Thomas W. Scott; Richard W. Miller,' and Fred W. Knapp 5

Transcription

1 FIELD EVALUATION OF DIFLUBENZURON BOLUSES WITH AND WITHOUT FLUCYTHRINATE EAR TAGS FOR CONTROL OF HORN FLIES, HAEMATOBlA IRRITANS,' AND FACE FLIES, MUSCA AUTUMNALIS, 1 ON PASTURED CATTLE' Thomas W. Scott; Richard W. Miller,' and Fred W. Knapp 5 Abstract: We studied pastured beef cattle in Maryland and Kenrocky to determine the efficacy of a diflubenzuron bolus alone and in combination with other treatments for control of face flies, Musca autumnalis De Geer, and born nics, HaeJrUltobia irritans (L.). Cattle received one of five treatments: bolus. bolus plus flucythrinate ear tags, flucythrinate ear tags, stirofos oral larvicide, or untreated control. Boluses reduced the number of horn flies infesting cattle in Kentucky from 56% to 88%. Horn fly populations in Maryland were lower than those in Kentucky, and they were not significantly reduced by the bolus treatment Bio8ssays with hom and face fly larvae showed that boluses released toxicant into feccs that killed immature flies for at least 56 days. Flucythrinate ear tags were the most effective technique studied for control of horn and face flies. Hom fly populations that we studied did not appear to be resistant to synthetic pyrethroids. The potential role of a diflubenzuron bolus in integrated Oy control programs is discussed. Key Words: Hom fly, Haemalobia ittitans, face fly, Musca au.tumnalis, bolus, larvicide, ear tag, cattle. J. Agric. Entomol. 3(2), (April 1986) Face nies, Musca autumnalis De Geer, and horn flies, Haematobia irritans (L.), are two common and important pests of cattle in North America. Face flies mechanically damage the eyes of cattle while they feed, as well as transmit Moraxella bouis, the causative agent of infectious bovine keratoconjunctivitis, or pinkeye (Hall 1984). Hom rues lacerate the epidermis and imbibe bovine blood. It has been suggested that large populations of both of these arthropods can reduce cattle weight gain or feed conversion (Hansens 1963; Kinzer et ai. 1984; Peterson and Boreherding 1962). Recent studies with face flies, however, indicate that other than transmitting pinkeye, large fly populations do not reduce performance of cattle (Arends et ai. 1982; Schmidtmann et ai. 1984). Efforts to control these ectop8fasites present unique problems because in their immature stages the ectoparasites develop in fresh manure on open pastures, and thus modification in management of manure is not practical. As a result, various chemical insecticides have been developed for fly control. Although most chemicals have been used to kill adult flies, there is now renewed interest in techniques to control immature flies in feces (Miller et al. 1979; Miller 197; Miller and Miller 1985). I DIPTERA: Muscidae. Accepted for publication I Much Use of trade names or products does not constitute endorsement, guarantee, or waltanty of the product by the nuthors and doer not imply approval of the product or the exclusion of other producls that may 1118 be suitable. 3 Department of Entomology. University of MllJ)'land, CoUege Park, MD Livestock Insects Laboratory, Beltsville Agricultural Research Center, ARS, USDA, Beltsville, MD Department of Entomology, University of Kentucky, Lexington, KY

2 16 J. Agric. Entomol. Vol. 3, No.2 (1986) Ear tags impregnated with synthetic pyrethroids initially provided the best control for hom flies but only moderate control of face flies (Knapp and Herald 1981; Miller et a a, 1984b; Williams and Westby 198). Recently, horn fly populations in the southern United States have become resistant to these compounds (Lancaster and Simco 1984; Sheppard 1984), suggesting that reliance on 8 single insecticide can result in selection for resistant and uncontrollable fly populations. We conducted our studies to evaluate diflubenzuron boluses under field conditions and, in so doing, to contribute to the development of an integrated program for long-term control of flies on cattle. We examined cattle in Maryland and Kentucky to determine the efficacy of 8 diflubenzufon bolus as compared to other available treatments