Control Of Black Flies Research Articles

Development and Application of Biopesticides for the Management of Disease Vectors and Pests of Public Health Importance

The development and practical use of natural products occurred in the late 1970s when a spore-forming bacterium producing enterotoxins was discovered. This organism was designated as Bacillus thuringiensis ssp. israelensis (Bti). By 1985, large quantities of Bti formulations were employed in mosquito and black fly control programs globally. As research efforts in this area continued, a second bacterium Bacillus sphaericus (Bsph) was isolated and found to be highly effective against most mosquito species. This entomopathogen found its way into mosquito control around 1997. Today, both these (Bti and Bsph) microbial control agents are produced by large-scale fermentation processes in many countries. Recent advances in formulation technology of both bacteria have increased their usefulness in vector control programs. Another soil bacterium known as Saccharopolyspora spinosa (Actinomycetes), was discovered, producing bioactive components known as spinosyn A and spinosyn D. Large-scale fermentation technology has been developed and the product known as spinosad was produced and developed in agriculture, and recently for use in public health. However, spinosad has not been used to any great extent in public health as yet. All three microbial control agents have a good margin of safety for mammals, birds, and wildlife and are environmentally friendly. Considerable efforts were directed toward developing plant extracts for vector control, especially mosquitoes. In this context, plant-based extracts were formulated for the control of larval and adult mosquitoes. Some of the plant parts were used in manufacturing mosquito coils which number into the billions on a worldwide basis; however, only a small proportion of coils are manufactured with plant-derived products. A major area for the development of plant-based products is the use of plant essential oils which are formulated in various ways for personal protection from the attack of hematophagous insects. A number of such insect-repellent products are commercialized in many countries. The public has the perception that plant-based and other natural products are environmentally friendly and safer to use for vector control or apply to human skin as personal protectants than synthetic chemicals. In this paper, we will dwell upon the research and development efforts leading to the development, production, and application of microbial control agents, and phytochemicals for the control of adult and preimaginal stages of disease vectors, as well as the development and use of plant essential oils for personal protection from anthropophilic insects.

Habitat preference of blackflies in Omo Gibe river basin (southwest Ethiopia): Implications for onchocerciasis elimination and control.

Ecological control of blackflies (Simulium damnosum) can be an alternative or additional tool to enhance onchocerciasis elimination efforts. However, limited research is conducted on the ecology of blackflies in Ethiopia. In this study, we determined the habitat preference of blackfly larvae and their relationship with aquatic macroinvertebrate predators in the Omo Gibe river basin of southwest Ethiopia. Environmental and biological data were collected from 150 sampling sites during both dry and wet seasons in 2019. Generalized Linear Models (GLMs) were used to identify factors affecting the occurrence and abundance of S. damnosum larvae. Canonical Correspondence Analysis (CCA) was used to investigate the relationship between environmental and biological variables and the abundance of S. damnosum larvae. The findings of this study indicated the abundance of S. damnosum larvae increased with increasing turbidity, alkalinity and altitude, but decreased with increasing concentrations of five-day Biological Oxygen Demand (BOD5), orthophosphate and magnesium ion. Both the presence and abundance of S. damnosum larvae decreased with the increasing abundance of stonefly larvae (Perlidae). Simulium damnosum larvae were found less likely in the presence of mayfly larvae (Baetidae) and were less abundant where Chironomidae are abundant. In conclusion, the findings of this study showed that the habitat preference of S. damnosum larvae is determined by environmental factors and that the presence and abundance of the larvae are affected by macroinvertebrate predators. It is essential to establish buffer zones as a part of watershed management to retain pollutants and prevent them from entering directly into water courses to improve water quality and the assemblages of macroinvertebrate predators and enhance biocontrol of blackflies.

