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1996 Movement & Dispersal Research

Developing an Aerial Collection Device for Weakly Flying Insects

Elson J. Shields (state representative, NY) & Paul S. Taylor

Cornell University, Ithaca, NY

For the past 2 years we have been developing an aerial collection device with the following project goals.

• To use 'off the shelf' technology if possible
• Capabilities to sample 10 cubic meters of air per second at altitudes of a few meters to many meters.
• Capabilities to operate in windy and turbulent conditions
• Relatively easy to operate and maintain.

Our current prototype is a model airplane with an eight foot wingspan capable of sampling 3.5 cubic meters per second and flies at 35 mph during sampling. At these speeds, most of the insect are alive and intact at the conclusion of the sampling run. The fine mesh net is mounted to the top of the plane and opens and closes remotely. During the past summer, we completed 48 recorded collection runs totaling nearly 12 hours of collection time. During this time, we sampled 110,000 cubic meters of air. This sampling record includes 7 successful night time sampling flights conducted from dusk to 10 PM. over several different evenings (4.5 hours total flight time).

Sampling flights were conducted both over agricultural fields (alfalfa & corn) and mixed hardwood forest. The duration of sampling flights ranged from 15-40 minutes depending on the prototype flying. At the current sampling capabilities, we will sample 10,000 cubic meters in ca. 40 minutes. The insect targeted for our sampling was potato leafhopper but a significant migration never arrived and populations never exceeded 1 leafhopper/20 sweeps in area alfalfa fields.

During the winter, we plan to evaluate and improve our design with the goal of sampling 10 cubic meters per second for the 1997 migration season. In addition, we plan to incorporate all of our individual developments into a single design for the 1997 collection season (autopilot, telemetry, in-air tuning, lights, on-board generator etc.). We have provided a list of insects collect during the 1996 season which have been rough sorted to family.

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The 1996 Forecast of Spore Transport and Spread of Tobacco Blue Mold

C. E. Main (state representative), J. M. Davis, T. A. Melton, T. Keever, and P. B. Shoemaker.

Dept. Plant Pathology, North Carolina State University, Raleigh, NC 27695.

Blue mold (mildiou) of tobacco (Peronospora tabacina) is a foliar disease disseminated long-distance by winds in the planetary boundary layer of the atmosphere. A NCSU Blue Mold Forecast system was operational from March 5 to August 8, 1996 providing county agents, growers, industry and the media with 350 forecast outlooks on 62 different days via the WWW Internet site http://www.ces.ncsu.edu/depts/pp/bluemold/. The North American forecasts provided timely information on the continental movement of inoculum (spores) into the US from south of the 30th latitude prior to May 6 and within the eastern US and Canada after the first occurrence May 6.

The HY-SPLIT trajectory model operates on the NOAA Nested Grid Model (NGM) data base, a numerical weather forecast model used nationally to predict 48-hour weather by the US Air Resource Laboratory, Silver Springs, Maryland. The trajectories represent the atmospheric pathway of a "packet" of air containing spores and calculates the temporal position(s) of spore clouds at 6 hour intervals for the projected 48-hour period after a spore cloud leaves its source.

Sources are reported to the NCSU forecaster via a direct e-mail reporting link by a network of state and foreign country coordinators. Disease sites throughout the US, the Caribbean, Mexico and Latin America are monitored. Forecasts include a trajectory map, a climatology describing weather at the source and along the pathway (spore survival), and a risk outlook. The Forecast Homepage also includes sections on the biology and epidemiology of the disease, a section on disease diagnosis and what to report, and current fungicide control recommendations.

A new MASS model (Mesoscale Atmospheric Simulation System by MESO, Inc., Troy, NY) was tested in 1996 and will be used in 1997 to supplement the trajectory line forecasts. The MASS model accommodates multiple sources, terrain features, and carries remaining atmospheric spores over from one day to the next. The output provides a 3-dimensional map showing wind arrows and atmospheric spore cloud concentration(s) from the combined sources. The input requirements are source location, source strength, physical data on spore size/weight, settling velocity, etc.

The 1996 forecasts were capable of predicting with reasonable success the blue mold first outbreak May 6 in Florida from inoculum arriving from Cuba on April 29. Other examples are the first outbreak in south central North Carolina on June 5 as predicted by spores arriving from Florida, and the first occurrence in Delhi, Canada as predicted from spores released in central Kentucky on June 5. Late in the season (August 8) spores were transported from Kentucky to Wisconsin tobacco fields where a blue mold epidemic subsequently resulted.

Management of mildew diseases like tobacco blue mold require a coordinated, continental approach since the pathogen is not known to overwinter north of the 30th latitude. It has been demonstrated that inoculum can be transported from the US southward toward the Caribbean and Mexico where the winter tobacco crop can be infected. The pathogen is now established (endemic) on several wild species of Nicotiana throughout Mexico and Latin America representing a continuous source.

