CONTROL OF BROWN ROT

Nelson Evening Mail, Volume LII, Issue 163, 8 July 1918, Page 7

CONTROL OF BROWN ROT

VALUABLE AMERICtAJST EXPERIENCE. (Concluded.) -Uany experiments have .shown that-well-made arsenate of lead is much the saiest of all available arsenicals for use on the poach. Arsenate of lead is to be foun-c! on the market both as a powder and as a putty-like paste, which latter must be worked free in water before it is abided to the lime-sulphur mixture, the paste iorm of the. poison is largely used at the rate of about two pounds to each 50 gallons of thojime-sulphur wash, and is added, after it has been well worked free in water, to the lime-sul-phur spray previously prepared As there are numerous brands of arsenate of lead upon the market, the grower should be careful to purchase from reliable firms. A decided change in colour will result wheru the arsenate of lead is added to the lime-sulphur mixture, due to certain chemical changes which in the experience of the writers, do not injuriously affect the fungicidal and insecticidal properties of ■the spray or result in injury to the foliage. .In large spraying operations it will be more convenient to prepare in advance a stock mixture of arsena.te of lead, as -follows:—Place 100 pounds of arsenate of lead in a Barrel, with sufficient water to work into a- thin paste, diluting finally with water to exactly 25 gallons. When thoroughly stirred each gallon of the stock solution will thus contain four pounds of arsena.te of lead, the amount necessary for ICO gallons of spray. In smaller spraying operations the proper quantity of arsenate of lead may be weighed out as needed, and thinned with water. In all cases the arsenate of lead solution should _ be strained before or as it is poured into the spray tank.

DAiXGiE-R 0:1- INJURY SPRAYING. The foliage of the peach is extremely sensitive to injury from such sprays as Bordeaux- mixture and arsenicals, such as Paris' green, arsenate of lead, etc. This sensitiveness has been the sole reason why/ it has been impracticable to spray peach orchards with fungicides and insecticides such as Bordeaux mixture or Paris green, as has fpr yerirs been the custom in the case of apples and other deciduous fruits. Of the various arsenicals available for use, well made arsenate of lead has proved to be the safest. When it was established that the seltboiled lime-sulphur wash was an effective fungicide, and entirely safe as a spray for the peach, one of the interesting questions presented was whether arsenate of lead, might be safely used with it to effect a combination spray for both insects and diseases. While on chemical grounds it appeared, that the addition of arsenate of lead to the selfboiled lime-sulphur mixture would result in an important decomposition of the spray, and greatly add to its probable injurious character, in practice the combined spray was found to be entirely safe. Observations extending over three seasons have failed to show any serious injury resulting from the use of this spray, even when as*many as three applications were made. It is n|t understood why the arsenate of lead apparently loses its injurious properties when used in the self-boiled lime-sul-phur wash, though its safe 'employment in this way is most .fortunate. The effect of the arsenate oi' lead upon the fruit is to increase its colour notably. This increase in colour from two applications in self-boiled lime-sulphm wash improves tho appearance of the fruit. Three or even two applications of the poison alone or in limewatei, however, result in a very excessive reddening,' espesially -oil "the side exposed to the sun, oh which later may appear -brown, sunken spots, of "variable size, accompanied with move rfv le«s extensne cracking of the :-::in. . The self-boiled lime-sulphur mixture, when properly prepared according o directions, does not -injure tne fruit .01 foliage, but" if allowed to remain hot m conefntrated form before dilution enough sulphur may go into solution to .P lod " c . injury to the foliage. .Users of this spray should, therefore, follow carefully the directions given for ite preparation, bearing in mind that a good, mechanic, mixture of the sulphur and hme suspended in water and only com Ed, is desired rather than to dissolveany considerable quantity of the su Jph" r " Dtiring the application of the sp ia .-, it i? very important that the mixture t kept well agitated to nsure .te un - form distribution. .As both the sel ed lime-sulphur wash and the- arsenate o W quickly settle when undisturbed, an excessive b applied to some trees, while " ceive an insufficient quantit}. it o bei d ng a properly in the tank S—t ItSf the of the spray ™ay so s ujig has TeeTobOTci tobe-the i