Domestic scorpion control with pyrethroid insecticides in Mexico

Scorpion stings cause more morbidity in Mexico than any other country, leading to about 100 deaths annually. In 1999, the State of Morelos reported nine deaths among 30663 cases of scorpion sting. To replace lindane used for scorpion control, field trials of pyrethroid pesticides were undertaken in Morelos during 1998-2000 at the village of Chalcatzingo (population initially with 2760 inhabitants and 530 houses). Pre-intervention surveys detected scorpions (Scorpiones: Buthidae) of two species in the majority of houses: Centruroides limpidus limpidus Karsch outnumbering Vaejovis mexicanus smithi Koch. Scorpion prevalence was assessed, pre- and post-spray, directly by searching (40 min/house) and by householder reports of sightings inside houses. Pre-intervention perceptions of scorpion abundance were similar for all areas, with sightings in 12-18% of houses, whereas daytime searches detected more infestations in eastern parts of the village (prevalence 17% indoors, 22% outdoors) than in other sectors (9% indoors, 14% outdoors). Pyrethroids were evaluated as residual treatments in separate sectors of Chalcatzingo, with almost complete coverage indoors and peridomestically, using the following four formulations: bifenthrin 10% wettable powder (WP) applied at 50mg a.i./m2, cyfluthrin 10% WP (Solfac 10 WP) at 44-55 mg a.i./m2, deltamethrin 2.5% suspension concentrate (Biothrin 25 SC) at 11 mg a.i./m2 and 5% WP (K-Othrine 50 WP) at 35 mg a.i./m2. Phase 1 compared bifenthrin 10 WP, Solfac 10 WP and Biothrin 25 SC sprayed in December 1998; phase 2 compared Solfac 10 WP and K-Othrine 50 WP sprayed in June and again in December 2000, with follow-up surveys of scorpions one month post-spray and subsequently. Scorpion prevalence was reduced by 64-77% peridomestically one month post-spray and by 83, 46 and 15% in houses sprayed with cyfluthrin WP, bifenthrin WP or deltamethrin SC, respectively. Householder reports of sighting scorpions indoors were 33-85% below pre-intervention levels. Cumulative effects of the three spray-rounds over 3 years reduced scorpion prevalence by approximately 60% in the deltamethrin WP re-sprayed area and by approximately 90% in the cyfluthrin WP re-sprayed area. Householder sightings also fell by 67 and 28% in the cyfluthrin and delta-methrin re-sprayed areas, respectively. Operational efficacy of these products against scorpions at the dosages applied was ranked as cyfluthrin WP > bifenthrin WP > deltamethrin SC > WP. Reported cases of scorpion sting intoxication fell by 17% during this study after having risen by approximately 40% over four previous years.     

Pyrethroid-impregnated hessian curtains for protection against mosquitoes indoors in South India

Abstract. Hessian curtains impregnated with deltamethrin 50 mg/m² were hung in the eaves and doorways of eight one-roomed huts in Madurai, Tamil Nadu State, South India. Statistically significant reductions of indoor-resting and man-biting densities of the mosquitoes Anopheles subpictus and Culex quinquefasciatus were observed for 14 weeks, in two field trials. Bioassays on curtains in the field showed over 50% mortality of Cx quinquefasciatus and An. stephensi for up to 8 weeks. The curtains were highly acceptable to the community, and cost approximately Rs.33.15 (US1.05) for material and Rs.10 (0.32) for deltamethrin per hut, totalling Rs 53.15 (1.70) for two impregnations giving 6 months protection. Comparative costs of house-spraying with residual insecticides are estimated as Rs.1.92 (0.06) for two rounds of DDT at lg/m², or Rs.40 (1.27) for three rounds of malathion at 2g/m². Therefore the relative annual cost of protection using deltamethrin-impregnated hessian curtains is 28× or 1.3× more than for house-spraying with DDT or malathion, respectively (excluding operational expenditure).     