The NCSU Forecasting system could have application to forecasting a wide number of other diseases such as potato late blight, movement of thrips in the southeast carrying the tomato spotted wilt virus, transport of Telicia indica, introduction of the karnal bunt pathogen of wheat into the US, and movement of aviary respiratory virus(s) into North Carolina from southern sources. The system could serve as a model for many plant and animal diseases involving aerobiology, long-distance transport of inoculum and mesoscale disease management.

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Aster Leafhopper Dispersal

C. W. Hoy (state representative, OH), L. R. Nault, S. A. Miller, X. Zhou, L. Beanland

Ohio Agricultural Research and Development Center

We have developed a mathematical model of aster yellows epidemiology to explore strategies for managing this important disease of vegetable crops. The model simulates yellows epidemics in fields of lettuce, celery, and carrots. Spatial effects are now being included in the simulation model to describe epidemiology for a validation experiment and for Ohio muck production areas. Interfield movement of leafhoppers initially is being simulated with transition probability matrices. Epidemics are started by immigrating aster leafhoppers, Macrosteles quadrilineatus Forbes, and are influenced by subsequent population dynamics and phytoplasma transmission. Leafhopper movement after arrival in the vegetable growing area influences two critical rates in the epidemiological model: the rate at which uninfected leafhoppers acquire the phytoplasma and the rate at which inoculative leafhoppers transmit the phytoplasma to uninfected plants. Both rates depend on two scales of movement, interplant and interfield.

Interplant movement has been examined in the laboratory. Marked leafhoppers in observation cages were censused frequently to determine frequency of interplant movement and proportion of leafhoppers above the canopy, which we hypothesize to be associated with longer distance (interfield or greater) flight. Males move much more frequently between plants than females. Males and virgin females are most likely to be found above the plant canopy, and the proportion above the canopy increases during a crepuscular flight period. Mated females tend to be sedentary, rarely moving between plants and being found above the canopy in lower proportions than either males or virgin females. Although males move between plants most frequently, in transmission studies they have not been observed to inoculate more than one plant in a 24 hr period. Our current hypothesis is that interplant flights by males have little effect on transmission rates within fields. Crepuscular flights above the canopy result in longer distance dispersal and movement of the phytoplasma between fields. We hypothesize that mated females, moving only infrequently and to nearby plants, are largely responsible for the clustered patterns of aster yellows infected lettuce plants in the field (Madden et al. 1995). We hypothesize that interfield and possibly regional movement of the phytoplasma is due to leafhopper flight above the canopy, largely during a crepuscular flight period.

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Colorado Potato Beetle Locomotion and Flight after Bacillus thuringiensis d­endotoxin Ingestion

C. W. Hoy, G. P. Head. D. N. Ferro, & A. Alyokhin

Research continues on evaluating the impact of behavioral responses to Bacillus thuringiensis delta endotoxin (Btt) on dispersal of Colorado potato beetle. For quantitative genetic analysis of behavioral responses and physiological tolerance, 53 full-sib families from individual mated pairs were reared. Each family was assayed for physiological tolerance by injecting purified endotoxin in buffer solution into the esophagus of 3rd instars and adults. Locomotion of larvae and adults after Btt ingestion was measured with an image analysis system. Locomotion was measured after ingestion of transgenic potato leaves expressing high and low Btt concentrations and standard potato foliage. Locomotion data analysis and estimation of heritability for behavioral response to Btt and its genetic correlation with tolerance is in progress. Preliminary results include: 1.) significantly lower proportion of beetles feeding on transgenic (high concentration) than standard foliage in both choice and no-choice tests, 2.) locomotion is unaffected in the first half hour after Btt ingestion but in the second half hour beetles that fed on transgenic foliage move significantly greater distances than those that fed on standard foliage.

Egg masses from 27 families were sent to David Ferro and Andrei Alyokhin, Univ. of Massachusetts, for analysis of adult flight behavior. A total of 654 beetles were tested during the experiment (220 beetles fed on high Btt concentration transgenic foliage, 219 beetles fed on low concentration foliar Btt treated foliage, and 215 beetles fed on standard untreated foliage). Forty-two percent of the tested beetles flew after being placed on the flight mill (32.27% of the beetles fed on transgenic foliage, 43.84% of the beetles fed on foliar Btt-treated foliage, and 50.23% of the beetles fed on standard foliage). The beetles fed on transgenic foliage spent 327.12 seconds (St. Error=48.57), 425.55 seconds (St. Error=51.86) and 589.60 seconds (St. Error=67.88) in flight after feeding on transgenic, foliar Btt treated, and standard untreated foliage, respectively. There was no significant correlation between mean flight and mean foliage consumption for beetle families. Quantitative genetic analysis of flight response to Btt is in progress.

