontal flight path shortly downwind of the release point. However, this crude measurement has allowed us to obtain preliminary data on aphid flight behavior and has validated our research approach.

In 1995, we switched from aphid species from R. padi to R. maidis and are working hard to develop a rearing environment in the growth chambers that will produce alatae that behave in a consistent manner during take-off and ascent. In addition, we are developing an electronic technique (ultrasonic) for recording the flight paths of aphids that can be used in the wind tunnel and in agricultural fields. We received limited funding to continue our research from the Illinois Agricultural Research Station and the University of Illinois. We applied for continued National Research Initiative funding in 1996.

We have developed and tested a phased array ultrasonic insect tracking system to be used in an agricultural setting to track aphids in flight through the surface layer of the atmosphere and into the PBL above. Our plan is to use acoustic echoes returned from insects flying in a tracking volume (2.5 m long, 1.5 m across, and 2.0 m high) to determine aphid flight trajectories. A phase array of 15 ultrasonic transmitters (3 by 5 grid with its long axis oriented downwind from the release vial) will emit a pulse at an ultrasonic frequency ( 42 KHz). The signals emitted from each bank of transmitters (3 banks of 5 transmitters oriented downwind or 5 banks of 3 transmitters oriented crosswind) will be phase delayed to enable the system to "sweep" across the entire tracking volume, alternating between the downwind and crosswind directions. The return echoes from insects flying in the SL will be picked up by 8 ultrasonic receivers, amplified, and passed to a Digital Signal Processor (DSP) and associated microprocessor controller where the return ultrasonic echoes will be converted to Cartesian coordinates (x, y, and z) for each insect, 20 times each second.

These data and associated time tag will be fed from the DSP unit into a portable computer and the aphid's position within the tracking volume and thus its rate and direction of movement through the tracking volume may be resolved, stored for further analysis, and displayed in near-real time. In all but the calmest wind conditions, an aphid will traverse the tracking volume in 2 to 5 seconds and consequently this system will provide between 40 and 200 sets of Cartesian coordinates for each flight trajectory. With the use of a sufficiently fast DSP and the appropriate software, it will be possible to track multiple insects flying through the tracking volume simultaneously and determine whether or not a particular insect initiated flight from the release vial.

Several technologies for tracking insect flight through the SL were considered and dismissed including: 1) microwave-based (radar) scanning systems (very complex and costly), 2) scanning systems involving visible light sources (high background contamination from sunlight and the artificial light source could effect aphid flight behavior), and 3) passive, narrowband audio receiver (microphone) systems to monitor aphids' wingbeat frequencies (weak wingbeat signal coupled with high background levels of the target acoustic frequencies would require at least 100 finely spaced (0.1-0.2 m) microphones). The ultrasonic system will have a spatial and temporal resolution that is similar to that of radar at close range (1 - 3 m) and the technology is relatively simple and low cost. We have conducted over 50 experiments in our flight chamber trying to determine whether or not the radiation from our ultrasonic transmitter impacts the take-off and flight trajectories of aphids. Our observations clearly suggest that the ultrasonic frequency (42 KHz) that we will employ has no effect on aphid flight behavior.

The hardware components for the phase array ultrasonic insect tracking and display system are available 'off-the-shelf'. Signal processing, computation, and graphics software modules designed for similar applications are also available; however, we anticipate that configuring the software to calculate and display the aphids' flight trajectories in near-real time will be a major undertaking.

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Dispersal of Stable Flies: Phenology of Dispersing Flies

Carl J. Jones, Gerald L. Green, and Scott Isard

Researchers received a grant to study the local movement and dispersal of stable flies in Kansas from the North Central-IPM Grant Program.