Sympatric occurrence of forest and savannah morphotypes of Simulium damnosum complex (Diptera: Simuliidae) in Osun State, Nigeria

Simulium damnosum Theobald complex is a group of black flies which vector filarial worms that cause onchocerciasis in Africa. Studies were conducted to investigate the morphological composition of adult S. damnosum complex in three ecological zones of Osun State, Nigeria. Adult black flies were sampled between October 2014 and September 2016, and the wing tufts, antennae, fore coxae and other morphotaxonomic characters were observed and classified following standard methods. The results revealed a sympatric occurrence of both forest- and savannah-dwelling groups (morphotypes) of black flies at each zone with the Guinea savannah zone (Iwo) having significantly higher abundance of forest than savannah black flies. The derived savannah (Ede) had higher abundance of savannah than forest black flies while the rainforest (Obokun) had more forest than savannah black flies but there was no significant difference between them. In Iwo, the highest abundance of forest flies was obtained in October and June while savannah flies were highest in November. The monthly abundance of each morphotype of black flies was significantly different in Ede but not in Obokun. Wing tuft colours among forest flies varied significantly in Iwo and Ede. This study indicates that there is substantial morphological diversity among sibling species of black flies which is useful for identification and could be exploited in black fly control. The presence of savannah flies in the three zones calls for surveillance for potential incursion of blinding parasite strain which migrant savannah flies could introduce to the communities.

Molecular characterization of black flies (Diptera: Simuliidae) in areas with pest outbreaks and simuliotoxicosis in Northeast Anatolia Region, Turkey

Accurate species identification provides the foundation for successful pest management and vector control of black flies. Accordingly, we examined the mitochondrial DNA cytochrome oxidase I (COI) gene sequences of four morphologically and chromosomally identified species of black flies (Simulium vernumgroup sp., S. bergi Rubtsov, S. bezzii (Corti), and S. kiritshenkoi Rubtsov) in Northeast Anatolia Region of Turkey where simuliid pest problems and simuliotoxicosis cases have been reported among cattle. COI gene sequences of these species and closely related species available in GenBank were used to provide species-level diagnoses and infer relationships. Both subgenera (Nevermannia and Simulium) were monophyletic, and subclades generally corresponded with species groups. Intraspecific genetic divergence was 0.2–1.6%, whereas the mean interspecific genetic divergence among the four species was 11.2–14.5%. The COI analysis produced results congruent with morphological concepts of the nominal species S. bergi and S. bezzii. Probable misidentifications in GenBank were revealed, especially for species in the S. ornatum and S. vernum groups, complicating identification capability. Sequence variation in the COI barcode region also might not be adequate for species delineation and identification among some species in these two species groups.

Optimisation of <i>Bacillus thuringiensis</i> var. <i>israelensis</i> (Vectobac<sup>®</sup>) applications for the blackfly control programme on the Orange River, South Africa

The Orange River, South Africa's largest river, is a critical water resource for the country. In spite of the clear economic benefits of regulating river flows through a series of impoundments, one of the significant undesirable ecological consequences of this regulation has been the regular outbreaks of the pest blackfly species Simulium chutteri and S. damnosum s.l. (Diptera: Simuliidae). The current control programme, carried out by the South African National Department of Agriculture, uses regular applications, by helicopter, of the target-specific bacterial larvicide Bacillus thuringiensis var. israelensis. While cost-benefit analyses show significant benefits to the control programme, benefits could potentially be further increased through applying smaller volumes of larvicide in an optimised manner, which incorporates upstream residual amounts of pesticide through downstream carry. Using an optimisation technique applied in the West African Onchocerciasis Control Programme, to a 136 km stretch of the Orange River which includes 31 blackfly breeding sites, we demonstrate that 28.5% less larvicide could be used to potentially achieve the same control of blackfly. This translates into potential annual savings of between R540 000 and R1 800 000. A comparison of larvicide volumes estimated using traditional vs. optimised approaches at different discharges, illustrates that the savings on optimisation decline linearly with increasing flow volumes. Larvicide applications at the lowest discharge considered (40 m3·s-1) showed the greatest benefits from optimisations, with benefits remaining but decreasing to a theoretical 30% up to median flows of 100 m3·s-1. Given that almost 70% of flows in July are less than 100 m3·s-1, we suggest that an optimised approach is appropriate for the Orange River Blackfly Control Programme, particularly for flow volumes of less than 100 m3·s-1. We recommend that trials be undertaken over two reaches of the Orange River, one using the traditional approach, and another using the optimised approach, to test the efficacy of using optimised volumes of B.t.i.

