Dynamics and Management of Insecticide Resistance in the Horn Fly, Haematobia Irritans Irritans (L.) (Diptera: Muscidae).

Studies on resistance of the horn fly, Haematobia irritans irritans (L.), to insecticides were conducted in Louisiana from 1989 to 1998. These studies included monitoring resistance and resistance dynamics under different strategies of insecticide use, monitoring the efficacy of insecticide products, establishing a relationship between bioassay findings and product efficacy, and evaluation of a new insecticide class. In four years (1989--1992), efficacy of 20% diazinon-impregnated car tags used yearly was reduced from greater than twenty to just one week of control, and tag failure was observed with resistance ratios (RR) from 1.8 to 5.7. Diazinon resistance developed more slowly and to a lower magnitude than that reported for pyrethroids. A strong correlation was found between RR and the frequency of flies (RF) surviving a 1.72 mug/cm2 discriminating concentration of diazinon. A high risk of diazinon tag failure was associated with a 5% RF in pre-season bioassays. Resistance among several organophosphate (OP) insecticides including fenthion, ethion, pirimiphos-methyl, and tetrachlorvinphos was observed following the development of resistance to diazinon. Esterase activity was significantly higher in OP-resistant flies than in susceptible flies from both laboratory colony and field population. From 1991 to 1997, the yearly rotation of lambda-cyhalothrin + piperonyl butoxide and pirimiphos-methyl ear tags was evaluated for control of pyrethroid-resistant horn flies in two locations. Control efficacy was reduced to a maximum of two and seven weeks for the synergized pyrethroid and OP tags in their last year of use, respectively. The rotation did not improve pyrethroid efficacy or prevent further development of resistance to the pyrethroid or the OP. During 1996 and 1997, the efficacy of experimental chlorfenapyr ear tags for horn fly control was evaluated under field conditions at one location, and the susceptibility of flies to chlorfenapyr was measured at seven locations in 1997. Ear tags containing either 30 or 40% chlorfenapyr were effective for fly control, and the number of weeks with \u3e90% fly reduction ranged from eight to eighteen. All field populations of horn flies, including those resistant to pyrethroids and OPs, were more susceptible to chlorfenapyr than were flies from a reference susceptible colony

Development of Haematobia irritans in bovine faecal masses maintained under laboratory conditions

Este estudo objetivou conhecer o período de desenvolvimento da mosca-dos-chifres (Haematobia irritans L., Diptera: Muscidae) em massas fecais (MF) de bovinos. Mensalmente, de maio/92 a abril/93, foram coletadas duas MF, 48 horas após deposição, e levadas ao Laboratório de Entomologia, em Corumbá, MS, para coletas diárias de insetos durante 30 dias. A emergência de H. irritans (n=171) ocorreu em 79,2% das MF, variando de 0 a 29 moscas/MF (média de 7,1). O período mínimo até a emergência (ovo-adulto) variou de 9 a 17 dias (temperaturas médias mensais de 23,2 a 30,2oC), respectivamente, durante o verão/início do outono, e no inverno, sugerindo que a H. irritans apresente cerca de 22 gerações anuais.This study investigated the developmental time of the horn fly (Haematobia irritans L., Diptera: Muscidae) in bovine manure. Monthly, from May 1992 to April 1993, two dung pats were collected 48 hours after dropping in the field, and brought to the Laboratory of Entomology, in Corumbá, MS, Brazil, for insect daily collections during 30 days. Emergency of H. irritans (n=171) was observed in 79.2% of the pats, ranging from 0 to 29 flies/pat (7.1 average). The period until fly emergency (egg to adult) ranged from 9 to 17 days (monthly mean temperatures ranged 23.2 to 30.2oC), during summer/autumn and winter, respectively, suggesting that H. irritans may have about 22 generations per year

Stable fly outbreaks in Brazil: a 50-year (1971-2020) retrospective

Abstract Over the last decades, stable fly (Stomoxys calcitrans) outbreaks associated with agricultural and/or livestock production systems have become a serious problem in some Brazilian locations. This article presents a survey on the history, evolution and mapping of such outbreaks in Brazil over five decades (1971-2020). Outbreaks (n= 579) were recorded in 285 municipalities from 14 states, mainly associated with by-products from the ethanol industry (82.7%), in natura organic fertilizers (12.6%) and integrated crop-livestock systems (3.1%). Few cases were reported until the mid-2000s, progressively increasing since then. Outbreaks associated with ethanol mills occurred in 224 municipalities, mainly in Southeast and Midwest states, while those associated with organic fertilizers (mainly poultry litter and coffee mulch) affected 39 municipalities, mostly in the Northeast and Southeast states. More recently, outbreaks in integrated crop-livestock systems during the rainy season have occurred in Midwest states. This survey highlights the magnitude of the problem of stable fly outbreaks in Brazil and its relationship with environmental public policies, agricultural production chains and regional trends. Specific public actions and policies are urgently needed to prevent their occurrence and impact in the affected regions

