John K. Westbrook

Brazilian free-tailed bats (Tadarida brasiliensis: Molossidae, Chiroptera) at high altitude: links to migratory insect populations

Existing information on the activity of bats in the aerosphere is restricted almost exclusively to altitudes that are within a few tens of meters above the ground. We report a total of 50.2 h of ultrasonic recordings made using radio microphonic bat detectors suspended from free-floating helium balloons and from kites. The data include a total of 22 353 echolocative calls from ground-level to 1118 m above ground level (AGL). These calls are attributed to Brazilian free-tailed bats based on acoustic features and the large numbers and high-altitude aerial dispersion of these bats over the local landscape. Bat activity varied significantly throughout the air column and was greatest at 400-500 m AGL and near ground level. Feeding buzzes, indicating feeding on aerial prey, were most abundant near ground level and at 400-500 m, and were detected to altitudes of ∼ 900 m AGL. The peak activity of bats at 400-500 m AGL is concordant with the altitude of the atmospheric boundary layer and the seasonal formation of the low-elevation southerly wind jet that has been identified as a major aeroecological corridor for the nocturnal dispersal of noctuid moths and other insects.

Noctuid migration in Texas within the nocturnal aeroecological boundary layer

Long-distance migration of adult corn earworm moths (Helicoverpa zea), and several other noctuid moth species, facilitates seasonal expansion of pest populations and consequent increased infestations of agricultural crops on a continental scale in North America. Long-term field studies of population dynamics and migratory flights of H. zea and fall armyworm (Spodoptera frugiperda) in the United States were evaluated using X-band radar observations and profiles of atmospheric conditions. These studies identified characteristic patterns of migratory flight that are largely associated with vertical profiles of temperature and wind speed. Collective patterns of moth migrations were generally highly correlated with wind headings, but often at a significant angular deviation. Preliminary analyses are presented between moth distributions in the aerosphere estimated from discrete moth counts using X-band radar and bulk reflectivity data from NEXRAD Doppler radar. Identification of associations between atmospheric factors and noctuid population dynamics and migratory flights will improve the ability to predict infestations by pest species throughout their broad seasonal range expansion.

BRAZILIAN FREE‐TAILED BATS AS INSECT PEST REGULATORS IN TRANSGENIC AND CONVENTIONAL COTTON CROPS

During the past 12000 years agricultural systems have transitioned from natural habitats to conventional agricultural regions and recently to large areas of genetically engineered (GE) croplands. This GE revolution occurred for cotton in a span of slightly more than a decade during which a switch occurred in major cotton production areas from growing 100% conventional cotton to an environment in which 95% transgenics are grown. Ecological interactions between GE targeted insects and other insectivorous insects have been investigated. However, the relationships between ecological functions (such as herbivory and ecosystem transport) and agronomic benefits of avian or mammalian insectivores in the transgenic environment generally remain unclear, although the importance of some agricultural pest management services provided by insectivorous species such as the Brazilian free-tailed bat, Tadarida brasiliensis, have been recognized. We developed a dynamic model to predict regional-scale ecological functions in agricultural food webs by using the indicators of insect pest herbivory measured by cotton boll damage and insect emigration from cotton. In the south-central Texas Winter Garden agricultural region we find that the process of insectivory by bats has a considerable impact on both the ecology and valuation of harvest in Bacillus thuringiensis (Bt) transgenic and nontransgenic cotton crops. Predation on agricultural pests by insectivorous bats may enhance the economic value of agricultural systems by reducing the frequency of required spraying and delaying the ultimate need for new pesticides. In the Winter Garden region, the presence of large numbers of insectivorous bats yields a regional summer dispersion of adult pest insects from Bt cotton that is considerably reduced from the moth emigration when bats are absent in either transgenic or non-transgenic crops. This regional decrease of pest numbers impacts insect herbivory on a transcontinental scale. With a few exceptions, we find that the agronomics of both Bt and conventional cotton production is more profitable when large numbers of insectivorous bats are present.