for control of face flies and horn flies. Our study had two specific objectives: 1) to determine the efficacy of the diflubenzuron bolus alone and in combination with other treatments for controlling horn and face flies and 2) to detennine how long toxicant in manure from treated cattle is capable of killing immature stages of hom and face flies. MATERIALS AND METHODS Cattle in our study received one of five treatments: 1) diflubenzuron bolus, 2) diflubenzuron bolus plus flucythrinate (Guardian) ear tags, 3) flucythrinate ear tags, 4) stirofos oral IllIVicide blocks (SOL) (Staley Sweetlik Rabon), or 5) untreated control. Boluses and ear tags were tested alone to determine their efficacies as the sole treatment. Boluses plus ear tags were examined because Miller and coworkers (1984b) observed that a combination of ear tags and oral larvicide was more effective than were ear tags alone. SOL was studied because it contains an active ingredient that is different from diflubenzuron, and SOL is currently available commercially. Untreated cattle provided data for comparison in our statistical analyses. The 1% diflubenzuron boluses used in this study were made by Dr. Allen Miller, Agricultural Research Service, Kerrville, Texas, according to U. S. Patent 4,166,17 (Miller and Miller 1985). Cattle studied in Maryland were inbred Angus; those in Kentucky were mixed breeds of an AnguslHolstein cross or an Angus/Hereford cross. Study herds in both states were cowmcalf operations except for the control herd in Maryland, which was composed of yearlings. Boluses were administered to cattle with a balling gun at a rate of one bolus per 25 kg of body weight to the nearest onem half bolus. We observed animals closely to see if boluses were regurgitated following administration; if this occurred. the bolus was readministered. SOL was provided in the fonn of Staley Sweetlik Rabon blocks and was supplied according to label directions. Cattle receiving flucythrinate ear tags had one tag placed in each ear using the Allflex Tagging system. In Maryland all treatments were administered on 5 July In Kentucky ear tags were put in on 13 June 1984, the bolus treabnents alone or in combination with ear tags were initiated on 21 June 1984, and treatment with the SOL was begun on 5 July Statistical analyses were conducted using one-way analyses of variance; Duncan's multiple range test was used to detennine differences (Zar 1974). Objective 1 was evaluated by recording the number of hom flies and face flies on 1 cattle. Horn flies were counted on one side of the animal; face flies were counted on the face and head of the same animal.

3 SCOTT et aj.: Bolus for Control of Flies on Cattle 17 Objective 2 was evaluated by conducting fly larvae bioassays with fecal samples from treated and control cattle. Five fresh fecal samples were collected at biweekly inten-als from the bolus, SOL, and control groups. Newly hatched, colonized horn fly and face fly laivae were then each placed on duplicate 1-2 g samples of feces. The number of larvae placed on each fecal sample was as follows: 25 face flies and 1 hom flies for samples collected in Maryland; 25 face flies and 25 horn flies for samples collected in Kentucky. Maryland horn fly analyses were conducted by Dr. A. Miller in Kerrville, Texas. All other bioassays were conducted at the site of fecal collection, ie. Maryland or Kentucky. Emergence of adult flies from fecal samples was the criterion used to measure the toxic effect of the treatment on developing flies. In addition to fly counts and bioassays, we also conducted studies of arthropods naturally inhabitating manure pats from cattle with different treatments. The identification of those specimens is still under way and will be reported at a later date. Data discussed in the results section on field collected manure pats concern only the emergence of face and horn flies. Ten fresh manure pats in Maryland and five pats in Kentucky were marked in the field at 3-wk intervals beginning at 2 wk posttreatment. Three days after marking, pats were uniformly collected and returned to the laboratory. Emerging adults