494 



DISEASES 



DISEASES 



use of remedial measures until after the fungi are in 

 evidence. With many quick-acting diseases it is then 

 too late, and in fact with some the spray pump, when the 

 trees are in full leaf and fruit, is of secondary impor- 

 tance. The fruit-rot or gray mold (MoniUa fnn'tiijexf^) 

 of the cherry, plum and peach is of this type. To eradi- 

 cate this pest, it is not enough to wait until the disease 

 is in the trees, for then, if the weather is warm and 

 moist, the crop is destroyed. Here, again, the work of 

 prevention should begin the winter before; by destroy- 

 ing all mummy fruit {Fig. 722) and blighted branches 

 the disease is attacked at its weakest point. 



Another point in this connection that must be kept in 

 mind is the general health of the plant. Every tree or 

 shrub should be well nourished and come to its ap- 

 pointed task in good health. This means the best 

 form of the plant for the purposes intended, obtained 

 by the use of the pruning knife or other means. Fungi 

 do not love the sunshine half as well as the shade, and 

 an open-topped tree needs less spraying than one with 

 the branches crowded. This will also obviate in some 

 measure another point of weakness, namely, overload- 

 ing. A peach tree attempting to carry a double comple- 

 ment of fruit will breed more decayed fruit and foliage 

 than many that are not overloaded. Thinning, in other 

 words, is often as essential to healthfulness as spraying, 

 and a congenial soil and situation are more important 

 than either. Naturally, the question of remedies for fun- 

 gous diseases comes in only after all the conditions for 

 the best growth of the plants have been met. 



The number of fungi injurious to the horticulturist is 

 large, and space permits of the mention of but a few 

 under the several crops. Apples: Aside from the rust 

 and scab used above for general illustration, there are 

 the ripe-rot {Glcposporium frttcfige^ium); powdery mil- 

 dew {Podosphara Oxyacanthw), and the fire-blight {Ba- 

 cillus a7niflororus). The first of the three grows also 

 upon the grape, and the fire-blight attacks the pear and 

 the quince, upon the former being a serious enemy. In 

 this tire-blight we have a bacterial disease in plants, 

 that resides during the winter in the twigs, and is con- 

 veyed to Howers by insects which gather on the ooze of 

 cracked, blighted stems in spring. All such diseased 

 branches should have been previously removed. 

 Quinces: The black-rot {Sphferopsis malorum) and 

 rust {MoEstelia aurantiaca, are often destructive. 

 Plums, in addition to the black-knot, have leaf-blight 

 i CiflindrosporinmPadi) , while the cherry has the "shot- 

 hole" fungus {Sepioria cerasina). Peaches are some- 

 times much afflicted with the leaf-curl ( Exoascus deform- 

 ans, Fig. 723), and the scab or "gray back" (Cladospo- 



The affected trees produce tufts of small branches upon 

 the older branches, with slender leaves, known as "Pen- 

 nyroyal sprouts" or "willow shoots." Trees with these- 

 "bushes" are fit subjects for the burn heap. 



Of the small fruits, the grape leads in the number of 

 fungi, the black-rot and ripe-rot previously mentioned 

 being among the chief, while the anthracnose {Sphace- 



724. Currant foliage attacked by the leaf-spot fungus {X ^4). 



rium carpophilinn ). The most obscure disease of the 

 peach is the "yellows," a name given to a contagious 

 disorder that manifests itself in a premature ripening of 

 thefruit, which takes on an unnattiral spotting of red or 

 purple, with the flesh streaked and the taste insipid. 



725. Strawberry leaf rolled up from the attack 

 of the leaf-blight. Natural size. 



loma ampeliiium ) and downy mildew (Plasmopara riti- 

 cola) are quite destructive. Blackberries and raspber- 

 rise suffer from similar diseases, the leading ones be- 

 ing the rust {Pitcchiia PecArmHrt ), requiring the destruc- 

 tion, root aud branch, of the infested plants, and the an- 

 thracnose {Glceo.tporium ^'euetnm), amenable to spray- 

 ing. Currants and gooseberries are similarly akin, and 

 have nearly the same fungi , as leaf-spot(^('/)foWrt Bibis, 

 Fig. 72-4) and anthracnose {Glceosporiutn Bibis), in ad- 

 dition to which the gooseberry is badly troubled with a 

 mildew {Sph(erotheca Mors-U'ccp), that may be kept off 

 by sulfide of potassium, one ounce to two gallons of 

 water, as a spray. Strawberries have the leaf-blight 

 (SphiPrella FragarifF, Fig. 725) as the leading fungous 

 trouble, and this sometimes requires heroic treatment, 

 even to the burning over of the bed in autumn to de- 

 stroy the infested leaves and the germs they contain. 



Annuiil Plunfs. In the previous discussion, peren- 

 nial crop plants only have been considered. With the 

 annuals the treatment is in large part the same, except 

 that there are no live plants in winter to be considered, 

 no stems and branches to be cleansed, and there is the 

 very important difference that it is possible to grow the 

 annuals upon new ground each season. While it is im- 

 possible to move the vineyard or fruit garden, it should 

 be the rule not to grow an annual upon the same piece 

 of soil continuously. In one sense the grower can move 

 away from his troubles by practicing a judicious rota- 

 tion of crops. However, the truck grower and the gar- 

 dener in a small way should not trust entirely to this 

 itinerancy, but instead should place the spraying ma- 

 chine upon the same footing as the plow or planter as a 

 necessar)' implement; and as insects compete with fungi 

 for the possession of his crops he should spray for both, 

 and usually this can be done at the same time. The 



