PLANT DISEASES CAUSED BY FUNGI. 



129 



leaves the following season; hence Potatoes 

 obtained from a crop that has suffered from 

 disease should on no account be used as " sets ". 

 " Peach leaf curl ", a disease often attributed 

 to the presence of insects, and characterized by 

 the blistering and curling of the leaves, most 

 frequently accompanied by an abnormal swell- 

 ing of the young shoots, is in reality caused by 



Fig. 167.— French Bean Canker (Glceosporium lindemuthianum). 

 1. Fruit of French Bean attacked by the fungus, which also attacks Scarlet- 

 runners (natural size). 2. Fruit of fungus (magnified 400). {Gard. 

 Chron.) 



a minute fungus called Exoascus deformans, which 

 eventually causes the affected parts to present 

 a delicately frosted appearance, due to the for- 

 mation of its fruit on the surface of the diseased 

 portions. The mycelium of the fungus remains 

 from year to year in the shoots, following the 

 young growth, and producing the disease every 

 season, which eventually kills the tree, as the 

 diseased leaves fall early and there is a lack of 

 reserve material, and the wood is not matured. 

 If diseased branches are cut back beyond the 

 point of infection, and diseased leaves collected 

 and burned, the disease can be arrested; the 

 means of prevention are not difficult, neverthe- 

 less the work must be done promptly and con- 



VOL. I. 



tinuously until a cure is effected. Other minute 

 fungi closely related to Exoascus deformans cau.se 

 blisters on Plum leaves, the disease known as 

 "bladder-plums " or " pocket-plums ", also those 

 dense clusters of branches common on the 

 Cherry, Birch, and other trees, popularly known 

 as " witches' brooms ", " bird's nests " &c, in 

 various parts of the country. 



In conclusion, the well-known disease called 

 "anbury", " finger -and -toe ", or "club-root" 

 attacking the roots of various kinds of wild and 

 cultivated crucifers, as Cabbage, Turnip, Ptadish, 

 Shepherd's -purse, &c, should be mentioned, 

 although the organism causing it — Plasmodio- 

 phora brassicce — is not now classed with the 

 fungi. This disease attacks the roots of plants, 

 causing them to become much distorted and 

 swollen, and finally the plants die. It has 

 been proved that the germs of the disease 

 possess the power of remaining in a living 

 condition in the soil for several years; there- 

 fore, when a crop has once been attacked, it 

 is not advisable to use the same ground 

 for the growth of plants susceptible to the 

 disease for some years. Addition of lime to 

 the soil effectually prevents the disease. 



Fungicides. 



The term fungicide is given to those sub- 

 stances used for the prevention or cure of plant 

 diseases caused by parasitic fungi. 



Sulphur. — This is used in the form of a dry 

 powder in the condition called " flowers of sul- 

 phur". It is most effective against the group of 

 fungi popularly called mildews, where the my- 

 celium is quite superficial, and forms a white 

 down on the surface of living leaves and fruit, 

 as the Hop Mildew, Vine Mildew, also similar 

 diseases attacking Peas, Marrows, Cucumbers, 

 &c. Better results often follow when finely 

 powdered quicklime is mixed with the sulphur. 

 always having about double the quantity of sul- 

 phur. Special bellows are sold for the distribu- 

 tion of the powder. 



Bordeaux Mixture. — This is a liquid, and r.s 

 a fungicide is undoubtedly the best known at 

 present. Owing to the lime present in its com- 

 position, plants that have been sprayed with it 

 present the appearance of having received a 

 thin coat of whitewash. This, of course, for- 

 bids its use in the conservatory, pleasure-garden, 

 or home park; on the other hand, in the nursery, 

 kitchen-garden, vinery, or other place where 

 appearances can be ignored, Bordeaux mixture 

 is undoubtedly the very best fungicide for 



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