Stable flies are a major constraint to cattle production in the Midwest; they are also a significant nuisance pest of humans and other domestic animals. Overwhelming numbers of adults have frequently been encountered hundreds of kilometers from the closest sites where larvae could have developed. Our research is intended to create fundamental understanding of the mechanisms of stable fly dispersal. Live stable flies will be collected from resting sites on or near the ground, in the surface layer of the atmosphere, and high in the planetary boundary layer. Captured flies will be examined to determine their chronological and physiological ages, sex, and mated status. Further information on fly population dynamics and atmospheric motion systems, combined with dispersal data from flies marked with fluorescent powders, will provide the critical understanding needed to describe dispersal patterns in this species.

We will study the physiological, behavioral, and meteorological factors that govern stable fly take-off and ascent. Once take-off occurs, We postulate that biological and meteorological factors interact to determine whether: (i) stable flies climb high into the planetary boundary layer (PBL) and consequently are in a position to move long distances (10s-100s km) or (ii) remain within the surface layer (SL) and disperse only locally (< 10 km).

We hypothesize that physiological and behavioral drives combine with physical forces in the lower atmosphere to govern the vertical distribution of stable flies within the planetary boundary layer during take-off and ascent into the atmosphere. The three scenarios that follow from our hypothesis can be tested because of unique characteristics of stable fly physiology that permit the use of relatively simple tests of chronological and physiological age:

1. Physiological status and behavioral drives act in conjunction with meteorological factors to govern stable fly ascent into the PBL. Physiological characteristics of flies in the PBL are homogeneous and significantly different from those in the SL and at rest on the ground.
   
   
2. Physiological status and behavioral drives lead to aerial movement of stable flies, and those specimens ascending into the PBL are a minor portion of the dispersing population. Physiological characteristics of flies in the PBL are homogeneous and similar to those caught in the SL, but differ from the status of the portion of the population at rest on the ground.
   
   
3. Meteorological factors lead to inadvertent ascent of stable flies into the PBL. Flies in the PBL, SL, and at rest are heterogeneous in physiological characteristics.

We will concurrently sample flies in PBL, SL, and at rest on the ground to measure important biological factors (e.g., physiological age of females, chronological age of males and females, and proportion of females inseminated) to evaluate these scenarios. Simultaneous vertical profile measurements of meteorological factors (pressure, temperature, humidity, wind speed and wind direction) will enable us to determine the atmospheric motion systems that influence ascent of stable flies within the PBL. The meteorological data and concurrent insect samples will be analyzed to determine whether ascent occurs: 1) when atmospheric instability creates strong upwardly moving convection currents, 2) in strong sudden updrafts associated with thunderstorms, or 3) throughout the diel period whenever atmospheric conditions do not exceed important temperature- and wind speed flight thresholds.

Although originally aerial sampling was expected to be conducted via the technology developed by Drs. Isard, Irwin and others for helicopters, current plans are to use an unmanned drone based on the system developed by Dr. Elson Shields of Cornell University. Although preliminary field research and laboratory research started during the past summer, plans call for intensive field work to commence during the summer of 1996.

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Orange Wheat Blossom Midge Distribution

Mike Weiss and Phil Glogoza

Department of Entomology, North Dakota State University, 231-7924 or 231-7581

Reports of the orange wheat blossom midge are widespread in North Dakota, resulting in considerable concern by growers. According to our conversations with growers and extension personnel, the midge population seems to be highest in Ramsey County and surrounding areas. Infestations extend northwest, with pockets of severe infestations all the way to Divide County. It also goes due North from Devils Lake. Populations in the northern Red River Valley appear to be below economic levels.

We have sampled North Dakota on a 12 mile grid from the eastern to the western border or from the eastern border to the Missouri River, North of I-94. We hope to continue the survey and develop distribution maps for this insect.

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Western Prairie Fringed Orchid Pollinators

David Rider and Gerald Fauske

Department of Entomology, North Dakota State University, Fargo, ND

The Western prairie fringed orchid (WPFO) is Federally listed as an endangered species. The three largest remaining populations are found in southern Manitoba, west-central Minnesota, and southeastern North Dakota, respectively. Known pollinators of this orchid are members of the family Sphingidae (hawkmoths). Two species which have been confirmed as pollen vectors are Sphinx drupiferarum (Wild cherry sphinx) and Eumorpha achemon (Achemon sphinx). Three additional species suspected Sphinx vashti (Vashti's sphinx), and Hyles lineata (white-lined sphinx).

