INSECT PESTS.

Press, Volume LXIX, Issue 20918, 27 July 1933, Page 16

INSECT PESTS.

WORK OF CAWTHRON INSTITUTE. LECTUKE BY DK. D. MILLER. An indication of the work of controlling insect pests and weeds carried out by the Cawthron Institute was given in an interesting lecture by Dr. David Miller, of the staff of the institute yesterday afternoon. The diamond-back moth, the grass grub, the cabbage vhite butterfly, and many other pesV were discussed by Dr. Miller, who also detailed the attempts being > ucle by parasitic control to reduce the damage which they cause. There was a large attendance at the lecture, which was held under the auspices of the Canterbury Agricultural and Pastoral Association, the Sheep Owners' Union, and the New Zealand Farmers' Union. Mr J. D. Hall, president of the North Canterbury branch of the New Zealand Farmers' Union presided. Lantern slides added interest to the lecture. Outstandingly Important. Dr. Miller commenced by stating that to all interested in farming, the subjects of insects and insect control were of outstanding importance. The struggle between world nations for supremacy in world markets made it exceptionally necessary for all factors detrimentally affecting exportable products to be controlled as much as possible. The annual loss caused by insect pests to the British Empire was estimated at £9,000,000 and to endeavour to reduce this huge amount institutes had been formed all over the Empire—all linked up with one central organisation, the Imperial Institute of Entomological Research. New Zealand had received a very large proportion—more than half the total output showed on one chart issued by the institute—of the specimens collected and classified by the central organisation. Cabbage White Butterfly. Speaking of the great and sudden damage which an insect pest could cause in New Zealand, Dr. Miller, referred to the cabbage white butterfly, which, first discovered in Napier three years ago, had now spread all over the North Island, and constituted a serious menace. Should this pest, Dr. Miller said, turn its attention to important fodder crops the outlook would be most unpromising. Fortunately, however, a parasite attacking and destroying the butterfly had recently been released, and was meeting with considerable success. Grass Grub. Dealing with the depredations of the grass grub beetle, Dr. Miller said that the secret of its control lay in the use of parasites which would attack the beetle. As the grass grub was at present attacked by no pests, New Zealand had a free hand in experimenting. There v-" a similar beetle fouhd in Japan, known as the Japanese beetle, and it had been found that the beetle caused little or no damage, its activities being restricted by parasites. Arrangements had been made for specimens of these parasites to arrive in New Zealand very soon. There were also specimens of parasites from Australia, which it was hoped would help to keep down the grass grub pest, and an Australian institute was assisting New Zealand in the matter. Southern Chile also had six series of parasites which preyed upon the grass grub. iV scientist of that country had sent a supply of these parasites to New Zealand, but although they had arrived safely, they had all been killed off by other parasites, before they could be set to work. It might be, said Dr. Miller, that the key to the control of the grass grub in New Zealand was to be found in the use of these Chilean importations, for climatic conditions in Chile were very closelv related to those of New Zealand.

Diamond-Back Moth. The diamond-back moth was the next insect pest referred to by Dr. Miller. This pest, which did such damage amongst turnip and rape crops, could be in some measure controlled, he said, by eliminating those places on a farm where grew weeds on which the diamond-back moth lived. Control could also be exercised by the use of parasites, said Dr. Miller, and there were at least 17 specimens which must be tried out. Another pest which, it was suggested, might greatly be reduced by the use of parasites was the cabbage aphis. Protection of Horses. An enquiry had some time ago been received by the institute regarding possible methods of protecting horses from bot-flies. The serious injury which these flies did to horses in New Zealand was not generally realised, he said, and there could be no doubting the discomfort and irritation caused to a highly-strung horse by these flies. The remedy was simple. There were two kinds of the flies, those which attacked the jaws, and those which laid their eggs on the shoulders, legs, and mane of the horse. The first species could be checked by putting a bib under the horse's mouth (as many farmers did), and the second by grooming the horse with warm water containing a little vinegar. The sheep-tick was the next pest to be dealt with, by Dr. Miller. This pest, which was not really a tick at all, could be stamped right out with a little expenditure, he said, the method to be adopted being dipping sheep twice yearly at an interval of 14 days. He was sure that the expenditure entailed in this dipping method would be repaid by the extinction of the pest. Dr. Miller also spoke of a parasite intended to kill sheep maggotflies which were already established in New Zealand. A field survey would be necessary to make an estimate of the amount of work that this parasite was doing, but the fact that these parasites already were so numerous in New Zealand seemed to indicate their success. Dr. Miller also dealt with the methods of parasitic control which were being tried on timber pests such as the horn-tail borer, the gum-tree scale, and the turquoise weevil. Control of Weeds. Besides the control of insects by parasites, the institute found another sphere of work in its attempts to control noxious weeds bv insects. At present the activities of the institute in this connexion were confined to attempts to control blackberry,' gorse, ragwort, and

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bidi bidi. Special efforts W®bJ| ing made to control the gorse in Central Otago, and Bl cess could be obtained it wwPgj of great importance to that Dr. Miller said that he had the bidi bidi pest in South where an insect, a saw-»|F»WjM be found which destroyed WW of the plant As soon as JttgW plies of these flies could be oWjH they would be liberated m fl| Zealand.