BLOW-FLY STRIKE

Nelson Evening Mail, Volume LXXII, 14 April 1939, Page 10

BLOW-FLY STRIKE

IMMUNITY FROM ATTACK During 1 the past week several cases of somewhat extensive blow-fly strike have been reported from some districts in Hawkes Bay, the ruling conditions being apparently favourable to this condition which is not only of great annoyance to the farmers concerned but also the cause of considerable economic loss each season, says the “Napier Telegraph.” Efforts have been made in New Zealand in recent years to bring about the control of blowflies by trapping but although almost unbelievable numbers of the pest have been caught in small areas by this means, the incidence of blow-fly strike on the sheep has not been reduced to any marked extent, and the system has tierefore failed to justify the expense, i method of treatment of sheep to proide lasting immunity has, however, een evolved, and should prove of inerest and value to many farmers in lawkes Bay who up to the present ime have found it necessary to make everal applications of any solution :sed for the control of the fly in cases vhere the strike has taken place. For the r armer who wishes to try he process for himself, the mixture s made up in the proportion of one gallon of glycerine to three pounds | if boric acid. A thick paste is formed j Dy mixing these two ingredients, and

this should be heated and thoroughly stirred until all the boric acid has been dissolved. The resulting liquid forms various borates of glycerine. After cooling, the mixture will be found to form a clear solution which should be bottled and kept until required for use. It is applied without dilution. METHOD OF APPLICATION The method of application recommended in regard to this solution is on the areas affected by blow-fly strike, and it will be found to adhere readily to the fleece and to the skin. iWthin a few minutes of application it will be found that the unpleasant odour emanating from affected parts will be greatly reduced. The maggots are killed, slowly, sometimes 24 or 30 hours elapsing after application before the last one is disposed of. but from the moment the application is made the maggots cease to worry the sheep and there is an almost immediate reduction in temperature, from as high as 106 or 108 to approximately normal. An important factor in regard to the solution is that under experiment it has been found impossible to effect a further strike on an area once it has been treated, while the mixture . has no hardening or harmful effects : upon the skin. In view of the number of lambs 1 and sheep which are affected by > strike during the summer season 1 further trials with this solution in Hawkes Bay would prove valuable and interesting. I ACUTE PROBLEM \ Blow-fly strike periodically be- ‘ comes an acute problem to the farmer, particularly on the higher country. Outbreaks of strike have been known for 30 and more years among < Merino and halfbred lamb and hog- [. | get flocks, but it is during the last eI 10 years only that much serious notice has been taken of the fly.

Formerly it was considered that both back and crutch strike could be explained as being the result of soiling with droppings. It is now clear, however, that crutch strike from faecal matter—that is. grass scour or dags, but seldom intestinal worm scour—accounts for less than 10 per cent, of the total strike. Urine staining, which results from breech wrinkles or a twisted or damaged vulva in ewe lambs, is at the root of the remaining 90 per cent, of crutch strikes. For a crutch to be properly susceptible to strike the skin must be scalded by urine, either caught in the wrinkles or misdirected on to the leg. It is the breakdown products of the skin that attract the flies to lay eggs. Urine on the wool alone is seldom susceptible.

STRIKE ON THE BACK Strike on the back or tail is less I easily accounted for. In less than e half of the cases of back strike there t is a growth of bacteria in the wool \ and on the skin during periods of I wet autumn and summer weather. . This fleece rot, or dry yolk helps to ? attract fly to the fine-wool sheep, but ! in many instances the wet-tipped wool itself can cause the fly to lay eggs , without the inducement of dip scald or fleece rot. The muggy weather that accompanies strike not only keeps the ' fleece wet but also allows the flies to remain active and encourages the de- , velopment of maggots. It is then apparent that strike takes place either as a result of the structure of the breech, independently of the weather, or because of the action of warm continuous rain on fine wools.

GLYCERINE SOLUTION PROVIDES EFFECTIVE CURE