Alfalfa hooper Alfalfa Webworm 



hang limp from the host plant at first, but finally the body becomes so 

 decayed that it drops to the ground. 



(d) ALFALFA WEBWORM* 



(Figs. 1, 2, 3 and 4, Plate VI, Page 21) 



During the summer of 1914 the alfalfa webworm J appeared in 

 large numbers in Northern Colorado, where it did considerable damage 

 to first cutting alfalfa. While they appear to prefer this crop and sweet 

 clover, the worms caused some anxiety among sugar beet growers by 

 feeding upon the leaves of sugar beets. 



NATURE OF INJURY 



When attacking alfalfa the worms spin masses of whitish web at the 

 tips of the plants, inclosing the new, tender leaves and blossoms. This 

 web furnishes protection for the worms while they feed upon the inclosed 

 parts. 



Injury to sugar beets is similar to that caused by the sugar beet web- 

 worm. Some of the leaves will be found partially covered by a web which 

 terminates in a long tube extending to the ground, the lower end being 

 among the clods on the surface. When but few worms are present there 

 is usually only one to a plant. 



METHODS OF CONTROL 

 Poison 



This worm can be controlled on sugar beets by spraying with any 

 arsenical poison. The same amounts of poison should be used as for the 

 control of the sugar beet webworm (pages 72 and 73), and should be 

 applied in the same way. 



Mowing 



In case alfalfa is being damaged it should be cut at once, cured and 

 put up to prevent loss. After removing the crop the stubble can be 

 sprayed. (See "Mowing," page 82.) 



Irrigation 



Irrigating after the worms have entered the ground to pupate will 

 seal them in, preventing many moths from emerging when mature. 



DESCRIPTION 

 The Worm 



Although closely related to the sugar beet webworm, this worm 

 (Fig. 1, Plate VI, Page 21) is easily distinguished from it by its coloring. 

 The central portion of the back is occupied by a light stripe tinged with 

 flesh color. On either side of this there is a dark stripe about the same 

 width. Along the upper and lower margins of these dark stripes there 

 are several dark circular spots, each bearing a hair-like bristle. With 

 the exception of those segments next to the head and at the tip of the 

 body, each segment has three of these spots, two on the upper border of 



*This is a local name applied to this insect in Northern Colorado. This insect should not be con- 

 fused with " Loxostege similaris Guen,*' which is also called the alfalfa webworm. (See Bulletin 109. Okla- 

 homa Agricultural Experiment Station. February. 1916). 



(') See explanation of "Reference Figures." page 2. 



84 



