PROGRESS REGARDING SUGAR-BEET WEBWORM. 



61 



This, however, is not the case, but their apparently sudden appear- 

 ance is explained by the fact that the young- web worms are easily 

 overlooked and that during the last few days before they reach 

 maturity their growth is very rapid. It frequently happens that 

 from 50 to 300 eggs are deposited on single beet plants, and in ex- 

 treme cases as many as 500 eggs may be so placed. The worms hatch- 

 ing from these eggs remain upon the beet on which they hatched 

 until they reach maturity, unless all the leaves are destroyed and they 

 are thus forced to crawl 

 to another beet to obtain 

 food. 



CHARACTER OF INJURY. 



It is impossible to state 

 definitely the damage to 

 sugar beets that an infes- 

 tation of webworms may 

 cause, as this may vary 

 from almost no percepti- 

 ble loss to the complete 

 destruction of the infested 

 plants, the extent of the 

 injury depending on the 

 number of webworms 

 present, the size of the 

 infested beets, and various 

 other factors, such as cli- 

 matic conditions, soil fer- 

 tility, and water supply. 

 As previously mentioned, 

 small beets may be killed 

 outright (see fig. 14), 

 while larger beets may 

 be completely stripped 

 of foliage. With large 

 beets new leaves will usually be put out promptly and their 

 apparent recovery will take place quickly, especially if they are 

 irrigated as soon as possible after the defoliation. Although new 

 leaves are soon put out, defoliation retards the growth of the beet 

 roots. (See fig. 13.) The writer has seen beet roots which at the 

 time the tops were defoliated, in early July, were more than an inch 

 in greatest diameter that made absolutely no gain in weight or 

 size for three weeks after the leaves were destroyed. It might be 

 added that these beets were in good, fertile soil and were watered 



51004°— Bnl J. TOO. pt 6—12 2 



Fig. 12. — Sugar beets defoliated by the sugar-beet 

 webworm in July. (Original.) 



