FIGHTING FRUIT PESTS.

Otago Witness, Issue 3862, 20 March 1928, Page 13

FIGHTING FRUIT PESTS.

THE USE OF PARASITES. Some interesting information concerning attempts to control orchard pests by means of parasites was given at a meeting of the Henderson Fruitgrowers’ Association recently by Mr D. Miller, Government entomologist, who has recently been appointed to succeed Dr R. J. Tillyard at the Ca,wthron Institute. Replying to congratulations upon his new appointment, Mr "Miller said, he hoped to give better service than in the past, because at the Cawthron Institute he would have better facilities at his disposal. The address dealt with three well-known "pests—the pear midge, the mealy bug, and the bronze beetle. The first attempt to secure parasites against the pear midge, said Mr Miller, had been made in 1925. There were many difficulties in the way, because it < was not a serious pest, even in Europe, wher . it originated, and little wa known of its life history or of the parasites which were believed to control it there. However Dr Fisher, of the Bureau of Entomology, London, with others, located four parasites. Infected material was sent to New Zea-

land, and the four parasites were identified in the Wellington laboratory and isolated. They were tried separately, and one, Platygasta, yas adopted for practical use. Several hundred of the parasites were liberated in orchards in Henderson and neighbourhood during 1925 and 1926. A number was found in 1927, showing that they had wintered well, and by now the parasite was well established. Similar results had been obtained in Nelson, where the whole district was being gradually stocked from one male and two females liberated in the first place. Platygasta attacked the midge by laying eggs in its eggs and killing the grub within. Where the parasite was established the trees this season had made healthy growth at a time when formerly the midge had prevented it. However, the midge had afterwards made great inroads, and it was doubtful if it was being controlled. Still, it was hoped to check the first two broods of the midge so as to give the first growth of leaves a chance and allow the fruit to set. Another parasite, a gree predaceous grub, was also being tried, and it was possible that the two in conjunction would give the desired control.

Mr Miller warned his hearers that biological methods alone would not solve the fruitgrower’s troubles, and must be regarded only as an auxiliary to spraying and general cultural methods. A universal insecticide, if one could be discovered, would probably do away with the use of parasites.

—w Dr R. H. Makgill gave a brief account of his experiences with sprays, which, he said, had so far proved virtually useless against the midge. s Dealing with the introduction of a ladybird to attack the mealy-bug, which troubled apple-growers, Mr Miller said the results had not been up to expectations. It now turned out that the mealy-bug found here was not the species (comstocki) it had been believed to be, but an insect which infested citrus trees in California. Thanks to a Californian entomologist, who had recently passed through Wellington on his way back to San Francisco, Mr Miller had obtained specimens of four Australian parasites, and was propagating them. He had every reason to believe they would give control. Mr W. H. Rice, orchard instructor, remarked at this point that it was doubtful if th? mealy-bug did much harm to a crop, but it was detrimental to the appearance, of the fruit. However, no apples could be exported to Honolulu unless the orchard of origin could be declared free from the insect. Such orchards were becoming fewer and .fewer., _■ Mr Miller referred briefly to researches being made at the Cawthron Institute, under a‘-special grant, into the-control of the bronze beetle. The investigations, he

said, covered winter cultivation, and the use of sprays and parasites. The first two methods were being tackled, and it was hoped later to obtain an enemy beetle from America. He expected that some information of value about spraying for the beetle would be available before the end of this year. In the course of some discussion on the codlin moth, Mr Miller stated that there was considerable variation in the moth in different districts. In the north there were definite indications of a second brood each year. He felt that a comprehensive investigation should be made in applegrowing districts throughout New Zealand.

In reply to a question, Mr Miller said there was no need to withhold spraying for the sake of whatever parasites might be at work.