Village trial of bednets impregnated with wash-resistant permethrin compared with other pyrethroid formulations

Abstract. A village-scale field trial of pyrethroid-impregnated mosquito nets was undertaken in The Gambia, West Africa, in the Mandinka village of Saruja (13^o13'N, 14^o55'W) during July-November 1989. Nearly all the villagers possessed and used their own bednets. Anopheles gambiae is the main vector of human malaria in the area.
An experimental wash-resistant formulation of permethrin was compared with standard emulsifiable concentrate (EC) formulations of permethrin and lambda-cyhalothrin, versus placebo-treated bednets. Target concentrations of pyrethroids on bednets were permethrin 500mg/m² and lambda-cyhalothrin 25 mg/m². The experimental design involved random allocation of a treatment to one net per family. Whereas 68% of people questioned said they washed their nets fortnightly, observations during the 16-week trial period showed that only 4/130 (3%) of nets involved in the trial had been washed as frequently as once per month.
Early morning searches for mosquitoes under bednets (1 day/week for 16 weeks) found significantly more mosquitoes (60% An. gambiae ) in placebo-treated nets than in pyrethroid-treated nets. The numbers found with each of the three pyrethroid treatments did not differ significantly from each other. Insecticidal efficacy of the treatments was tested by bioassays using wild-caught unfed mosquitoes exposed to netting for 3min. Linear regression analysis of bioassay mortality against number of times that a net had been washed by villagers showed that nets impregnated with the wash-resistant permethrin retained their insecticidal properties better than nets impregnated with lambda-cyhalothrin or with the standard permethrin formulation.     

Toxicity of six commercially formulated insecticides and biopesticides to third instar larvae of mushroom sciarid, Lycoriella ingenua Dufour (Diptera: Sciaridae), in New South Wales, Australia

Abstract  Lycoriella ingenua is one of the major pests of cultivated mushrooms, Agaricus bisporus (Lange) Imbach . Insecticide resistance among mushroom sciarid populations has been reported from other countries, and there is a need to determine the toxicity of currently approved and potential pesticides to sustain control of mushroom sciarid populations in Australia. The present study investigated the toxicity of six commercial formulations of insecticides or biopesticides against third instar larvae of L .  ingenua using laboratory bioassays. Insecticide treatments were incorporated into the growing medium for sciarid larvae and the concentration of the pesticide, which killed 90% of the test population (LD₉₀) determined the efficacy of selected insecticides. Triflumuron was the most effective insecticide against L. ingenua with an LD₉₀ of 53.12 mg active ingredient (a.i.)/m² followed by cyromazine (LD₉₀, 179.68 mg a.i./m²) and diazinon (LD₉₀, 261.72 mg a.i./m²). Abamectin and Bacillus thuringiensis ssp. israelensis were ineffective against L. ingenua . Steinernema feltiae , an entomopathogenic nematode, reduced the number of third instar larvae of L. ingenua only when applied at a higher rate (LD₉₀, 732 422 nematodes/m²) than was recommended on the label.     

Evaluation of deltamethrin-impregnated bednets and curtains against phlebotomine sandflies in Valle del Cauca, Colombia

Abstract. The effectiveness of bednets and curtains (nylon mesh 64 per cm²) impregnated with deltamethrin at 26 mg a.i./m² in reducing the biting nuisance caused by three phlebotomine sandfly species: Lutzomyia columbiana, Lu. lichyi and the predominant Lu. youngi (Diptera: Psychodidae), was evaluated at La Guaira, a rural settlement in Valle de Cauca near Cali, Colombia.
Pairs of volunteers collected sandflies under impregnated bednets, in rooms protected by impregnated curtains or in unprotected rooms in a randomized matched design. Collections were made in three houses per night on three consecutive nights, so that each house was sampled under each of the three treatments. This routine was repeated at 2-week intervals for 6 months. There was no significant difference between the overall numbers of sandflies collected in rooms with or without impregnated curtains. Only 0.14 sandflies/man-hour were caught on human bait under impregnated bednets, significantly fewer than the numbers collected on human bait outside the nets in the same room (1.91) or in unprotected rooms (3.29).
In a second set of experiments carried out in La Guaira and the neighbouring community of Jiguales, the effect of deltamethrin impregnation was evaluated by comparing numbers of sandflies collected on human bait under treated and untreated nets. Significantly fewer were collected under the impregnated nets (0.25 v. 0.69/man-hour). Wild-caught female Lu. youngi exposed to treated netting for 2 min in the laboratory all died with 24 h. The impact of deltamethrin-impregnated bednets was considered to be useful against Lu. youngi and other potential vectors of leishmaniasis in such communities.     

