Field Efficacy Trials Research Articles

Toxicity and efficacy of spiromesifen, a tetronic acid insecticide, against sweetpotato whitefly (homoptera: aleyrodidae) on melons and collards

Laboratory bioassays were conducted to determine the toxicity of spiromesifen, a tetronic acid insecticide to eggs, nymphs, and adults of the sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype “B”, on melon and collard. Two field trails we also conducted to determine the efficacies of spiromesifen at four different rates (96, 112, 114, and/or 149 g [AI]/ha) against B. tabaci on melon and collards. Foliar sprays of thiamethoxam and/or buprofezin were used for comparisons. In laboratory bioassays, spiromesifen was highly toxic to nymphs of B. tabaci on both melon and collard, causing ≈100% mortality to young nymphs (first and second instars). Spiromesifen was moderately toxic to old nymphs (third and fourth instars), but not toxic to eggs (2.8–6.3% on melon and 2.9–6.4% on collard and slightly toxic to adults 4.5–15.1% on melon and 25.1–37.0% on collard). Spiromesifen was also highly toxic to the early first instars or crawlers that hatched from the survived spiromesifen-treated eggs, and they died shortly after they became sessile on treated leaf surfaces. Field efficacy trials indicate that spiromesifen showed excellent promise as a foliar spray. One application of spiromesifen at a rate of 149 g [AI]/ha or two applications at 122 and 149 g [AI]/ha were as effective as two applications of thiamethoxam and buprofezin on melons. On collards, three rates of spiromesifen (96, 114 and 149 g [AI]/ha) provided similar control to buprofezin. Because of its unique mode of action and chemistry, spiromesifen might have potential in integrated whitefly management programs and insecticide resistance management on vegetables and other field crops.

Immune response measured in human volunteers vaccinated with autoclavedLeishmania majorvaccine mixed with low dose of BCG

The immune responses induced against Leishmania antigens in volunteers who were vaccinated in a double-blind, randomized field efficacy trial of a preparation of autoclaved Leishmania major (ALM) mixed with a low dose of Bacille Calmette-Guerin vaccine (BCG) who developed either a cutaneous leishmaniasis (CL) lesion due to exposure to infected sandfly bite(s) or did not develop a lesion during the course of the trial were studied and compared with those of non-vaccinated controls. Blood samples were also assayed from different groups including volunteers with history of CL and volunteers with previous positive or negative leishmanin skin test (LST) without a history of CL. The vaccinated volunteers had received a single dose of either ALM mixed with a low dose of BCG or the same dose of BCG alone. The LST and in vitro proliferative response (stimulation index, SI), interferon gamma (IFN-gamma) production and, in a few cases, interleukin (IL)-4 production of peripheral blood mononuclear cells to soluble Leishmania antigens were measured. The results indicated that volunteers who developed CL in the vaccine arm showed a slightly higher SI than cases who received BCG alone. Volunteers with history of CL and volunteers with positive LST demonstrated the strongest proliferation indices and IFN-gamma production. The data suggest that a single dose of ALM + BCG induces a weak Th1 response in vaccinated volunteers that is far lower than that in volunteers with prior subclinical infection or volunteers with history of CL, who are presumed to be immune.

Staple food fortification with iron: a multifactorial decision.

Iron deficiency is not restricted to infants and pregnant women; it also affects school-age children, adolescents, elders, and even adult males in developing countries, including those of Latin America. Therefore, interventions with extensive coverage are suitable to prevent and to control this deficiency. Fortification of staple foods is an adequate strategy to provide additional iron to populations. However, unlike fortification with vitamin A, iodine, and B vitamins, food fortification with iron has not been very successful. Iron is a reactive compound, whose level in foods is limited because iron causes negative changes in the original properties of the food that is being fortified. This feature combined with the low absorption of iron compounds used for fortification – usually not higher than 10%2 – makes prevention of iron deficiency through food fortification of very few commodities a great challenge. This review will cover several factors that need to be taken into consideration to plan, understand, evaluate, and make a decision about fortification of staple foods with iron. Included is a discussion regarding bioavailability, technologic compatibility, and cost effectiveness. To conclude, the review mentions additional advantages of fortifying staple foods with iron and the indispensable need to combine this strategy with other interventions. All of these factors must be considered before launching a field efficacy trial, which should be the ultimate proof for a decision made wisely and with possibilities of success.

