Simulated Field Trials Research Articles

Chemical Stem Barriers for the Control of Ants (Hymenoptera: Formicidae) in Vineyards

Ants significantly reduce the efficacy of biological control of the mealybug Planococcus ficus (Signoret) in vines. Two trials were conducted to find a cost-effective method for ant control that is environmentally friendly, practicable and acceptable in an integrated pest management programme. Thirteen chemical stem barriers were assessed for the control of two ant species, Linepithema humile (Mayr) and Anoplolepis custodiens (Smith), in two field trials during two seasons. Four of the treatments that showed high efficacy in the field trials were also evaluated in two simulated field trials for the control of L. humile and Anoplolepis steingroeveri (Forel) due to high variability in pre-treatment counts that occurred in the field trials. Treatments showing the highest efficacy against L. humile and A. custodiens in field trials were the chlorpyrifos-impregnated band and the terbufos slow-release band. Alphacypermethrin SC at 10 mL/L was effective against L. humile and has subsequently been registered as a chemical stem barrier on vines. The treatment showing the highest efficacy against A. steingroeveri in the simulated field trial was alphacypermethrin SC at 20 mL/L. In the simulated field trial, a decline in ant infestation was observed five to six weeks after application of treatments. The most likely explanation is that chemical stem barriers result in ant mortality, although other reasons for this decline are discussed. It is recommended that suitable bioassay techniques, which expose ants to the treated substrate for a limited period, thereby simulating field conditions, be developed in order to determine if chemical stem barriers result in ant mortality.

The Application of PSO-AFSA Method in Parameter Optimization for Underactuated Autonomous Underwater Vehicle Control

In consideration of the difficulty in determining the parameters of underactuated autonomous underwater vehicles in multi-degree-of-freedom motion control, a hybrid method that combines particle swarm optimization (PSO) with artificial fish school algorithm (AFSA) is proposed in this paper. The optimization process of the PSO-AFSA method is firstly introduced. With the control simulation models in the horizontal plane and vertical plane, the PSO-AFSA method is elaborated when applied in control parameter optimization for an underactuated autonomous underwater vehicle. Both simulation tests and field trials were carried out to prove the efficiency of the PSO-AFSA method in underactuated autonomous underwater vehicle control parameter optimization. The optimized control parameters showed admirable control quality by enabling the underactuated autonomous underwater vehicle to reach the desired states with fast convergence.

Cooperative Path Planning for Range-Only Localization Using a Single Moving Beacon

Underwater navigation that relies solely on dead reckoning (DR) suffers from unbounded position error growth. A common approach for alleviating the problem is to have the underwater vehicle surface occasionally for a Global Positioning System (GPS) fix, at the risk of jeopardizing the vehicle's safety and consuming precious mission time. Other alternatives include deploying a long-baseline (LBL) acoustic positioning system in the mission area; this involves substantial deployment effort. The idea of having active mobile beacons as navigational aids has recently gained interest. We explore the use of a single-beacon vehicle for range-only localization to support other autonomous underwater vehicles (AUVs). Specifically, we focus on cooperative path-planning algorithms for the beacon vehicle using dynamic programming and Markov decision process formulations. These formulations take into account and minimize the positioning errors being accumulated by the supported AUV. This approach avoids the use of LBL acoustic positioning systems as well as allows the supported AUV to remain submerged for a longer period of time with small position error. Simulation results and field trials data demonstrate that the beacon vehicle is able to help keep the position error of the supported AUV small via acoustic range measurements.

