Cattle-Tick

New Zealand Herald, Volume LXXV, Issue 23181, 29 October 1938, Page 10 (Supplement)

Cattle-Tick

By R. A. FALLA, M.A

IN replying to a North Auckland correspondent who asks for details of the life-history of the cattle-tick found in his district, I propose to offer an outline for which full acknowledgment must be made to, Bulletin 116 of the New Zealand Department of Agriculture. The study of this particular pest is one of which the department may well he proud. It was favoured in two respects: the area of heavy infestation was limited to North Auckland and therefore easily covered, and the investigation was undertaken by Dr. J. G. Myers, then in the service of the department, but now better known for his brilliant researches in other parts of the world. Related to Spider It is perhaps necessary to mention that a tick is not an insect, but a mite, of the class Arachnida to which spiders also belong. As intermittent parasites ticks spend part of their lives attached to some animal host and gorge themselves with blood therefrom. Some ticks are dependent on one host; others, with a more complicated life-history* require more than one. The cattle-tick with which we are concerned in this country is Haemaplivsalis bispinosa, of Asiatic origin, and 'first definitely recorded in New Zealand in 1910. hen Dr. Myers began his work in 192.1 nothing had been published in any part of the world on its life-history and habits. Three Hosts .At different seasons farm animals arc found to be infested with different stages of the parasite. The minute larvae, known as seed ticks.are the most abundant. At a later stage the more perfect but still immature.nymphs are found attached to animals, and finally

the adult ticks, usually females, engorging themselves in preparation for dropping to the ground to deposit their eggs. The cattle-tick thus requires three successive hosts on which to feed, but spends the intervening periods of moult and the final one of egg-laying, in shelter on the ground. Cluster of Eggs For two months the clusters of eggs deposited bv the females lie at the base of grass and rushes, and when they hatch the larvae swarm up the stems and leaves. When a suitable host animal brushes past they attach themselves and commence to feed 011 blood and lymph drawn through suctorial mouth-parts. The skin soon becomes distended to its full capacity and then the larvae drop to the ground. Here for three weeks they undergo the change to nymph stage and again ascend the stems to look for another host. The process of engorgement is repeated and then the nymphs, like the larvae, drop to the ground and about three weeks later become adult. t Seasonal Cycle Adult ticks repeat the whole process already described for larvae and nvmphs. When fully replete, but not before, the females drop to the ground for the last time and die shortly after laying their eggs. At each stage the rate of development depends on conditions of temperature and moisture, but there is a definite seasonal cycle, resulting in a heavy infestation of nymphs in late winter and early spring, adult infestation at its height in midsummer, and a pure infestation of larvae in late summer and autumn. Undesirable Parasite Stock in infested areas lias therefore little respite and the total effect may lie serious. The general health of animals' is affected by the irritation caused by constant bites. They may lose condition and thus become more susceptible to sickness. In the' actual spread of infectious disease the cattle-tick is not known to lie an agent, but the sum total of its activity is to produce a condition of ill-health, and fortius reason it is a most undesirable parasite. The bites also are severe enough to disfigure the skin and consequently the hides are reduced in value to the farmer. When it is considered that* man also is sometimes attacked 'and that children particularly may suffer from painful bites, the importance of dealing with the cattle-tick problem becomes apparent. Methods of Control Dr. Myers reviewed both natural and artificial methods oi. control of cattletick. Of the former he mentions both dry heat and excessive moisture as

A Farm Pest of the North

inimical to the pest. As such climatic conditions cannot be expected to opciate with any regular certainty, natural enemies become important. 01 these birds arc especially mentioned and the introduced European starling is held to be the most important. There is abundant circumstantial evidence of its association with farm animals in infested areas, and it is significant that one farm on which starlings had good nesting cover was almost entirely free from cattle-tick. Control by Birds Dr. Myers took the view that as the starling had apparently established itself as a controlling factor, it would be unwise to import further birds that might possibly become tick-eaters. Most of them would simply replace the starling or be driven out by it, and nothing would be gained in either case. It may be remarked, as a digression, that we cannot afford to accept for all time and all places either wholesale praise or.blame for any bird that is as common as the starling, and that there is need for a much fuller and more continuous survey of bird habits throughout the country. Time for Dipping Artificial control is also discussed by Dr. Myers but arranged so as to supplement rather than overlap natural control. When so many ticks arc destined to perish from natural causes it is more efficient to direct artificial destructive measures against the survivors. When stock is dipped or sprayed the most farreaching results are achieved if engorged female ticks are the victims, and if they are the first adults of spring much potential increase is checked. Burning herbage which would appear to deal with resting stages is not always practicable in country where paspalum is grown, but the close cropping of grass and the elimination of rushes is recommended.