were collected and later identified. RESULTS Tables 1-3 show results from fly counts and bioassays. At both study locations, a minimum of 14 cattle or 8 maximum of 53 cattle were included in each treatment group. When applied separately, the bolus caused a significant and consistent horn fly reduction only on cattle in Kentucky (Table 3). This occurred between the seventh and fourteenth weeks posttreatment. Percentage reduction ranged from 56% to 88%. Hom flies in Maryland were not reduced by the bolus treatment (Table 2); it should be noted that their population was lower than that in Kentucky. Face fly populations were low in both states (Table I), but in Maryland they were one or fewer per animal and, therefore, too low for meaningful statistical analysis. Ear tags significantly reduced horn flies in Maryland (Table 2) and face flies in Kentucky (Table 1). Horn flies in Kentucky were completely eliminated with this technique (Table 3). The tags worked well without any obsen-able difference if they were applied alone or in combination with the bolus. In Kentucky during the last 11 wk of the study, the bolus plus ear tag and ear tag treatments significantly reduced face fly infestations during all but 2 wk (Table 1). During the same time period, the bolus alone reduced face flies during 4 wk, whereas the SOL reduced them during only 1 wk. Bioassays showed that toxicant from the bolus in feces reduced the number of emerging face and hom flies for 8 wk in Maryland (Tables 4-5) and wk in Kentucky (Tables 6-7). For the period of time it was active, the bolus in Maryland was as effective as the SOL for face flies and horn flies. In Kentucky the bolus was more effective on both fly species than the SOL. Examination for face and hom flies naturally inhabiting and then emerging from field-collected manure pats suggests that the bolus reduced fly populations in Kentucky. During the 4 collection periods, 528 face flies emerged from control pats, and 47 emerged from bolus pats (91% reduction). For horn flies, 247

4 18 J. Agric. Entomol. Vol. 3. No.2 (1986) T.ble 1. The mean number of face flies on cattle after various fly control tre.tments in Kentucky during Mean number of Dies, by treatment Weeks post Bolus Oral treatment Control Cow only Cow + calf + Ear tagf Ear tag larvicide:t 1 7 (4)bf 8 (4)b 9 (4)b 6 (2).b 4 (3). NC 2 NC NC NC NC NC NC 3 8 (3)e 5 (3)b 6 (4)be 3 (2)b 1 (I). NC 4 I (I).b 2 (2).b 2 (2).b I (I). I (I). 3 (3)b 5 NC NC NC NC NC NC 6 9 (4)d 5 (3)be 6 (3)e 2 (1). 3 (l).b 12 (4)e 7 14 (5)b 8 (4). 8 (5). 6 (4). 5 (3). 2 (l1)b 8 15 (7)e 11 (4)be 1 (5)b 4 (3). 6 (3).b 28 (7)d 9 13 (5)b 12 (2)b 13 (6)b 5 (2). 6 (3). 2 (6)e 1 11 (4)e 8 (3)b 9 (3)be 4 (3). 4 (3). 12 (4)e 11 9 (4).b 8 (4). 8 (4). 5 (3). 5 (3). 13 (9)b (1)b 6 (3). 7 (3). 5 (3). 6 (3). 18 (8)b 13 NC NC NC NC NC NC 14 4 (2). 4 (3). 4 (2). 2 (2). 4 (2). 5 (2) (2)e 2 (2)b 2 (I).b I (I). I (I).b 2 (2)b 16 3 (2)b 2 (1).b I (1). I (1). I (1). 3 (3)b Diflubenzuron bolub_ t Flucythrinate ear tag. t: Stirofo8 oral larvicide. 11 MCIlJl and standard deviation () for the number of nics on the (accs of ten cattle. Meana, in a tow, that are not followed by a common letter are different UJ.s.5). Flies not counted for that treatment and date. Table 2. The mean number of hom flies on Angus cattle after various fly control tre.tments in M.ryl.nd during Mean number of flies, by 'treatment Weeks post Bolus + Or.l treatment Control ear tag t Ear t.g larvicide* 1 6 (4).~ 5 (3). 3 (3). 3 (3). 5 (3). 2 3 (3). 4 (2). 2 (2). 2 (2). 3 (2). 3 1 (I). 3 (3).b 1 (1). 1 (2). 5 (3lb 4 4 (3). 13 (1lb 5 (4). 1 (1). 2 (9)e 5 3 (3). 11 (6)b 3 (4). 2 (2). 8 (4)b 6 12 (8)ed 15 (7)d 5 (3).b I (1). 7 (4)be 7 16 (12)b 21 (19)b 2 (2). 3 (3). 1 (4).b 8 25 (li)b 29 (16)b 2 (2). 1 (I). 24 (18)b 9 2 (14)b 39 (13)e 4 (5). 2 (1). 34 (li)e 1 37 (22)b 33 (23)b 8 (4). 1 (I). 34 (IO)b 11 9 (38)e 49 (2)b 3 (3). 2 (2). 4 (18)b Diflubenzuron bohl8. t Flucythrinate ear tag. t StirofoB oral larvicide. 11 Mean and standard deviation (n) for the number of mea on one side of ten Angus cattle. MelUls, in a row, that are not followed by 8 common letter are different (p:5.5).

