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There are numerous fungi which occur as parasites on scales 
and other insects. The destruction of the fungus only lends 
encouragement to the insects on which they occur. If the insects 
are destroyed both will disappear, since the fungus cannot live 
on the plant tissues. At the present time many experiments are 
being conducted especially in Florida with a view to using such 
fungi for combating the insect pests. This method of the employ- 
ment of the natural enemies to combat plant diseases has, up to 
the present time, given remarkable results and much more is 
hoped for it in the future 
Ercot oF Rye. 
The ergot of rye is a fungous disease which has several eco- 
nomic bearings. The ergot which replaces the healthy grain 
consists of a very hard slender body about one-half inch in length 
and represents the resting stage of a fungus. This fungous body 
is poisonous and when eaten by cattle causes a characteristic dis- 
ease known as ergotism. When present in rye flour in suffici 
quantities it causes trouble among people; it also causes a slight 
reduction of crop. These fungous structures are gathered and, 
having medicinal properties, are sold as an official drug under 
the name of ergot. 
DIsEAses OF PEACHES, PLUMS AND CHERRIES. 
The leaf-curl is one of the most common diseases of the peach. 
Asa result of this disease the leaves become curled, distorted and 
twisted. They finally become discolored and fall. The plum- 
pocket is caused by a fungus similar to that of leaf-curl. Plum- 
pocket causes the fruit to become much enlarged, hollow and 
deformed, the outside of the pocket being entirely covered with 
the fruit of the fungus. Witches’ brooms are sometimes caused 
by a similar parasite (fig. 35). The black-knot is another disease 
of fungous origin which attacks both plums and cherries, caus- 
ing the branches to become enlarged, deformed and blackened 
by the fruit of the fungus. 
Leaf-curl can be controlled by spraying with proper fungicides 