Container volume and growing density influence western larch (Larix occidentalis Nutt.) seedling development during nursery culture and establishment

Larch tree species (Larix Mill.) are both ecologically and commercially valuable in their native range and are the focus of many restoration, afforestation, and commercial reforestation efforts in the boreal forests of the northern hemisphere. Land use change, shifting climate, and poor natural regeneration are making it increasingly difficult to establish the species; therefore, artificial regeneration is critical to ensure this timber species maintains its productive role on the landscape. New stocktypes are continually being developed to aid target seedlings for difficult sites, and critical, non-confounding evaluations of them are needed for target seedling development. This research evaluates the effect of container parameters on potential target seedlings. It examines tolerance thresholds of western larch (Larix occidentalis Nutt.) with respect to moisture and temperature status in the rhizosphere during early establishment. A suite of morphological measurements was used to assess seedling quality and relative performance following transplant. Modifying a commercially available container developed four distinct stocktypes of 111, 143, 175 and 207 ml that were paired with a volume-dependent nutrient regime at two culturing densities. Seedling phenotype was affected to a greater extent by container density than by container volume. Despite changes to container volume, root:shoot were found to be similar, indicating benefits of a tailored nutrient regime during nursery culture. Simulated field trials revealed that a low density growing arrangement improved post-transplant seedling growth, specifically root growth. Also, the 207 ml container facilitated greater growth in dry soil conditions compared to smaller containers. Lower (10 °C) rhizosphere temperature hindered root growth; however, seedling survival was 100 %, warranting the testing of earlier outplanting windows for this species. This evaluation of stocktype performance contributes to a greater body of work with this species and its congeners, which will ultimately benefit reforestation and afforestation efforts alike.

Bio-efficacy and persistence evaluation of Dimilin<sup>®</sup>GR-2% and Mosquiron<sup>® </sup>10 EC insect growth regulators against <i>Anopheles gambiae</i> s.l (diptera: Culicidae) larvae

Expansive chemical-based vector control has resulted in development of vector resistance to different insecticides harnessed for prevention of disease transmission in public health. The environmentally safe insect growth regulators and microbial larvicides provide potential tools for insecticide resistance management. The efficacy and persistence of Dimilin GR-2% and Mosquiron 10 EC insect growth regulators were evaluated against Anopheles gambiae s.l larvae under laboratory and simulated field conditions. In laboratory bio-efficacy trials, complete emergence inhibition was achieved at higher concentrations with 96 hours post exposure of mosquito aquatic stages to the two larvicides. In simulation field trials, persistence of both larvicides at higher concentrations increased gradually with complete inhibition attained at 7 days and maintained up to 21 days. In the quest of deploying non insecticide based interventions for a sustainable environment, insect growth regulators can be recommended for operational scale larviciding for mosquito larval control in the context of integrated vector management.

Field efficacy of expanded polystyrene and shredded waste polystyrene beads for mosquito control in artificial pools and field trials, Islamic Republic of Iran

Concerns about traditional chemical pesticides has led to increasing research into novel mosquito control methods. This study compared the effectiveness of 2 different types of polystyrene beads for control of mosquito larvae in south-east Islamic Republic of Iran. Simulated field trials were done in artificial pools and field trials were carried out in 2 villages in an indigenous malaria area using WHO-recommended methods. Application of expanded polystyrene beads or shredded, waste polystyrene chips to pool surfaces produced a significant difference between pre-treatment and post-treatment density of mosquitoes (86% and 78% reduction respectively 2 weeks after treatment). There was no significant difference between the efficacy of the 2 types of material. The use of polystyrene beads as a component of integrated vector management with other supportive measures could assist in the control of mosquito-borne diseases in the Islamic Republic of Iran and neighbouring countries.

Field trials to attract questing stages of brown dog tick, Rhipicephalus sanguineus using tick pheromone–acaricide complex

