DISEASES OF TREES AND SHRUBS. 73 



having a scarcity of forage it is pruned from the trees and fed to 

 cattle. 



Specimens collected : Llano, 1737 ; Cotulla, 2183 ; Luling, 2277 ; Seguin, 2297. 



Leaf -blight (Cercospora prosopidis Heald and Wolf, 32). — This 

 disease is characterized by the presence of irregular, angular, brown 

 patches which occupy one side of the midrib of the leaflets or extend 

 across the whole leaflet and are generally bounded by a narrow, 

 brown border. The spots may be either terminal or removed from 

 the apex of the leaflets, and they frequently advance until the whole 

 leaflet is killed or drops from the tree. In some cases it is very 

 abundant and causes considerable defoliation. Its greatest develop- 

 ment may be found in the dense mesquite thicket. 



The conidiophores are amphigenous, densely fasciculate, uniformly 

 brown, continuous, 18 to 30 by 3 to 4 /z; spores straight, cylindrical 

 to slightly club shaped, brownish, 20 to TO by 4 to 5 p, and one to 

 many septate. (PL III, fig. 2.) 



Specimens collected: Uvalde, 1959 (type specimen) ; Luling, 2264; Falfnrrias, 

 2468: Gonzales, 2663; Kennedy, 2824; Floresville, 2847. 



Powdery mildew (Erysiphe sp. ?). — The young mesquites are fre- 

 quently affected with powdery mildew, but it is rare on older trees. 

 It produces no apparent injury and is abundant only near the end 

 of the growing season. Immature perithecia were found in one 

 locality, but all other collections represent only the conidial stage. 

 Salmon in his monograph does not record a powdery mildew for this 

 host, hence the specific determination can not be made. 



Specimens collected: Austin, 200, 2917; Beeville, 1867; Uvalde, 1960; San 

 Marcos, 2091; Cotulla, 2172; Luling, 2278; Seguin, 2315; Farfurrias, 2491; 

 Cuero, 2579 ; Stockdale, 2610 ; Gonzales, 2684 ; Skidmore, 2815 ; Kennedy, 2837 ; 

 Floresville. 2841; Hallettsville, 2900. 



Rust (Ravenelia arizonica Ell. and Ev.). — This rust is very incon- 

 spicuous, producing a few minute brown sori on both surfaces of the 

 leaflets. There was no other discoloration of the leaves in the speci- 

 mens collected. Specimens obtained from a single locality. 



Specimen collected: Falfurrias. 2492. 



MULBERRY. 



Die-back (MyxospoAum diedichei Syd.). — The branches of young 

 mulberry plants {Moras spp.) in the nursery rows were covered with 

 whitish or pink pustules protruding through the epidermis. The ter- 

 minal portions of the twigs had apparently been killed by this 

 fungus. 



Specimen collected: On Morns alba L. — Georgetown, 2359. 

 226 



