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At least 73 records · Page 4Linked to original sources
PubMed1999

Influence of permethrin, diazinon and ivermectin treatments on insecticide resistance in the horn fly (Diptera: Muscidae).

The history of insecticide resistance in the horn fly, Haematobia irritans, and the relationship between the characteristics of horn fly biology and insecticide use on resistance development is discussed. Colonies of susceptible horn flies were selected for resistance with six insecticide treatment regimens: continuous single use of permethrin, diazinon and ivermectin: permethrin-diazinon (1:2) mixture; and permethrin-diazinon and permethrin-ivermectin rotation (4-month cycle). Under laboratory conditions, resistance developed during generations 21, 31 and 30 to permethrin, diazinon and ivermectin, respectively. The magnitude of resistance ranged from < 3-fold with ivermectin to 1470-fold with permethrin. Field studies demonstrated that use of a single class of insecticidal ear tag during the horn-fly season resulted in product failure within 3-4 years for pyrethroids and organophosphates, respectively. In laboratory studies, use of alternating insecticides or a mixture of insecticides delayed the onset of resistance for up to 12 generations and reduced the magnitude of pyrethroid resistance. In field studies, yearly alternated use of pyrethroids and organophosphates did not slow or reverse pyrethroid resistance (Barros et al., unpublished data), while a 2-year alternated use with organophosphates resulted in partial reversion of pyrethroid resistance. When pyrethroid and organophosphate ear tags were used in a mosaic strategy at two different locations, efficacy of products did not change during a 3-year period.

Animals↗
PubMed2000

Chlorfenapyr ear tags to control Haematobia irritans (L.) (Diptera: Muscidae) on cattle.

The efficacy of ear tags containing 30% chlorfenapyr (total tag weight=13g) to control natural Haematobia irritans (L.) infestations was evaluated for Holstein heifers in Rafaela, province of Santa Fe, Argentina. A group of heifers (TG) was treated with two ear tags (one tag per ear). A control group (ACG) was maintained in a paddock adjacent to the TG paddock and, a distant control group (DCG) was maintained 700m apart from the other groups. From day 4 to day 98 after treatment, H. irritans infestations of ACG were significantly higher (P<0.05, test of Kruskal-Wallis) than the corresponding infestation of TG, but significantly lower than infestation in DCG, probably due to the proximity of TG. The chlorfenapyr control period, with an efficacy higher than 90% to reduce horn fly populations, lasted for 9 weeks when TG infestation was compared to fly numbers in ACG, but increased to 12 weeks in comparison to DCG. The results of this study show that ear tags impregnated with chlorfenapyr are a useful alternative to pyrethroids and organo-phosphate compounds for horn fly control.

Administration, Topical↗
PubMed2001

Horn fly (Diptera: Muscidae) resistance to organophosphate insecticides.

Insecticidal ear tags impregnated with organophosphate (OP) insecticides were used each year from 1989 to 1998 at Rosepine, LA. Weekly fly counts were conducted to evaluate control efficacy of the treatments, and bioassays were conducted at least twice per year to measure fly susceptibility to OP and pyrethroid insecticides. Between 1989 and 1992, the efficacy of 20% diazinon-impregnated ear tags was reduced from >20 to just 1 week of control. A high risk of control failure was observed when a resistance frequency of approximately 5% was measured in pre-season bioassays. Resistance to diazinon, fenthion, ethion, pirimiphos-methyl, and tetrachlorvinphos was observed. Esterase activity toward alpha-naphthyl acetate was significantly higher in flies collected at Rosepine in 1997 than in flies from a laboratory colony and from a susceptible field population.

Administration, Topical↗
PubMed2001

Toxicity of cypermethrin and diazinon to Haematobia irritans (Diptera: Muscidae) in its American southern range.