Evaluations were made to assess the efficacy of assembly pheromone, attractant sex pheromone and the kairomone carbon dioxide in attracting the questing larval nymphal and adult stages of the brown ear dog tick, Rhipicephalus sanguineus. Ticks attracted to one location were killed using the acaricide deltamethrin. Initially, simulated field trials were conducted to observe the percentage of attraction of ticks from different distances. Tick lure comprising of carbon dioxide as kairomone and 2,6-dichlorophenol in combination with assembly pheromone and deltamethrin on a thermocol platform was prepared and field trials were conducted in the kennels of Blue Cross Society of India, Velachery, Chennai. The tick lure attracted larval, nymphal and adult stages of R. sanguineus ticks in and around the kennels. Observations were made after 24h of placing the tick lure. In simulated field out of the 50 ticks used for each distance trials, positive response was exhibited by a total number of 20 (40%), 17 (34%) and 14 (28%) ticks from 0.5, 1 and 1.5m, respectively. Field trials conducted revealed considerable attraction of larvae and nymph to the tick lure. Few adult ticks (2-5) were also lured to the pheromone impregnated filter paper disc.

Evaluation of the insect growth regulator Lufenuron (Match®) for control of Aedes aegypti by simulated field trials

The insect growth regulator, Lufenuron, at concentrations of even multiples of LC(90) (determined under laboratory conditions) was tested against the III instar larvae of Aedes aegypti under simulated field conditions. For all concentrations tested, 100 % mortality of the larvae was observed within 24 h of exposure to Lufenuron-treated water. In experiments with LC(90) × 4 Lufenuron concentration and where 15 % of water volume was replaced daily, percent mortality of the larvae was reduced to 40 % after the 54th day of treatment. Percentage mortality of the III instar larvae on the 54th day was higher in water with LC(90) × 6 concentration than that observed for water with LC(90) × 4 of Lufenuron. In the experiments with LC(90) × 4 and LC(90) × 6 concentrations of Lufenuron where 15 % of water volume was replaced weekly, larval mortality obtained after the eighth week was 68.75 and 88.33 %, respectively. In LC(90) × 4 and LC(90) × 6 of Lufenuron-treated stagnant water (without replacement of water), the percent mortality of the larvae on the 55th day was 65 and 90 %, respectively. Introducing a fresh batch of III instar A. aegypti larvae in the Lufenuron-treated waters revealed that residual activity of Lufenuron was sustained for 45 days after the treatment. All these experiments revealed that Lufenuron not only affects the prevalence of the A. aegypti larvae but also induces the development of abnormal adults.

Larvicidal activity of micronized aqueous suspension of calcium hydroxide against Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae)

In the search of alternatives for the control of mosquitoes of medical importance, we evaluated the larvicidal activity of micronized suspensions of calcium hydroxide [Ca(OH)₂] against Aedes aegypti and Culex quinquefasciatus. Tests conducted under laboratory conditions determined a LC50 = 0.027% (LC90 = 0.096%) for A. aegypti and a LC50 = 0.092% (LC90 = 0.2%) for C. quinquefasciatus, at 24 h post-treatment. Considering that the LC50 for the less susceptible species killed 100% of larvae for both species at 48 h post-treatment, we decided to use the diagnostic concentration of 0.1% which eliminated 100% of larvae at 48 h under a simulated field trial. There was a residual effect for up to 84 and 70 days for A. aegypti and C. quinquefasciatus, respectively. Evaluation of Ca(OH)₂ on breeding sites showed a larvicidal activity of 100% for up to 56 days. When the micronized Ca(OH)₂ was incorporated at concentrations from 0.02% (w/v), a superficial film was formed which killed 100% of the larvae of both species after 24 h of contact, and the activity remains until the film broke apart due to stirring. The fact that Ca(OH)₂ is cheap and the people in rural areas of Mexico and other countries know the handling procedures for this compound led us to consider that 0.1% suspensions of Ca(OH)₂ could be used for mosquito control in deposits of water placed in human premises both in urban and rural areas.

Development of a Practical Method for Using Ozone Gas as a Virus Decontaminating Agent

Our objective was to develop a practical method of utilizing the known anti-viral properties of ozone in a mobile apparatus that could be used to decontaminate rooms in health care facilities, hotels and other buildings. Maximum anti-viral efficacy required a short period of high humidity (>90% relative humidity) after the attainment of peak ozone gas concentration (20–25 ppm). All 12 viruses tested, on different hard and porous surfaces, and in the presence of biological fluids, could be inactivated by at least 3 log10, in the laboratory and in simulated field trials. The ozone was subsequently removed by a built-in catalytic converter.

