N^EW York Agricultukal Experiment Station. 199 

 CURRA^^T DISEASES. 



LEAF SPOT. 



The fungi which cause leaf spot of currants in the Hudson 

 Valley are Septoria rihis Desm., Cercospora angulata Wint., and 

 Gloeosporium rihis (Lib.) Mont. & Desm. During the season of 

 1899 none of these did any damage worth mentioning. Only 

 traces of fungous leaf spot were found in a few localities. Experi- 

 ments by Pammel/''^ GofF/^ and others have shown that at least 

 the first two and most common of these fungous leaf spot diseases 

 can be controlled by spraying' with Bordeaux mixture. How- 

 ever, at various times complaints have been received that spraying 

 does not prevent currant leaf spot. 



The observations in the Hudson Valley throw some light on the 

 cause of these failures. One of the best informed fruit growers in 

 Columbia County called our attention to a bad case of currant 

 leaf spot whichi he had tried in vain to prevent by spraying mth 

 Bordeaux mixture. Several thousand currant cuttings had been 

 sprayed with Bordeaux during the first week in May and again 

 about two weeks later. In spite of this treatment the plants 

 were severely attacked during the last week in May by a dis- 

 ease which the owner did not doubt was the fungous leaf spot 

 said to be amenable to treatment. An examination of the 

 affected plants revealed the fact that the trouble was entirely the 

 work of the four-lined leaf-bug/^ Poecilocapsus lineatus. The 

 leaves were thickly covered with small, reddish-brown, angular 

 spots. In the early stage the spots were black and water soaked 

 in appearance, but they soon became brown, dry and transparent. 

 (See Plate XVI, fig. 1.) The epidermis, on both sides of the leaf, 

 was depressed, but no gnawing of the tissue was evident. The 

 insect thrusts its beak into the leaf and sucks out the juices. 



"Pammel, L. H. Iowa Agv. Exp. Sta. Bui. 13: 45-46; Bui. 17: 419-421; 

 Bui. 20: 716-718; Bui. 30: 289-291. 



iSGofT, E. S. Wis. Agr. Exp. Sta. Bui. 72: 30. 



19 P'or an account of the habits, life history, etc., of this insect, see Cornell 

 Agr. Exp. Sta. Bui. 58. 0. 1893. 