Synthetic pyrethroids are considered currently less effective than organophosphate insecticides for controlling Haematobia irritans on cattle in its American southern range. To test the validity of this hypothesis, horn fly populations from 95 cattle herds in central-northern Argentina and southern Brazil were evaluated to determine 50% lethal concentrations (LC(50)) to cypermethrin and diazinon, respectively. Horn flies were exposed to filter papers and glass vials treated with cypermethrin and diazinon, respectively, and LC(50) values were determined using probit analysis. Two and 78 fly populations showed LC(50) values indicating susceptibility and resistance to cypermethrin, respectively, in comparison to historical LC(50) values obtained when the horn fly populations were susceptible to cypermethrin. Five fly populations had an undetermined resistance status to cypermethrin. The diazinon tests showed no obvious indications of H. irritans resistance. Thirty nine percent of farmers still rely on pyrethroids to control horn fly populations on cattle which represents a decreasing proportion from a few years ago when horn fly control was carried out using pyrethroids almost exclusively. Organophosphates could provide control for horn flies resistant to pyrethroids; however, the reliance on chemicals alone to control H. irritans is not considered a proper approach for the future.

Animals↗
PubMed2002

Comparison of two methods (visual estimates and filming) for counts of horn flies (Haematobia irritans irritans) (L.) (Diptera: Muscidae).

Visual estimates are generally used for counts of horn flies, Haematobia irritans (L.) and play an important role as an instrument to quantify fly populations in scientific studies. In this study, horn fly counts were performed on 30 Nelore steers in the municipality of Araçatuba, SP Brazil, from January to December 1998. Flies were counted weekly by two methods: the estimate method whereby estimates of the number of flies on one side of the animal are obtained by visual observation, and the filming method whereby images of flies from both sides of the animal are recorded with a video camera. The tape was then played on a videotape recorder coupled to a television and the flies were counted on the screen. Both methods showed variations in horn fly population density during the period studied. However, significant differences (p < 0.05) were observed between the two methods with the filming method permitting the visualization of a larger number of flies than the estimate method. In addition, the filming method permitted safe and reliable counts hours after the images were taken, with the advantage that the tape can serve as an archive for random re-counts.

Animals↗
PubMed2002

A study of relative horn fly, Haematobia irritans (Diptera: Muscidae), abundance on Holstein steers and steers of two Holstein crosses.

A study was performed to determine if the number of horn fly (Haematobia irritans) adults differ significantly on Holstein (black and white coat color), Holstein x Holstein Friesian (black and white coat color) and Holstein x Jersey (black coat color) steers, 10-12 months old at the onset of the study. All steers were run together on lucerne paddocks and the number of flies counted at 30-day intervals from September 2000 to August 2001. No significant differences (P > 0.05, test of Kruskal-Wallis) were found in fly numbers, even in the period April-May 2001 when the infestation reached its peak. We were unable to demonstrate that coat color influenced horn fly abundance in the present study. It appears that none of the biotypes evaluated had any advantage for natural control of H. irritans.

Animals↗
PubMed1999

Evaluation of a yearly insecticidal ear tag rotation for control of pyrethroid-resistant horn flies (Diptera: Muscidae).

From 1991 to 1997, the yearly alternated use of synergized pyrethroid (lambda-cyhalothrin + piperonyl butoxide) and organophosphate (pirimiphos-methyl) ear tags was evaluated for the control of two pyrethroid-resistant horn fly populations in Louisiana. At each site, weekly fly counts were used to assess product efficacy. Control achieved by synergized pyrethroid ear tag treatments was reduced from 7 to 2 weeks and from 4 to 0 weeks at St. Joseph and Winnsboro, respectively. Control by organophosphate ear tags decreased from 15 to 3 weeks and from 10 to 7 weeks at St. Joseph and Winnsboro, respectively. The rotation of synergized lambda-cyhalothrin and pirimiphos-methyl ear tags did not improve pyrethroid ear tag efficacy or prevent further development of resistance to the pyrethroid or OP compound.

Animals↗
PubMed2006

The life-cycle of Philornis downsi (Diptera: Muscidae) parasitizing Darwin's finches and its impacts on nestling survival.

The fly, Philornis downsi Dodge & Aitken, was first collected in 1964 on the Galápagos Islands and is now widespread across the archipelago. Virtually nothing is known about the behaviour and ecology of the fly as well as for the genus in general. Here, we describe all larval instars for the first time, and discuss infection intensity and impacts of parasitism on nestling survival of Darwin's finches. Adult P. downsi are non-parasitic free-living flies, whereas the larvae are obligate blood-feeding parasites on nestling birds. The larvae show a marked shift in their host site specificity--a novel finding for the genus Philornis: the first and early second larval instars live as agents of myiasis in finch nostrils and other tissues, while the older second and third instar larvae reside in the nest material and feed externally on the blood of nestlings, leading to blood losses in nestlings of 18-55%. Pupation occurs in the bottom layer of the nest. The combined effects of tissue damage by the endoparasitic instar larvae and anaemia by nest-dwelling haematophagous instar larvae account for the high nestling mortality (76%) due to Philornis parasitism. This represents the highest mortality by Philornis reported in the literature and emphasizes the extremely serious threat this parasite poses for the endemic passerine fauna of the Galápagos Islands.