As a group, the Sphingidae are known for their long-distance movements. Specimens have been collected at sea more than 1000 km from the nearest land. Additionally, it is usual to find species far outside the range of an known larval host-plants as well as finding subtropical species in north temperate areas.

Of the five sphingids known or possibly associated with the WPFO: Eumorpha achemon and Sphinx vashti overwinter in southeastern ND, Sphinx drupiferarum and S. chersis should overwinter in ND, while Hyles lineata does not overwinter in ND. However, the picture is complicated in that in any year, the sphingid population round in a given area is made up of both local moths and immigrants. Our continuing research into the ecology of the WPFO is presently aimed at determining how isolation of orchid populations affects pollination, whether larval host plant distributions on the local level correlate to WPFO pollination, and to what extent local sphingid populations are augmented by annual immigrants.

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Local Dispersal of Woodland Moth Species

D. J. Horn & S. E. Teraguchi

D. J. Horn is continuing research on local dispersal of common moth species in order to assess potential impact of gypsy moth management on fauna of isolated woodlots in the Midwest. Moths captured at a standard blacklight in a deciduous forest are dusted on the thorax with fluorescent powder and immediately released at varying distances from the blacklight. Moths present in the trap the following morning are examined under ultra violet light for traces of fluorescent powder. Species recaptured over 100 m are generally common and widespread in mainland habitats and on the Lake Erie Islands. Species that are less common, local, and infrequent on the Lake Erie Islands are infrequently recaptured. This research will continue on a modest scale in 1996.

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Forecasting the Transport of Spores and the Spread of Tobacco Blue Mold

C.E. Main, J.M. Davis, Thomas Keever and T.A. Melton

Departments of Plant Pathology and Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC, 27695-7616,USA.

Blue mold of tobacco (Peronospora tabacina) is a foliar fungus disease disseminated by tiny, microscopic spores in the lower atmosphere. The forecasting system described provides agricultural extension personnel, researchers, and other interested parties with timely information of the future movement of inoculum (spores) within the U.S. southeast and mid-Atlantic states from known sources such as infected fields, plant beds, or greenhouses. The forecast should provide clients with a projected future pathway or trajectory of spore movement. The trajectory is illustrated by a visual map of the eastern U.S. showing the pathway. Weather conditions favoring sporulation, survival during transport, deposition and new out breaks along the pathway are described together with a summary of the general weather across the tobacco production region.

Disease Reports

The forecasting system is dependent on timely and well-documented reports of blue mold occurrence. Blue Mold Coordinators located in tobacco producing states report new and/or important continuing sources directly to the forecasting office located at North Carolina State University, Department of MEAS, North Carolina State University (KEEVER@climate.nrrc.ncsu.edu) on a daily basis or as often as necessary. The disease report specifies the geographic location of the source, i.e., the nearest town or other landmark, so reasonably accurate map coordinates can be assigned. Multiple source sites grouped closely together (for example, within the same country) should be reported as a single central location. It is also important for state coordinators to prioritize the disease locations. The forecaster's time can then be best used to address the most serious disease situations. If a source ceases to exist, for whatever reason, this information should be reported as well. The forecaster uses the most recently reported and important continuing source sites to initiate a new set of trajectories each day. Forecasts are typically made in the afternoon after the present day's morning weather data becomes available. If a situation of extreme urgency presents itself, forecasts can be made available at other times.

