1919 ENTOMOLOGICAL SOCIETY. 61 



become covered externally with the spores but pass many of them uninjured 

 through their body in the excreta. AY hen this is deposited on healthy leaves or 

 on other parts of the plant it affords an additional source of possible infection, 

 either through the spores germinating and working their way through the un- 

 injured tissues or through their being washed by rains into wounds. 



Examples of Fungus Diseases Disseminated by Insects. 



Eegot of Eye {Claviceps puriyurea). This disease of cereals and grasses 

 is said by plant pathologists to be spread in the summer chiefly through insects, 

 especially flies, which are attracted to the sweetish, somewhat milky fluid in which 

 the conidia produced on diseased ovaries of florets float. As this fluid is sticky 

 the flies become contaminated and carry the spores to healthy florets, thus setting 

 up new infections.* 



Downy Mildew of Lima Beans {Plujtophtliora phaseoJi). Sturgis has 

 shown that this disease is apparently largely distributed by bees. He found that 

 the Mildew failed to appear to any appreciable extent until the flowers began to 

 expand, but that it became well established by the time the blossoms had fallen. 

 He also found that it began regularly in those inner parts of the flower which 

 were touched by the bee when seeking nectar, thus strongly indicating that the 

 bees were the carriers and inoculators. 



Chestnut Blight (Endothia ;;a rasjfica). This is a recently introduced 

 disease and therefore its distribution to each new locality is much more important 

 than would be the dissemination from tree to tree of some old, well established 

 fungus. Studhalter, Ruggles, Metcalfe and others have studied the relation of 

 insects to the Blight and have shown that while many insects distribute the spores 

 it is chiefly those insects that cause wounds on the trees that are important as 

 disseminators : because the disease can enter the tree only through wounds in 

 the bark. Euggles discovered that the Seventeen-year Cicada and a bast-miner 

 were important agents and that the disease in many cases had entered througli 

 wounds made by them. The Cerambycid. Leptosiylus macula, is important as a 

 carrier and possibly also as an incculator. 



White Pine Blister Eust {Cronartium rihicola). This is, as everyone 

 knows, another recently introduced disease, and it is not yet established in our 

 northern pine forests. Its spores lend' themselves to wind dissemination, but it 

 is thought that insects play an important role in the spread of the disease. Only 

 a few months ago Gravatt and Posey gave an account of their finding tiny Gipsy 

 Moth larva? feeding greedily upon the spore pustules of the disease on pine trees, 

 and becoming almost yellow with the countless spores that adhered to the hairs 

 of their body. It has been shown that these tiny larvte can be carried even 20 

 miles by the wind, so that distant spread of spores of the disease by them would 

 be expected. Gravatt and Posey examined wind-borne larvre found on Eibes (the 

 alternate host of the disease) and found aeciospores on them. They also found 

 that leaves fed upon by the larvse contracted the disease. There seems to be no doubt 

 that such larv» are in the New England States important agents in distributing 

 the White Pine Blister Eust. ' 



Goosfbekey Twig Disease (Undetermined fungus). In Burlington I have 

 seen a large, well-oared-for garden of gooseberries in which almost every plant 



*NoTE. — Since writing the above I liave been informed by Prof. Howitt that it has 

 recently been demonstrated that -wind plays a more important part in distribution of 

 crtnidia of ergot of rye than was formerly believed possible. 



