462 Journal of Agricultural Research voi. xii, no. 7 



infested plants showed areas producing uredospores, and in four instances 

 the only leaves showing blister-rust infections were those which had been 

 injured by insects. 



Sixty larvae collected on species of Ribes were examined for aeciospores. 

 Of these one larva collected on June 14 on the und^er surface of a wild 

 gooseberry plant showed 280 aeciospores and 520 uredospores on its 

 body. The gooseberry plant was heavily infected with blister-rust, 

 being located only 20 feet from pine infections. Germination tests of 

 the spores from this larva gave two germinating aeciospores and many 

 germinating uredospores, thus bearing out the fact that gipsy-moth 

 larvae do carry viable spores to Rihes spp. and also showing the part 

 which insects may play in local distribution of the disease by uredospores. 



PRACTICAL importance: 



The facts given in regard to the gipsy-moth larvae show that these 

 insects are certainly a factor in the spread of the blister-rust locally 

 from pines to Rihes spp. Their habit of feeding and crawling over the 

 lower leaf surface, where the stomata are located, gives the spores borne 

 on their bodies a good opportunity for causing infection. The prob- 

 ability of the spread of blister-rust from pines to distant Rihes spp. is 

 undoubted, since Collins' work shows that the gipsy-moth larvae are 

 blown by winds of varying intensity for distances of 20 miles. Though 

 wind is considered to be the most important factor in aeciospore dissemina- 

 tion, gipsy-moth larvae undoubtedly play an important part. Other 

 insects have been collected from infected pines with thousands of aecio- 

 spores on their bodies, but these insects were not present in sufficient 

 numbers to make them of importance in comparison with the number of 

 gipsy-moth larvae present. 



SUMMARY 



(i) The period of hatching and of wind dissemination of gipsy-moth 

 larvae came within the period of spore production of the blister-rust on 

 pines. 



(2) Larvae fed abundantly on spores and injured the fruiting layer of 

 the pustules so that further spore production was arrested. 



(3) Larvae from blister-rust cankers had thousands of viable spores on 

 their bodies. A small percentage of the larvae collected from fly paper 

 and from species of Ribes near infected pines showed aeciospores on their 

 bodies. 



(4) Gipsy-moth larvae were found feeding on leaves of Rihes spp., 

 and in some cases the only infected leaves on plants of this genus were 

 those showing insect injury. 



(5) The Bureau of Entomology has shown that these larvae are 

 blown by the wind up to a distance of 20 miles. Within this distance 

 the larvae are potential agents in the spread of the white-pine blister- 

 rust (within the area infested by the gipsy moth). 