5 Table 3. The mean number of horn flies on cattle after various fly control treatments in Kentucky during Weeks post Bolus Or.l treatment Control Cow only Cow + calf + Ear tag! Ear tag larvicide; rj> () 1 21 (12).~ 345 (161)b 37 (95)b 272 (I 32)ab 24 (81). NC ::j (93)b 335 (IlI)c 325 (98)c.. NC ~ 3 NC NC NC NC NC NC 4 29 (7)b 345 (9)b 335 (85)b (11)b ~ 5 NC NC NC NC NC NC (12)c 145 (72)b 213 (114)c On On 13 (4)n '" C (146)c 125 (67)b 145 (86)b On On 35 (13)c go (16)d 51 (3).b 8 (54)b On On 26 (84)c () 9 36 (1I7)d 5 (26)nb 68 (27)b On On 235 (88)e, 1 36 (143)c 45 (26)n 63 (32). On. 13 (82)b " ~ (92)c 53 (3)b 49 (33)b On On 68 (41)b ~ (125)c 6 (32)b 1 (31)b On. 58 (31)b :=l ~ (53)d 8 (42)b 12 (58)be On On 123 (55)c (82)d 63 (32)b 128 (52)d. On 31 (I13)e 15 3 (62)d 128 (85)b 128 (6)b On On 2 (71)c () Diflubenzuron bolus. to t Flucythrinate ear tag. ; Stirofos oral larvicide. ~ Mean and standard deviation (n) for the number of flies on one side of ten cattle. Means, in a row. that are not followed by a common letter nre different (p.:s.5). Flies not counted for that treatment and date. ::; "'

6 11 J. Agric. Enlomol. Vol. 3, No.2 (1986) Table 4. The mean number of face nies emerging from manure Crom Angus cattle after various treatments. Twenty five rust mstar larvae were placed on ten 1-2 g manure specimens. The analysis was conducted in Maryl.nd during Weeks post Diflubenzuron Stirofos oral treatment Control bolus larvicide 2 7 (1).' 1 (1). O (I6)b O. O (4)b o. o. 8 1 (6). O. 5 (11) (2)b 24 (22)b O (2)b 9 (2). O (5)b 1 (1). NCt (3). 35 (2). NC Mean and standard deviation (n). Means, in a row, that. are not. rollowed by a common letter are different (p ~.5). t Flies not assayed ror that treatment and date. Table 5. The mean number of hom flies emerging from manure from Angus cattle after various treatments. One hundred first mstar larvae were placed on ten 1-2 g manure specimens. The analysis was conducted in Maryl.nd during Weeks post Diflubenzuron Stirofos oral treatment Control bolus larvicide 2 7 (11).' NC 8 (12). 4 7 (1). 3 (4). NC 6 58 (17). 7 (I5)b 3 (3)b 8 35 (16). 11 (I4)b 7 (I3)b 1 2 (13). 11 (11). 1 (2)b (I7)b 51 (13). (O)e (14). 2 (2). NCt 16 6 (9). 5 (27). NC Mean and standard deviation (n). Means, in a row, that are not rollowed by a common letter are dirrerent. (p :s;.5). t Flies not assayed ror that treatment and date. emerged from control pats, and 5 emerged from bolus pats (98% reduction). No horn flies were recovered from pats until 13 wk posttreatment. The number of muscids inhabiting manure pats in Maryland was too low for meaningful analysis (me.n = 2). DISCUSSION The most effective method of fly control in our study was the flucythrinate ear tag. Ear tags worked equally well if they were used alone or in combination with

7 SCOT1' et 1.: Bolus for Control of Flies on Cattle 111 Table 6. The mean number of face rues emerging from manure from cattle after various treatments. Twenty-five frrst instar larvae were placed on ten 1-2 g manure specimens. The analysis was conducted in Kentucky during Weeks post Diflubenzuron Stirofos oral treatment Control bolus larvicide 2 18 (2)b' 1 (l)a Net 5 18 (2)b Oa 19 (3)b 7 15 (2)b 3 (4)a 14 (3)b 9 21 (l)b Oa 1 (l)a l! 15 (3)b Oa 5 (6)a (2)c 9 (9)b Oa 15 2 (3)b 12 (li)b Oa Mean and standard deviation (n). Means, in a row. that arc not follo...ed by 8 common leuer arc different (fj:s.5). t Flies not ilhsllycd for that trclitment and date. Table 7. The mean number of horn flies emerging from manure from cattle after various treatments. Twenty-five frrst instar larvae were placed on ten 1-2 g manure specimens. The analysis was conducted in Kentucky during Weeks post Diflubenzuron Stirofos oral treatment Control bolus larvicide l! (l)b' 13 (2)c 2 (4)b 2 (5)b 15 (5)b 19 (5)b 14 (2)b 1 (1). 