Efficacy and effectiveness of attenuated, cold-adapted, trivalent intranasal influenza vaccine

Cold-adapted, live, attenuated, trivalent, intranasal influenza vaccine (CAIV-T) is well accepted, well-tolerated, highly protective against culture-confirmed influenza, and provides significant health benefits to children and adults. A 2-year, multicenter, double-blind, placebo-controlled efficacy field trial of CAIV-T in children aged 15–71 months with annual re-immunization revealed the vaccine to be highly protective against culture-confirmed influenza. Overall, during 2 years of study, vaccine was 92% protective against culture-confirmed influenza. During the second year of study, the vaccine was 86% protective against A/Sydney, a significantly drifted strain not well-matched to the vaccine. Antibody studies on children given CAIV-T revealed that high titers of cross-reacting antibodies to influenza A/Sydney were induced with vaccination by live attenuated influenza A/Wuhan. Effectiveness measures revealed significant reductions in febrile illness (21% reduction in year 1, 19% reduction in year 2), febrile otitis media (33% reduction in year 1, 16% reduction in year 2) and associated antibiotic use among vaccinated children compared with placebo recipients. In adults, vaccination with CAIV-T resulted in protection during experimental challenge with virulent wild-type viruses. An effectiveness trial in adults demonstrated significant benefits of CAIV-T vaccine (28% reduction in days of missed work for febrile illness days with associated 45% reduction in days taking antibiotics). General use of CAIV-T has the potential to significantly reduce the impact of influenza in children and adults.

Safety, efficacy and effectiveness of the influenza virus vaccine, trivalent, types A and B, live, cold-adapted (CAIV-T) in healthy children and healthy adults

Influenza is a major cause of illness. We have assessed the safety, efficacy, and effectiveness of CAIV-T vaccine. A two year, multicenter, double-blind, placebo-controlled, efficacy field trial in pre-school aged children was conducted; 1602 enrolled in Year One and 1358 (85%) returned in Year Two. In both study years combined, the overall vaccine efficacy against culture-confirmed influenza was 92% (95% CI: 88, 94). The vaccine efficacy was 95% (95% CI: 62, 99) against lower respiratory illness, 94% (95% CI: 90, 96) against febrile illness and 96% (95% CI: 88, 99) against otitis media associated with culture-confirmed influenza. A multicenter, double-blind, placebo-controlled, effectiveness field trial was conducted in 4561 working adults aged 18 to 64 years. Episodes and days of febrile illness (FI), severe febrile illness (SFI), febrile upper respiratory illness (FURI), work loss, and health care use were assessed. Vaccination significantly reduced the numbers of SFI, 18.8% reduction (95% CI: 7, 29), and FURI, 26.3% reduction (95% CI: 13, 33); and led to fewer days of illness (22.9% reduction for FI, 27.3% reduction for SFI), fewer days of work lost (17.9% reduction for SFI, 28.4% for FURI), and fewer days of health care provider visits (24.8% for SFI, 40.9% for FURI). Prescription antibiotics and over-the-counter medications were also reduced. The vaccine was generally safe and well tolerated with no vaccine related serious adverse events. LAIV represents an additional important option for the control of influenza.

