BORING IN MAIN ROOT-STALK OR TUBER 117 
check injury or to prevent it. Clover, if infested, should not be allowed 
to stand after the second season's haying. 
The Sweet Potato Root-borer (Cylas formicarius Oliv.) 
In some sections in the Gulf states the tubers of sweet potatoes, both 
in the field and in storage, are infested with borers, whitish in color, 
robust, one fourth of an inch long. The adult is a small snout beetle 
with dark blue wing covers and brown thorax. It lays its eggs in the 
end of the tuber where it chances to project from the ground, or some- 
times at the base of the vine. There are several generations annually. 
Eggs may be laid on potatoes in storage. 
The only means of control is to keep the tubers well covered with 
earth. If infested, the crop should be harvested early and at once 
fumigated with carbon bisulphide. 
The Potato-tuber Worm (Phthorimea operculella Zell.) 
In California this tiny insect is a pest of prime importance to potato 
growers. Injury is twofold. The stalks of potato vines are tunneled, 
the vines badly damaged or killed; and the tubers themselves are 
= 
Fig. 83.— Adult of the Potato-tuber Worm. Enlarged 
and natural size. Original. 
