110 Diseases of Economic Plants 



Blue-stem^'''* (Vertidllium caulophagus (Law). — Rasp- 

 berries and blackberries in the Pacific Northwest are affected 

 by blue-stem, the first appearance of which was noted in 

 1904. The fruit dries up before maturity, the leaves become 

 discolored and wilt. Less commonly the canes turn dark, 

 the first blue-black, striped discoloration of the shoot occur- 

 ring near the ground. Internally in stems, and even in 

 roots, reddish streaks are evident in the wood. Many 

 affected canes die, others merely show the symptoms men- 

 tioned above. 



BLUEBERRY AND HUCKLEBERRY 



No diseases involving special treatment are to be noted. 

 Numerous parasitic fungi are recorded, among them Exo- 

 basidium, Gibbera, Guignardia. 



CRANBERRY i-^-i-« 



To lessen storage decay, cranberries should not be picked 

 when wet, nor stored with admixture of infected material 

 likely to result from deep "scooping." They should also be 

 well ventilated. 



Scald, blast {Guignardia vaccinit Sh.).- — -The fruits are 

 attacked as soon as the blossom falls, or even the blossom 

 itself may be blighted. The affected l^erry shi'ivels, turns 

 black, and is covered with pycnidia. From such fruits the 

 disease spreads to other fruits and to the leaves. In some 

 bogs as much as 50 per cent of the crop is thus de- 

 stroyed. This form of disease is commonly designated 

 as "blast," while still another form of it has been termed 

 "scald." 



Scald may appear upon the berries, causing small, light- 

 colored, softened, watery spots. These rapidly increase in 

 circumference, and even envelop the whole fruit. Sometimes 

 the diseased portion shows more or less distinct brownish 

 zones. In other cases the zones are lacking, and the whole 

 fruit becomes very soft and translucent. Upon the leaves 



