Mosquito control programs are utilizing cost-effective long-term autocidal traps targeting the gravid population of container-inhabiting and other mosquito species, with the aim of reducing vector populations and disease transmission risk. In this field study we directly compared the efficacy of the Autocidal Gravid Ovitrap (AGO) and In2Care mosquito traps in St. Augustine, Florida. Total numbers of eggs (Aedes aegypti and Ae. albopictus) and adult mosquitoes were calculated at different weeks of trap deployment, pre-treatment (wk1-2), during-treatment (wk3-6), and post-treatment (wk7-8). There was a 72% reduction in both Aedes eggs in the two sites tested post-trap deployment, compared to pre-trap deployment. The mean numbers of eggs collected in the post-treatment, compared to pre-treatment showed that the In2Care traps had a higher reduction of mosquito oviposition (80%) than the AGO traps (23%). A total of 19 mosquito species included non container-inhabiting mosquitoes, Aedes taeniorhynchus, Culex quinquefasciatus, and Cx. nigripalpus, were collected by BG traps baited with BG lure and dry ice from the test sites. The species abundance varied between the two sites and collection weeks. The container-inhabiting mosquitoes, Aedes aegypti and Ae. albopictus were the major species. There was a significantly higher reduction in mosquito Aedes aegypti populations in the AGO (mean ± SE) (1.3 ± 1.7) and In2Care (4.9 ± 4.6) sites (X2= 20.13, P < 0.0001) post trap deployment, compared to pre-trap deployment. By week 8, the recovery rate of mosquito populations was highest in the In2Care trap site, followed by the AGO site. This result suggests that AGO traps were more effective than In2Care traps in reducing Ae. aegypti mosquito populations. For Ae. albopictus, the In2Care site had 100% reduction, and this was higher than the AGO site.
Background Attractive Toxic Sugar Baits (ATSBs) successfully reduced Anopheles mosquito vector populations and malaria parasite transmission in Mali, but application methods need to be improved for wide-scale use, and effects on non-target organisms (NTOs) must be assessed. The goals of this study were to determine on a village level the effect of different outdoor configurations of ATSB bait stations to 1) achieve > 25% Anopheles mosquito vector daily feeding rate for both males and females and 2) minimize the effect on non-target organisms. Methods Dye was added to Attractive Sugar Bait Stations (ASB – without toxin) to mark mosquitoes feeding on the sugar baits, and CDC UV light traps were used to monitor mosquitoes for the presence of the dye. Yellow plates, pitfall traps, Malaise traps, UV light traps, UV tray traps, and sweep nets were used to trap and sample non-target organisms (NTOs) for dye, indicating feeding on the ASB. ASB stations were hung on outer walls of village homes to determine the impact of different densities of ASBs (1,2, or 3 per home) as well as the impact of ASB height (1 m or 1.8 m above the ground on sugar feeding by anophelines. These experiments were carried out separately, on consecutive nights for mosquito and NTO monitoring. Eight villages in the Koulikoro province were chosen as the experimental locations. Results The use of one ASB station per house marked 23.11% of female and 7.11% of male An. gambiae s.l. While two and three ASB stations per house gave feeding rates above the 25% goal, there was no statistical difference in the percentage of marked mosquitoes (p=0.3141 females; p=0.9336 males). There was no difference in sugar feeding on ASB stations when hung at 1.0 and 1.8 m and (p=0.5170 females; p=0.9934 males); however, ASBs at 1.8 m had less accidental damage from village residents and animals, and subsequent invasion of non-targets through rips or holes produced. ASB stations at 1.8 m above ground were fed on by three of seven monitored insect orders. Feeding rates were less than 0.015% of total trap catches and as low as 0.0001%. The monitored orders were: Hymenoptera [ants (Formicidae), bees (Apidae), and wasps (Vespidae)], Lepidoptera (Rhopalocera, Bombyces, Geometroidea, Noctuoidea, Sphingidae, Pyraloidea), Coleoptera (Carabidae, Tenebrionidae, Scarabaeidae, Cerambycidae, and Chrysomelidae), Diptera (Brachycera, Chironomidae), Hemiptera (Cicadomorpha and Heteroptera), Neuroptera (Myrmeleontiformia) and Orthoptera (Caelifera and Ensifera). Using one or two stations limited evidence of NTO feeding to ants (Hymenoptera), Brachycera, Heteroptera, Noctuiodea, Rhopalocera, wasps (Vespidae) and wild bees (Apidae) (both Hymenoptera) and had a significantly reduced percentage of stained individuals compared to three stations which had the highest feeding rates amongst NTOs. The percentages of stained individuals were as follows: 6.84 ± 2.03% Brachycera were stained followed by wasps (Hymenoptera: Vespidae) 5.32 ± 2.27%, and Rhopalocera 2.22 ± 1.79%. Hanging the optimal number of stations per house for catching mosquitoes (two) 1.8 m above ground, limited the groups of non-targets to Brachycera, Chironomidae, Noctuoidea, Rhopalocera, parasitic wasps and wasps (both Hymenoptera: Vespidae). The three most commonly stained non-target insect groups at this height were wasps (Vespidae) (1.65 ± 0.75%), Chironomidae (0.99 ± 0.37), and Brachycera (1.55 ± 0.69%). Feeding at this height only occurred when stations were damaged.Conclusions The goal of marking one quarter of the total Anopheles mosquito vector population per day was obtained using 2 bait stations at 1.8 m height above the ground on the outer walls of houses. This configuration of ATSB stations also had minimal effects on non-target insects: only 0.0001% to 0.013% of specimens (in three orders) were marked. Stations hung 1.8 m above the ground had less accidental damage from passing people and livestock. The minimal marking of non-target insects may be attributed to visual orientation of non-mosquito insects while mosquitoes, are mostly guided by olfactory cues. Furthermore, the bait stations have a membrane cover, which if intact, is impenetrable to most sugar feeding non-target insects but is pierced by the stylets of the mosquito proboscis. Thus, most non-target insects are not exposed to the toxin even if they approach the bait stations.