Habitat and environmental factors influencing the control of migratory locusts ( Locusta migratoria) with an entomopathogenic fungus ( Metarhizium anisopliae)

Locusts are important pests in warm, semi-arid regions of the world. Traditionally, chemical insecticides have been used to control bands and swarms, but this is coming under great scrutiny. Metarhizium anisopliae is an entomopathogenic fungus, which is formulated in an oil to produce a biopesticide that has been tested in several countries. In Australia, field trials have indicated that efficacy is dependent on rate of application and vegetation cover, while rate of development of both the locust and Metarhizium is influenced by temperature. A model has been developed to assess the importance of these factors in the rate and effectiveness of control of migratory locusts ( Locusta migratoria) with Metarhizium using the Australian isolate FI-985. Model simulations suggest that three application rates may be required in field control operations: a low dose of 1×10 12 spores/ha when herbaceous cover was low; a high dose (5×10 12 spores/ha) where high cover will reduce the likelihood of locusts receiving spores directly from the spraying operation or from pickup from the vegetation; and a moderate dose where cover is moderate but where locusts are likely to pick up an infection from spores on the vegetation. Field efficacy trials are currently underway against the Australian plague locust ( Chortoicetes terminifera), spur-throated locust ( Austracris guttulosa) and wingless grasshopper ( Phaulacridium vittatum) and this model may be extended to these species in the future.

Evaluation of bait stations for control of urban rabbits

The acceptability of four different bait station designs (drum, slab, tyre, corrugated iron) to rabbits was tested in the field using unpoisoned oat bait. The drum (200 L, cut longitudinally) and the raised concrete slab (60 × 60 cm) designs were the most acceptable to rabbits. The raised tyre design was unacceptable, and this was supported by later field efficacy trials that compared the drum and tyre designs using 1080 One-shot oats. The efficacy of three of these designs (drum, slab, tyre) against ‘urban’ rabbits was assessed more fully using pindone oat bait. The tyre stations were again found to have little impact on rabbit numbers. With the exception of one drum site where pindone bait stations were totally ineffective, the proportional reductions in rabbit numbers for the remaining sites were similar between the drum (69%, n = 3) and slab (70%, n = 5) designs. However, the slab design provided much easier access to bait by non-target species (particularly birds), and we therefore recommend that the drum design would be the best bait station for controlling rabbits. The overall proportional reduction in rabbit numbers achieved with pindone bait stations was 48% (range 0–80%, n = 13), which is less than that usually achieved during broadacre control programs with pindone (60–90+%). In addition, these kills took 30–60 days to achieve, and as rabbit damage still occurred over this period, the use of pindone bait stations did not always result in damage mitigation or, ultimately, an economic benefit. Some potential problems associated with the use of pindone bait stations, such as the possibility of the development of ‘resistance’ to pindone bait and the risk to non-target species, are also discussed. The combined use of track counts and a ‘digs’ index proved a reliable indicator of changes in rabbit abundance.

Efficacy of vaccination with live attenuated, cold-adapted, trivalent, intranasal influenza virus vaccine against a variant (A/Sydney) not contained in the vaccine

Objective: To determine the safety, immunogenicity, and efficacy of revaccination of children with live attenuated influenza vaccine. Study design: A 2-year multicenter, double-blind, placebo-controlled, efficacy field trial of live attenuated, cold-adapted trivalent influenza vaccine administered by nasal spray to children. This report summarizes year 2 results, a year in which the epidemic strain of influenza A/Sydney was not well matched to the vaccine strains. Each year, vaccine strains were antigenically equivalent to the contemporary inactivated influenza vaccine. In year 2, a single intranasal revaccination was administered. Active surveillance for influenza was conducted during the influenza season by means of viral cultures. Influenza cases were defined as illnesses with wild-type influenza virus isolated from respiratory secretions. Results: In year 2, 1358 (85%) children, 26 to 85 months of age, returned for revaccination. The intranasal vaccine was easily accepted, well tolerated, and immunogenic. Revaccination resulted in 82% to 100% of the vaccinated children in a subset studied for immunogenicity being seropositive as compared with 26% to 65% of placebo recipients, depending on the influenza strain tested. No serious adverse events were associated with the vaccine. In addition to the strains in the vaccine, antibody was induced to the variant strain A/Sydney/H3N2. In year 2, influenza A/Sydney/H3N2, a variant not contained in the vaccine, caused 66 of 70 cases of influenza A; nonetheless, intranasal vaccine was 86% efficacious in preventing A/Sydney influenza. Eight cases of lower respiratory tract disease were associated with A/Sydney influenza; all cases were in the placebo group. Conclusions: This live attenuated, cold-adapted influenza vaccine was safe, immunogenic, and efficacious against influenza A/H3N2 (including a variant, A/Sydney, not contained in the vaccine) and influenza B. The characteristics of this vaccine make it suitable for routine use in children to prevent influenza. (J Pediatr 2000;136:168-75)