Use of an electrostatic sprayer for control of anopheline mosquitoes

The Electrodyn sprayer was compared with a compression sprayer (Hudson X-pert) for residual application of cypermethrin, a pyrethroid insecticide, to control the malaria vectors Anopheles arabiensis Patton and An. funestus Giles in experimental huts at Magugu in Tanzania. The time taken for hut spraying, 2-2.5 min per hut, was similar for both types of sprayer. Two or three huts were treated internally with cypermethrin at 40 or 80 mg a.i./m2 using Electrodyn formulation for comparison with 80 mg a.i./m2 using wettable powder formulation. Each of the twelve huts (including five untreated controls) was fitted with window exit traps and either louvre or verandah traps for mosquito sampling. The Electrodyn sprayer was fitted with a pair of elbowed deflectrodes to direct the positively charged spray droplets onto walls and ceiling. All treatments gave 94-100% mortality-rates of indoor-resting anophelines throughout the evaluation period of 11 weeks post-spray. Reductions of An.arabiensis and An.funestus females by 10-42% and 62-91%, respectively, in rooms and by 72% and 51% in exit traps indicated that cypermethrin deterred mosquitoes from entering the huts. Overall mortality-rates of mosquitoes were 66% of both species in huts treated with 40 mg/m2 Electrodyn, 43% An.funestus and 71% An.arabiensis due to 80 mg/m2 Electrodyn formulation and 49% An.funestus and 64% An.arabiensis due to 80 mg/m2 WP formulation (no significant differences). It is concluded that the Electrodyn sprayer with deflectrodes is a convenient and effective means of residual house-spraying with pyrethroid insecticide for malaria vector control.     

Control of tsetse and trypanosomiasis transmission in Uganda by applications of lambda-cyhalothrin

The pyrethroid insecticide lambda-cyhalothrin was evaluated in field trials against Glossina f.fuscipes and sleeping sickness transmission in Iyolwa sub-county, Tororo District, Uganda. The insecticide was applied selectively to the resting-sites of tsetse, by bush-spraying, using 10% wettable powder (10WP) formulation at an application rate of 11.6 g a.i./ha over an area of 28 km2, or by a 2% Electrodyn formulation (2ED) applied at 0.9 g a.i./ha over 30 km2. In a third trial area of 32 km2, 215 pyramidal traps treated with lambda-cyhalothrin 100 mg/m2 were set. The best impact was obtained with 10WP lambda-cyhalothrin which eliminated tsetse within 1-2 months, whereas G.f.fuscipes persisted at very low density in part of the area treated with 2ED lambda-cyhalothrin. In both treated areas the numbers of human sleeping sickness cases fell to no more than one per month, compared with four to twelve per month previously. The overall rate of cattle trypanosomiasis (T.brucei and T.vivax) was also reduced slightly. Insecticide-treated traps remained fully effective for at least 6 months under field conditions and catches were reduced 20-90-fold. These results in the control of tsetse and trypanosomiasis transmission lead us to recommend lambda-cyhalothrin for tsetse control operations.     

