Pesticide use and residues on Queensland wool

Objective To determine practices for control of louse infestation and blowfly strike in Queensland sheep flocks that are associated with organophosphorous and synthetic pyrethroid residues on wool.
Design Information on residues was obtained from a survey of Queensland wool clips. Information on pesticide use was obtained from a trace-back postal survey. The association between pesticide use and residues was assessed using generalised linear models, controlling for potential confounding by flock location.
Procedure Between 1995 and 1997 Queensland wool clips were randomly sampled. Samples were tested for the presence and amount (mg per kg of greasy wool) of organophosphorous and synthetic pyrethroid pesticides. A questionnaire seeking information on flock characteristics and pesticide use was sent to the manager of each flock from which a wool sample was tested.
Results The median amount of OP and SP residue was 0.8 and 0.25 mg/kg, respectively, and 91 and 95% of wool samples contained < 8 mg/kg of OP and SP residues, respectively. The frequency of OP pesticide use for louse control was significantly (P = 0.005) associated with mean OP residue amount, and the timing of SP use for louse control, in relation to shearing, was significantly (P < 0.001) associated with mean SP residue amount.
Conclusion Most Queensland wool clips have acceptable amounts of residues after the use of OP and SP pesticides, but wool growers can further reduce residues by effectively controlling louse infestation with pesticide applications early after shearing and the use of non-chemical methods of ectoparasite control.     

Surveys to assess the amount of pesticide in wool and the use of pesticides by woolgrowers in Queensland.

OBJECTIVE: To measure the amounts of pesticide residue in wool grown in Queensland between 1997 and 1999, and to describe the use of pesticides for the control of lice infestations and blowfly strike in Queensland sheep flocks. DESIGN: Pesticide residues were measured in a random sample of wool from Queensland clips offered for sale during 1998 and 1999. Information on pesticide use was obtained from a trace-back postal survey. PROCEDURE: Samples taken from wool lots were tested for the presence and amount of organophosphorus (OP), synthetic pyrethroid (SP) and insect growth regulator pesticides. A questionnaire seeking information on flock characteristics and pesticide use was sent to the manager of each flock from which a wool sample was tested. RESULTS: The mean amount of OP and SP residue was 2.0 and 0.8 mg/kg, respectively. Ninety-five and 98% of wool samples contained < 9 mg/kg and 7 mg/kg of OP and SP residues, respectively. The mean amount of cyromazine, diflubenzuron and triflumuron was 12.7, 5.8 and 13.0 mg/kg, respectively. The amounts of OP, cyromazine and triflumuron residues were greater in wool from flocks located in southern Queensland. CONCLUSION: Most (95%; 95% CI, 92-97%) Queensland wool clips grown between 1997 and 1999 meet the suggested Australian maximum acceptable residue amounts for OP and SP pesticides.     

Inspection of wool lots at sales as a diagnostic test for louse infestation

The accuracy of visual inspection of wool lots for lice as a test for louse infestation was estimated using information provided by 178 woolgrowers in Queensland, Australia. The estimated sensitivity of inspection was 36% (95% confidence interval, 19-58%) and the specificity was 95% (95% CI, 88-98%). Accuracy was influenced by timing, after shearing, of pesticide application for louse control and by class of pesticide last applied after shearing. Visual inspection was less sensitive (29%) if pesticides were applied >3 months after shearing and less sensitive (21%) if an insect growth regulator was the class of pesticide last used after shearing. Based on 36% sensitivity, it was estimated that 16 inspections would have to be conducted to reduce the false negative test rate to <20% in the study population. We suggest that visual inspection of wool lots could be used to efficiently monitor the prevalence of louse infestations in Queensland sheep flocks. Positive inspection results are more likely to represent real louse infestations, rather than a false test result, in flocks grazed in the more extensive regions of Queensland.     

Sheep blowfly strike reduction using a synthetic lure system

The effectiveness of a synthetic lure system to reduce the incidence of blowfly strike in sheep flocks was assessed, using randomised field trials. Four field trials used eight total groups of sheep randomised to treatment (flytrap) or control on two properties in southern Queensland between 1999 and 2001. Treatment consisted of the operation of flytraps in paddocks as per manufacturer's recommendations. All sheep were inspected physically each month for flystrikes. Flytraps were associated with a reduction in flystrike incidence of 38-55%, compared to control sheep. Results confirm that traps are a useful component of a flystrike-control program. The use of fly traps by a substantial proportion of woolgrowers could assist the Australian wool industry to meet targets of reduced pesticides on shorn wool.     

