NO. 8.

New Zealand Mail, Issue 1206, 12 April 1895, Page 7

NO. 8.

' STRAWBERRY-LEAF BLIGHT. {SplwereUa fragarice.) Compiled by J. C. Biackmore. The following description is from the pen of F. Lamson-Scribner, the wellknown vegetable pathologist. " The strawberry-leaf blight, although of a microscopic size, is a plant like the

strawberry itself, and consists of a vegetative and reproductive system. The latter is quite complex, and, although studied very carefully, is not yet understood, except to determine three spore forms, and possibly a fourth. Heat and moisture favour its development, and at any time during the summer when the weather is moist the plants are likely to be affected. Heavy dew or rain are essential to infection, but the disease may

continue its work of destruction during dry weather, and it not infrequently happens that it develops in its worst form in dry, hot weather succeeding a period of frequent or heavy rain. " It is first noticed by very small, deep purple or red spots appearing on the upper surface of the leaves. These spots

rapidly increase in siMe, and at the same tiixte their colour changes from purple to reddish-brown. Eventually they become grey or white in the centre, so that they finally present a grey or white central area surrounded by a dark purple border, shading off towards the healthy tissues to reddish-brown. The spots vary in diameter from l-6th inch to nearly £ inch, but it very frequently happens that several contiguous spots coalesce and form ■large irregular-shaped blotches. The bright colour which these spots impart to the leaves renders the latter particularly conspicuous. ... The leaves badly

affected soon turn brown, the discolouration usually beginning at their tips, and become shrivelled and finally die. Similar spots to those above described sometimes appear on the calyx and on tha stems supporting the young berries or fruit. The effect of this blight upon the foliage of the plants, even in mild cases, must be detrimental to the process of assimilation, and when the attack is severe it results in the early destruction and death of the plants. The disease under favourable conditions spreads very rapidly. For instance, if after a prolonged rain a drop of water from a diseased leaf, or from an apparently healthy one growing close by, is examined by a good microscope, large numbers of conidia in various stages of germination will usually be seen. It is during such periods that the healthy leaves are infected. The germ-tubes enter the leaf either by directly penetrating the cuticle,

or through the breathing pores, and once within the tissues they may continue to grow independently of external circumstances."

The disease is -well known in Europe and America. In several districts of this country it has lately been noticed on the leaves of the strawberry. Growers should keep a look-out for the first appearance of this pest, and endeavour to stamp it out. Where the,disease is prevalent the practice among growers is to mow the beds immediately after the fruit is hnrvested, rake the leaves together and burn, then cultivate the soil, at the same time adding a quick fertiliser. A simgle line of treatment to be recommended, which will give satisfactory results, is the application of the ammoniacal carbonate of copper solu* tion, which will prevent the germination of the conidia falling upon the leaves. Apply with a spray pump a very fine spray early in spring, and frequently during the season. Hyposulphate of soda, lib to 20 gallons of water, or sulphide of potassium, Boz to 20 gallons, may be used. .The copper solution will, however, be found the most effectual, as the preventive action of the copper lasts longer. It should be borne in mind.that the value of whatever remedy may be employed depends entirely upon its power to prevent the germination of the conidia of the fungus. The necessity of making the application early is obvious.