Behaviour of Anopheles albimanus in relation to pyrethroid-treated bednets

Abstract. Responses of the malaria vector Anopheles albimanus to pyrethroid impregnated bednets made of cotton or nylon, compared with untreated nets, were investigated in houses occupied by two people inside and/or outside two bednets, in coastal Chiapas, México. The pyrethroid used was lambdacyhalothrin 30mga.i./m². Bioassay mortality rates of An.albimanus exposed to treated nets for 3 or 15min, rose from 40–55% to 90–100% for nylon nets 3–19 weeks post-treatment, but were consistently lower for treated cotton nets. An.albimanus females (collected unfed on human bait) were released in houses surrounded by curtains for trapping mosquitoes that exited from the house. Floor sheets were used in and around each experimental house for retrieving any mosquitoes knocked-down and/or killed. During post-treatment assessment for 17 weeks, An.albimanus blood-feeding success rates were 23–24% with untreated nets, 14–18% with treated cotton nets and 8–15% with treated nylon nets, significantly reduced when both human baits were inside the treated bednets, but not when one or more baits were outside the treated bednet(s) within the house. Proportions of mosquitoes leaving houses <3 h post-release were 53–59% from houses with untreated bednets versus 65–78% with treated bednets. Except in one case (when both humans were outside treated cotton nets), these increased early exit rates were significant, whether or not the human baits were inside the treated bednets indoors. Mortality rates of An.albimanus females exiting overnight (22.00–06.00 hours) averaged 15–39% from houses with treated cotton and 16–46% with treated nylon nets, very significantly greater than the control mean rates of 6–8% mortality with untreated nets. Observations on wild-caught An. albimanus females marked with fluorescent powder and released indoors revealed that few mosquitoes (3–11 %) actually contacted the bednets unless both human baits remained under them - when contact rates were 22% on treated nylon, 23% on treated cotton and 42% on untreated nets (P= 0.05). The mean resting time was significantly longer on untreated (14.4min) than on treated nylon (5.8min) or cotton (9.5 min) bednets, whereas mean resting times on other surfaces indoors were 16.5–19.8min. Proportions exiting within 2h of release were significantly more from houses with treated houses (33–35%) than with untreated nets (8%). However, mortality rates of mosquitoes that landed on treated nets were very significantly greater (90–100%) than after landing on untreated nets (10%). Thus, despite some excito-repellency, lambdacyhalothrin-impregnated bednets (especially made of nylon) proved to be effective as an alternative to house-spraying against An.albimanus.     

Differential application of lambda-cyhalothrin to control the sandfly Lutzomyia longipalpis

Abstract. To study the impact of residual pyrethroid insecticide on the abundance and distribution of peridomestic Lutzomyia longipalpis , the sandfly vector of visceral leishmaniasis in Brazil, lambda-cyhalothrin was applied at 20 mg a.i.m^-2 in the following interventions: (i) spraying of all animal pens in a village (blanket coverage); (ii) treatment of a subset of animal pens, either by spraying, or by installation of insecticide-impregnated 1 m² cotton sheets as 'targets' (focal coverage).
By sampling with CDC light traps, and using a novel analytical approach, we detected a 90% reduction in Lu. longipalpis abundance in sprayed sheds of the focal intervention. However, there was no discernible effect on the abundance of other phlebotomines trapped in sheds, or on the abundance of Lu. longipalpis in untreated dining-huts and houses. This differential impact on Ludongipalpis abundance is explained in terms of the disruption of male pheromone production. Treated targets were approximately half as effective as residual spraying in reducing the abundance of Lu.longipalpis in sheds.
Following blanket intervention, the abundance of Lu.longipalpis in traps fell by only 45% (not significant): catches at untreated dining-huts actually increased, possibly because the blanket coverage diverted Lu. longipalpis away from major aggregation sites at animal pens. It is recommended that care be taken during vector control programmes to ensure that all potential aggregation sites are treated. The possible consequences of leaving some sites untreated include poor control of peridomestic sandfly abundance and an increase in the biting rate on dogs and humans.     

Mechanism of calcium-dependent salt tolerance in cells of Nitellopsis obtusa: role of intracellular adenine nucleotides

Abstract. The tonoplasts of internodal cells of Nitellopsis were removed by perfusing the vacuoles with media containing a Ca² chelator, EGTA. Treatment of tonoplast-free cells with 100 mol m³ NaCl induces a large membrane depolarization, a drastic decrease in the membrane resistance and an increase in Na⁺ influx. These events are identical to those that occur in intact cells subjected to high NaCl. These responses to NaCl are prevented if 10 mol m³ Ca²⁺ is supplied together with 100 mol m³ NaCl. The protective effect of Ca²⁺ is evident only when the intracellular ATP concentration exceeds 0.1 mol m³ and does not occur full when the intracellular ATP is removed. AMP at concentrations greater than 0.5 mol m³ or 0.25 mol m³ AMPPNP can replace ATP. It is concluded that ATP does not act as an energy source nor as a substrate for protein phosphorylation. ATP seems to exert its effects as a coeffector with Ca²⁺ in regulating the Na⁺ permeability of the plasma membrane.     