Prevalence and clustering of louse infestation in Queensland sheep flocks.

Information provided by wool growers in Queensland, Australia between 1995 and 1997 was used to assess the prevalence and spatial distribution of louse (Bovicola ovis) infestation in sheep flocks. The estimated prevalence of louse-infested flocks was 40% (95% confidence interval, 35-46%). Although the prevalence of infestation was higher in western regions (41-50%) compared to the south region of Queensland (31%), the difference was not statistically significant (P > 0.05). Significant (P = 0.02) clustering of infested flocks was detected in the south region where two foci were apparent. We conclude that Queensland sheep flocks have a moderate prevalence of louse infestation, and that clustering of infestation is not strong. The control of lice is an industry-wide issue that needs to be addressed by most wool growers in Queensland.     

A postal survey of blowfly strike occurrence in two Queensland shires

OBJECTIVE: To describe the occurrence of blowfly strike in sheep flocks in two shires located in south-eastern Queensland. DESIGN: Postal survey of woolgrowers within Stanthorpe and Inglewood shires. PROCEDURE: Questionnaire posted to woolgrowers in June 1999 seeking information on the monthly occurrence of flystrike and number of sheep at risk. RESULTS: Incidence of body strike and breech strike between August 1998 and May 1999 was 1.1 and 0.5%, respectively. The highest incidence of body strike and breech strike was reported in lambs (6.1%) and weaner sheep (1.5%), respectively. The seasonality of the incidence of body strike was bimodal (November and February), whereas the seasonality of the incidence of breech strike was unimodal (April). Occurrence of body strike within a 3-month period in flocks located within 40 to 50 km of each other was significantly (P < 0.05) clustered. CONCLUSION: Body strike appears to be more common than breech strike in the study area, mainly affects lambs and weaners and high-risk periods occur during late spring and autumn. Study results provide valuable information for planning blowfly strike control programs in the area such as timing of management procedures, use of fly traps), and enable the economic impact of flystrike on the industry in this area to be assessed.     

Effectiveness of a synthetic lure to reduce blowfly strike incidence: preliminary observations

The effectiveness of a synthetic lure system (Lucitrap) to reduce blowfly strike incidence was assessed in a field trial conducted on two properties located in southern Queensland, Australia. Nine hundred and fifty sheep were randomised to treatment (one or more Lucitrap per 100 sheep) and control paddocks. Sheep were physically inspected for flystrike each month between August 1999 and May 2000. On one property, the risk of flystrike in the control group was 1.86 times (95% confidence interval, 1.19-2.90) greater than that in the treatment group. On the other property, two cases of flystrike were detected in the control group, but no cases were detected in the treatment group. These preliminary observations suggest that the use of Lucitrap can reduce the incidence of blowfly strike by up to about one-half. Blowfly traps have a role in controlling flystrike in circumstances in which sheep are susceptible to flystrike and the likelihood of flystrike occurring is at least moderate. The use of fly traps could assist the Australian wool industry to meet targets of reduced pesticide use.     

Prevalence and regional distribution of scab, lice and blowfly strike in Great Britain

The prevalence of psoroptic mange (sheep scab), louse infestation and blowfly strike in sheep in Great Britain between March 2003 and February 2004 was investigated by means of a retrospective postal survey, stratified by region. Of the 3530 questionnaires sent out, 1067 were returned completed, a response rate of 30.2 per cent. Overall, 9 per cent of the farmers reported at least one outbreak of scab, 10.7 per cent reported an outbreak of lice and 75 per cent reported at least one case of blowfly strike. A mean of 1.4 per cent of ewes were struck by blowfly and 2.8 per cent of lambs. There were strong regional variations in disease prevalence, with scab and lice infestation being highest in Wales, Scotland and the north of England and blowfly strike highest in the south west of England.     

A survey of the prevalence of blowfly strike and the control measures used in the Rûens area of the Western Cape Province of South Africa