1 (I). 4 (6)a 3 (8)a Oa 6 (6). 5 (5). Net 8 (3)b 19 (4)b 1 (2)a l! (8)b 3 (l). 2 (3)a Mean and standard de"'iatioll (n). Means, in 8 row, that are not followed by n common letter are different (p:s:.5). t Flies not as!l8yed for that treatment and date. the bolus. We did not observe the enhanced control of 8 bolus-ear tag combination that Miller and coworkers (l984b) reported for the SOL and fenvalerate ear tag combination. Results from our eartag treatments also suggested that the horn fly populations we studied were not resistant to synthetic pyrethroids. Only when fly populations were high, for example hom flies in Kentucky (Table 3), did the bolus treatment alone consistently reduce the number of flies infesting cattle. Face flies in Kentucky (Table 1) were intermittently reduced by the bolus when it was the sale treatment. In Maryland horn and face flies were not controlled by the bolus as a separate treat.ment. This suggests that large fly populations are necessary for the diflubenzuron bolus to provide consistent control. A potential bias in our study, however. is that flies may have immigrated

8 112 J. Agric. EntomoL Vol. 3, No.2 (1986) to our bolus~treated groups from untreated nearby herds. If this is true, then the bolus would be most effective when applied uniformly over a large geographic area or when administered to isolated herds, such as those in the southwestern United States. Results from our bioassays and the analysis of field collected manure pats in Kentucky demonstrate that boluses release toxicant into feces that kills developing face and horn flies for at least 56 days (Tables 4-7). The boluses we used were designed to last 9 days. The duration of toxicant release can, however, be manipulated (A. Miller, USDA, Kerrville, TX, pers. comm.). Although in field experiments the bolus treatment did not dramatically reduce fly infestations, the diflubenzufon bolus is a novel and promising technique for control of face and horn flies on cattle for at least two reasons. First, by administering an effective insecticide in a slow release bolus, known amounts of toxicant can be provided to cattle at selected times, This cannot be done as precisely with a free choice supplement, such as the SOL, as with a bolus because animals consume different and unpredictable amounts of the compound (Miller et a c), Second, our bioassays show that in the formulation we investigated, diflubenzuron kills immature face and horn flies before they can reproduce or migrate from treated areas. Regional recommendations for use of the diflubenzuron bolus most likely will be required. For example, the bolus may be effective by itself for isolated herds of range cattle. In other areas, however, because of closer herd proximity and fly movement among herds, the bolus may be best applied as one part of an integrated