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Ohio's Cooperative Project with NC-193

R. B. Hammond

The Ohio State University

Ohio is participating in the regional project NC-193 "Spatial Dynamics of Leafhopper Pests and Their Management on Alfalfa". Sweep samples are taken in the spring to determine the first arrival of migrating adult potato leafhoppers. First arrival in Ohio was detected around 11-12 May. Ohio is also using yellow-sticky trap samples in numerous habitats to determine the extent of interhabitat movement of the leafhoppers. Collections of adult potato leafhoppers were large in two apple orchards 1-2 weeks prior to significant increases in the population size of leafhoppers that was observed in alfalfa fields. This suggests that the orchards might have served as a source of leafhoppers that moved into alfalfa in early July.

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A Dispersal Study of Stelidota geminata (Coleoptera: Nitidulidae)

R. N. Williams, M. S. Ellis & D. S. Fickle

The Ohio State University

The strawberry sap beetle, Stelidota geminata (Say), is a major pest of strawberries in the northeastern United States. They attack the fruit as it becomes ripe, chewing holes in the berries rendering them unmarketable. Further knowledge of the dispersal habits of this insect pest can enhance the effectiveness of pest management strategies. This nitidulid was shown to disperse from its overwintering sites, local woodlots, to one of its primary reproductive sites, strawberry fields, in late May. A series of traps spaced approximately 25 m apart were placed in a line from the nearest woodlot to the center of a strawberry field. Whole wheat bread dough, a prime attractant for this species, served as the bait in all traps which were collected weekly. The beetle population peaked around the third week in July in the strawberry field and then gradually declined. This trend remains consistent having been tested from 1993 through 1996. Furthermore, S. geminata was concentrated in the transition areas surrounding the strawberry fields prior to the ripening of the fruit.

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Monitoring Flower Thrips Activities in Strawberry Fields at Two Ohio Locations

R. N. Williams & M. S. Ellis

The Ohio State University

A commercial strawberry field in each of two Ohio counties (Wayne in northeast Ohio and Warren in southwest Ohio) were monitored for the flower thrips, Franklinella tritici (Fitch), in 1995 and 1996. This study was initiated after a major outbreak of flower thrips in 1994 which caused extensive damage (75% loss in some cases) to commercial strawberries in northeastern North America. It is generally accepted that the flower thrips overwinters in the South and is carried northward on frontal systems in early spring. Two trapping methods were employed in 1995, trays filled with water, glycerin, and a surfactant and yellow sticky traps (Pherocon(r) AM). The yellow sticky traps were deemed superior in the 1995 trial and were therefore the only traps used in 1996. Five or six (depending on the year) of each unbaited trap were placed in each field and collected weekly. Although high populations were encountered, the threshold limits were not breached in either of the years.

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Publications

Madden, L. V., L. R. Nault, D. J. Murral and M. R. Apelt. 1995. Spatial pattern analysis of the incidence of aster yellows disease in lettuce. Res. Popul. Ecol. 37(2): 279-289.

Head, G., C. W. Hoy, and F. R. Hall. 1995. Permethrin droplets influence larval Plutella xylostella (Lepidoptera: Plutellidae) movement. Pestic. Sci. 45: 271-278.

Hoy, C. W., J. A. Wyman, T. T. Vaughn, D. A. East and P. Kaufman. 1996. Food, ground cover and Colorado potato beetle (Say) (Coleoptera: Chrysomelidae) dispersal in late summer. J. Econ. Entomol. 89: 963-969.

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Towards a Postive Identification of Flying Insects, Bats, & Other Organisms in Migration Research

Participants: J.K. Westbrook, W.W. Wolf, J.R. Raulston, J.R. Coppedge, R.S. Eyster, P.G. Schleider, J.F. Esquivel, J.D. López and G.D. Jones

Collaborators: V.A. Drake and I.T. Harman, Univ. of New South Wales; J.H. Matis and J. Kiffe, Texas A&M Univ.; G.F. McCracken, Univ. of Tennessee; J. Ward, S. Allen and P. Yura, National Weather Service

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The USDA-ARS Areawide Pest Management Research Unit (APMRU) conducted migration research aimed at positive identification of migrating insects, a significant portion of which were suspected to be adult corn earworms, Helicoverpa zea (Boddie). Dr. V.A. Drake and I.T. Harman of the Univ. of New South Wales, and Dr. G. McCracken of the Univ. of Tennessee collaborated in the field efforts which will lead to significant progress on the identification of flying insects, bats, and other organisms.

