Wet sum­mer prompts warn­ing

Southern Riverina news - - News -

Last sum­mer was prob­a­bly the worst sheep blowfly sea­son for nearly 20 years ac­cord­ing to Live­stock ealth and Pest Au­thor­ity district ver­t­eri­nar­ian Dan Salmon, who is hop­ing to avoid a re­peat.

To be sure, he said there are a few lessons we should learn.

Dr Salmon said although a re­peat of last year is un­likely, the fore­cast of an­other wet sum­mer should make pro­duc­ers think se­ri­ously about how they are go­ing to man­age sheep blowflies.

‘‘One thing that we learnt last year was very few of the prob­lems were due to chem­i­cal re­sis­tance,’’ he said.

‘‘The chem­i­cals which have been work­ing for the past thirty years still work, and the chem­i­cals which have not worked prop­erly for the last thirty years still don’t work.

‘‘New chem­i­cals work, although some of them are not as good as their man­u­fac­tur­ers would like us to think.

‘‘There are some good chem­i­cals avail­able for sheep blowfly con­trol, but none of them are per­fect and all of them re­quire a cer­tain amount of man­age­ment to get sat­is­fac­tory re­sults in a bad fly year.’’

For in­stance, Dr Salmon said cy­ro­mazine still works as well as it did in 1972 but heavy rain such as we saw last sum­mer will wash it out of the wool and al­low fly­strike.

Di­cy­clonil is ex­traor­di­nar­ily ef­fec­tive against fly­strike, he said, but it has a very long with-hold­ing pe­riod so that it has to be ap­plied with a view to when the sheep will be shorn or slaugh­tered rather than wait­ing for blowflies to be­come ac­tive.

‘‘If a pro­ducer is go­ing to use di­cy­clonil use it early, that way the flies will never get a chance to build up,’’ he said.

‘‘There are good chem­i­cals avail­able to con­trol blowflies and with the cur­rent good sheep prices the pay­off is good, but try­ing to treat sheep in the mid­dle of a fly-wave is a lot harder and less ef­fec­tive than tak­ing a pre­ven­tive ap­proach.’’

Con­tact your lo­cal LHPA of­fice for more in­for­ma­tion about blowfly pre­ven­tion.

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