Floristic composition, structure, and dynamics of an upper montane rain forest in Southern Ecuador

Two 1 ha plots of undisturbed upper montane rain forest in southern Ecuador were sampled for all trees with a dbh ≥ 5 cm. An extraordinarily high α-diversity for a forest near treeline is described. The "non-ridge forest" plot at 2900 m elevation has 75 species and 28 families ha^-1 and is believed to represent an advanced stage of succession whereas, the "ridge forest" plot at 2700 m elevation with 90 species and 38 families ha^-1 has a more rapid turn-over rate probably due to a more unstable environment. Downslope forces (soil creep) are discussed as a possible cause for 32–44% of all trees being inclined more than 30° in the moderately steep terrain (average slope 20° in both study plots). The plot of "non-ridge forest" is characterized by a much greater biomass whether expressed as basal area (44 m² versus 15 m²) or stem volume (214 m³ versus 52 m³), while the density is equally high (2310 versus 2090 trees ha^-1) in both plots. Families with Family Importance Value >25 / ha^-1 are Clusiaceae, Cunoniaceae, Melastomataceae, Myrsinaceae, and Ternstroemiaceae.     

Efflux of ions and ATP depletion induced by pediocin PA-1 are concomitant with cell death in Listeria monocytogenes Scott A

Domination of Carnobacterium divergens LV13 by a bacteriocin-producing (bac⁺) organism Carnobacterium piscicola LV17 was dependent on the level of inoculum of the producer strain and its bacteriocin production. When C. piscicola LV17 was grown in APT broth from an initial inoculum of α-10⁴ cfu ml^-1, bacteriocin was not produced (bac^-) although maximum population was reached. The culture remained bac^- during subsequent inoculation at 10²-10⁷ cfu ml^-1 unless it was first grown on solid medium or if heat-treated supernatant fluids from a bac⁺ culture of C. piscicola LV17, LV17A or LV17B were added to the culture prior to the stationary phase of growth. Use of purified carnobacteriocins from C. piscicola LV17A and LV17B confirmed their role in regulation of the bac⁺ phenotype. The need for induction might account in part for differences in bacteriocin production by cultures in liquid and on solid growth media.     

Permethrin-impregnated bednets are more effective than DDT house-spraying to control malaria in Solomon Islands

Abstract. A field trial compared DDT house-spraying with permethrin-impregnated bednets for malaria control in Solomon Islands from 1987 to 1991. Mortality-rates of malaria vector Anopheles farauti in exit window traps were 11.6% from an untreated hut, 10.1% from a hut sprayed with DDT 2 g/m², and 98% of those from a hut in which the occupants used bednets treated with permethrin 0.5 g/m². Since bioassays of the DDT-sprayed walls (15 min exposure in W.H.O. standard test cones) gave 77% mortality of Anfarauti , it was concluded that the insignificant impact of DDT could be explained by the exophilic behaviour of endophagic vectors, whereas the greater impact of permethrin was attributed to the more effective exposure of Anfarauti females to the impregnated bednets - attracted by the occupants. The parous rate was higher indoors, except in the area with permethrin-impregnated bednets. It was therefore concluded that permethrin-impregnated bednets reduced the mean longevity of Anfarauti and hence its vectorial capacity. The circumsporozoite (CS) antigen positivity rate of Anfarauti in the DDT area was 0.18% outdoors, significantly less than 1.42% indoors. In the comparison area CS rates were 0.65% outdoors and 0.75% indoors. CS antigen was not detected in Anfarauti from the bednet area, indicating the apparent prevention of malaria transmission. As DDT spraying was so much less effective, it was discontinued in 1993 and permethrin-impregnated bednets are now the principal malaria control method in Solomon Islands.     

Effects of regulated discharge on burbot migration

Burbot Lota lota movement and river discharge were studied in the Kootenai River, Idaho, U.S.A. and British Columbia, Canada, downstream of Libby Dam, Montana, U.S.A. A total of 24 adult burbot with transmitters were tracked from 1994 to 2000, for analysis of a travel distance of ≥5 km in ≤10 days termed 'stepwise movement'. Of 44 'stepwise movements', significantly greater movements during pre‐spawning and spawning were observed when average daily discharges from Libby Dam were <300 m³ s⁻¹, with a mean of 176 m³ s⁻¹, similar to pre‐dam conditions. Burbot travelled at a greater rate during all seasons (3·36 km day⁻¹) at discharges >300 m³ s⁻¹(mean = 1·84 km day⁻¹) than at discharges >300 m³ s⁻¹ but no difference was found for the pre‐spawning and spawning period. Burbot that started 'stepwise movements' in low discharge conditions frequently stopped during low discharges.     