Eleven different carbohydrates were evaluated to determine the behavioral response of adult Anopheles quadrimaculatus Say and Aedes albopictus Skuse using an olfactometer. The carbohydrates used in the study are arabinose, fructose, glucose, maltose, melezitose, meliniose, raffinose, rhamnose, sucrose, trehalose, and turanose. The results showed that both species of mosquitoes regardless of the sex had significantly higher attraction to arabinose, maltose, meliniose, and trehalose than other 7 carbohydrates tested. Both sexes and both species responded to maltose and trehalose in considerable numbers, and the least responses were to sucrose except by male Ae. albopictus. These findings may provide insights to the development of more effective sugar-based toxic baits for the operational application in mosquito control programs.
Four novel commercial insecticide mixtures, composed of pyrethroid and nicotinoid active ingredients, were evaluated in a series of experiments in the laboratory, semi-field and field to determine acute toxicity (LC50) against pyrethroid-susceptible (ORL1952) and resistant (Puerto Rico) strains of Aedes aegypti L., and non-target adult European honey bees, Apis mellifera L. The four products were Tandem, Temprid FX, Transport Mikron, and Crossfire. The acute toxicity data showed that pyrethroid-resistant Ae. aegypti PR exhibited decreased sensitivity to all 4 insecticide mixtures, compared to pyrethroid-susceptible Ae. aegypti ORL1952. Tandem, Temprid FX, and Transport Mikron were more toxic to Ae. aegypti ORL1952 than to A. mellifera, but Crossfire was the least toxic. Transport Mikron was also more toxic to Ae. aegypti PR than to A. mellifera. The Honey bee Tolerance Indexes, determined with LC50 data of pyrethroid-susceptible mosquitoes, demonstrated that while Transport Mikron, Tandem, and Temprid FX were more toxic to Ae. aegypti ORL1952 than to A. mellifera, Crossfire was less toxic. The honey bee Tolerance Indexes decreased substantially when calculated with LC50 data from pyrethroid- resistant mosquitoes, but honey bees remained tolerant of Transport Mikron. Notably, while the insecticide mixtures did not control the PR resistant Ae. aegypti strain when applied as residual sprays to perimeter vegetation at label rates, susceptible Ae. aegypti ORL1951 were controlled, but applications affected honeybees (A. mellifera) for up to 28 days after treatment. Temprid FX resulted in 74% and 99% mortality, in adult Ae. aegypti ORL1952 and A. mellifera, respectively, for 28 days post-treatment. Transport Mikron and Tandem residues killed Ae. aegypti ORL1952 for up to 21 days post-treatment, while the effect of Crossfire lasted only 14 days. All three insecticides killed A. mellifera for up to 28 days post-treatment but at decreased mortality rates. For operational mosquito control, these data indicate that Transport Mikron has a reasonable safety margin (~25%) when targeting susceptible mosquitoes, compared to Tandem, Temprid FX, and Crossfire. The tested insecticide formulations need to be applied in higher doses to control resistant strains of mosquitoes that may be detrimental to honey bees. The ULV data indicated that pyrethroid resistance can be overcome with the insecticide mixtures.
Application of permethrin products by ultra-low volume (ULV) spraying against the container-inhabiting mosquito Aedes albopictus (Skuse) has been used for many years, but the impact of the insecticides on domesticated honey bees, Apis mellifera (Linnaeus) is still lacking. The present study was carried out to evaluate the impact of the permethrin product, Aqualuer® 20-20 (active ingredient: 20.6% permethrin+20.6% Piperonyl butoxide) ULV sprays on caged Ae. albopictus and A. mellifera in open semi-field conditions with cages spaced at 3 m, 22.8 m, and 45.7 m downwind of the spray-truck path. The results indicated that ULV spray of Aqualuer 20-20 is highly effective against Ae. albopictus achieving 94% mortality at 22.8 m and 82% mortality up to 45.7 m downwind distance. The highest mortality of A. mellifera was only 72% at 3 m downwind distance, but the spray killed 42% of the exposed bees up to 45.7 m down the spray path. This semi-field study conducted during the day time indicates the high effectiveness of the ULV spray of permethrin against Ae. albopictus and its comparatively low impact on the direct exposed non-target honey bee, A. mellifera. Further studies designed to be conducted in the natural environment during its real-time operations following label instructions of the insecticide will help establish spraying guidelines to minimize any unfavorable impact on domesticated A. mellifera while having expected mortality effects on Ae. albopictus.
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