August, '16] HY8LOP: TRIPHLEPS AND CORN-EAR ROT 435 



TRIPHLEPS INSIDIOSUS AS THE PROBABLE TRANSMIT- 

 TOR OF CORN-EAR ROT (DIPLODIA SP., FUSARIUM SP.) 



By J. A. Hyslop, Bureau of Entomology, Washington, D. C. 



In the fall of 1912 we were advised of a severe outbreak of insects 

 attacking corn in Maine. The writer was dispatched to investigate 

 this outbreak and reached New Paris, Maine, on September 20, only 

 to find that the injury was due to a form of ear rot which was doing 

 its most severe damage to sweet corn in the large and important corn 

 canning districts of that state. As the various forms of ear rot are not 

 confined to sweet corn and, as Mr. Morrill, of the Burnham & Morrill 

 Canning Company, believed that insects were largely responsible for 

 this damage, a preliminary investigation was undertaken. I here 

 wish to express my appreciation of the many favors shown to me by 

 Messrs. Burnham and Morrill at whose plant most of the experiments 

 were carried on. 



The disease first makes it appearance as a small yellowish discolora- 

 tion of that part of the kernel immediately about the point where the 

 silk is attached and first appears when the corn is in the milk stage. 

 This discoloration spreads over the entire kernel and eventually the 

 epidermis ruptures. A viscid yellow liquid is exuded and finally the 

 kernel breaks down into a putrid mass. The diseased areas are scat- 

 tered and often run together, entirelj^ destroying the ear. In the ad- 

 vanced stages of the disease, a compact white mycelium often covers 

 the infected areas and several instances were noted wherein this 

 mycelivnn had a decided pink cast. Material of this nature was sent 

 in to Washington and was tentatively determined by the Mycologist 

 of the Bureau of Plant Industry as Bacterium siewarti Erw. Sm. 

 However, Bacterium stewarti is generally recorded as attacking the 

 corn when it is very young, and when ears are infested the husk shows 

 manifest symptoms. In the disease under consideration the husk 

 was never damaged, the disease not being detected until the corn was 

 husked. The second shipment of this material with brief notes was 

 determined as Fusarium spp. or Diplodia sp., the material being in too 

 poor condition for exact determination. I am quite convinced, from 

 the symptoms described by Burrill and Smith, that Diplodia is the 

 actual causative agent. The cause of the disease, however, was not 

 the phase of the problem that immediately interested us. Its method 

 of transmission was the important entomological problem. 



Fresh corn ears in the milk stage were used in the following experi- 

 ment. The ears were carefully gathered from an uninfested field. 



