FUNGOUS DISEASES OF INSECTS 273 



by a fungus belonging to this group, developing a curious 

 growth that generally projects from the head. 



White Fly Fungi 



One of the most noted illustrations of the effect of para- 

 sitic fungi upon injurious insects is found in the case of 

 the White Fly or Aleyrodes, various species of which are 

 destructive to orange and other trees in the Southern and 

 Pacific coast states. Similar species are also 

 destructive in greenhouses in the North. 

 At least seven distinct forms of the fungi are 

 known to attack these insects, and many 

 successful experiments have been made in 

 spreading the diseases artificially. The most 

 effective way is by washing into water the 

 spores that have developed on the insects killed by dis- 

 ease, and spraying the water on the infested plants. The 

 Florida Experiment Station has shown that this method is 

 easy and effective. The spraying apparatus must have no 

 copper in it, except the nozzle, as faint traces of copper are 

 liable to kill the spores. Another method is simply to pin 

 leaves covered with the dead insects upon the branches of 

 trees that are infested by White Flies. The disease- 

 producing fungi are most likely to spread during wet 

 weather. 



Bacterial Diseases 



The diseases of insects due to Bacteria are perhaps 

 more important than any others. When tent caterpillars, 

 cutworms, army worms, or various other insects become ex- 

 tremely abundant, they often die suddenly in great num- 

 bers, seeming to be affected by a sort of cholera that causes 

 death and rapid decay. This is a bacterial disease. 