Assessing the relative culpability of Simulium (Diptera: Simuliidae) species in recent black fly outbreaks along the middle Orange River, South Africa

Black fly along the Orange River are major pests of livestock and labour-intensive agriculture, causing annual estimated industry losses in excess of US$30 million. The problem is attributed to winter high flows, with the main pest species being Simulium chutteri Lewis, 1965, although Simulium damnosum Theobald, 1903 and Simulium impukane de Meillon, 1936 may also be periodically problematic. During 2011, black fly outbreaks along the middle Orange River were perceived by farmers to have worsened and attributed to S. impukane. Here, we investigate the likelihood of this being the case, using a weight-of-evidence approach incorporating ecohydrological data. Results showed that it is unlikely that the 2011 outbreaks were caused by S. impukane, and more likely that the main outbreak cause remains S. chutteri. Sustained high flows and turbidity levels favour S. chutteri species over the other species of black fly, while flow conditions for a species such as S. impukane were favourable for 1% of the time only. However, during periods of lower flow and lower turbidity, other species of black fly may be favoured and contribute towards periodic outbreaks. We conclude that black fly control should focus on management issues around the control programme.

Survey of blackfly (Diptera: Simuliidae) annoyance levels and abundance along the Vaal and Orange Rivers, South Africa

Blackflies (Diptera: Simuliidae) are pests in the livestock and labour-intensive farming systems along the major rivers in South Africa. Since 1995, blackflies have been controlled in the Orange River with the larvicide Bacillus thuringienses var. israelensis (Bti). During 2006-2007, the views of livestock farmers concerning blackfly annoyance were determined by means of questionnaires. The results of the questionnaires were substantiated by seasonal abundance surveys of the sub-adult stages of blackflies, conducted in 2007 at 13 sites in the Orange River and 11 sites in the Vaal River. More than half (52%) of the 39 participating farmers along the Orange River and 79% of the 52 participating farmers along the Vaal River stated that they experienced severe blackfly problems. The majority of farmers were unaware of the availability of products that could be used to protect their animals against blackfly attacks and were willing to be involved in blackfly research. High numbers of blackfly sub-adult stages found in both rivers supported the high annoyance levels reported by the respondents. Simulium chutteri, Simulium damnosum s.l., Simulium hargreavesi, Simulium adersi and Simulium alcocki were identified at Christiana and Delportshoop on the Vaal River, whilst S. chutteri, S. damnosum s.l., S. adersi, S. alcocki and Simulium gariepense were identified at Marksdrift and Ses Bridge on the Orange River. Despite the extensive control of blackflies, farmers still experience problems and this contention is supported by surveys conducted along the rivers.

Identification Keys to the Larvae and Pupae of New Jersey Black Flies (Diptera: Simuliidae)

Multichotomous identification keys are provided to the black fly larvae and pupae of New Jersey and neighboring states. Control of black flies is targeted at the aquatic immature stages, making proper identification of larvae and pupae vital for suppression purposes. The key includes 40 species known from NJ and an additional 24 species from surrounding states. A species confirmation table is also included to increase identification accuracy. Diagnostic images of simuliid pupae and larvae are also provided.

Evaluation of larvicides in developing management guidelines for long-term control of pest blackflies (Diptera: Simuliidae) along the Orange River, South Africa

In 2000 and 2001 Orange River levels were higher than normal: associated serious outbreaks of blackfly had a substantial detrimental impact on the local economy. The poor control was attributed to the suspected development of larval resistance to temephos. A long-term solution to blackfly control, through the identification of a suitable replacement to temephos for use during high flow conditions, was proposed. This study, however, failed to identify or register a suitable larvicide for use during high flow conditions. Although permethrin was highly effective against blackfly larvae, it was rejected because of its detrimental impacts on non-target fauna. Various formulations of locally produced dry Bacillus thuringiensis var. israelensis (B.t.i.) were tested, but these were ineffective against blackflies. The study also confirmed that resistance to temephos has developed among Simulium chutteri in the middle and lower Orange River. The feasibility of "reversing" the resistance to temephos through the use of the synergist piperonyl butoxide (PBO) was investigated, but the results were not favourable. Furthermore, PBO was highly toxic to blackflies and non-target organisms, and was not recommended for further testing. This means that B.t.i. currently remains the only symptomatic measure of treatment currently applied. Although resistance to B.t.i. has not been reported for blackflies elsewhere in South Africa, there is a need to remain vigilant and to implement an operational strategy that minimizes the risks of resistance developing.