Blowfly strike and the methods used to combat blowfly strike were recorded on 33 properties in the R?ens area of South Africa during 2003/2004. Data were recorded on Merino and Dohne Merino hoggets (n = 4951) with at least 3 months' wool growth. The following data were captured: presence or absence of strike, site of the strike (body or breech), presence or absence of dermatophilosis as well as subjective scores for wool quality and wool colour. Control measures recorded include: chemical treatment (preventative and spot treatment), crutching, mulesing and the use of the Lucitrap system. Blowfly strike was not significantly influenced by gender or breed. Hoggets suffering from dermatophilosis were more likely to be struck, compared with contemporaries not suffering from the skin disorder (0.057 vs 0.027; P < 0.05). Merino hoggets generally had higher scores than their Dohne Merino contemporaries for wool quality (32.6 vs 27.4; P < 0.05) and wool colour (29.0 vs 27.2; P < 0.05). There was an indication that the Lucitrap system may have reduced flystrike, but the effect was not statistically significant (P = 0.19 for overall strikes and P = 0.12 for body strike). The Mules operation benefited overall flystrike (0.013 vs 0.110; P < 0.05); mainly through an effect on breech strike (0.010 vs 0.109; P < 0.05). The proportion of fly strikes increased with wool length, and declined with an increase in farm size in wool colour score. None of the ethically acceptable control measures assessed could substantially reduce blowfly strike on their own, and an integrated pest management programme was proposed.     

Forecasting blowfly strike in Queensland sheep flocks

The occurrence of blowfly strike between 1993 and 1999, derived from the reported use of pesticides for flystrike control, was investigated in 247 sheep flocks in Queensland, Australia using autoregressive techniques. Although there was a small increase (0. 0016 per year) in flystrike incidence during the study period, this long-term linear trend was not significant (p=0.53). The occurrence of flystrike was best described by an autoregressive model that included flystrike in the previous 2 months: flystrike(t)=0.0170+0. 0392 flystrike(t-1)+0.3589 flystrike(t-2). Flystrike was associated with the southern oscillation index (SOI). The SOI is based on barometric pressure readings and is associated with periods of below- (negative SOI) and above-average (positive SOI) rainfall in northern Australia. Flystrike incidence was significantly (p=0.03) greater in months in which the SOI was positive. The strongest correlation (r=0.33) was found between flystrike incidence and the SOI 2 months previously. Using the SOI, the best-fitting autoregressive model describing flystrike was flystrike(t)=0.0238+0. 3033 flystrike(t-2)+0.0009 SOI(t-2). The incidence of flystrike was significantly (p<0.05) correlated with average monthly radiation (r=0.26), but not with average monthly maximum and minimum temperature, total rainfall, evaporation and vapour pressure. The best-fitting autoregressive model describing flystrike occurrence based on these variables was flystrike(t)=-0.0259+0.3610 flystrike(t-2)+0.0022 radiation(t). Results suggest that a useful early-warning system could be developed based on the correlation between flystrike incidence and the SOI up to 2 months previously. Such attempts to forecast flystrike may assist decision-making by wool producers with respect to flystrike control options, leading to more efficient control of blowfly strike in their industry.     

Organophosphorus residues in wool grease resulting from specified on-farm lice and flystrike control treatments

Objective To investigate wool organophosphorus concentrations resulting from a range of farm pesticide application methods.
Design Random sampling of wool for pesticide residues and on-farm interviews to determine associated treatments.
Procedure Tasmanian fleece wool lots were sampled at random and tested for organophosphorus residues. The grower was identified and the pesticide treatments applied to the sheep were ascertained by on-farm interview.
Results The residue concentrations showed a large variation that was not accounted for by differences in treatments by growers. Organophosphorus concentrations were proportional to the number of treatments applied, and inversely related to the time between pesticide application and the subsequent shearing, and were significantly influenced by the method of application. After allowing for the time of application, plunge dipping resulted in pesticide residue concentrations 2 to 2.5 times greater than shower dipping, using spray races or hand jetting, and the use of these methods caused larger residues than the use of jetting races.
Conclusions We recommend that plunge or shower dipping should not be used more than 7 weeks after shearing, nor at higher concentration than the standard dose rate used for lice control, whereas jetting may be satisfactory for up to 7 months after shearing, provided only one application is administered.     

Temporal relationship between infestation with lice (Bovicola ovis Schrank) and the development of pruritic behaviour and fleece derangement in sheep

