ANTHRACNOSE OF CUCURBITS. 11 



On muskmelon the leaf lesions are quite similar to those on cucum- 

 ber. The attack on petiole, stem, and fruit is more severe. Petiole 

 and stem lesions are sunken and dark colored, penetrating deeply 

 and finally girdling. A red gummy exudate is often present. Fruit 

 lesions vary with the host variety (PL III, A and B) and are less 

 conspicuous on the netted varieties. In general, fruit lesions are 

 oval or circular and sharply depressed (PL III, B). On some varie- 

 ties the depressed epidermis may form a white background for the 

 pink spore cushions. The latter are represented by black dots after 

 sporulation ceases and may be arranged in concentric lines if the 

 lesion is on the upper exposed surface of the fruit. Rotting of the 

 fruit in the field may result from anthracnose lesions on its lower 

 surface. 



In the field, anthracnose of muskmelons is characterized by rather 

 complete defoliation, due to the severity of petiole attack, and by 

 the death of whole runners. Fruit lesions are also very conspicuous. 



The symptoms on watermelon have been well described by Sheldon 

 (46) . On watermelon leaves the lesions are black rather than brown 

 (PL IV). Petiole and stem lesions resemble those on muskmelon in 

 appearance and severity, and as a rule such lesions cause the death 

 of the distal portions. Infection of young fruits results in their 

 abortion or malformation. Small lesions on such fruits are black 

 depressed spots, soon bearing pink acervuli (PL V, C). On older 

 fruits the lesions first appear as elevated pimples with a yellow trans- 

 lucent center. More common on mature fruits is the nailhead type, 

 consisting of a rather flat-topped, circular, water-soaked elevation. 

 Such lesions soon become sunken and bear the familiar pink spore 

 masses on a black or cream-colored background. Lesions on the 

 under side of the melon where it is in contact with the soil may become 

 black and corky. It is from lesions thus situated that rotting in the 

 field may result. 



In the field, watermelon anthracnose is characterized by the 

 scorched appearance of the foliage and by the bare, leafless areas at 

 the centers of the hills, the stem lesions, and the disfiguration of the 

 fruit. 



On Lagenaria vulgaris, or gourd, the leaf lesions are also black 

 and the petiole and stem lesions resemble those on muskmelon and 

 watermelon. Lesions on young fruits are black, while on older white 

 fruits the lesions are brown at first, with conspicuous yellow and 

 water-soaked borders, and crack transversely while rather small 

 (PL VI). 



The symptoms on Cucumis melo var. dudaim, C. melo var. Jlexuosus, 

 and the mango melon are much like those on muskmelon. On the 

 leaves of Cucumis dipsaceus the spots are very fight tan colored. 

 Fruit lesions on Trichosanthes colubrina are illustrated in Plate V, A, 

 and on the mango melon in Plate V, B. 



