Gilles Boiteau

Harmonic radar transceiver design: miniature tags for insect tracking

The design and operation along with verifying measurements of a harmonic radar transceiver, or tag, developed for insect tracking are presented. A short length of wire formed the antenna while a beam lead Schottky diode across a resonant loop formed the frequency doubler circuit yielding a total tag mass of less than 3 mg. Simulators using the method-of-moments for the antenna, finite-integral time-domain for the loop, and harmonic balance for the nonlinear diode element were used to predict and optimize the transceiver performance. This performance is compared to the ideal case and to measurements performed using a pulsed magnetron source within an anechoic chamber. A method for analysis of the tag is presented and used to optimize the design by creating the largest possible return signal at the second harmonic frequency for a particular incident power density. These methods were verified through measurement of tags both in isolation and mounted on insects. For excitation at 9.41 GHz the optimum tag in isolation had an antenna length of 12 mm with a loop diameter of 1 mm which yielded a harmonic cross-section of 40 mm/sup 2/. For tags mounted on Colorado potato beetles, optimum performance was achieved with an 8 mm dipole fed 2 mm from the beetle attached end. A theory is developed that describes harmonic radar in a fashion similar to the conventional radar range equation but with harmonic cross-section replacing the conventional radar cross-section. This method provides a straightforward description of harmonic radar system performance as well as provides a means to describe harmonic radar tag performance.

Detection of stylet-borne and circulative potato viruses in aphids by duplex reverse transcription polymerase chain reaction

A reverse transcription polymerase chain reaction (RT-PCR) assay was designed to amplify stylet-borne potato virus Yo (PVYo) in aphids using primers located in the viral capsid gene. A 480 bp long product was detected in aphids exposed to PVYo-infected potato plants. Approximately 40% of Myzus persicae and 15% of Aphis nasturtii exposed briefly to PVYo-infected plants acquired the virus. This rate of acquisition by both species of aphids was typical of our earlier observation of the virus transmission tests. No significant difference in virus detection was observed whether the aphids were tested immediately after exposure to virus sources or stored for up to 45 days in ethanol at room temperature. The addition of a second pair to primers located in the capsid gene of circulative potato leafroll virus (PLRV) allowed simultaneous amplification of two viruses (duplex RT-PCR) in single aphids. Acquisition of PVYo by the aphids already viruliferous with PLRV was significantly reduced, compared to aphids not carrying PLRV. Duplex RT-PCR for PVYo and PLRV could be applied to analyze aphids collected from the field to ascertain the relative presence of both viruses in a single test.

Detection of potato leafroll virus in single aphids by the reverse transcription polymerase chain reaction and its potential epidemiological application

A reverse transcription and polymerase chain reaction (RT-PCR) system was developed using two 20-mer primers located in the potato leafroll virus (PLRV) capsid gene. A 336-bp PCR product was detected from aphids (Myzus persicae) which had been fed on PLRV-infected plants. The PCR band was specific to PLRV as determined by Southern blots and detection by a PLRV-specific probe. As little as 5 min exposure of aphids to PLRV-infected leaves resulted in the presence of PLRV-specific bands in 13% of aphids. However, the percentage of PLRV-positive aphids increased with longer exposure to infected sources and reached 90% after 3-4 days of feeding. PLRV can be detected from a single viruliferous aphid or a single viruliferous aphid combined with up to 29 non-viruliferous aphids. PLRV can be detected from freshly collected aphids, those stored at -70 degrees C, or those stored in 70% ethanol at room temperature for extended periods. This method is applicable to assess the viruliferous nature of aphids caught in yellow-pan traps during the growing season or stored for over a year.