Numerous producers in the Lower Rio Grande Valley (LRGV) of northeastern Mexico and southern Texas planted sorghum rather than corn or cotton in 1996, due in large part to a significant drought and catastrophic cotton production in 1995. The production of corn -- the major nursery crop for corn earworms -- decreased 90% from a 10-year average of about 200,000 ha in the LRGV. This agronomic anomaly was expected to dramatically decrease the population of corn earworms in the LRGV. Consequently, a significant decrease in the population of corn earworms in the LRGV will be used as a (proxy) statistical control group against which to test the hypothesis that migrant corn earworms from the LRGV are largely responsible for infestations throughout the south-central U.S.

Estimated moth flight trajectories from the LRGV in Feb.-Mar., 1994, were closely associated with locations where corn earworms were captured in south-central Texas, but were not closely associated with captures at Del Rio (Westbrook et al. in press). Five entomological radars were deployed at Moore Air Base (Edinburg), Laredo and Del Rio, Texas, to determine the migratory flux of insects across the southern border of Texas and validate estimated moth flight from the LRGV in March 1996. An Insect Monitoring Radar (IMR) (Drake et al. 1994) was operated at Moore Air Base to continuously measure the vertical profile of airborne biota, and to collect radar data from which to develop and test radar target classification algorithms. More information about the IMR is available on the World Wide Web at http://www.pems.adfa.edu.au/~adrake/trews/. A vertical looking radar was operated at Moore Air Base to measure the vertical profile of insect flux which could be compared with that of the IMR. A scanning radar and a tracking radar were operated at Laredo, and another scanning radar was operated at Del Rio. Preliminary analysis of the scanning radar data at Del Rio indicated substantial flight activity of large insect-size targets in the arid region of southwestern Texas.

The entomological radars were deployed along the approximate mean wind heading from the LRGV in June 1996. A scanning radar operating at the location of previous long-term radar measurements south of Donna, Texas, in the center of the LRGV detected much lower airborne insect concentrations than in previous years. The IMR was again deployed at Moore Air Base to establish a baseline for comparison with the measurements in March. The second scanning radar and a tracking radar were operated at Hebbronville, but no notable moth overflights were detected. The vertical looking radar was moved to Uvalde near cotton production areas which were possible recipient areas for migrating corn earworm moths from the LRGV. A feeding attractant/stimulant mixture containing distinctive Lycopodium spores was applied onto mature corn fields at Hargill, Texas, on the northern perimeter of the LRGV. Moths fed prolifically on treated corn and ingested Lycopodium spores. Adult male corn earworms marked internally with Lycopodium spores were caught in pheromone traps 32, 59, and 234 km downwind of Hargill at Moore Air Base, La Gloria, and Tilden, Texas, respectively.

Scanning radar measurements near Hondo and Uvalde, Texas, in July indicated significant insect and bat activity to at least 2 km AGL. Radiomicrophones attached to drifting tetroons detected host-finding echoes by the Mexican free-tail bat, Tadarida brasiliensis. The radiomicrophones detected ultrasonic bat signals; converted the signals to the audible range; then transmitted the audible signals to a radio receiver and tape recorder in a tetroon chase vehicle. The tape recordings revealed that Mexican free-tail bats were feeding as high as 750 m above ground level (AGL) and echo-locating for insects as high as 1200 m AGL (McCracken 1996). Bat guano removed from caves in central Texas is being analyzed to determine the proportion of H. zea moths in the diet of Mexican free-tail bats.

Four USDA entomological radars and the IMR were co-located at Kingsbury, Texas, about 20 km east of the (NEXRAD) WSR-88D doppler radar at New Braunfels, Texas, in August 1996. The entomological radars were operated adjacently to cross-check performance of the entomological radar systems and to evaluate the capability of the WSR-88D to detect flying insects. Preliminary analysis of the Level IV WSR-88D data showed that base reflectivity increased with greater insect concentration (Fig. 1), and base velocity deviated by as much as 5 knots from the radial component of wind velocity (Fig. 2). More precise relationships between WSR-88D data and insect concentration, insect true air velocity, and wind velocity will be derived from analyses of Level II data.

More information is available from Dr. J.K. Westbrook, Areawide Pest Management Research Unit, USDA-ARS-SPA-SCRL, 2771 F & B Road, College Station, TX 77845, tel.: (409) 260-9531, fax: (409) 260-9386, References Cited Drake, V.A. 1993. Insect monitoring radar: a new source of information for migration research and operational pest forecasting. In S.A. Corey, D.J. Dall and W.M. Milne (eds.), Pest Control and Sustainable Agriculture. pp. 452-455. CSIRO Publications, Melbourne, Australia. 514 pp. McCracken, G.F. 1996. Bats Aloft: a study of high-altitude feeding. BATS 14(3): 7-10. Westbrook, J.K., W.W. Wolf, P.D. Lingren, J.R. Raulston, J.D. Lopez, Jr., J.H. Matis, R.S. Eyster, J.F. Esquivel and P.G. Schleider. Early-season migratory flights of corn earworm (Lepidoptera: Noctuidae). Environ Entomol. 26(1): 12-20.

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