H.—34,

Tussock Grassland. Work has had to be somewhat curtailed under present conditions, but the taxonomic work has nearly all been completed up to the publication stage, while much has been done on life-history studies of the more important species. Special attention has also been paid to the possibility of introducing suitable legumes, seed-supplies being sought for from various grassland areas of similar types in other Nassella Tussock—k detailed survey was completed in collaboration with the Department of Agriculture, the acreages affected being summed up in the following table :—

Nassella is so concentrated on classes 1 and 2 that the land is virtually useless and requires special treatment. Class 3 has scattered plants that could be dealt with by concentrated effort, while class 4 is land liable to early invasion by seed, wind or animal borne, from established areas. A survey revealed that about 5,000 acres are infested in Marlborough, 300 acres heavily so. Experimental work on the life-history of the tussock, and its response to various treatments, is being carried out, and largerscale work is planned for the first opportunity. Weeds. Field work on hard fern is being completed, and a report prepared. General survey work has continued and detailed reports on the needle grasses and certain thistles prepared. Special attention has been given to gorse in the Wellington area. Miscellaneous. Brief mention is made of only a few of the further researches of the Division in progress. Preliminary work on linen-flax fibre shows that the relations of fibre to soil conditions and manurial treatment are worth following up. A report on the tung situation has been prepaied, with recommendations as to possible further action. The growth of hemp (Cannabis sativa) on the experimental area has been poor this season, but again a good crop of seed has been obtained. Collection of spores of Lycopodium volubile was organized, some 15 lb. being secured. This was submitted to a vulcanizing firm for test on a factory scale. The local material was found equal to that of the best European lycopodium powder. _ _ , Assistance was given to the Army medical services in the location, collection, and testing of koromiko (Hebe salicifolia) as a dysentery remedy. ENTOMOLOGY DIVISION, NELSON. Director: Dr. D. Milleb. White Butterfly (Pieris rap®).—The pupal parasite, Pteromalus puparum, continues to exert a major control on this insect. The larval parasite, Apanteles glomeratus, received some three seasons ago from American-bred material, shows every indication of having become successfully established in the Nelson region. _ . . Another recently imported parasite for use against the white butterfly is a tachmid fly (Lompsilura), from Canada. This fly has a very wide host range, including Pieris. No liberations of the tachinid have been made. . . Diamond-back Moth (Plutella maculipennis).—Field surveys strengthen the opinion formed earlier that the parasitic control of the diamond-back moth will be secured. Of the two parasites (Angilia cerophaga —larval, and Diadromus collaris —pupal), the pupal is found to be exerting the greater influence. Field surveys in the Waimea Plains show that the combined attack of both parasites has given 81-2 per cent, control—l 9-9 per cent, by Angitia and 61-3 by Diadromus. ' Cheese-mites. —Owing to the need for protecting cheese in storage, an investigation into the control of cheese-mite is being developed on a considerable scale. This work is being carried out in co-operation with the Diary Research Institute. _ Subterranean Grass-caterpillar (Oxycanus sp.), or Porina. Last seasons work indicated that the use of poison baits was the most practicable and efficient method of controlling Oxycanus, and that Paris green was the most effective of the poisons which were tested in such baits. The pre-eminence of Paris green as a poison for use in baits against Oxycanus was confirmed by this season's work. A bait containing 2 lb. of Paris green, 50 lb. of bran, and 16 lb. of molasses per acre gave a reduction in numbers of Oxycanus caterpillars of 70 per cent, to 80 per cent, with one application of bait. It was found that a reduction in the quantities of molasses or even its complete elimination produced no significant lowering of the efficiency of the bait. In many infestations "the quantity of bran might be reduced to 251b. without lowering the efficiency of the bait. The cost of material for the original formula was about 12s. per acre, and the elimination of half the bran and all the molasses would reduce this to Bs. per acre. The use of the bait resulted in a reduction in the numbers of Oxycanus caterpillars. On untreated areas only 25 per cent, of the ground was covered with pasture at the conclusion of the experiment, while on the treated areas 58 per cent, of the ground was still covered by pasture. On the basis of experience this season, it is estimated that a population of Oxycanus caterpillars exceeding 10 per square foot is sufficient to completely defoliate a pasture by early autumn. The treatments last year were applied at the end of May. The main work in the coming season will be to determine whether similar baits will give good results when applied to heavy infestations in February or March.

8

county. | class 1. j Class 2. | Class 3. | Class 4. Total. Waicara .. 2,700 3,700 60,000 118,400 184,800 Kowhai .. .. •• 950 1,900 9,900 28,900 41,650 Cheviot •• •• •• •• 90 > 200 90 • 200 Amuri .. .. •• 20 100 3,000 14,400 17,520 Total .. .. 3,670 5,700 72,900 251,900 334,170