Colorado I^lant Diseases 
43 
although it never §>i*o\vs as serious. The spots characterizing the 
injury produced l)y Phoma betae are light l)rown in color and from 
a quaifei* to one-half inch in diameter. Numerous small black 
specks, often arranged in concentric rings are found scattered over 
the surface of the spots. These black specks are the small flask 
shaped spore cases (pycnidia) of the fungus. The spores escape 
from these pycnidia and are scattered to healthy leaves where new 
spots are formed. The same control measures recommended for the 
control of Cercospora leaf spot apply to Phoma leaf spot. 
A crown rot of mature beets and a damping off of young beets 
are caused by this same fungus. 
Nematodes"' (Heterodera schachtii and Heterodera radicicola) 
(37) — Nematodes, or eel Avorms as they are sometimes called, are 
very small eel-like worms that live in the soil and feed upon the roots 
of various plants. There are two nematodes attacking sugar beets 
in Colorado, the sugar-beet nematode and the root-knot nematode. 
Both species, so far as knoAvn, occur on river bottom lands more 
commonly than on uplands. The damage caused by them is greatest 
on light, sandy soil. This is due to the fact that the nematodes thrive 
better in such soil. 
The effect upon sugar beets is two-fold. The yield is very greatly 
lowered and the sugar content of the crop reduced. In severe cases 
the young beets are killed and the stand destroyed. 
Control measures consist of (1) preventing the spread of the 
nematodes, (2) preventing their multiplication. 
1. Nematodes are spread : By waste Avater from infested fields ; on 
implements used in Avorking infested land; by being carried from 
infested fields to uninfested ones on the feet of animals and persons 
Avorking them ; by feeding beet tops from infested fields and 
applying the manure produced to uninfested land. 
2. The multiplication of nematodes is checked by rotation of 
crops. Small grain, with the exception of oats, may be used where 
land is infested Avith sugar beet nematodes. Corn, cabbage, turnips, 
oats, and beans should not be planted on infested land. 
Where the root-knot nematodes occur any of the small grains 
or corn may be planted. Potatoes, cabbage, tomatoes, and other 
vegetables or root crops should not be groAAUi. 
BLACKBERRY 
Anthracnose (Plectodiscella veneta) (41), (42), (43) — see Rasp- 
berry. Leaf-Spot (Septoric rubi) — see Raspberry. 
*Thanks are due to Mr. Asa C. Maxson of the Great Western Sugar Company 
for the information on this disease in Colorado. 