Hen eggs poisoned with sodium monofluoroacetate (1080) for control of stoats (Mustela erminea) in New Zealand

Control of stoats (Mustela erminea) using sodium monofluoroacetate (1080) injected into hen eggs was investigated in pen and field trials. For captive stoats, the LD50 of 1080 in hen eggs was 0.49 mg/kg and the LD90 was 0.70 mg/kg. In a field efficacy trial using 1080‐poisoned hen eggs in bait stations, consumption of eggs was reduced by 91.9% in the poison area relative to the non‐poison area within 22 days. Video recordings showed stoats, a possum, and a kea approached bait stations, but only stoats entered and ate eggs. In subsequent live‐trapping, one stoat was caught in 91.5 trap nights (1.09/100TN) in the poison area and eight stoats in 101 trap nights (7.92/100TN) in the non‐poison area. Assuming stoat numbers in the two areas were similar before poison‐baiting (a reasonable assumption based on egg consumption rates), this represents an 86.2% reduction in the number of stoats in the poison area relative to the non‐poison area. Success should be even greater in management operations, because 1080‐poisoned eggs could be left in the field for longer. Further trials using live‐trapping or radio‐telemetry to monitor stoat survival are needed to substantiate these results.

The use of bacterial larvicides in mosquito and black fly control programmes in Brazil.

Bacillus spp. based larvicides are increasingly replacing, with numerous advantages, chemical insecticides in programmes for controlling black fly and mosquito populations. Brazil was among the pioneers in adopting Bacillus thuringiensis israelensis (B.t.i) to control black flies. However, the major current mosquito control programme in Brazil, the Programme for Eradication of Aedes aegypti launched in 1997, only recently decided to replace temephos by B.t.i based larvicides, in the State of Rio de Janeiro. In the last decade, works developed by research groups in Brazilian institutions have generated a significant contribution to this subject through the isolation of B. sphaericus new strains, the development of new products and the implementation of field trials of Bacillus efficacy against mosquito species under different environmental conditions.

Laboratory testing of a lethal ovitrap for Aedes aegypti

Laboratory tests were conducted to determine the feasibility of making the mosquito ovitrap lethal to Aedes aegypti (L.) when they attempt to oviposit in the trap. Heavy-weight velour paper strips (2.54 x 11 cm) were used as an alternative to the wooden paddle normally provided as a substrate for mosquito oviposition. The paper strips were pretreated with insecticide solutions and allowed to dry before being used in oviposition cups of 473 ml capacity, filled with water initially to within 2.5 cm of the brim. Insecticides chosen for their quick knock-down efficacy were bendiocarb 76% WP (1.06 mg a.i./strip) and four pyrethroids: permethrin 25% WP (0.16 mg a.i./strip), deltamethin 4.75% SC (0.87 mg a.i./strip), cypermethrin 40% WP (2.81 mg a.i./strip), and cyfluthrin 20% WP (0.57 mg a.i./ strip). For experimental evaluation, two oviposition cups (one with an insecticide-treated strip and one with an untreated strip) were placed in cages (cubic 30 cm) with gravid female Ae. aegypti mosquitoes (aged 6-8 days) from a susceptible laboratory strain. Mortality-rates of female mosquitoes were 45% for bendiocarb, 47% for permethrin, 98% for deltamethrin, 100% for cypermethrin, and 100% for cyfluthrin. Young instar larvae added to the treated cups died within 2h. After water evaporation from the cups for 38 days, fresh mosquito females had access to previously submerged portions of the velour paper paddle, and mortality rates of 59% or more occurred. Cups that had water (360 ml) dripped into them, to simulate rain, produced female mosquito mortality rates of > 50% and all larvae died within 3 h of being added. These tests demonstrate that the ovitrap can be made lethal to both adults and larvae by insecticidal treatment of the ovistrip. Field efficacy trials are underway in Brazil to access the impact of this simple, low-cost, environmentally benign approach on populations of the dengue vector Ae. aegypti.