Evaluating a nonionic surfactant as a tool to improve water availability in irrigated cotton

AbstractNonionic surfactants have been well researched in turf grass environments as a tool to ameliorate water‐repellant conditions. However, few studies have evaluated the risks and benefits of nonionic surfactant applications in row‐crop agricultural systems. The objective of this study was to evaluate the impact of a nonionic surfactant on cotton (Gossypium hirsutum L.) production on a Faceville loamy sand (fine, kaolinitic thermic Typic Kandiudult) in the coastal plain region of Georgia. The experiment consisted of two components: (1) on‐site rainfall simulation and (2) agronomic cotton field trials. Treatments were designed to test the impact of rate and frequency of surfactant applications using six combinations of application rates and timings. For the rainfall simulation component, only the control (0·0 L ha−1) and high rate (0·51 L ha−1) of surfactant applications were evaluated. During the field trial, soil water content, cotton stand counts, and yield were measured. Rainfall simulations showed that the addition of surfactant increased runoff, decreased infiltration, and promoted surface sealing. Despite the demonstrated potential for water loss, agronomic field trials showed that crop yields were not significantly different between surfactant‐treated and untreated plots. No differences in soil water content were observed between treatments at 5 and 15 cm depths; however, soil water content was significantly higher in untreated control plots at the 30 cm depth. Data demonstrate the need for clarification of soil physical/chemical properties and surfactant interactions that may lend themselves to the creation of surface seals and how these seals impact soil/water conservation and crop yield. Published in 2009 by John Wiley & Sons, Ltd.

Efficacy of Agnique® MMF Monomolecular Surface Film Against Anopheles stephensi Breeding in Urban Habitats in India1

Efficacy of Agnique MMF, a monomolecular film formulation, was tested against immatures of Anopheles stephensi, an urban malaria vector in India, in simulated and natural habitats. Simulated field trials carried out in cement tanks showed 100% inhibition of adult emergence for up to 1 wk at 0.4 ml/m2 and up to 3 wk at 1 ml/m2. A small-scale field trial in tanks and wells at 1 and 2 ml/m2 produced more than 75% reduction of late instars and 100% reduction of pupae on day 1. The reduction in pupae at 1 and 2 ml/m2 lasted up to 2 wk in tanks and 5 wk in wells. These results suggest that Agnique MMF could be used as one of the choices in an urban malaria control program.

Road Slope and Vehicle Mass Estimation Using Kalman Filtering

SUMMARYKalman filtering is used as a powerful method to obtain accurate estimation of vehicle mass and road slope. First the problem of estimating the slope when the vehicle mass is known is studied using two different sensor configurations. One where speed is measured and one where both speed and specific-force is measured. A filter design principle is derived guaranteeing the estimation error under a worst case situation (when assuming first order dynamics). The simultaneous estimation problem required an Extended Kalman Filter (EKF) design when measuring speed only whereas the additional specific force ease yielded a simple filter structure with a time-variant measurement equation. Additionally the filter needs present propulsion force which in our case is calculated form the engine speed and amount of fuel injected. When the vehicle uses the foundation brakes the estimates are frozen since varying friction properties makes the braking force unknown. Both sensor configurations are concluded to be robust and accurate by simulation and experimental field trials.

