32 A PLANT-DISEASE SURVEY IN TEXAS. 



Bacterial twig-canker. — The first indication of the disease on the 

 twigs is the swollen longitudinal ridges of the cortex. In cross 

 section this ridge shows numerous radial rifts extending outward to 

 just below the ej)idermis. Eventually these radial rifts extend 

 outward through the epidermis, and open longitudinal slits are pro- 

 duced. Bacteria are abundantly present in the cankered tissue. 

 This may be the same organism which attacks the leaves and fruits. 

 It has been previously reported (29) on the twigs. This is a very 

 general trouble of the plums of this section. (PI. VIII, fig. 3.) 



Specimens collected : Sau Antonio, 1400 ; Austin, 1433 ; Seguin, 2290. 



Die-back {Valsa leucostoma (P.) Fr.). — The symptomatology is 

 identical with a trouble described under the same name as occurring 

 on the peach. This, too, is present to a very considerable extent. 



Specimens collected: Austin, 1439; Kerrville, 1597; Beeville, 1S62; Seguin, 

 2285 ; Round Rock, 2422 ; Victoria, 2522 ; Stockdale, 2627 ; Gonzales, 2669. 



Leaf -spot {Phyllostlcta congesta Heald and Wolf, 32). — On the 

 upper surface of the leaf are very numerous brown areolae bounded 

 by the veins of the leaf. The lower surface may not be discolored. 

 These minute spots, 0.5 to 0.8 mm. in diameter, fuse. Each contains 

 at its center a single black pycnidium 50 to 125 /x in diameter. The 

 pycnidia contain globular or slightly oval clear spores 6 to 9 j;. in 

 diameter. 



Specimen collected: Boerne, 1554 (type specimen). 



Kust {Tranzschelia punctata (P.) Arth.). — The sori are frequently 

 so abundant as to make the leaf seem uniformly chocolate brown. 

 In one orchard the trees were very seriously affected. 



Specimens collected : Austin, 450, 467 ; Cuero, 2595. 



Shot-hole {Cylindrosporium, padi Karst.). — This is the most gen- 

 eral trouble of the plum, producing brown, circular areas w^hich drop 

 out, giving the " shot-hole " effect. 



Specimens collected: Austin, 449, 1279, 1431; San Antonio, 1387; Brenham. 

 1461 ; Kerrville, 1593 ; Boerne, 1655 ; New Braunfels, 1704 ; Llano, 1758 ; Beeville, 

 1839, 1800; Elgin, 1882; Bastrop, 2030; Luliug. 2244; Seguin, 2291; Georgetown, 

 2364; Round Rock, 2404; Victoria, 2508; Nursery, 2550; Cuero, 2598; Stock- 

 dale, 2620 ; Gonzales, 2672 ; Flatonia, 2734 ; Hallettsville, 2781. 



Silver-twig. — The bark on the twigs becomes silvery in appearance. 

 It is found to be infested with the brown septate filaments of a 

 fungus, which grow just beneath the epidermis. The surface cells are 

 raised so as to admit air, thus producing the silvery coloration. 



Specimen collected: Falfurrias, 2457. 



