H.—29.

Control of Mould Fungi in Poods. Experiments for the control of moulds on the woodwork of dairy factories and meat-works have been partially completed. Work is being continued on the effects of these organisms on deterioration of food. Stebilizino-agents. A series of tests -have been conducted to ascertain effective methods of sterilizing woodwork of dairy factories, meat-works, and the like. It has been shown that chlorine compounds, generally used for the purpose, have little (if any) toxic effect on the moulds present in these places. ENTOMOLOGY SECTION. J. Muggeridge, Entomologist. During the past year this section has been particularly busy both in regard to (a) routine and (b) research activities. ROUTINE. Routine activities involved a large amount of correspondence and time in replying to requests for the identification of insect specimens sent in, and methods of control to be adopted in regard to them. That phase of routine activities concerning the care and attention of the insect collection and correct filing of literature unfortunately did not receive the amount of attention which it needed. The neglect of this work was entirely unavoidable as other laboratory and field activities more than occupied all available time. RESEARCH. Experimental Wokk on the Control of Pieris kapae (White Butterfly) by Means op Parasites. The most important work that this section has had to deal with during the past year has been in connection with the biological control experiments on white butterfly. A survey in the field of the places where parasites had been liberated during the previous season indicated that the larval parasites (Apanteles glomerulus) were at work though they were not sufficiently prevalent to offer any serious check to an increase of the butterfly. The pupal parasite (Pteromalus puparum), on the other hand, was found to have spread considerably from its original point of liberation, and that out of a total of 415 butterfly pupee collected at random in the field 58 per cent, were found to be parasitized. During the present season further consignments of both larval and pupal butterfly parasites were imported and liberated. Pour hundred and twenty-five thousand cocoons of the larval parasite were received from Farnham Royal, England, and from this material 240,000 parasites emerged and 5,000 hyperparasites. All of the latter on emergence were promptly destroyed. Two hundred and thirty thousand of the parasites which emerged were sent into the field. These were mainly concentrated in the Hawke's Bay locality, though a few were distributed in Gisborne, Tauranga, Taihape, Te Kuiti, and parts of the Manawatu district. Prom a brief survey of the Hawke's Bay locality, where the bulk of these parasites were liberated, only a small percentage of parasitized butterfly larvae were obtained —not more than 3 per cent, were parasitized. It is not to be inferred from this, however, that these parasites are unsuccessful, as it often happens in biological control work that the insect which is the most difficult to establish subsequently proves the most effective. With reference to the pupal parasites, namely Pteromalus puparum, 11,500 of these were distributed in the field, and again most of these were concentrated in the Hawke's Bay locality, though a few consignments were distributed in other places, including the Manawatu and Taihape districts. Of these 11,500 pupal parasites liberated, 8,000 were reared at the Station. A recent survey in the Hawke's Bay District, where the main body of parasites was concentrated, indicates that they have become thoroughly established there and are doing good work. They have spread over hundreds of square miles of the Hawke's Bay territory, and there seems little doubt that they were at least partly, if not wholly, responsible for the large reduction in the prevalence of the butterflies in that district. In one survey it was found that, out of a total of 5,300 Pieris rapae pupaa collected at random in the field, 90 per cent, were parasitized. This work to date has been so successful that it has been deemed advisable to extend our activities to the extent of attempting to rear pupal parasites in very large numbers during the coming year in order, if possible, to be able to liberate them in selected localities throughout New Zealand where the butterfly is prevalent. The work is now proceeding very satisfactorily, and we have at present 20,000 butterfly pupse for parasitizing, and it is expected that at least another 20,000 or 25,000 will bo secured before the commencement of the coming season. Apart from the biological control methods in connection with the control of the butterfly, a certain amount of information has been gathered from experiments conducted with chemical control methods. Out of a number of materials tried, the most successful control obtained was from the use of calcium-arsenate dust used in the proportions of 1 part of calcium arsenate to 5 parts of hydrated lime. This material, if dusted at the requisite intervals as required, gives an effective control of the pest. The method, however, is only suitable for garden use or for the commercial grower of cabbages and cauliflowers. It is not a method that can be economically adopted in general farming practice in this country. Diamond -backed Moth (Plutella maoulipennis). During the past season there has been no opportunity of furthering our studies in regard to this pest owing to the exceptionally large amount of work involved in the conduct of the white-butterfly investigations and other projects. A most important part of the work—a thorough investigation of its parasites in Europe—must remain in abeyance until further funds are available. Greenhouse White Ply (Trialeurodes vaporariorum). In my previous report it was mentioned that preparations for the receipt of the natural enemies of white flies from Farnham Royal were being made. I now have to report that the parasites (Encarsia formosa) of this pest which were imported have been successfully established, and in the late spring of last year we were able to distribute a small quantity of parasitized material to tomato-growers from the small colony which we were able to rear successfully during the winter months. Very few reports have yet come to hand concerning the effectiveness of this parasite, though in one case the report on its control was very favourable, and the grower in whose tomato-house the material had been liberated states that he had no further trouble from white fly.

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