Abundance of stable flies on heifers treated for control of horn flies with organophosphate impregnated ear tags.

Ear tags containing 40% organophosphate insecticides (diazinon or diazinon plus chlorpyrifos-ethyl) were applied to control Haematobia irritans (L.) (Diptera: Muscidae) in treated (TG01 and TG02) and untreated (UG01 and UG02) groups of Holstein heifers born in 2001 and 2002, respectively. Control and treated groups were assessed for the abundance of Stomoxys calcitrans (L.

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.

Dynamics of cypermethrin resistance in the field in the horn fly, Haematobia irritans.

The toxicity of cypermethrin to the horn fly Haematobia irritans (L.) (Diptera: Muscidae) was determined for samples collected from untreated herds at a farm in central Argentina from October 1997 to May 2001. Field tests of the efficacy of cypermethrin against horn flies were first carried out at this farm in 1993, when the fly was shown to be susceptible to pyrethroids.

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.

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.