THE LIME-SULPHUR SPRAY AT RUAKURA.

New Zealand Journal of Agriculture, Volume XIII, Issue 4, 20 October 1916, Page 285

THE LIME-SULPHUR SPRAY AT RUAKURA.

T. B. ROACH,

Horticultural Overseer, Ruakura Farm of Instructor

During the past season lime-sulphur was the principal spray used at Ruakura, and, in the main, it gave highly satisfactory results. Though much has still to be learnt about the merits of this spray, enough proof is forthcoming to satisfy the orchardist that he has something superior to anything available in the past as far as a summer spray is concerned.

During the season experiments with lime-sulphur versus Bordeaux mixture were tried on several varieties of apples and - pears, and in every instance the lime-sulphur solution showed its superiority, particularly on the apples Gravenstein and Willie Sharp. These varieties when sprayed with lime-sulphur carried respectively a crop of 193 lb. and 137 lb. per tree, against 114 lb. and 124 lb. yielded by those trees sprayed with Bordeaux mixture. A noticeable feature was the effect of the respective sprays -on the fruit of these varieties. With lime-sulphur no russeting of fruit followed, but fruit on the trees sprayed with Bordeaux mixture russeted to such an extent as to render 30 per cent, unsaleable.

A further trial with lime-sulphur, covering trees of numerous varieties, provides important data with regard to the strength at which the spray may or may not be used. Most readers are aware that some varieties of apples and pears are more tender than others, and care should therefore be exercised when applying the spray mixtures. Lime-sulphur applied at a strength of i gallon of solution to 80 gallons of water gave results fluctuating to a considerable extent. On the varieties of apples Dougherty, Irish Peach, Sharp’s Midseason, Allington- Pippin, Welcome, Jonathan, and Commerce results were all that could be desired. Only fair results followed its use on Byford Wonder, Cox’s Orange Pippin, and Cleopatra. Severe scorching was a result of its use on the varieties Lady Sudley and Roundway’s Magnum Bonum.

A similar experiment conducted over several varieties of pears also showed fluctuating results, though not so marked as in the apple experiment. Russet markings on the skin of the pear do not decrease the value of the fruit on the market to the same extent as on the apple. Scorching of the foliage represented the main damage done by the lime-sulphur to those varieties- included in this experiment. Williams Bon Chretien, Thompson, Beurre

Diel, Winter Bartlett, Emile de Heyst, and Howell showed no scorching of foliage. Poire de Berriays, Harrington’s Victoria, Richmond Beauty, Beurre Bose, and Marie Louise D’Uccle were varieties , badly scorched, Harrington’s Victoria suffering to the greatest •extent. Russeting of fruit occurred on P. Barry and Directeur Hardy. A weaker strength than 1 in 80 should therefore be applied to those more tender varieties, and a strength of 1 in 100 may be recommended instead. The strength at which the limesulphur should be used is certainly a very important point to the ■orchardist, for the stronger the solution is applied without being detrimental to the fruit or tree the more completely will fungoid and insect pests be controlled.

It may be stated that the initial experiments with lime-sulphur at Ruakura gave anything but satisfactory results. The first ■season’s trials were conducted at too great a strength. Repeated experiments, covering a wide field of variations, are the only means of gaining definite information on subjects of this nature. One experiment must follow another if anything of real value is to be achieved. Suggestions for future trials must have for their foundation data emanating from the results of former trials. Results are in most instances neither glaring nor conspicuous, and can only be arrived at after careful observation and study.

Since lime-sulphur has become one of the principal sprays in the Ruakura orchard powdery mildew has been practically wiped out. This disease was very prevalent in 1913, and, according to past records, was then on the increase, though all trees received regular sprayings of Bordeaux mixture. Exactly the same results as regards red mite followed the introduction of lime-sulphur. This pest is one that can do an immense amount of damage, and the extent to which it may rob a tree of its vitality is seldom fully recognized by the orchardist.

There can be but one conclusion from the above facts—namely, that lime-sulphur as a summer spray must command precedence over Bordeaux mixture.

Chatting recently with an officer of the Department a Marlborough farmer put in a good word for the small birds. He mentioned that many years ago, when the birds had not multiplied to their present numbers in his district, the barley crops were frequently ravaged by caterpillars. As showing the severity of the pest, he told of a case in which a neighbour’s barley had been wiped out by the caterpillar. The insects then began to cross a road dividing the destroyed crop from a paddock of barley on the opposite side. The owner of the threatened field successfully met the invasion by driving a roller up and down the road, crushing the caterpillars in masses. Of late years (presumably owing to the increase in the numbers of birds) Marlborough has been free of the pest.