Determination of the tree row volume in stone‐fruit orchards as a tool for adapting the spray dosage

The tree row volume model is a method for adapting dosage and spray volumes to tree crops. The method can potentially facilitate the comparison of field efficacy trials and can contribute to fanners’effective and rational use of plant protection products. It has been developed and applied in pome fruit but not yet in stone fruit. Stone‐fruit orchards vary considerably in tree size, tree shape and distance between tree rows. Based on 700 detailed measurements of stone‐fruit trees in south‐eastern France, in southern Germany and in Switzerland, a multiple linear regression was computed that allows the calculation of tree row volume from the height and maximum width of the tree crown, and the distance between tree rows. Seasonal increases of tree row volumes in stone‐fruit orchards were most pronounced in May and June, and the increase was usually greater in young orchards than in older ones.

An intranasal challenge model for testing Japanese encephalitis vaccines in rhesus monkeys.

Placebo-controlled field efficacy trials of new Japanese encephalitis (JE) vaccines may be impractical. Therefore, an animal model to evaluate efficacy of candidate JE vaccines is sought. Previous work has shown that exposure of monkeys to JE virus (JEV) via the intranasal route results in encephalitis. Here we report the further development of this model and the availability of titered virus stocks to assess the protective efficacy of JE vaccines. To determine the effective dose of our JE challenge virus, dilutions of a stock JEV (KE-93 isolate) were inoculated into four groups of three rhesus monkeys. A dose-dependent response was observed and the 50% effective dose (ED50) was determined to be 6.0 x 10(7) plaque forming units (pfu). Among animals that developed encephalitis, clinical signs occurred 9-14 days postinoculation. Infection with JEV was confirmed by detection of JEV in nervous tissues and IgM to JEV in the cerebrospinal fluid. Viremia with JEV was also detected intermittently throughout infection. Validation of the model was performed using a known effective JE vaccine and saline control. One ED90 of virus (2.0 x 10(9) pfu) was used as a challenge dose. Four of four animals that received saline control developed encephalitis while one of four monkeys administered the JE vaccine did so. This study demonstrates that the virus strain, route of inoculation, dose, and the outcome measure (encephalitis) are suitable for assessment of protective efficacy of candidate JE vaccines.

COMPARISON OF SURFACE AND SUBSURFACE APPLICATION OF AN EXPERIMENTAL INSECTICIDE FOR THE CONTROL OF MOLE CRICKET NYMPHS IN TURF, 1998

COMPARISON OF SURFACE AND SUBSURFACE APPLICATION OF AN EXPERIMENTAL INSECTICIDE FOR THE CONTROL OF MOLE CRICKET NYMPHS IN TURF, 1998: A field efficacy trial was performed to evaluate rate and application placement of an experimental insecticide (CGA-293343) for the control of mole cricket nymphs. Plots 16 ft x 85 ft were established on a heavily infested bermudagrass driving range at Oyster Bay Golf Links near Sunset Beach in Brunswick Co., NC. Treatments were replicated four times and randomly assigned to the plots. The timing of application was targeted to coincide with peak hatch for the control of small nymphs. Two of the treatments (Dursban Pro 2E, subsurface appliedand surface-applied Merit 75 WP) were applied on 25 Jun. All subsurface treatments were applied using a tractor-drawn ToroR Subsurface Liquid Injector delivering a volume of 150 gpa of liquid insecticide mixture at 150 psi. All broadcast applications were applied using a John Deere Turf Gator-mounted research sprayer delivering 23 gpa. The fairway irrigation system was used to apply 0.25 inch of water to the entire test site immediately after application. All other treatments (CGA-293343 25WG) were applied on 28 Jun. Soapy water flush sampling of the test site indicated that the population was approximately 79% MC and 21% TMC. The first evaluation of the plots on 14 Jul involved flushing three separate one m2 previously damaged areas of each plot with soapy water and counting the number of nymphs that came to the surface. The average number of nymphs found in each plot is reported in the Table. Plots were evaluated for fresh damage on 21 Jul, and 5, 20 Aug using a 1 m2 grid. The grid, divided into nine subsections, was placed randomly in each plot and a damage rating (0-9) was given depending on the number of subsections in which fresh damage was observed (with 0 = no damage and 9 = severe damage). Ten damage ratings were taken in each plot on each sampling date. Actual damage means are presented in the Table. All data were transformed (check)X + 0.5 prior to ANOVA and Tukey's Studentized Range Test (HSD).