Pruritic behaviour and deranged fleece are often used as indicators of sheep louse infestation but the exact relationship between infestation and the observation of signs of pruritis was unclear. Two studies were conducted to examine this association. In the first, 24 castrate Merino sheep were randomly assigned to six pens in groups of four and the sheep in three pens infested with 10 lice each on the right mid-side. Louse numbers were counted, fleece derangement scored and pruritic behaviour assessed periodically on each sheep until 38 weeks after infestation. In the second study a single moderately infested sheep was paddocked for 15 weeks with 32 uninfested sheep and louse numbers and fleece derangement monitored for 41 weeks. In the pen studies, differences between infested and non-infested sheep in fleece derangement and pruritic behaviour first became significant (p<0.05) at 8 and 14 weeks, respectively and at louse densities of 0.06 and 0.27 per 10 cm wool part. Some sheep showed definite signs of deranged fleece as early as 5 weeks after initial infestation. In the paddock studies, it took 37 weeks until lice were detected on all sheep in the flock. The correlation between louse numbers and fleece derangement score first became significant (r=0.44 and p<0.05) at 9 weeks after introduction of the lousy sheep, reached a maximum of r=0.79 (p<0.001) at 22 weeks when 84% of sheep had lice detected and the mean louse density was 0.29 per part, and then declined to r=0.12 (n.s.) at 41 weeks when all sheep were infested and the mean louse density was 3.04 per part. It is concluded that fleece derangement is a powerful early indicator of the presence of lice and that sheep may exhibit signs of pruritis well before lice can be readily found by direct inspection. Fleece derangement may be useful as a basis for establishing economic thresholds for the application of long wool treatments in developing louse infestations but appears to be a poor indicator of louse numbers once the infestation is advanced.     

Dual deficiency of copper and cobalt in Hawke's Bay

The comparative efficacy of 13 of the sheep dips currently registered in New Zealand was investigated using sheep infested with the louse Bovicola ovis and carrying wool which was about 10 cm long at the shoulder.

With the exception of one synthetic pyrethroid “pour-on” formulation, all products were able to effect a significant reduction in louse populations, relative to untreated controls, for 37 days after treatment. Only four products proved capable of “eradicating” lice and preventing their re-establishment up to 37 days after treatment.

Variations in manufacturers' recommendations relating to the length of wool at dipping, and mode of application of dips are discussed in relation to the results.     

Time-space clustering of reported blowfly strike in Queensland sheep flocks

The reported occurrence of blowfly strike in 57 sheep flocks in Queensland, Australia, was investigated for time-space clustering in an exploratory study using Knox's method. Flystrike occurrence peaked in late spring and early summer, with an additional late-autumn peak in southern-Queensland flocks. A total of 1596 case-pairs was examined. Significant clustering (P = 0.07) was only detected for case-pairs occurring within 3 months and 150 km of each other; 164 case-pairs were declared close compared to an expectation of 151. We suggest that factors common to a district (such as rainfall and temperature) are responsible for clustering of flystrike in Queensland.     

Efficacy of ivermectin in a controlled-release capsule for the control of breech strike in sheep

Objective To investigate the efficacy of ivermectin in an intraruminal controlled-release capsule (CRC) against blowfly strike.
Design Pen and field trials with controls.
Animals Pen studies: Two breech strike trials involving 60 Romney and 60 Merino sheep. One body strike trial using 100 Merino sheep.
Field trials: Eight trials in New Zealand used 1000 Romney and Romney-cross sheep. Fifty Merino lambs in one trial in Australia.
Procedure Pen studies: Sheep were allocated to two equal groups. One was not treated, the other sheep received a CRC that delivered ivermectin at 20 μg/kg/day for 100 days. In the breech strike trials, each animal was given an oral laxative 2 days before exposure to adult Lucilia cuprina . In the body-strike trial, the sheep sheep were kept wet to increase susceptibility prior to the release of blowflies.
Field trials: Fifty or 200 sheep allocated to equal groups of nontreated or treated with the CRC and grazed at pasture exposed to natural blowfly challenge.
Results Pen studies: Breech strikes developed in 24 of 60 controls but in none of 60 CRC-treated sheep. There was a 35% reduction in the number of CRC-treated sheep struck on the body.
Field trials: The average number of breech strikes in CRC-treated sheep was reduced by 86% (P < 0.001). The number of body strikes in the treated groups was a reduced by 27% (P < 0.05).
Conclusion The ivermectin CRC is a useful aid in controlling breech strike, but provides only moderate reduction in the incidence of body strike.     

Efficacy of zeta-cypermethrin as pour-on or spray formulations for the control of buffalo fly (Haematobia irritans exigua) in cattle

Objective To determine the efficacy of zeta-cypermethrin in controlling buffalo fly ( Haematobia irritans exigua ).
Design Five field trials in northern and central Queensland.
Procedure Zeta-cypermethrin pour-on at 2.5 mg/kg, spray at 62.5 ppm, deltamethrin pour-on and pour-on vehicle were applied to groups of 20 cattle. Buffalo fly counts were conducted three times before treatment and 3, 7, 14, 21, 28 and 35 days after treatment.
Results In central Queensland where synthetic pyrethroid resistance in buffalo fly populations was rare, 2.5 mg/kg of zeta-cypermethrin pour-on gave good control of buffalo fly for 4 weeks and was better than a deltamethrin product. A zeta-cypermethrin spray used at 62.5 ppm gave 14 days control. In far-north Queensland where resistance to synthetic pyrethroids and heavy rain was common, the maximum period of efficacy of zeta-cypermethrin pour-on was reduced to 2 weeks.
Conclusion In areas where there is low resistance to synthetic pyrethroids among buffalo flies, zeta-cypermethrin pour-on can be expected to give good control for 4 weeks.     

