Influence of selective treatment on Haematobia irritans infestation of untreated cattle

Abstract

6To reduce the use of insecticide treatments against Haematobia irritans we evaluated the 7 impact of treating 15% of the bovines, with the greatest number of flies including bulls, 8 with 40% diazinon ear tags, on the infestation of untreated cows. Horn fly susceptibility 9 to diazinon was measured before and after treatment, and peaks of infestation were 10 recorded. Three groups of Bradford bovines were evaluated: Group 1 (control untreated), 11 Group 2 (15% treated) and Group 3 (control 100% treated). Weekly counts of horn flies 12 were performed on the same animals for 78 days. Two peaks of infestation were recorded, 13 and a higher number of horn flies occurred in the untreated control group than in the 14 untreated cows of the selectively treated group throughout the entire period of the study, 15 except for a single week. The horn fly field population was significantly more susceptible 16 to diazinon than the reference susceptible strain both before and after insecticide 17 treatment. In conclusion, treatment of 15% of the most infested animals from a herd, with 18 40% diazinon ear tags, quickly reduced horn fly infestations of the entire herd and may 19 be a practical approach for horn fly control, reducing costs and chemical use. 20

Susceptibility of field populations of Haematobia irritans to fipronil in Uruguay

“…When generational treatments for R. microplus are in place (Cuore et al 2015), it is not necessary to overlap treatments targeting horn flies; furthermore, control of the second generation of R. microplus (two treatments are recommended) coincides with the strategic control of H. irritans, so control efforts can be optimized and the same insecticide can be used (Nari et al 2013). For livestock producers that are free of cattle ticks, the treatment of bulls (Miraballes et al 2018) or of bulls and 10% of the most infested cows may be used (Miraballes et al 2019), and for dairy farmers, walkthrough traps may be a good choice (Miraballes et al 2017).…”