High Pressure Liquid Injection of Imidacloprid for the Control of Mole Cricket Nymphs, 1997

Abstract A field efficacy trial was performed to evaluate the timing and placement of imidacloprid (Merit 75 WP) applications for the control of mole cricket nymphs. Plots 16 ft X 70 ft were established on a heavily infested bermudagrass fairway at the Fox Squirrel Country Club in Brunswick Co, NC. Treatments were replicated four times and randomly assigned to the plots. The first insecticide treatments (egglay/hatch) were applied on 4 Jul. The 4-inch soil temperature on this date was 88°F. Air temperature was 93°F. Broadcast applications were made using a CO2-powered backpack sprayer delivering 30 gpa. Subsurface treatments were applied using a self-propelled SGI™ Subsurface Injection System to inject the liquid insecticide mixture to a depth of 1 inch using high-pressure (2800 psi) pulses. At this depth the equipment applies approximately 1.0 gal/100 ft2. Insecticides were injected every 4 inches in 4-inch strips to produce a 4-inch X 4-inch treatment pattern. According to the equipment’s designer, the insecticide spreads out below the soil surface into a circular treatment area approximately 1 inch in diam. The fairway irrigation system was used to apply 0.25 inch of water to the entire test site immediately after application. The same equipment was used again on 31 Jul to apply the subsurface treatment directed against early and midsize nymphs. Soil was moist at the time of application and the 4-inch soil temperature was 75°F. Soil at the test site was classified as a Kureb fine sand with a pH of 5.8 and 0.56% humic matter. Soapy water flush sampling of areas adjacent to the test indicate that the fairway population was approximately 85% SB and 15% SV. Plots were evaluated for fresh damage on 14, 20 Aug, and 10 Sep using the damage grid evaluation method of Mack and Cobb (1989). A m2 grid divided into nine subsections was placed randomly in each plot and a damage rating (0-9) given depending on the number of subsections in which fresh damage was observed. Five damage ratings were taken in each plot on each sampling date. Actual damage means are presented in the Table. All data were transformed x + 0.5 prior to ANOVA and Tukey’s Studentized Range Test.

Specific issues in the design and implementation of an efficacy trial for a Lyme disease vaccine.

Lyme disease is an emerging infection that has now become the most commonly reported vector-borne disease in the United States. In the 20 years since its initial description, scientific and technological advances have led to candidate vaccines for the prevention of Lyme disease. Recombinant outer surface protein A (OspA) vaccines have been successful in protecting mice in tick-challenge experiments. A candidate OspA vaccine has been found to be safe and immunogenic in phase I and II studies. This article describes some of the lessons that were learned and some of the unique obstacles encountered in the design and implementation of a large phase III efficacy field trial. Pivotal trials of vaccines for Lyme disease can be a major investment of time and resources for subjects, investigators, and sponsors. If properly conducted, they also present unique opportunities to expand our knowledge of the disease.