Seasonality and prevalence rates of microsporidia in Simulium pertinax (Diptera: Simuliidae) larvae in the region of Serra dos Órgãos, Rio de Janeiro, Brasil

A major means of fighting arthropod-borne diseases is control of the vector species. Successful vector control began in the 1940s with the synthesis of the first organochloride (DDT), and has continued with compounds such as organophosphates, carbamates, and pyrethroids (Margalit and Dean, 1985). Chemical insecticides have been effective and economical due to their broad spectrum of action and long residual effects. However, resistance to these pesticides in vector species, as well as harmful environmental effects has led to increased research into efficient and environmentally friendly control methods (Zahner et al., 1993). Biological control provides agents with greater specificity for vector species with fewer negative environmental consequences. For the Simuliidae, the shift from chemical to biological control began in the 1980s with the use of Bacillus thuringiensis serovar israelensis (BTI). In Brazil, the first program for black fly control with BTI began in 1989 in S~ao Paulo state. This program has been successful but expensive (Ara ujo-Coutinho, 1995); therefore, despite good results with BTI, efforts continue to discover natural pathogens in Brazilian simuliid species as alternative or complementary control methods of equal effectiveness. Microsporidia are common pathogens of black flies, but species diversity and seasonal occurrence are poorly known in most localities and mechanisms for transmission are unknown (Lacey and Undeen, 1986). Simulium pertinax is the most common and widely distributed black fly species in southwest

Factors Affecting Black Fly Larval Mortality and Carry of Two Formulations of Bacillus thuringiensis subsp. israelensis Tested in the Same Stream During a 3-Year Experiment

Over the last 20 years, many formulations of Bacillus thuringiensis subsp. israelensis (Bti) have been commercialized for the biological control of black flies in abatement programs. However, products were tested in different streams and under different environmental conditions, thus rendering the evaluation of the performance of liquid formulations of Bti very arbitrary or even impossible. Using a new field procedure, two commercial liquid formulations of Bti, Teknar HP-D and Vectobac 1200L, were for the first time tested within short time intervals in the same stream and under environmental conditions that allowed better comparison of the behavior and the performance (carry) of both products. Field results from tests using the products tested in either the same (replicate) or different environmental (abiotic) conditions were analyzed and compared. Results of the 3-year experiment showed that both water temperature and discharge had an important effect on the performance of both products (Teknar HP-D and Vectobac 1200L). In temperate water temperature (16°C) and similar discharge (70 l s -1 ), Teknar HP-D and Vectobac 1200L did not show a significant difference in their carry50 (distance where 50% of black fly larvae mortality is recorded). However, an increase in water temperature (20- 22°C) or in the discharge (250-350 l s -1 ) enhanced significantly the carry50 of both products with Vectobac 1200L having a longer carry than Teknar HP-D. Other abiotic elements such as the hyporheic zone and adsorption onto periphyton were also identified as factors affecting the behavior and the carry of the products. However, more work should be done on the loss of the residual dosages along the stream to better understand the relation between the dosages and the resulting field mortality that would lead to suggestions on how to improve Bti formulations.

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.

122 薩摩黒島におけるブユとその対策 : 殺虫剤の効力実地試験

122 薩摩黒島におけるブユとその対策 : 殺虫剤の効力実地試験

Biological control program against simuliids in the State of São Paulo, Brazil

In Brazil, the use of biological vector-control methods has been largely confined to experimental research, with little or no application of such techniques by public institutions responsible for implementing control programs. The notable exceptions have been the black fly control program carried out by the Health Secretariat in the State of São Paulo. Since the 1980s, São Paulo's "Superintendência de Controle de Endemias" has been conducting studies on the viability of using Bacillus thuringiensis (H-14) for simuliid control, and the results have been so encouraging that the agency has now incorporated this method into its Simuliid Control Program.

18 薩摩黒島におけるブユとその対策

18 薩摩黒島におけるブユとその対策

Residues of p,p′-DDE in lake trout in Little Moose Lake in New York State

Residues of p,p′-DDE were found in lake trout sampled in 1993 from Little Moose Lake located remotely in the Adirondack region of New York State. Length accounted for 81% of the variation in p,p′-DDE concentration when the data was fit to an exponential model. The presence of p,p′-DDE in the fish was believed due to its long persistence in the aquatic environment following applications of DDT in the 1950s for control of black flies and mosquitoes.