Short-term thermal acclimation induces adaptive changes in the inner mitochondrial membranes of fish skeletal muscle

In the oxidative muscles (musculi laterales superficiales) of crucian carp Carassius carassius acclimated for 6 weeks to either 5 or 25° C, the volume density and the surface density of fibres per tissue did not differ significantly between the control and experimental groups. The correlation ratio (μ²) for these values was below 50, 39·3 and 43·9 respectively. After acclimation to 5° C, the surface density of outer mitochondrial membrane per fibre increased significantly from 0·93 to 1·23m² cm⁻³ in the summer population but dropped from 0·94 to 0·67 m² cm⁻³ in the winter population. The surface density of outer mitochondrial membrane per mitochondrion increased from 3·24 to 4·52 m² cm⁻³ in summer fish. After acclimation to 25° C, the surface density of inner mitochondrial membranes per muscle fibre decreased from 4·04 to 1·79 m² cm⁻³ in summer fish and from 3·86 to 1·07 m² cm⁻³ in winter fish. The surface density of inner mitochondrial membranes per mitochondrion increased from 14·17 to 15·60 m²cm⁻³ in summer fish but dropped from 13·91 to 10·67 m² cm⁻³ in winter fish. Correlation matrices demonstrate a negative correlation of the surface density of outer mitochondrial membrane per mitochondrion with the volume density of mitochondria per fibre and temperature, suggesting cold-induced proliferation of small mitochondria. It was concluded that short-term cold acclimation increased surface area of the inner mitochondrial membranes in summer fish.     

The forest of Vorsø, Denmark: Succession towards a natural, decidous boreal forest influenced by breeding cormorants

The forest on the strictly protected island Vorsø in Horsens Fjord has since 1952 been examined every ten years to discover the number, basal area, wood volume and aboveground biomass of the species. This paper describes the results from 1982 and the development up to that. The dominating species are Fraxinus excelsior, Ulmus glabra and Fagus sylvatica. The two forests, "Vesterskov" (6.09 ha) and "Østerskov" (2.48 ha) respectively, were, in 1982, still immature. Their number of stems per ha were: 756 and 509; basal area: 38 m² and 45 m². volume: 544 m³ and 615 m³; biomass 207 t and 268 t. The annual increase 1972–1982 was respectively 8.8 m³/ha and 0.3 m³/ha. The impact of the cormorant ( Phalacrocorax carbo sinensis ) is especially in "Østerskov" increasing, since the colony here was established in 1976. The succession of the forest is discussed in relation to the disturbance by the cormorants.     

The cytotoxic and photodynamic inactivation of micro-organisms by Rose Bengal

Rose Bengal was cytotoxic to the following bacteria at the concentrations given in parentheses (highest concentrations of dye in mol/1 at which growth occurred on nutrient medium): Brochothrix thermosphacta and Deinococcus radiodurans (1 times 10^-6 or less); Streptococcus, Micrococcus, Staphylococcus, Bacillus, Arthrobacter and Kurthia spp. (1 times 10^-5–1 x 10^-4), and Pseudomonas spp. and Enterobacteriaceae (5 times 10^-3–1 x 10^-2 or greater). These organisms were killed rapidly when suspended in illuminated (170 μE/m²/s) solutions of Rose Bengal (1 times 10^-4 mol/1) providing oxygen was present. Singlet oxygen was identified as the lethal agent, because the rate of killing was increased by dissolving the dye in deuterium oxide while the organisms were protected against photoinactivation by L-histidine or crocetin. Yeasts from chilled foods were killed in illuminated solutions of Rose Bengal but a light intensity of 315 μE/m²/s was needed for a death rate comparable with that of bacteria. The yeasts present in a range of chilled meat and dairy products failed to form colonies on Rose Bengal (5 times 10^-5 mol/1) media exposed continuously to modest illumination (55–80 μE/m²/s).     