Survey of pyrethroid and organophosphate resistance in Brazilian field populations of Rhipicephalus (Boophilus) microplus: Detection of C190A mutation in domain II of the para-type sodium channel gene

AbstractThe cattle tick Rhipicephalus (Boophilus) microplus causes expressive damage to livestock in Brazil and other countries. Its control is becoming more difficult due to the development of resistance in populations. Early detection of resistance can help in developing effective control strategies. This study evaluated the susceptibility of R. microplus to cypermethrin and chlorpyriphos and was the first attempt to identify the mechanism of resistance (target site insensitivity) in cattle tick populations from Minas Gerais state (Southeastern Brazil). Engorged female ticks were collected from 10 ranches within the state of Minas Gerais, and susceptibility was evaluated with the larval packet test (LPT) using technical grade cypermethrin and chlorpyriphos. It was possible to analyze LPT results of seven populations. Target site insensitivity was investigated in all 10 isolates by using molecular approaches for detection of the T2134A substitution within the domain III S6 segment and the C190A in the domain II S4-5 linker from the para-type sodium channel gene. LPT showed that all seven populations were resistant to cypermethrin with resistance ratio (RR) ranging from 16.0 to 25.0 and 85.7% were resistant to chlorpyriphos (RR=2.2–15.6). Although the T2134A mutation was not detected, the C190A mutation was highly prevalent, being present in 82–100% of the alleles sampled in field populations. A significant correlation was found between the LC50 values for cypermethrin and the frequency of the C190A mutation suggesting that it might be responsible for the phenotypic resistance detected

Desenvolvimento de Haematobia irritans em massas fecais de bovinos mantidas em laboratório

Este estudo objetivou conhecer o período de desenvolvimento da mosca-dos-chifres (Haematobia irritans L., Diptera: Muscidae) em massas fecais (MF) de bovinos. Mensalmente, de maio/92 a abril/93, foram coletadas duas MF, 48 horas após deposição, e levadas ao Laboratório de Entomologia, em Corumbá, MS, para coletas diárias de insetos durante 30 dias. A emergência de H. irritans (n=171) ocorreu em 79,2% das MF, variando de 0 a 29 moscas/MF (média de 7,1). O período mínimo até a emergência (ovo-adulto) variou de 9 a 17 dias (temperaturas médias mensais de 23,2 a 30,2ºC), respectivamente, durante o verão/início do outono, e no inverno, sugerindo que a H. irritans apresente cerca de 22 gerações anuais

Anti-tick potential forrage. Volatile substances effect on infestive larvae of Boophilus microplus (Can., 1887)

Foram investigadas as espécies Andropogon gayanus cv. Planaltina, Brachiaria brizantha cv. Marandu, Melinis minutiflora, Stylosanthes guianensis cv. Bandeirante e Stylosanthes viscosa (CPAC 1403), quanto à ação de substâncias voláteis antilarvas de Boophilus microplus. Nas forrageiras, cultivadas em canteiros, foram depositados envelopes contendo larvas em diferentes localizações nas plantas, de forma a não haver contato direto entre larvas e forrageiras. Em um primeiro experimento, as coletas dos envelopes foram realizadas aos dois e cinco dias, e no segundo, aos cinco e dez dias, analisando-se a atividade e sobrevivência das larvas nestes períodos de exposição. Nenhuma das forrageiras apresentou qualquer efeito causado por substâncias voláteis que possa ser considerado como prejudicial às larvas de B. microplus, independentemente de sua localização e do tempo de exposição.In the pasture species Andropogon gayanus cv. Planaltina, Brachiaria brizantha cv. Marandu, Melinis minutiflora, Stylosanthes guianensis cv. Bandeirante and Stylosanthes viscosa the presence of anti-tick volatile substances that act against infestive Boophilus microplus larvae was investigated. Gauze sachets containing tick larvae were deposited in the pasture plots in different places, without direct contact between pasture and larvae. In a first experiment, collections were made at two and five days, and in the second experiment, at five and ten days, analysing the activity and survival of tick larvae. No species showed any effect that could be considered as anti-tick effect with respect to localization of B. microplus larvae or exposure time

Tabanidae (Diptera) of Amazônia XX. Description of Tabanus pseudonebulosus n.sp.

Tabanus pseudonebulosus , new species, is described based on 217 female specimens and 5 males collected in Venezuela (Guarico, Aguaio, Santa Elena, and Palmarito) and in Brazil (Pará: Santana do Araguaia, Serra das Andorinhas in São Geraldo do Araguaia, Serra Norte Carajás and Gorotire; Amazonas: Canutama; Mato Grosso do Sul: Corumbá), mostly in open vegetation, scrub forest and in rocky environments. Observed intraspecific variation in the specimens is presented and related to collection localities, and morphological differences are diagnosed in relation to the similar species Tabanus nebulosus DeGeer 1776 and T. importunus Wiedemann 1828. Morphometrical data and indices for specimens in different localities are provided. Drawings and photo of the new species are presented