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esions, and cultures prepared from them remained sterile. The evidence obtained so far would seem to indicate that, it would be safe to export fruits exhibiting discoloration at the calyx. (e) Black-spot. The usual notification service in connection with the maturity of ascospores lias been maintained in Nelson by the Cawthron Institute. Spray experiments of the Plant Diseases Division for control of this disease are reported later under the section " Spraying Experiments." (d) European-canker.—To test the efficacy of wound dressings recommended overseas for treatment of fruit-tree cankers, fifty-two apple-trees were inoculated with the European-canker fungus, Nectria galligena, in 1939 by the Plant Diseases Division. When cankers had become well established they were pre-treated by two methods : (i) superficial discoloured tissues were removed, and (ii) all discoloured tissues were excised. Wounds were then painted with Bordeaux paste, two concentrations of zinc chloride, mercuric chloride, mercuric cyanide, and a proprietary emulsified bitumen paint. Cankers continued to develop in most instances when dressings were applied to those from which only superficial, discoloured tissues had been removed, but were checked in all instances, irrespective of the dressing applied, when all diseased tissues were excised. Results indicate that successful canker treatment lies in thorough excision of diseased tissues, rather than in the use of chemical agents. (e) Bitter-rot.—Several Bordeaux substitutes were tried at Huapai for control of bitter-rot, Glomerella cingulata. Results were inconclusive, since the disease did not appear in the orchard. As compared with Bordeaux, however, all the substitutes caused severe fruit injury to an extent which condemns them as summer sprays. 111. Physiological Studies. (a) Internal Cork.—Cawthron Institute: Chemical examination of apples from trees treated in 1935 with hydrated borax at the rate of 50 lb. and 100 lb. per acre shows these fruits still to have an augmented boron content, four years after applications were made. At one centre, however, where internal cork had originally been severe, the boron content of the fruit had again dropped to a critical level at which the disorder might be expected if climatic conditions favoured its development. The influence of boron on cold-storage quality is noted in the Fruit Cold Storage section of this report. (b) Magnesium, Deficiency.—" Premature defoliation" was noted in last annual report as apparently being due to a deficiency of magnesium. The Cawthron Institute has continued its investigations in this connection. The magnesium content of leaves from affected trees is less than one-third that of leaves from healthy trees. Defoliation is invariably more severe where liberal potassic manuring has been carried out for several years. Remedial treatments are being tested in three typical orchards, and the varieties include Cox's Orange, Jonathan, Delicious, and Sturmer. The compounds used are (1) magnesium sulphate (Epsom salt) at the rate of 7 lb. per tree, (2) ground dolomite. (magnesium-calcium carbonate) at the rate of 12 It), per tree, and (3) magnesium carbonate at the rate of 21b. per tree. At Lower Moutere, magnesium sulphate greatly improved the trees. With the Stunner variety, all treatments were beneficial, hut magnesium carbonate was outstanding in its effect. At Tasman the results obtained from soil applications of magnesium were not decisive, but injection of magnesium sulphate into the branches of the trees controlled the defoliation symptoms. Liberal potassic manuring had been practised, and this appeared to operate adversely against a quick response to soil applications of magnesium compounds. Chemical analyses of leaf material are incomplete, but reflect the trends shown in the field experiments. A series of mineral injections was carried out at the Appleby Orchard on the trees that were showing abnormal defoliation there, but none of the treatments have proved effective up to the present. IV. S-praying Experiments. (a) Modified Spray Programmes.-—Field experiments of the Plant Diseases Division have been continued in the experimental orchards at Huapai, Havelock North (Hawke's Bay), and Appleby. The main interest in these lies in the evidence which is accumulating to show that greater dilutions than were formerly employed can be used in commercial orchards with safety. Work is necessarily correlated with greater efficiency in the application of sprays. In Hawke's Bay a programme with lime-sulphur 1-300 plus colloidal sulphur (50 per cent, sulphur content) at 1 lb. per 100 gallons gave control of black-spot when adjacent check trees showed up to 20 per cent, infection of fruits. At Huapai, lime-sulphur 1 -200 plus colloidal sulphur (25 per cent, sulphur content) at 2 lb. per 100 gallons gave control of both black-spot and powdery-mildew, although check trees were heavily infected. In one programme at Huapai in which Bordeaux replaced sulphur from December onwards, apparent control of powdery-mildew was secured, since the fungus was prevalent in check trees but absent from those sprayed with Bordeaux. A similar result was secured in the previous season. Further tests were made in the Huapai Orchard to ascertain the conditions under which the wetting agent, Agral 2, is liable to induce injury. During the season under review no fruit injury was produced except when the wetter was used in excess with Bordeaux. (b) Russet awl Spray Injury. —Experiments of the Plant Diseases Division to ascertain the russet-susceptible period have been extended to the varieties Delicious and Dougherty, and have been continued on Sturmer. Apples have again shown a fairly well-defined period during which they are specially susceptible to spray-induced russet, although the limits vary somewhat from season to season. Modified spray programmes are being tested with a view to reducing or eliminating r upsetting induced by sprays,

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