Feb. 26,1917 Squash Disease Caused by Choanephora cucurbitarum 321 
APPEARANCE OF THE DISEASE 
The symptoms of the disease on flowers and fruits of squashes is quite 
characteristic. The fungus covers the affected parts with a luxuriant 
crop of conidiophores, with no evidence of any vegetative mycelium. 
The fructifications of two other fungi, Rhizopus nigricans Ehr. and 
Botrytis vulgaris Fr., may appear on the surface of decaying squash 
fruits, but neither of them possesses the metallic luster which charac¬ 
terizes the fructifying filaments of C. cucurbitarum . 
The first evidence of attack on the flowers usually appears on the day 
following the opening of these flowers. Early in the morning of the 
second day, the fuhgus will have reached its most luxuriant development, 
especially immediately after a shower, and the fading flowers will be 
covered by a dense coating of immature, white conidial heads. Within 
a few hours these fructifications will have matured and will have changed 
in color from white to brown and at length to purplish black. When 
staminate flowers are attacked, the mycelium may pass downward into 
the flower pedicel, converting the tissues into a soft, translucent condi¬ 
tion. Abscission of the flowers generally occurs before the pedicels 
become invaded. The appearance of the disease on flowers and flower 
pedicels is shown in Plate 87, A. 
When pistillate flowers are attacked, the fungus passes from the 
fading flower into the young squash. Incipient decay from infection 
through the corolla is shown in Plate 87, D y as is also complete decay 
involving the fruit in a soft, wet rot with a profuse envelopment of 
conidial branches. The decay of fruits progresses with remarkable 
rapidity, as is shown in Plate 87, B, C. The photographic exposure for 
figure B was made about 15 hours after the one for figure C, the squash, 
meanwhile, having been kept in a moist chamber. Occasional fruits 
were found in which the fungus appeared not to have gained entrance 
through the corolla. 
ETIOLOGY AND DEVELOPMENT OF THE FUNGUS 
Choanephora cucurbitarum , the cause of this squash disease, is unique 
in that it is the only known American representative of the family 
Choanephoraceae. Two other species have been described from India, 
one C. infundibulifera (Curr.) Cunn. on the flowers of Hibiscus rosa- 
sinensis and the other, C. Simsonii Cunn. on Ipomoea rubro-coerulea and 
Zinnia elegans. The former of these was described by Currey 1 in 1873 
as Cunninghamia, a new genus of mucedinous fungi, and was referred by 
Cunningham 2 in 1879 to the Mucorineae. 
1 Currey, Frederick, On a genus in the order of Mucedines. In Jour. Linn. Soc. [London], Bot., v. 13, 
P. 333-334, Pi- 7* 1873. 
2 Cunningham, D. D. On the occurrence of conidial fructification in the Mucorini, illustrated by Choa¬ 
nephora. In Trans. Linn. Soc. London, s. 2, Bot. f v. 1, p. 409-422, pi. 47. 1879. 