Partly cloudy with a chance of migration: Weather, radars, and aeroecology

Aeroecology is an emerging scientific discipline that integrates atmospheric science, Earth science, geography, ecology, computer science, computational biology, and engineering to further the understanding of biological patterns and processes. The unifying concept underlying this new transdisciplinary field of study is a focus on the planetary boundary layer and lower free atmosphere (i.e., the aerosphere), and the diversity of airborne organisms that inhabit and depend on the aerosphere for their existence. Here, we focus on the role of radars and radar networks in aeroecological studies. Radar systems scanning the atmosphere are primarily used to monitor weather conditions and track the location and movements of aircraft. However, radar echoes regularly contain signals from other sources, such as airborne birds, bats, and arthropods. We briefly discuss how radar observations can be and have been used to study a variety of airborne organisms and examine some of the many potential benefits likely to aris...

Rapid identification of rice samples using an electronic nose

Four rice samples of long grain type were tested using an electronic nose (Cyranose-320). Samples of 5 g of each variety of rice were placed individually in vials and were analyzed with the electronic nose unit consisting of 32 polymer sensors. The Cyranose-320 was able to differentiate between varieties of rice. The chemical composition of the rice odors for differentiating rice samples needs to be investigated. The optimum parameter settings should be considered during the Cyranose-320 training process especially for multiple samples, which are helpful for obtaining an accurate training model to improve identification capability. Further, it is necessary to investigate the E-nose sensor selection for obtaining better classification accuracy. A reduced number of sensors could potentially shorten the data processing time, and could be used to establish an application procedure and reduce the cost for a specific electronic nose. Further research is needed for developing analytical procedures that adapt the Cyranose-320 as a tool for testing rice quality.

Detection and evolution of resistance to the pyrethroid cypermethrin in Helicoverpa zea (Lepidoptera: Noctuidae) populations in Texas.

Abstract The bollworm, Helicoverpa zea (Boddie), is a key pest of cotton in Texas. Bollworm populations are widely controlled with pyrethroid insecticides in cotton and exposed to pyrethroids in other major crops such as grain sorghum, corn, and soybeans. A statewide program that evaluated cypermethrin resistance in male bollworm populations using an adult vial test was conducted from 2003 to 2006 in the major cotton production regions of Texas. Estimated parameters from the most susceptible field population currently available (Burleson County, September 2005) were used to calculate resistance ratios and their statistical significance. Populations from several counties had statistically significant (P ≤ 0.05) resistance ratios for the LC50, indicating that bollworm-resistant populations are widespread in Texas. The highest resistance ratios for the LC50 were observed for populations in Burleson County in 2000 and 2003, Nueces County in 2004, and Williamson and Uvalde Counties in 2005. These findings explain the observed pyrethroid control failures in various counties in Texas. Based on the assumption that resistance is caused by a single gene, the Hardy-Weinberg equilibrium formula was used for estimation of frequencies for the putative resistant allele (q) using 3 and 10 μg/vial as discriminatory dosages for susceptible and heterozygote resistant insects, respectively. The influence of migration on local levels of resistance was estimated by analysis of wind trajectories, which partially clarifies the rapid evolution of resistance to cypermethrin in bollworm populations. This approach could be used in evaluating resistance evolution in other migratory pests.

Determination and Consideration of Flight Potential in a Laboratory Population of True Armyworm (Lepidoptera: Noctuidae)

Abstract Flight potential, a poorly understood phenomenon in the migratory true armyworm, Pseudaletia unipuncta (Haworth), was investigated in a laboratory population using tethered-flight techniques. True armyworm exhibited strong flight potential relative to other known migratory noctuids whose flight potentials were previously determined by similar techniques. Flight potential was generally low for 1-d-old moths and increased with age to day 5 of adult life. Flight speed and distance flown decreased for female moths from day 5 to day 10 as their reproductive system developed. The greatest average flight speed, total flight duration, and distance flown was exhibited by 5-d-old females and 10-d-old males, suggesting that flight potential may differ by sex. Ten-day-old moths had the longest flight duration. Factor analysis showed that total flight distance, total flight duration, and average flight speed are strongly correlated to the factor variable, but the correlation for longest flight duration was weaker. The significance of these findings to migratory flight and reproductive behavior of P. unipuncta is discussed in the light of published findings.