南方三省杨梅中甜蜜素和农药残留风险监测分析

目的 了解南方三省杨梅农药残留和甜蜜素添加状况,维护杨梅鲜果质量安全,应对舆论关切,促进产业良性发展。方法 通过线上和线下购买杨梅主要产区浙江、福建、云南的市售新鲜杨梅作为检测样本,采用气相色谱法对杨梅中甜蜜素进行检测分析,采用气相色谱-质谱联用法对杨梅中43项农药残留进行检测分析。对检出农药作急性膳食摄入风险评估和慢性膳食摄入风险评估,并采用相对强度系数法 (RPF)对检出率较高的拟除虫菊酯类农药进行累积急性膳食评估。结果 213批次杨梅中,甜蜜素均未检出,171批次样品检出农药残留,样品农药残留检出率为80.3%,其中66.7%样品检出两项及以上农药。检测的43项农药中,9项农药有检出,其急性膳食摄入风险评估最高值为60%,慢性膳食摄入风险评估最高值为0.024%;拟除虫菊酯类农药累积急性膳食评估值为93%。结论 未发现南方三省杨梅违规添加甜蜜素。对成年人而言,农药残留的各项膳食摄入风险评估值均＜100%,在安全范围内,风险可接受。     

Further evidence that zinc sulphate compromises the efficacy of dipping treatments using diazinon to control sheep lice (Bovicola ovis)

Objective To compare the wettability and efficacy of diazinon dip wash made with and without the addition of zinc sulphate.
Design Field experiments using a shower and a plunge dip complemented by in-vitro wettability experiments.
Procedure A flock of infested sheep was divided into groups and treated in a shower dip with clear or cloudy dam water plus up to 1.5% zinc sulphate. Another infested line of sheep was treated using a plunge dip with nil or 1% zinc sulphate. In both experiments, wetting was assessed after dipping and louse counts were conducted for 9 months after treatment. Five in-vitro experiments compared the wettability of dip wash containing diazinon with up to 1.5% zinc sulphate added.
Results In the shower dipping experiment, live lice were found at 1 month after dipping in the cloudy water groups with 0.75%, 1.0% and 1.5% zinc sulphate and at 2 months in the 0.75% zinc sulphate group. No lice were found at subsequent inspections or at any time in the groups that were plunge dipped. Zinc sulphate decreased the amount of dip wash retained by wool staples in all in-vitro experiments (P < 0.05).
Conclusion Zinc sulphate should be considered as a risk factor that could cause failure to eradicate a lice infestation. The risk can be overcome by ensuring that all sheep are saturated at dipping and that the dip wash, and any holding tanks, are agitated throughout the dipping event.     

Prevalence of sucking and chewing lice on cattle entering feedlots in southern Alberta

Beef calves from 2 sources entering southern Alberta feedlots in the winters of 1997-98 and 1998-99, were surveyed for the presence of lice. A random sample of multiple source (MS), that is, auction market-derived, calves entering commercial feedlots and single source (SS) calves entering a backgrounding feedlot were examined for the presence of lice at entry to the feedlot. A standardized examination, which involved hair-part examination of 8 louse predilection sites, was conducted on each selected calf to determine prevalence and intensity of infestation. The long-nosed sucking louse, Linognathus vituli, was the most commonly encountered species. This species infested from 57.8% to 95.6% of the calves selected from both MS and SS calves during both winters. Louse index values, indicating intensity of infestation, for L. vituli ranged from 1 to 243 lice per animal. The chewing louse, Bovicola bovis, was present on MS and SS calves only in the winter of 1998-99. The louse index values for B. bovis ranged from 1 to 230 lice per animal. Mixed infestations of the L. vituli and B. bovis were common. The little blue cattle louse, Solenopotes capillatus, was present only on the SS calves in the winter of 1997-98. The short-nosed sucking louse, Haematopinus eurysternus, was present at very low intensities, 1-2 lice per animal, on 2.6% to 4.4% of the MS calves during both winters. Comparison of results from the current study with published literature suggests that efforts to determine the economic impact of louse infestations are confounded by the lack of a uniform method to assess louse population levels.