control program. The timing of bolus application as compared to other techniques in an integrated program and the duration of bolus erosion are topics that merit further investigation. ACKNOWLEDGMENTS Dr. John L. Hellman, Ruth S. Sllivaggio, Jeffery Burr, Terry Patton, Jonathan Grove, and Joseph Sexton contributed to this study by consultation on experimental design, field work, and data analysis. Dr. Eldin A. Leighton kindly allowed us to conduct field studies with the Wye Angus herd in Maryland. Dr. J. Allen Miller and Larry Shade conducted bioassays on manure collected in Maryland. DUPHAR provided a gift to support livestock insect research that made this project possible. Judith M. Grumstrup-Scott, Larry G. Pickens, and Ray Noblet edited various drafts of this manuscript REFERENCES CITED Arends, J. J., R. E. Wright, K. S. Lusby, and R. W. McNe Effect of face flies (Diptera: Muscidne) on weight gains and feed efficiency in beef heifers. J. Econ. Entomol. 75: Hall, R. D Relationship of the face fly (Diptera: Muscidae) to pinkeye in cattle: A review and synthesis of the relevant literature. J. Med. Entoma!. 21: Hnnsens, E. J Face Fly and Its Control. Rutgers Univ. Ext. Servo Leaflt Knapp, F. W., and F. Herald Face fly and horn fly reduction on cattle with fenvalerate ear tags. J. Econ. Entomol. 74: Kinzer, H. G., W. E. Houghton, J. M. Reeves, S. E. Kunz, J. D. Wallace, and N. S. Urquhart Influence of horn flies on weight loss in cattle with notes on prevention of loss by insecticide treatment. Southwest. Entomol. 9:

9 SCOTT et al.: Bolus for Control of Flies on Cattle 113 Lancaster, J. L., Jr., and J. S. Simco Reduced efficacy of ear tags for control of horn flies. Arkansas Farm Res. 5: 5. Miller, J. A., F. W. Knapp, R. W. Miller, and C. W. Pitts Sustained-release boluses containing methoprene for control of the horn fly and face ny. Southwest. Entomol. 4: Miller, R. W Larvicides for fly control- a review. Bull. Entomol. Soc. Am. 16: Miller, R. W., and J. A. Miller Feed-through chemicals for insect control in animals, pp in J. L_ Hilton led.], Agricultural Chemicals of the Future. Rowman and Allanheld, Ottawa_ Miller, R. W., R. D. Hall, F. W. Knapp, R. E. Williams, K. E. Daisy, F. Herald, and C. A. Towell Permethrin ear tags evaluated in four states for control of the hom fly and face fly. J. Agric. Entomol. 1: Miller, R. W., L. G. Pickens, E. T. Schmidtmann, and W. E. Kunkle b. Fenvalerate ear tags with and without stirofos oral larvicide for control of born flies and face flies. Southwest. Entomol. 9: Miller, R W., L. G. Pickens, and D. M. Nafus. 1984c. Use of white tetrahedral traps and stirofos oral larvicide for area wide control of the face fly. J. Agric. EntomoI. 1: Peterson, C., Jr., and J. R. Boreherding Face up to foce flies and their "stablemates." Success. Fanning 6: Schmidtmann, E. T., D. Berkebile, R. W. Miller, and L. W. Douglas The face fly (Diptera: Muscidae): Effect on Holstein milk secretion. J. Econ. EntomoL 77: Sheppard, D. C Fenvalerate and flucythrlnate resistance in horn fly populations. J. Agric. Entomol. I: Williams, R. W., and E. J. Westby Evaluation of pyrethroids impregnated in cattle ear tags for control of face flies and horn flies. J. Eean. Entomol. 73: Znr, J. H Biostatistical Analysis. Prentice-Hall, Inc., Englewood Cliffs, NJ, pp. 328.