dicyclanil and cyromazine

To determine whether a cyromazine-resistant strain of Lucilia cuprina was able to establish strikes sooner than a susceptible strain on cyromazine- or dicyclanil-treated sheep.. Groups of 7 sheep were treated with cyromazine or dicyclanil in accordance with label directions. Beginning 5 weeks after treatment, 5 sheep from each group were challenged by implantation of neonate larvae belonging to the cyromazine-resistant strain 'Nimmitabel-selected' and the susceptible blowfly strain 'Field 2011' according to standard larval implant technique. The implant sites were alternated between the shoulder, mid-back and rump within the treatment zone. Similarly, implants of the resistant and susceptible strain larvae were alternated at each challenge such that the strain implanted on the left side of the sheep at one challenge was implanted on the right side at the next. Challenges were conducted at 3-weekly intervals until the susceptible larvae formed strikes on at least 2 of the 5 sheep in a treatment group or until 29 weeks after treatment.. Sheep treated with cyromazine or dicyclanil were protected from flystrike by the cyromazine-susceptible strain for periods consistent with, or longer than, the registered product label claims. The cyromazine-resistant strain created strikes several weeks sooner after treatment than did the susceptible strain. Accordingly, the protection periods provided by cyromazine and dicyclanil against the resistant strain were reduced from 14 and 18-24 weeks to <8 weeks and <11 weeks, respectively.. Resistance, even in the pure-breeding resistant strain, was not so severe as to cause treatment failure with cyromazine or dicyclanil, but was sufficient to reduce the protection period provided. It is recommended that producers adopt management practices that minimise the development of resistance to these and other compounds.

Topics: Animals; Diptera; Insecticide Resistance; Insecticides; Juvenile Hormones; Larva; New South Wales; Sheep; Sheep Diseases; Triazines

Late in 2017, field samples of the Australian sheep blowfly, Lucilia cuprina, were submitted by sheep producers from three states of Australia (South Australia, Victoria and New South Wales). Some were collected by submitters concerned about shortened periods of flystrike protection from dicyclanil based products. Neonate larval offspring from the NSW field samples survived and successfully completed their life cycles following exposure to dicyclanil and cyromazine at susceptible discriminating concentrations in vitro. The in vivo study reported here used dicyclanil resistant neonate larvae to assess the flystrike protection provided by a cyromazine jetting fluid and a number of dicyclanil based spray-on products, when applied to sheep six weeks after shearing. The two dicyclanil resistant blowfly strains used in this study showed in vitro resistance ratios, at the LC50, of approximately 13- and 25-fold relative to a dicyclanil and cyromazine susceptible strain. Compared to the levels of resistance that L. cuprina has developed to other insecticides these are relatively low, however, three dicyclanil based spray-on products (active ingredient 12.5 g/L, 50 g/L and 65 g/L) had protection periods reduced by 73%, 78% and 69% respectively when compared to the maximum protection periods claimed by the manufacturer. A 50% and a 33% reduction in protection period was also observed to a cyromazine and an ivermectin based jetting fluid respectively. In contrast, protection periods were attained or exceeded regardless of the treatment used against field derived dicyclanil susceptible neonate larvae. For the first time we confirm that dicyclanil resistance enables the completion of the L. cuprina life cycle following flystrike initiation on dicyclanil or cyromazine treated sheep when insecticide levels are considered high and protective. This study also provides in vivo information on the effect of dicyclanil resistance on the protection provided by a product with an active ingredient belonging to an unrelated insecticide group. Dicyclanil resistance is of major concern to the Australian sheep industry.

Topics: Animals; Australia; Calliphoridae; Diptera; Humans; Infant, Newborn; Insecticide Resistance; Insecticides; Juvenile Hormones; Sheep; Sheep Diseases; Triazines

To demonstrate the protection of Merino sheep from flystrike by Lucilia cuprina with cyromazine or dicyclanil in an implant study and in the field.. In the implant study, sheep were treated with cyromazine or dicyclanil and implanted with 1st-stage larvae from a newly isolated field strain of L. cuprina (CYR-LS) or a reference strain (DZR50), then assessed over 3 days and compared with the implants on untreated control sheep. In the field study, weaner lambs were treated with cyromazine or dicyclanil and monitored weekly for flystrike over 18 weeks of grazing on the same farm from which the L. cuprina were isolated.. Implant study: cyromazine (6%) provided effective protection against CYR-LS and DZR50 L. cuprina for a minimum of 13 and 10 weeks, respectively. Dicyclanil (5%) provided at least 18 weeks' protection against both strains. Field study: only 1 of 386 lambs in the cyromazine-treated group was struck in the first 14 weeks of the trial. No strikes occurred in the 198 sheep treated with dicyclanil (5%). Rainfall, temperature and flytrap data indicated consistent fly pressure during the study.. Based on the results of these studies, there was no evidence of reduced susceptibility to cyromazine or dicyclanil and the periods of protection of sheep against L. cuprina were unaffected and consistent with the registered label claims.

Topics: Administration, Topical; Animals; Diptera; Ectoparasitic Infestations; Insecticides; Juvenile Hormones; Male; Random Allocation; Sheep; Sheep Diseases; Triazines

Cyromazine and dicyclanil are both used as insect growth regulators. This paper describes an easy and innovative simultaneous extraction method for residues of cyromazine and dicyclanil in food of animal origin, and a confirmation procedure using UHPLC-MS/MS. The sample was extracted, deproteinised by 1% trichloracetic acid in water-acetonitrile, followed by selective defatting using hexane based on the degree of matrix complexity; cleaned-up on an mixed-mode cation exchange (MCX) cartridge; and quantified by using matrix-matched calibration. The mean recoveries were all between 62.0% and 99.2%, and the RSDs were all below 9.94%. The present method was rapid, sensitive and reliable, which was applied to the quantitative analysis of these residues in animal tissues.

Topics: Animals; Calibration; Chromatography, High Pressure Liquid; Juvenile Hormones; Limit of Detection; Meat Products; Pesticide Residues; Reproducibility of Results; Tandem Mass Spectrometry; Triazines

In three multicentered field trials run during 1995 to 1997, involving a total of 12,928 lambs, the preventive effects on blowfly strike of a ready-to-use 5 per cent dicyclanil pour-on formulation and of a ready-to-use 6 per cent cyromazine pour-on formulation were compared with untreated controls for periods of up to 22 weeks. Their efficacy was assessed by calculating the consolidated cumulative strike rate for each treatment group and the consolidated percentage reduction of flystrike achieved by the two formulations. The consolidated cumulative strike rate for all three years together reached 29.2 per cent for the untreated control lambs at week 22, 2.8 per cent for the dicyclanil-treated lambs at week 22, and 6.9 per cent for the cyromazine-treated lambs at week 20. The consolidated cumulative percentage reduction of blowfly strike remained above 89 per cent for the dicyclanil-treated lambs. For the cyromazine-treated lambs the consolidated cumulative percentage reduction of blowfly strike reached 90 per cent during weeks 9 to 10, and 80 per cent during weeks 11 to 12.

Topics: Animals; Diptera; England; Insect Bites and Stings; Insecticides; Juvenile Hormones; Proportional Hazards Models; Rain; Sheep; Triazines