DISEASES OF EEUIT TREES. 27 



of yellowing of the foliage results. This fungus is responsible for 

 much early defoliation of fig trees. (PI. II, fig. 7.) 



Specimens collected: Austin, 1907; Luling, 2243; Seguin, 2320; Georgetown, 

 2363; Victoria, 2333; Cuero, 2601; Stockdale, 2643; Gonzales, 2674; Halletts- 

 ville, 2787. 



ORANGE AND LEMON. 



Damping-off {Phoma sp.). — This is the most serious trouble of the 

 young plants of Citrus trifoliata L. in the nursery. Often a large 

 percentage of the plants will be yellow or completely dry and dead. 

 Near the ground level will be found a sunken area, 12 to 19 mm. long, 

 on which are black dots, the pycnidia. These pycnidia are 150 to 

 200 fi in diameter and the spores are 5 to 7 hj 3 /*. Several plants in 

 the row may be dead and the adjacent plants apparently unaffected. 

 The manner in which the fungus gains entrance is not known. Where 

 the ground has been allowed to remain wet in low places the loss is 

 greatest. 



It is not possible definitely to assign this Phoma to any of the many 

 species of Phoma described as occurring on citrus hosts. 



Specimens collected: On Citrus trifoliata L. — Beeville, 1847; Flbresville, 2855. 



Leaf -spot (Cercospora aurantia Healcl and Wolf, 32). — This fun- 

 gus forms large spots, 6 to 10 mm. in diameter, and suborbicular ex- 

 cept when they are marginal. They are dark brown in color with a 

 lighter brown center, and are surrounded by a region of yellow which 

 fades out into the green of the leaf. The conidiophores are formed 

 on the under surface in small groups, brown, septate, 100 to 180 by 

 5 to 6 fi, showing plainly the points of attachment of the conidia. The 

 conidia are dilutely colored, clavate, 75 to 135 by 4 to 5 /*, and many 

 septate. (PL I, fig. 8.) 



Specimen collected: On Citrus aurantium sinensis L. — Falfnrrias, 2446 (type 

 specimen). 



Twig-blight (Diplodia aurantii Catt.). — The ends of the branches 

 are killed and the black pycnidia which are formed beneath the bark 

 at length protrude. 



Specimens collected : On Citrus trifoliata L. — Nursery, 2546 ; Falfnrrias, 

 2447. 



Twig-blight (Sphaeropsis malorum Pk.). — This fungus has been 

 found on blighted twigs and less frequently on the leaves of Citrus 

 trifoliata L. The trouble was observed at the Austin station in a 

 hedge which stood adjacent to some apple trees which were very seri- 

 ously infected with black-rot. 



Specimen collected: On Citrus trifoliata L. — Austin, 1324; Cuero, 2596; Fal- 

 furrias, 2447; Gonzales, 2677; Nursery, 2544. 



Wither-tip [C olletotrichum gloeosporioides Penz.). — Both leaves 

 and twigs are attacked. The leaves form brown areas which become 



226 