SHORT-TERM IMPACTS OF FORMULATIONS OFBACILLUS THURINGIENSISVAR.ISRAELENSISDE BARJAC AND THE ORGANOPHOSPHATE TEMEPHOS, USED IN BLACKFLY (DIPTERA: SIMULIIDAE) CONTROL, ON RHEOPHILIC BENTHIC MACROINVERTEBRATES IN THE MIDDLE ORANGE RIVER, SOUTH AFRICA

Summary The impacts of larvicides used in the control of blackflies (Diptera: Simuliidae) on macroinvertebrates in the stones-in-current biotope were assessed during 8 field trials in the middle Orange River, South Africa. Two Bacillus thuringiensis var. israelensis (B.t.i.) products (VectobacR 12AS and TeknarR HP-D) and the organophosphate temephos (AbateR 200EC) were applied at recommended and high dosages to simulate “operational” and “worst-possible” scenario's respectively. Mortality was evaluated either by direct counting of invertebrates on stones before and after application, or by ranking invertebrates on a 4-point relative abundance scale before and after application. In addition, the re-appearance of benthic invertebrate population densities after temephos application was examined. At the recommended dosage (1.2 ppm/10 min), B.t.i. significantly reduced blackfly larval numbers (P<0.001) and those of the chironomid Rheotanytarsus fuscus Freeman (P<0.05). At high dosage (20 ppm/10 min), numbers o...

FIELD EVALUATION OF THE PHOTOTOXIN, ALPHA-TERTHIENYL, FOR REDUCING LARVAL POPULATIONS OF BLACK FLIES (DIPTERA: SIMULIIDAE) AND ITS IMPACT ON DRIFT OF AQUATIC INVERTEBRATES

AbstractThe efficacy of alpha-terthienyl (α-T) for reducing larval populations of black flies was determined in two streams in southeastern Ontario. By 24 h post-treatment, larval black fly population reductions greater than 90% resulted from exposure to calculated dosages of 0.04 and 0.10 mg-L−1 α-T emulsifiable concentrate over distances of 1.0 and 1.5 km, respectively. Significant population reductions were not observed 2.3 km downstream from injection of the 0.10 mg·L−1 dosage, probably because a marshy area upstream from this sampling site slowed the transport and enhanced photodegradation of α-T. Alpha-terthienyl initiated catastrophic drift of benthic invertebrates that was not selective for any functional feeding group. Significant increases in post-treatment drift, relative to pre-treatment densities, were observed downstream from treatment for eight of 10 taxa studied and included filter-feeders, grazers, and predators. Upstream from treatment, significant increases between sampling days were observed for only two taxa. The catastrophic and nonselective impact of α-T on invertebrate drift preclude its usefulness as an alternative to black fly larvicides used currently, although specialized applications for α-T may exist in integrated black fly control programs.

Contingent Valuation of a Public Program to Control Black Flies

Contingent valuation is used to measure the benefits of a proposed public program to control black flies. Respondents’ reported values are analyzed from three perspectives: data outliers, consistency between respondents’ reported values and their perceptions of black flies, and the temporal reliability of the values expressed by respondents. The results suggest that the estimated contingent values are plausible even though a majority of respondents expressed a value of zero dollars for the black fly control program.

Empirical Models Predicting Ingestion Rates of Black Fly Larvae

Field experiments were performed in a gutter system to examine the effect of body size, water temperature, seston concentration, and particle type on the ingestion rate of Simulium venustum/verecundum larvae. Ingestion rates rose exponentially with increasing temperature between 9 and 19 °C (Q10 = 2.19, 95% CI 2.09–2.29) and rose asymptotically with seston concentration (range 0.7–30 mg∙L−1). Small larvae were more sensitive to variations in seston concentration than older instars. The type of particles offered also influenced the ingestion rate of larvae. Once corrected for body size, water temperature, and seston concentration, the data show that larvae ingested more of the natural seston and of a yeast suspension than of suspensions containing kaolinite. Ingestion rates of other simuliid species generally co-occurring at the outflow of lakes in early summer were of the same magnitude as those of S. venustum/verecundum, although significant differences were detected among species. Specific ingestion rates of simuliids decline with increasing mass, are similar to those measured for benthic detritivores, and tend to be higher than those of marine and freshwater zooplankton of similar size. The models are discussed with respect to black fly control with particulate larvicides.