32 



showed that the dry "honey dew" still contains conidia capable of germina- 

 tion, hut Stager (256) was the first to demonstrate the same by inoculation 

 escperiments. 



Dissemination of spores 



Dissemination of conidia 



Various factors are laiown to take part in the dissemination ' 



of the conidia found in abundance in the "honey dew". The secretion of 



"honey dew" continues for a considerable time, thus giving a chance for 



many different agents to tsike part in the dissemination of the spores. 



T/inds during the sphacelia stage are especially important, as any motion 



of the heads, loaded heavily with dew.will bring them in contact with other 



healthy heads. The spores are spread in this way in a horizontal direction. 



This has been experimentally tested by Bonorden and confirmed by Rose. 



Rain helps also in spreading the conidia. 



Probably the most common method by YBaidi the conidia are 



spread is by insects. As early as 1847 Leutiis (153) mentions that a certain 



beetle { Cantharis melanura ) visits in great manbers the infected heads 



for the"honey dew". Kolaczek (139) mafces the saime statement in his book. 



StSger made a careful study of the relation of insects (a list of which he 



gives for certain hosts ) , while visiting the infected plant for the dew, 



become loaded with conidia which they carry to healthy plants. The leaf 



louse, so commonly found on rye usually on all parts of the heads, because 



of their sweet secretion, attract many insects. These insects, v/hen coming 



after the secretion of the iouse during the period of anthesis, nay carry 



the conidia and spread the infection. 



Mercier (173) found that Sciara thomae L. visits very often 



Lolium nerenne . He found sphacelial spores on this insect, in its digestive 



organs, and later uninj ured in the excretions of the insect. He concludes 

 i See list of insects I-jsIoviT. 



