HELP FOR THE ORCHARDIST

Otago Daily Times, Issue 22908, 16 June 1936, Page 10

HELP FOR THE ORCHARDIST

RESEARCH WORK AT BRISTOL (From Our Own Correspondent) (By Air Mail) . LONDON, May 13. Although it is too early to claim that the time has arrived when research has discovered a single remedy for all kinds of pests attacking fruit orchards, very great progress has been made during recent years towards the production of a spray of the type known as a combined wash. This will give control of a considerable number of insect pests and fungus diseases simultaneously, and its perfection is gradually being attained by the University of Bristol's research station at Long Ashton, Bristol. The work carried out at this station was recommended to the notice of New Zealand farmers by Lord Bledisloe when he attended the openinz of the New Zealand apple season in London recently. The latest work achieved by the station with these combined washes is recorded in its annual report for 1934, in which the experiments carried out by Messrs H. G. H. Kearns, R. W. Marsh, and 11. Martin are explained and commented upon. In their introduction to the report it is pointed out that the need for the combination, in one wash, of two or more toxic materials, normally applied separately, arises from the overcrowded spraying programme now required for the production of clean and profitable crops ° m ' MANY PROBLEMS.

The derivation of a satisfactory combined wash involves insecticidal, fungicidal, and phytocidal problems, for it must not be inferior in practice to the separate insccticidal and fungicidal 6prays it is intended to replace. Successful field trials repeated for several seasons must be the basis of general recommendations. The major problem concerning washes for apples has been the discovery ot methods whereby the protective ingredient in the combined washes, that is the lime sulphur, lead, arsenate, or Bordeaux mixture, could be applied in heavy amounts necessary for the contact wash without loss of protective ability or increase in plivtocidal properties. For this purpose two methods were found of promise: (1) The use of watersoluble spreaders which appear to function by reducing the tendency to drop formation upon the sprayed foliage, and (2) the incorporation of either glycerine or hydrocarbon oils which, in themselves of some insccticidal value, improve the retention of the protective deposit, and also serve as effective carriers for other contact insecticides.

For black currants the use of lime sulphur at the pre-blossom stage is a recognised method of obtaining big bud control, and the late application of petroleum oils as ovicides for capsid control would appear a promising alternative to the use of such oils as winter washes. None of the washes caused any damage, and there was no retardation of growth following the petroleum oil-lime sulphur mixture. In one instance it was estimated that unsprayed plants were affected by 100 per cent, infestation while those sprayed were subjected to 10 per cent, iiffeHtntion. . ... The use of lime sulphur or or suitable petroleum oil emulsions at petal fall is known to give a satisfactory control of red spider on plums. At the same stage caterpillar is controllable by lead arsenate. Within the past few years attacks of plum eawfly have become increasingly serious, and from a consideration of the life bistorv of this pest it was thought that it might also he amenable to control at the petal fall stage. Trals were therefore carried out in 1934 to find a jioii-phvtocidal combined wash that would simultaneously control red spider, eaterpillar, and plum eawfly.

The control of red spider and caterpillar was most satisfactory. The plum eawfly attack on the control trees was negligible, and therefore no indication of the effectiveness of the spray against this pest could be obtained.