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The Pamphlet Collection of Sir Robert Stout: Volume 62

Insect Pests

Insect Pests

The question of insect pests next came up for discussion. The remarks of the Sub-Committee were as follows :—"The services of a thorough entomological expert would be of great service to the colony. As an instance of the value of such a department, it may be stated that the orange and lemon groves of California were threatened with utter destruction caused by the spread of the cotton cushion scale, Icerya Purchasi, when the Entomological Department took the matter up and sent an expert to New Zealand to collect the ladybird beetles, which were known to feed upon this scale. The result is that the experiment has proved entirely successful, and hundreds of thousands of pounds sterling have been saved to the owners of orange groves by the action of that department. Insect pests are spreading with alarming rapidity in New Zealand. The codlin moth is ravaging the orchards in many parts of the North Island and in Nelson as well. The grass grubs have done an immense amount of injury to our grass lands throughout the colony. The potato crop has been seriously injured by grubs from time to time in various parts. Whether the ordinary wireworm (the larvæ of one of the click beetles) or that of the potato moth (Lita solanella) which has proved so terribly destructive to the potato crops in New South Wales, and indeed in most of the other colonies, is the cause, has not been satisfactorily settled. A small paddock of potatoes in this neighbourhood was so badly infested by grubs a few years ago, as to be utterly worthless. It was taken in hand by the late Mr Reeves, then in charge of the Agricultural Department, who, acting on advice, took drastic measures. He had the crop carefully dug and destroyed. Since then we have not heard of a similar case in this neighbourhood Efforts were made to hatch the larvæ for the purpose of identification, but without success. There is little doubt but that this was an attack of potato moth, erroneously called wireworm. This case is mentioned to show the value of drastic measures when pests first make their appearance. Again, the Hessian fly made its appearance in the North Island. It was at first hoped that it was a case of mistaken identity. But Dr. Hector pronounced the specimens submitted to him to be the veritable Hessian fly. There is little doubt about the mode of its introduction, which was either in imported seed wheat or in straw used for packing reaping machinery imported from America or England. And now report has it that this destructive fly has j made its appearance in the Taieri, Otago; but beyond reporting the ravages caused to; the wheat crop nothing more seems to have J been done. That on being introduced to; America it spread inland at the rate of fifteen to twenty miles per year. It is quite possible to stamp this pest out if taken in time. Again, a fly, said to be the brown farrier bot fly, has made its appearance in Canterbury and other parts of New Zealand, threatening to become a serious nuisance. The deaths of several horses having recently occurred the bot is charged with the offence. It must, however, be remembered that such authorities as Youatt are of opinion that the larvæ of the bot are not injurious to the horse, if not in too great numbers. It is not, therefore, wise to jump to conclusions regarding the actions of these pests without more expert observation. Cases have been reported (more frequently of late) where sheep, especially dirty ones, have been struck by a fly whose eggs soon hatch out, and if the maggots are not destroyed they burrow under the skin, causing great suffering to the animal, and frequently its death. Whether this fly is a native one, or whether it is the fly so troublesome to British sheep farmers (Musca vomitoris) has not been de-determined; should it prove to be so, and become numerous, it will be a source of infinite trouble and expense to owners of sheep. The diamond-back moth, the caterpillar of which has committed such ravages amongst our turnip crops during the last four or five dry seasons, has cost the colony quite a quarter of a million of money. It has been allowed to work its ruin without, so far as we are aware, any systematic attempt having been made to check its progress or to become acquainted with its life history. Last season in Great Britain its ravages were so great that from a return made we find that the losses inflicted on the turnip crop have been estimated at from £2 to £10 per acre. Need we say more in support of expert treatment and investigation.'

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Mr E. T. Rhodes moved—"That this conference is in favour of the appointment of an entomologist, with a view to a thorough investigation of insect and parasite pests, and especially with reference to the life history and the means of dealing with the bot fly." He need say but little, as the remarks of the Sub-Committee were so full. They had all seen the ravages made by the codlin moth in Auckland, and further than this he knew of the existence of the bot fly in Timaru.

Mr Bidwell seconded the motion. The Hessian fly had mads its appearance in the Wairarapa some four years ago, but nothing had been done to check its ravages, as the settlers did not know what to do. If a Government entomologist were appointed the settlers would be informed what these pests meant.

Mr W. Henderson mentioned a case on the Rakaia in which the bot fly had been responsible for the death of four horses.

Captain Willis said that Youatt was of opinion that the bot fly did not kill animals as it had no mouth.

Mr J. Holmes said it was only necessary for one to go out into the garden to see the number of pests. They did not want the Government entomologist to stamp out the pests, but simply to instruct them as to how they could do the work for themselves.

Mr Douglas McLean suggested that the services of Miss Ormerod might be obtained.

The motion was then put and carried unanimously.