Crop border and mineral oil sprays used in combination as physical control methods of the aphid‐transmitted potato virus Y in potato

BACKGROUND The objectives of this work were to determine if the control of potato virus Y (PVY, genus Potyvirus, family Potyviridae) in seed potato could be improved by combining border crops and mineral oil sprays, and if the border crop acts as a barrier or a virus sink. RESULTS Field tests over 3 years confirmed that mineral oils alone are an effective barrier to PVY, and showed that borders alone act as a PVY sink. Combining the familiar mineral oil and the more recent crop border methods was almost twice as effective in reducing PVY incidence as either one used alone. The combination provided consistently high PVY control compared with the variable and often lower level of control by either method alone. The contribution of the oil to PVY reduction was similar whether it was applied to the border, the center seed plot, or both. Oil application to the border alone should not affect efficacy and would help keep control costs down. CONCLUSION Combining border and oil provided the best reduction in PVY incidence 3 years out of 3, providing producers with a tool to reduce year-to-year variation in the effectiveness of crop borders or oil sprays used separately.

Evaluation of a vacuum collector for insect pest control in potato

A field scale vacuum insect collector designed for the control of the Colorado Potato Beetle,Leptinotarsa decemlineata (Say) was tested on potatoes in 1990. The vacuum collector was more effective against adults and small larvae than against large larvae. Results suggested that a large proportion of potato aphids can also be removed from plants. The spread of plant diseases PSTVd and PVX, readily transmitted by contact, was not increased by the repeated use of the vacuum collector.CompendioUn colector al vacío de insectos, para el campo, diseñado para el control del escarabajo de la papa de Colorado,Leptinotarsa decemlineata (Say), fue probado en plantas de papa en 1990. El colector al vacío resultó más efectivo para adultos y larvas pequeñas que para larvas grandes. Los resultados indicaron que también se puede eliminar una gran proportión de áfidos de las plantas de papa. La diseminación de enfermedades producidas por PSTVd y PVX, fácilmente transmisibles por contacto, no se incrementó con el uso constante del colector al vacío de insectos.

The spread of PVYo in New Brunswick potato fields: Timing and vectors

Field tests at three sites over a period of three to four years have shown that PVYo spread in New Brunswick starts in mid-to late July when plants reach maximum height. Some 62 different genera or species of aphids were collected in experimental plots. Only seven of these were known vector species. Of the colonizing species, the alate green peach aphid,Myzus persicae (Sulzer), seems to be the most important vector. However, because it is not always present when disease spread starts, non-colonizing aphids are probably responsible for the early spread of PVYo. Five of these species of aphids were tested in the laboratory to determine their vector efficiency. A list of potential vectors is presented. The impact of these findings on the management of PVYo is discussed.CompendioPruebas de campo en tres lugares, sobre un período de cuatro años han demostrado que la diseminación de PVYo en Terranova comienza entre mediados y fines de Julio, cuando las plantas alcanzan su altura máxima. En parcelas experimentales se colectaron unos 62 géneros o especies diferentes de áfidos. Solamente siete de estos fueron especies conocidas de vectores. De las especies colonizadoras, el áfido verde del melocotoneroMyzus persicae (Sulzer) parece ser el vector más importante. Sin embargo, debido a que no siempre se encuentra presente cuando se inicia la diseminación de la enfermedad, los áfidos no-colonizantes son probablemente los responsables para una diseminación anticipada de PVYo. Se probaron en el laboratorio cinco de estas especies de áfidos para determinar su eficiencia como vector. Se presenta una lista de vectores potenciales. Se discute el impacto de estos hallazgos sobre el manejo de PVYo.

Sperm utilization and post-copulatory female-guarding in the Colorado potato beetle, Leptinotarsa decemlineata

Crosses between white and black color morphs of the Colorado potato beetle, Leptinotarsa decemlineata Say, used as genetic markers, showed that male beetles ride and guard females to achieve the three copulations required to fill the spermatheca. Multiple matings are necessary for the females to realize their full reproductive potential. Sperm mixing occurs in the spermatheca providing partial sperm precedence. The data support the competitive mate searching theory.