Biological Control of Anopheles sinensis with Native Fish Predators (Aplocheilus and Aphyocypris) and Herbivorous Fish, Tilapia in Natural Rice Fields in Korea

ABSTRACT A confined field experiment was conducted to investigate biological control of malaria and inland filariasis vector, Anopheles sinensis Wied. by combined use of larvivorous fishes, Aplocheilus latipes or Aphyocypris chinensis and herbivorous, Tilapia mossambicus niloticus in natural rice fields at Banwol near Suwon, Gyeonggi province from June through October, 1989. In the presence of naturally breeding Aplocheilus at the density of 0.8 fish/m² water surface, the natural control of Anopheles larvae ranged 34.4% to 51.6% from June through August; later supplemental introduction of herbivore (Tilapia) at the release rate of 1-pair per 10 m² resulted in 67.8% increased to 80.0% control of Anopheles sinensis in 3rd and 5th week respectively. In a combined fish release at the rate of 1.0 fish/m² of Aphyocypris and 1-pair/10 m² of Tilapia produced 67.3% and 82.1% mosquito larval reduction in 3rd and 5th week periods, respectively. The similar pattern of gradual but significant suppression of mosquitoes was also evident in separate rice paddy in 4-5 week period, maintaining ca. 75'82% for the subsequent mosquito breeding season in comparison with control plot.     

Field evaluation of a lethal ovitrap against dengue vectors in Brazil

Field evaluation of a "lethal ovitrap" (LO) to control dengue vector Aedes mosquitoes (Diptera: Culicidae), was undertaken in two Brazilian municipalities, Areia Branca and Nilopolis, in the State of Rio de Janeiro. The LO is designed to kill Aedes via an insecticide-treated ovistrip (impregnated with deltamethrin). In each municipality, the intervention was applied to a group of 30 houses (10 LOs/house) and compared to 30 houses without LOs in the same neighbourhood. Five LOs were put outside and five LOs inside each treated house. Three methods of monitoring Aedes density were employed: (i) percentage of containers positive for larvae and/or pupae; (ii) total pupae/house; (iii) total adult females/house collected by aspirator indoors. Weekly mosquito surveys began during the month before LO placement, by sampling from different groups of 10 houses/week for 3 weeks pre-intervention (i.e. 30 houses/month) and for 3 months post-intervention in both treated and untreated areas. Prior to LO placement at the end of February 2001, Aedes aegypti (L) densities were similar among houses scheduled for LO treatment and comparison (untreated control) at each municipality. Very few Ae. albopictus (Skuse) were found and this species was excluded from the assessment. Post-intervention densities of Ae. aegypti were significantly reduced for most comparators (P < 0.01), as shown by fewer positive containers (4-5 vs. 10-18) and pupae/house (0.3-0.7 vs. 8-10) at LO-treated vs. untreated houses, 3 months post-treatment at both municipalities. Numbers of adult Ae. aegypti females indoors were consistently reduced in LO-treated houses at Areia Branca (3.6 vs. 6.8/house 3 months post-intervention) but not at Niloplis (approximately 3/house, attributed to immigration). These results demonstrate sustained impact of LOs on dengue vector population densities in housing conditions of Brazilian municipalities.     

Habitat edges as a potential ecological trap for an insect predator

Abstract.  1. Ecological traps, where animals actively select poor habitat for reproduction over superior habitat, are generally associated with birds at forest edges. This study examines oviposition preference, predation, and parasitism rates in the mantid Stagmomantis limbata to determine the potential generality of this phenomenon.
2. Egg case (oothecae) densities were measured across two edge types (cottonwood and desert scrub) within desert riparian ecosystems. A positive edge effect in oothecae density was found with an approximate three-fold increase in density at cottonwood ( X _edge = 0.05 oothecae/100 m² vs. X _interior = 0.015 oothecae/100 m²) and desert scrub ( X _edge = 0.20 oothecae/100 m² vs. X _interior = 0.06 oothecae/100 m²) edges ( P  < 0.01).
3. Rates of bird predation were significantly higher for oothecae at desert scrub edges and showed a trend of higher predation rates at cottonwood edges, suggesting that riparian habitat edges may be acting as an ecological trap for this mantid species. There was no effect of edges on oothecal parasitism rates.
4. These results provide an example of the effect of habitat edges on a generalist insect predator and indicate that an ecological trap may exist with respect to one of its natural enemies.