Forecast Model

Spore transport in the atmosphere is calculated using the HY-SPLIT trajectory model. The trajectory model operates using meteorological data from NOAA's Nested Grid Model (NGM), a member of the family of numerical weather prediction models used to forecast short-term weather conditions over the United States and nearby areas. The data of primary interest are the forecast wind fields in the atmospheric boundary layer. The HY-SPLIT trajectory model and a specially formatted NGM weather data base are provided by NOAA's Air Resources Laboratory at Silver Springs, Maryland. The trajectory is a plot of the future atmospheric pathway of a "parcel" of air likely to contain spores; in other words, the prediction of the spatial and temporal positions of a spore cloud center for the future two days following release from a source site.

Outlook

Each day's forecast is archived at NC State University by date and source location. The forecast includes maps of the latest trajectories available. A Trajectory Weather section describes the recent past, present, and near future weather conditions at the source and along the anticipated pathway. Mentioned here are factors important to sporulation at the source (temperature, rainfall, cloud cover), survivability during transport (cloud cover: related to UV radiation and desiccation effects), and deposition from rainout and washout (potential rainfall). General weather conditions in the southeast that may influence the movement of spores or provide opportunities for subsequent infection are discussed in a Regional Weather section. An Outlook section combines these elements describing the likelihood of inoculum spread and disease risk 48 hours into the future.

Map Description

The source site is represented on the map by a geographic point (noted by the symbol'*'). The time-labeled dashes on the pathway represent the spore cloud position at six-hour intervals. Chronological time is given in Universal Time (UTC-formerly known as Greenwich Mean Time; subtract 4 hours to get Eastern Daylight time). Header labels detail the time and date of the trajectory start (14Z 02 JUN UTC), and the time and date of the meteorological forecast file used to compute the trajectory (00Z 02 JUN NGMTO48 FORECAST INITIALIZATION). The latitude and longitude of the disease site used for the source is given along the left edge of the map. The small rectangular graph underneath the map shows the vertical motion of the spore cloud. The solid line represents the pathway, with the dashes on the solid line corresponding to the time dashes on the horizontal trajectory shown on the map. Broken lines below the vertical trajectory give a semblance of the terrain over which the cloud will move. To the left of the vertical pathway are several numbers and a label reading 'HPA'; the numbers are values and "HPA' stands for "HectaPascals" which are numerically equivalent to millibars. Both are measures of pressure, which is a common method in meteorology to indicate altitude. The values decrease as height increases, since air pressure decreases with altitude. Average sea-level pressure is about 1013 millibars (or HectaPascals). At the terminal end of the trajectory on the main map, there can be found in parentheses a pressure value which indicates the altitude of the source from which the trajectory BEGAN.

Summary

Many factors are involved in predicting the future movement of fungal spores and the associated weather conditions. The weather forecasts are quite reliable, but not perfect. The HY-SPLIT model represents state-of-the-art atmospheric trajectory analysis. Using the data available, even the best HY-SPLIT trajectories can deviate from the true path by about 15% of the transport distance; many trajectories are off between 25% to 30%. Complex weather situations can produce errors of 40% or more. Research with HY-SPLIT and similar models using historical data of actual epidemic spread provide good qualitative guidelines for evaluating the accuracy and usefulness of the forecasts. Each Blue Mold Forecast includes a measure of the anticipated quality of its trajectory pathway. It is important that users of this information continue to pay close attention to local weather conditions and forecasts. During the 1995 U.S. epidemic, a total of 97 forecasts were prepared and distributed on 11 separate days from June 7-30. Analyses on how well the predicted and actual trajectories correspond, and how well the forecast predicted actual new outbreaks is being investigated. The Blue Mold Forecast should prove to be a very useful product in the continuing battle against the unpredictable tobacco disease called blue mold.

For the latest information see: http://www.ces.ncsu.edu/depts/pp/bluemold/

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Oklahoma Mesonet

Oklahoma is pleased to feature the operation of the Oklahoma Mesonet, a 111 state-of-the-art weather stationed networked together to give real-time weather every 15 minutes and to integrate into products for clientele. This system also networks county based National Weather Service forecasts and NEXRAD data. It is available at no cost for educational institutions and has been used extensively by Extension and in school systems. Contact: J.D. Carlson (405-744-5427).

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