An Airborne Multispectral Imaging System Based on Two Consumer-Grade Cameras for Agricultural Remote Sensing

This paper describes the design and evaluation of an airborne multispectral imaging system based on two identical consumer-grade cameras for agricultural remote sensing. The cameras are equipped with a full-frame complementary metal oxide semiconductor (CMOS) sensor with 5616 × 3744 pixels. One camera captures normal color images, while the other is modified to obtain near-infrared (NIR) images. The color camera is also equipped with a GPS receiver to allow geotagged images. A remote control is used to trigger both cameras simultaneously. Images are stored in 14-bit RAW and 8-bit JPEG files in CompactFlash cards. The second-order transformation was used to align the color and NIR images to achieve subpixel alignment in four-band images. The imaging system was tested under various flight and land cover conditions and optimal camera settings were determined for airborne image acquisition. Images were captured at altitudes of 305–3050 m (1000–10,000 ft) and pixel sizes of 0.1–1.0 m were achieved. Four practical application examples are presented to illustrate how the imaging system was used to estimate cotton canopy cover, detect cotton root rot, and map henbit and giant reed infestations. Preliminary analysis of example images has shown that this system has potential for crop condition assessment, pest detection, and other agricultural applications.

Multidisciplinary fingerprints: forensic reconstruction of an insect reinvasion

An unexpected outbreak of boll weevils, Anthonomus grandis, an insect pest of cotton, across the Southern Rolling Plains (SRP) eradication zone of west-central Texas, USA, was detected soon after passage of Tropical Storm Erin through the Winter Garden district to the south on 16 August 2007. The synchrony and broad geographic distribution of the captured weevils suggest that long-distance dispersal was responsible for the reinvasion. We integrated three types of assessment to reconstruct the geographic origin of the immigrants: (i) DNA fingerprinting; (ii) pollen fingerprinting; and (iii) atmospheric trajectory analysis. We hypothesized the boll weevils originated in the Southern Blacklands zone near Cameron, or in the Winter Garden district near Uvalde, the nearest regions with substantial populations. Genetic tests broadly agree that the immigrants originated southeast of the SRP zone, probably in regions represented by Uvalde or Weslaco. The SRP pollen profile from weevils matched that of Uvalde better than that of Cameron. Wind trajectories supported daily wind-aided dispersal of weevils from the Uvalde region to the SRP from 17 to 24 August, but failed to support migration from the Cameron region. Taken together the forensic evidence strongly implicates the Winter Garden district near Uvalde as the source of reinvading boll weevils.

Migration pathways of corn earworm (Lepidoptera: Noctuidae) indicated by tetroon trajectories

The corn earworm moth, Helicoverpa zea (Lepidoptera: Noctuidae), is a nocturnal pest insect that is capable of long-distance flights. Buoyant superpressure balloons (tetroons) with attached transponders were tracked as surrogate markers of moths migrating from three corngrowing regions in Texas. Launches were synchronized with peak emergence of corn earworm moths in June and July 1992. The tetroons were launched at the time (approximately 0.5 h after sunset) of peak take off (ascent of moths into the boundary layer) from the corn-growing areas, and ballasted to drift near the altitude (500-1000 m a.g.1.) of the maximum insect flight concentration. Each tetroon was followed by a tracking vehicle or the Argos satellite for maximum distances of 466 km per 9 h night flight, and for one to four successive nights. The endpoints of four of the six tetroons that were tracked for 9 h from Weslaco, Texas were clustered within a 40 km radius circle centered 35 km east of Uvalde, Texas. The prorated (9 h) vector-average of National Weather Service forecast trajectories at the surface and 85.0 kPa geopotential-height estimated mean atmospheric displacements 57% as long as, and 3” clockwise from seven observed 9 h tracks of tetroons. Implications of these findings are discussed relative to the prediction of insect migrations and development of area-wide pest management.