260 DISEASES OF TROPICAL PLANTS 



CH. 



Pytliium De Baryanum, Hesse, is another very 

 widely distributed organism which is very destructive 

 to seedling trees. It has previously been referred to in 

 this work. 



The Rhizoctonias are also very destructive to many 

 species of seedling and also to plants which are quite 

 large. They are especially injurious to nursery 

 stock. 



ENTOMOGENOUS FUNGI 



The fungi are not only the causes of diseases 

 among plants, but many of them are also the cause of 

 diseases of animals. Fish are attacked by Sa.prolegnia, 

 and young fish are frequently destroyed in great 

 numbers ; the higher animals are attacked by certain 

 fungi which cause diseases of the skin, and other parts ; 

 but by far the greatest sufferers are the insects, which 

 are subject to the attacks of a large number of species 

 of fungi. No doubt many insects are held in check by 

 their inconspicuous fungus enemies, most of which are 

 unknown to us. 



Some of the earliest observations on these interesting 

 fungi were made in the tropics. In 1754, Father 

 Torrubia collected specimens in the vicinity of Havana, 

 Cuba, and wrote a popular description of what is now 

 supposed to have been Cordyceps sphecocephala. Since 

 that time many species have been reported and described, 

 and many efforts have been made to turn our knowledge 

 of these species to some advantage in combating certain 

 species of injurious insects. 



The entomogenous fungi are most common on the 

 larva of insects, but some species also attack the adults. 

 Aquatic and other insects which live in moist places 

 are especially susceptible to the attacks of these fungi. 

 Among the most conspicuous of these entomogenous 

 fungi are the species belonging to the genus Cordyceps 

 (see page 46). However, this genus is of no very great 

 economic importance in the control of insects. 



Of the many efforts which have been made to use 