Anemia↗
PubMed2001

Long-term study of Haematobia irritans (Diptera: Muscidae) seasonal distribution in central Argentina with focus on winter fly abundance.

The seasonal distribution of Haematobia irritans (Linnaeus, 1758) was evaluated at 31 degrees 12' S-61 degrees 29' W, Santa Fe, Argentina from November 1992 to August 2000 by weekly fly counts on 20 Holstein cows not treated against ectoparasites. The analysis was mainly focused on winter fly abundance. Two peaks of abundance were found from spring to autumn. Adults of H. irritans were consistently found on cattle during winter, with increasing numbers from the end of July to late August. The only climatic parameter soundly correlated with the four week period, before each winter fly count, was the mean air temperature with the exception of year 1998. No significant relationship was found between level of cow infestation and relative humidity, saturation deficit and rainfall. Horn fly infestation on cows was lower than 20% from end of June to end of August only in 1995, when mean air temperature was consistently lower than 11 degrees C during the four week period previous to most fly counts. Conversely, the mean temperature was higher than 12 degrees C previous to fly counts in 1998, when most cows remained infested. The results indicate that a proportion (unknown) of immature stages of H. irritans were insensitive to diapause inducing factors and developed through winter.

Animals↗
PubMed2001

A shoot-fly Atherigona tritici sp. n. (Diptera: Muscidae), attacking wheat Triticum aestivum in Egypt.

The two 'forms' of the Afrotropical shoot-fly Atherigona rubricornis Stein are shown to be good species. A neotype is designated for the true A. rubricornis, which is restricted to tropical Africa. The other form is described as A. tritici sp. n. It is widespread in tropical Africa, but is known also from Egypt, where the larvae attack wheat seedlings, Israel and Yemen. Infestation levels of larvae, with maxima between 9% and 32%, indicate that it is a significant pest of wheat seedlings in Egypt.

Animals↗
PubMed2006

The effects of host physiology on the attraction of tsetse (Diptera: Glossinidae) and Stomoxys (Diptera: Muscidae) to cattle.

In Zimbabwe, studies were made of the numbers of tsetse (Glossina spp.) and stable flies (Stomoxys spp.) attracted to cattle of different nutritional status, age and sex. Host odours were analysed to determine the physiological basis of these differences and improved methods are described for measuring rates of production of kairomones. Seasonal fluctuations in host weight, related to changes in pasture quality, had no significant effect on attraction of tsetse or Stomoxys. However, both attraction to different individuals and carbon dioxide production by these individuals were strongly correlated with weight, suggesting a possible link. Attraction to the odour from different types of cattle decreased in the order ox>cow>heifer>calf, and oxen were twice as attractive as calves of less than 12 months old. Lactation did not alter the relative attractiveness of cows. Calves less than six months old produced lower levels of carbon dioxide, acetone, octenol and phenols than oxen, but for older calves and cows, levels of production of known kairomones and repellents were similar to those of an ox. Carbon dioxide produced by cattle varied according to time of day and the animal's weight; cattle weighing 500 kg produced carbon dioxide at a mean rate of 2.0 l min(-1) in the morning and 2.8 l min(-1) in the afternoon compared to respective rates of 1.1 and 1.9 l min(-1) for cattle weighing 250 kg. Artificially adjusting the doses of carbon dioxide produced by individual cattle to make them equivalent did not remove significant differences in attractiveness for tsetse but did for Stomoxys. Increasing the dose of carbon dioxide from 1 to 4 l min(-1) in a synthetic blend of identified kairomones simulating those produced by a single ox, increased attractiveness to tsetse but not to the level of an ox. The results suggest that the main sources of differences in the attractiveness of individual cattle are likely to be variation in the production of carbon dioxide and, for tsetse, other unidentified kairomone(s). The biological and practical implications of these findings are discussed.

Acetone↗