CHE REFERENCE LIBRARY - ZetaTalk

192 THE NilJRSERY-MAN [JAI-,chinr. With the dust method, the time of application is notlimited by soil conditions, inasmuch as the lightness of theout.fit permits its transportation at all times ; also blocks oftrees on rough or hilly ground or in localities remote from anadequate water supply nlay be protected without unusualdifficulty. The dusting method can be employed in controllinga large percentage of the leaf diseases and foi+e-eating insectsin the nursery. The cost of spraying solutions is less thandust materials. The actua,i expense for the dust method,however, is practically the same as for the liquid since thehandling of a large bulk of water is eliminated, the outfit isless expensive, and the operators are fewer in number.The nursery-stock diseases caused by fungi a,nd bacteriaare particularly baffling because the organisms are not seenand recognized. In former da,ys these disorders were ascribedto the weather, t,o t?iect,ric currents and to other little understoodor occult phenomena.FIRWHLIMW. - The fire-blight disease is most destructiveon the cultivated varieties of pear, apple and quince. Usuallyin the nursery it means total loss or” t,he trees afleeted a,nd oftenwithin a comparatively short t,ime thousands of young treesare ruined by its rapid spread t,hrough the blocks.Ik.script km . - The limbs, blossoms, twigs and fruit may heattacked. In the nursery the disease is most commonly foundin the twigs (Fig. 210). In the case of two- and three-year-oldquince stock, however, the trees often blossom profusely inthe spring and when this happens blossom-blight (due to thesame organism) frequently occurs. The blight usually firstappears two or t.hree weeks after the blossoming period. Thefirst evidence of the trouble is the brown and subsequent