Electronic tags for the tracking of insects in flight: effect of weight on flight performance of adult Colorado potato beetles

The wing loading of the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), was found to decrease slightly with increasing size over a wide range of individual sizes and independent of sex. This makes it possible to use tags of the same weight for beetles of all sizes and suggests that if the addition of light electronic tags has any effect on the beetles flight it will be similar across beetle size. The wing loading of individual potato beetles ranged from an average minimum 10.9 N m−2 to an average maximum of 15.6 N m−2 as their weights fluctuated over time following water and food uptake or dispersal. However, tests carried out in flight chambers indicate that beetles become incapable of upward flight as they go beyond an average wing loading of 11.8 N m−2, that is 101 μN (10.3 mg) beyond their minimum weight. It is estimated from our results that electronic tags should weigh no more than 23–33% of the potato beetles acceptable extra loading for the technique to have no or minimal impact on the number and quality of upward flights taken.

Recruitment by Flight and Walking in a One-Generation Colorado Potato Beetle (Coleoptera: Chrysomelidae) Environment

Abstract Adult Colorado potato beetle, Leptinotarsa decemlineata (Say), recruitment on potato plots by flight or by walking occurred throughout the 1991–1993 crop seasons. Most recruitment occurred by walking. Yearly recruitment by flight ranged from 9.5 to 49.4%. It is suggested that the proportion of recruitment occurring by flight is determined largely by environmental factors such as air temperature and solar radiation. The presence of well-developed flight muscles is necessary for flight but was not a limiting factor until late August and even then only for part of the population. The proportion of beetles with developed thoracic muscle masses, developed ovaries, high abdominal fat content levels, and sperm in the spermatheca did not significantly differ between beetle populations recruited by flight or by walking but did differ between the overwintered and summer groups. A significant proportion of beetles that colonized potato plots by flight emigrated from the plots by walking on the same day throughout each crop season. This suggests that most beetles use both flight and walking to disperse throughout the day depending on the “task” and environmental conditions. A large proportion of summer adults in prediapause condition retain the ability to disperse by flight when conditions are appropriate such as in 1991 in this study. Results confirm that potato beetle recruits counted on plants or collected in ground traps have an overall 0.41 sex ratio but those collected in flight traps have a 0.52 sex ratio. There was no indication that the sex ratio plays a significant role in determining the relative contribution of walking and flight to recruitment. A diapausing switch in early August responsible for prediapausing conditions in the summer population of beetles occurs in New Brunswick. The switch did not entirely prevent dispersal to the crop by flight as reported elsewhere for more southern locations.

Effectiveness of Glues Used for Harmonic Radar Tag Attachment and Impact on Survival and Behavior of Three Insect Pests

ABSTRACT The ability of three cyanoacrylate glues to ensure a durable bond between the Colorado potato beetle, Leptinotarsa decemlineata (Say), the plum curculio, Conotrachelus nenuphar (Herbst), or the corn rootworms (Western Corn Rootworm, Diabrotica virgifera virgifera LeConte and Northern Corn Rootworm, Diabrotica longicornis Smith and Lawrence) and the harmonic radar tag without impact on behavior and survival was assessed as part of a study on the use of harmonic radar technology to track these insect pests. Droplets of 0.1 mg of Krazy Glue, Loctite, and Bowman FSA applied to the pronotum had no effect on the survival of the Colorado potato beetle or plum curculio after 5 and 7 d, but caused >40% mortality after only 4 h with both the western and northern corn rootworms. The three glues created an effective bond lasting 4–5 d between the harmonic radar tag and the Colorado potato beetle in >85% of cases and the plum curculio in almost 50% of cases. There was no detectable impact of the glue treatment on feeding or walking behavior of the Colorado potato beetle. Analysis of the same behaviors with the plum curculio showed no impact on the ability to walk on a vertical surface, the speed of travel, or the duration of travel. There was no significant impact on feeding by female plum curculio but indication that males treated with Krazy Glue fed less. Overall, results quantified the effectiveness of the cyanoacrylate glues at providing a durable bond with no significant impact on mobility or behavior of the Colorado potato beetle or plum curculios. However, the toxicity of the glues against the corn rootworms suggests that similar toxicity or sublethal effects may exist with other insects.