Safety and immunogenicity of investigational Shigella conjugate vaccines in Israeli volunteers

The safety and immunogenicity of investigational conjugates, composed of the O-specific polysaccharides of Shigella sonnei and Shigella flexneri type 2a covalently bound to Pseudomonas aeruginosa recombinant exoprotein A (rEPA), were evaluated in 192 Israeli soldiers. None had significant local reactions or fever. Fourteen days after injection, 90% of S. sonnei-rEPA recipients and 73 to 77% of S. flexneri-rEPA recipients had a fourfold or greater increase in serum immunoglobulin G (IgG) and IgA anti-lipopolysaccharide (anti-LPS) levels; at 2 years, these remained higher than at prevaccination (P < 0.01). There was a fourfold or greater increase in IgM anti-LPS in 20% of vaccinees at 2 weeks, but levels returned to prevaccination values at 6 to 12 months. IgG was the highest and most sustained class of LPS antibodies. Reinjection at day 42 did not boost antibody levels. Eighteen of 23 (78%) who received S. sonnei-rEPA and 13 of 19 (68%) who received S. flexneri-rEPA. had significant IgA-secreting cell responses. Significant IgG antibody-secreting cell responses were detected in 19 of 23 (83%) and 11 of 19 (58%) volunteers following vaccination with S. sonnei-rEPA and S. flexneri 2a-rEPA, respectively. On the basis of these data, further evaluation of the Shigella conjugates for protective efficacy in field trials in Israel was started.

Enteric viral vaccines for calves

Rotavirus and coronavirus are significant causes of diarrhoea in young calves. The means by which efficacious vaccines can be developed are discussed. Most of the viral calf diarrhoea vaccines currently available in the European Union are unsupported by published evidence of their efficacy in field trials or even of their ability to produce seroconversion.

A Rapid Method for Screening Insecticides in the Laboratory

An efficient method for rapidly mass-screening insecticides for use against sap-feeding virus vectors is presented with a case study of 30 chemicals. The method permits large numbers of insecticides to be tested simultaneously and relatively inexpensively in a sequence of laboratory bioassays. The sequence is designed to find the most effective pesticide at the lowest concentration giving control without phytotoxicity. The system was derived to test candidate insecticides to control tomato yellow leaf curl virus vectored by the tobacco whitefly, Bemisia tabaci Gennad., the most serious pest of greenhouse and field tomatoes in the Middle East. Although the insecticides were all more efficacious in the laboratory than in the field, bioassay results were highly correlated with results from field trials, giving high confidence that the screening process selected only the most efficacious insecticides. Most of the insecticides accepted by the screening process have since been adopted by vegetable growers in Israel. The method is not intended to eliminate field efficacy trials, but to reduce the number of trials and treatments that need to be performed, thereby reducing costs. The method provides for the optimization of application rates which will contribute to the expected life of insecticides before resistance develops, and will also help to reduce environmental contamination. In addition, the method is suitable for estimating relative efficacy for pesticide benefits assessments, a required part of the (re-)registration process for pesticides in some countries. Although developed for screening insecticides against virus-transmitting sap-feeding insects, the method could be modified to assess the efficacy of insecticides in controlling other insect pests.

Acellular Pertussis Vaccine Scores High in Trial

A UNIQUE monovalent acellular pertussis vaccine composed only of detoxified pertussis toxin (toxoid) has passed its first efficacy field trial with flying colors. In a study involving nearly 3500 children, the vaccine, which had earlier undergone smaller safety and efficacy studies (<i>JAMA</i>. 1992;268:958-959), was shown to be more than 70% effective and elicited no serious adverse effects. The trial was randomized, double blind, and placebo controlled. It was conducted in Göteborg, Sweden, under the supervision of Birger Trollfors, MD, and John Taranger, MD, both of whom are professors of pediatrics at the University of Göteborg. Taranger reported the latest findings at the 95th meeting of the American Society for Microbiology, held in Washington, DC. "In the vaccinated children who did acquire pertussis, the disease was less severe and lasted for a shorter period than among nonvaccinated controls," he said. <h3>First Field Trial Results</h3> This study marks the first results in