LONGYEAR ON DISEASE OF THE HUCKLEBERRY. . 61 



A SCLEROTIUM DISEASE OF THE HUCKLEliERRY. 



B. O. LONGYEAR, AGRICULTUIIAL COLLEGE, MICH. 



Doubtless few persons -who have gathered huckleberi'ies have failed 

 to notice the dry and shriveled ones Avhich seem to be covered with a 

 whitish powder or bloom. An examination of some of this powder in 

 1898 from specimens collected in a swamp near Michigan Agricultural 

 College sIioAved it to be composed of fungus spores resembling the 

 conidia of Munilia in their manner of growth. These spores are some- 

 what egg-shaped bodies, united by their ends into chains, which are often 

 branched and which readily break up when mature. Further study led 

 to the belief that this was the conidial form of a sclerotium disease, 

 several species of Avhich are known in Europe on species of Vaccinium 

 and Oxyco<;cus. Consequently search was made the following spring, 

 early in May, with the result that the ascigerous form was found grow- 

 ing from the mummified berries which had lain under the bushes all 

 winter. The fungus has been identified as Sclerotinia vaccinii Wor. 



The life history of the disease is as follows: The dry shrunken fruits 

 which lie on the ground through the winter are permeated with the 

 mycelium of the fungus and form the sclerotia from which grow the 

 ascophores. These latter are little cup-like bodies raised on slender 

 stalks which are furnished with root-like fibers or rhizoids where they 

 start from the sclerotium. The hymenium or spore bearing layer lines 

 the interior of the cup-shaped extremity and is composed of slender asci, 

 each containing eight well developed spores of an oval shape. These 

 spores are ejected at about the time when the young shoots are appear- 

 ing on the host plant. The tender epidermis of these shoots is pierced 

 by the germ tubes of the ascospores and the mycelium soon permeates 

 the tissues, causing the shoot to wither and die. while portions of the 

 affected part become covered with an outgrowth of whitish, powdery 

 conidia. These conidia have a strong odor of bitter almonds, attractive 

 to flies, which carry the spores on their bodies to the stigmas of the 

 flowers that are opening at this time. In this way the fungus gains 

 entrance to the ovary of the young pistils. 



These develop, apparently, in the normal manner, until the time of 

 ripening of the healthy fruits, when they change to a pallid color, dry 

 up and fall to the ground to furnish sclerotia for the coming season. 



Some of these diseased fruits were collected in July, 1800, kept dry 

 until autumn and then placed on the ground in the bog house in the 

 botanic garden. A few of them, removed on July 5 following, showed 

 two or three slender pointed outgrowths about one-fourth of an inch 

 long, and on April 28 other specimens possessed growths one-half to 

 two-thirds of an inch long, furnished with rhizoids and enlarging tips. 

 These would later form the mature ascophores. 



Young shoots affected with the conidial stage were collected May 18, 

 and some of the spores were placed on the stigmas of Vaccinium flowers, 

 in the botanic garden, where the disease had not appeared. On July 



