H.—34.

(c) Grass Diseases. (J) Blind-seed of Rye-grass (Helotium sp.^.—Evidence lias now been obtained to show that the fungus responsible does not perennate within the vegetative tissues of rye-grass, infection being confined to the seed. Drying or conditioning the seed greatly reduces the amount of infection in heavily infected seed intended for sowing in the autumn following harvest. Field experiments at Owairaka on the relation between percentage germination of seed sown in the autumn and the number of apothecia and amount of infection in spring were inconclusive, since no apothecia developed nor was there any natural infection in the plots. (2) Ergot. —A study made of strains of ergot isolated from various grasses showed that two species of fungi only are present. One, Claviceps paspali, is confined to paspalum ; the other, C. purpurea, infects a wide range of grasses, including rye-grass, cocksfoot, Yorkshire fog, tall fescue, &c., as well as barley, wheat, and oats. Proof has been secured that the fungus does not perennate in the host plant, therefore cannot be toxic to stock other than when grasses are allowed to seed. (3) Lolium Endophyle (Helotium. sp.j.—Much has been learned about the occurrence and distribution of the fungus, and a simple means of control has been evolved should it be found that the organism is harmful to rye-grass or to stock fed upon rye-grass pastures. A field grazing trial is being laid down by the Department of Agriculture at Ruakura with seed of the same strain of rye-grass with and without the fungus. (4) Cocksfoot and Meadovi-foxtail Midge. —Seed heads of these grasses infested with midge, collected from various parts of the Dominion by officers of the Department of Agriculture, were forwarded to Rothamsted by the Entomologist. The midge infesting meadow-foxtail was identified by Dr Barnes, of Rothamsted, as Stenodiplosis geniculati, that attacking cocksfoot as S. geniculati var. Nov. (d) Potato Diseases. Late-blight ( Phytophthora infestans)'. —A technique has been developed for testing resistance of potatoes to attacks from this fungus. Some ninety-three potato selections produced by the Agronomy Division were tested, several being found to possess a high degree of resistance to late-blight," (e) Legume Diseases. (1) Bacterial-wilt (Bacillus medicaginis). —All varieties of French beans were infected in the trial plots, resistance to wilt being displayed by two only —namely, Burnley selection of Canadian Wonder and Pale Dunn. (2) Pea-m,osaic.—Various crosses of garden peas produced by the Agronomy Division are being grown at Owairaka and tested for resistance to this virus. (3) Bean-mosaic. —A variety of French bean, said to be imjnune to this virus, has been introduced from the United States and is being grown for test at Owairaka. (4) Lucerne Nodule Organism.— During the season cultures of the organism, sufficient to inoculate 148,530 lb. of lucerne-seed, were distributed to 1,603 farmers throughout the Dominion. This shows an increase in inoculated seed of 31,710 lb. over that of last year, and exceeds that of any previous year. (5) Clover Nodule Organism. —While at the East of Scotland College of Agriculture, Edinburgh, in 1939, the bacteriologist continued his researches on the organism producing nodules on white clover. With the outbreak of war he was forced to return to New Zealand before the work had been completed, and subsequently has correlated results secured in Scotland with those secured in the Dominion. Results suggest that the different bacterial strains isolated vary in their efficiency in different districts and that, under practical conditions, it will be necessary to select and test specific strains for each of the provinces of Auckland, Wellington, Canterbury, and Otago. (/) Fruit-tree Diseases. (See Fruit Research report, p. 45.) (g) Small-fruit Diseases. Tomato Diseases. —Blotchy-ripening': A further series of soil treatments was undertaken in two glasshouses in which the disease was prevalent. None of the materials used gave any measures of control. Potassium sulphate, which has been claimed to give adequate control in England, failed to do so in these trials. Hard-core : At Owairaka in the experimental plots this physiological disease was widespread. Injections and soil treatments were carried out with borax, cobalt, copper, iodine, iron, magnesium, manganese, nickel, nitrogen, phosphorus, potassium, and zinc. As all failed to remedy blotchyripening or hard core, it is evident both are not caused by deficiencies of these elements. Verticillium-wilt (Verticillium albo-atrum) : To enable work to be undertaken on soil treatment for control of this disease, soil of a small experimental glasshouse was inoculated with cultures of the fungus. One hundred plants were set out and many subsequently developed the disease. Soil treatments are now being applied. Tomato-streak: This serious disease has been found to be caused by a combination of tobaccomosaic and a second unidentified virus which is under further study. Leaf-mould (Cladosporium fulvum): Seed of two tomato varieties resistant to the disease have been imported from the United States. Preliminary work has shown that they remain resistant under New Zealand conditions. Further tests under commercial conditions will be made during the coming season.

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