A lantern color vision test for the rail industry

Correct identification of wayside signal colors is critical for safe operation of railway equipment. However, evaluating color discrimination using just a screening test may not be occupationally relevant. A lantern test (CNLAN) was designed to provide a functional assessment of color discrimination for the rail industry. It was validated against a simulated field trial. 81 individuals with normal color vision and 74 individuals with congenital red-green defects participated. Color vision was classified using the Nagel Anomaloscope. Using a criterion based on the worst-normal performance, 97% of the individuals with a color vision defect failed both the CNLAN and simulation trial. This value is slightly lower than the 100% who failed both the Ishihara test and simulation. However, the Ishihara test also failed 3.7% of the color-normals who passed both the simulation and lantern, whereas by definition none of the color-normals failed the lantern. This lantern test provides a reasonable functional assessment of one's ability to identify rail signal colors; especially when a strict failing criterion is applied to screening tests.

A MATHEMATICAL MODEL FOR PREDICTING THE PERSISTENCE AND EFFICACY OF BACILLUS THURINGIENSIS VAR ISRAELENSIS IN RELATION TO WATER POLLUTION

In a simulated field trial, the bead formulation of Bacillus thuringiensis var israelensis (Bti) was found to be more persistent in moderately polluted as compared to highly polluted water. A mathematical model was built up to study the influence of time (independent variable) on larval reduction (dependent variable) in relation to degree of water pollution. Two predictive models for different grades of water pollution were developed, which estimated that the larval mortality in moderately polluted water was likely to decline by 3.79 as compared to 5.02 on an average, in highly polluted water with each passing day.

Microbial Control of Schistocerca americana (Orthoptera: Acrididae) by Metarhizium flavoviride (Deuteromycotina): Instar Dependent Mortality and Efficacy of Ultra Low Volume Application Under Greenhouse Conditions

The entomopathogenic fungus Metarhizium flavoviride Gams & Rozsypal has been widely tested for the suppression of African grasshoppers, but there has been no research on Nearctic species. We examined the potential of M. flavoviride for the control of the American grasshopper, Schistocerca americana (Drury). When tested under conidial dosages of 1.2 x 10 3 , 1.2 x 10 4 , and 1.2 x 10 5 , 4th-instar S. americana were significantly more susceptible to M. flavoviride than 6th-instar and adult S. americana. At the conidial dosage of 1.2 x 10 5 , M. flavoviride produced 89.7, 12.8, and 17.6% mean mortality 7 d after treatment in 4th-instar, 6th-instar, and adult S. americana, respectively. By the 14th d after treatment, the M. flavoviride conidial dosage of 1.2 x 10 5 produced 99.4, 86.1, and 80.8% mean mortality in 4th-instar, 6th-instar, and adult S. americana, respectively. The LD 50 estimates for M. flavoviride of 1.7 x 10 4 conidia for the 4th-instar, 1.3 x 10 4 conidia for the 6th-instar, and 3.1 x 10 4 conidia for the adult S. americana are generally greater than those used for other acridids. Furthermore, mortality in M. flavoviride-treated S. americana was positively dosage dependent, as described by mean percentage of cumulative mortality and LT 50 estimates. Greenhouse trials evaluating ultra low volume application to grasshoppers, foliage, or grasshoppers and foliage produced from 78.1 to 92.0% mean mortality 14 d after treatment. In this simulated field trial, grasshoppers and M. flavoviride were exposed to temperatures ranging from 10 to 40°C, which demonstrated the potential of M. flavoviride to be effective under large temperature fluctuations, as may occur in the field.

Simulated Field Trials to Evaluate the Effect of Sargochromis codringtoni and Tilapia rendalli on Snails in the Presence and Absence of Aquatic Plants

Two cichlid fish were studied under semi-natural conditions to evaluate their potential as agents for the biological control of schistosome intermediate host snails. Sargochromis codringtoni is known to eat snails, whereas Tilapia rendalli survives primarily on aquatic plants but may ingest snail egg masses and juvenile snails. Sargochromis codringtoni reduced snail numbers significantly, but this effect was less pronounced when plants were present. Tilapia rendalli did not significantly reduce the biomass of aquatic plant species used in the experiment, but did significantly reduce snail numbers, albeit to a much lesser extent than observed for S. codringtoni. It was concluded that the two fish species may complement each other in the control of schistosome intermediate host snails, but further investigations are needed to determine: whether they can co-exist in nature, and the extent to which T. rendalli can control other species of aquatic plants under natural conditions.

FIELD TRIAL OF Bacillus thuringiensis var israelensis PELLET FORMULATION IN THE CONTROL OF MOSQUITOES

In a simulated field trial Bacillus thuringiensis var israelensis (BTI) pellet formulation exhibited an enhanced efficacy with increasing dose. A dosage of 1.0 and 1.5 ppm was most effective under simulated field conditions. In field trials persistence of BTI pellet (1.0 ppm) was observed for 35 days in moderately polluted water collection as compared to 21 days in highly polluted water bodies.

Fahud Field Review: A Switch From Water to Gas Injection

Summary The water injection schemes implemented in the Fahud field during the early 1970's led to poor recoveries because the reservoirs were both fractured and oil-wet. On the basis of the results of a thorough performance review, it was decided in 1983 to promote gas/oil gravity performance review, it was decided in 1983 to promote gas/oil gravity drainage fully by drilling rows of downdip producers and switching completely from water to gas injection. This paper investigates the reasons behind each stage of development and reviews recent efforts to evaluate the future production potential through the use of dual-porosity simulators. Introduction The Fahud field (Fig. 1), which has a stock-tank oil initially in place (STOIIP) of 1000 × 10(6) stock-tank m3 [6,300 × 10(6) STB], is an elongated monocline with an eroded fault escarpment. The field is divided by a permeability barrier into two accumulations, Fahud North-West (NW) and South-East (SE), each of which contains three fractured Natih limestone reservoirs. The three Fahud NW reservoirs (NW-A, NW-C/D, and NW-E/F/G) are separated by continuous shales but are in communication with each other across the eroded fault escarpment (Figs. 2 and 3). The same applies to the three Fahud SE reservoirs (SE-A, SE-C/D, and SE-E). The oil has a density of 870 kg/m3 [31 deg.API] with initial reservoir fluid properties as presented in Table 1. The field was discovered in 196 properties as presented in Table 1. The field was discovered in 196 and started production in 1967. To date, 12 % of the field's STOIIP has been produced. This paper reviews the field's performance during four distinct phases of development: initial, waterflood, reassessment, and present development. Initial Development 1967–71. The field was initially produced under natural depletion supplemented in 1968 by gas injection. The high offtake rates led to a rapid displacement of the gas/oil contact (GOC), which resulted in the early gassing out of a number of relatively downdip completions. Simulation studies and field trials were conducted, which concluded that better recoveries would be obtained through waterflooding. Waterflood Period-1972–80. Following the recommendations, water injection schemes were implemented in four of the six Fahud reservoirs. However, they failed to arrest either the pressure or oil production decline. Reassessment Period-1981–83. The poor performance of the waterflood led to a thorough review during which a number of thermal decay time (TDT) logs and tracer tests were conducted. It was concluded that because the reservoir rock was both fractured and oil-wet, recovery factors from waterflooding were low and could be substantially improved by reverting to full-scale gas/oil gravity drainage. Present Development-From 1984. The present policy is to promote gas/oil gravity drainage fully. This ongoing development promote gas/oil gravity drainage fully. This ongoing development requires the phasing out of water injection, the completion of downdip grids of producers, and the full replacement of voidage by gas injection. Dual-porosity simulation studies are currently being conducted to optimize the remaining development and to predict the future field performance.

Mathematical models of the population biology of Ostertagia ostertagi and Teladorsagia circumcincta, and the economic evaluation of disease control strategies

The construction and use of mathematical models of the population biology of Ostertagia ostertagi and Teladorsagia circumcincta is discussed. Simulated field trials implemented by deterministic mathematical models currently share with actual field trials the disadvantage that they convey no information concerning the risk associated with the net return demonstrated by the trial. This has important implications when it is necessary to rank disease control strategies in order of usefulness.