Yellow-bear Caterpillar 



(e) YELLOW-BEAR CATERPILLAR 



(Figs. 15 and 16, Plate V, Page 19) 



The yellow-bear caterpillar is always in evidence, in small numbers, 

 on Russian thistle, lamb's-quarters and other weeds along the fence 

 rows, ditch banks and roadsides. As a rule they are not numerous enough 

 to cause noticeable damage to crops. Occasionally, however, they become 

 so numerous that the wild food plants are not sufficient for their support. 

 At such times the caterpillars attack whatever growing crop happens to 

 be nearest at hand. Such an outbreak occurred during August and Sep- 

 tember, 1909, in the Arkansas Valley in Southern Colorado.* 



NATURE OF INJURY 



When young the worms eat only the surface of the leaves but as they 

 become older and larger the margins of the leaves are eaten away and holes 

 are eaten into them. When very numerous, crops are completely defoli- 

 ated by these caterpillars, or in the case of sugar beets the stems, midribs 

 and young heart leaves only are left untouched. Severe attacks on sugar 

 beets result in a lowering of the yield and sugar content of the crop. 



The yellow-bear is one of the most general feeders among the whole 

 list of crop pests. The following list of plants injured is given by Mr. 

 Marsh in the bulletin already referred to : 



Sugar beet Radish Squash 



Stock beet Celery Watermelon 



Table beet Carrot Cantaloupe 



Rhubarb Parsnip Sweet potato 



Cabbage Egg plant Corn 



Cauliflower Potato Lima bean 



Turnip Pumpkin String bean 



Asparagus Dahlia Amaranthus 



Pea Cherry Chenopodium 



Peanut Gooseberry Helianthus 



Alfalfa Blackberry Solanum rostratum 



Hollyhock Raspberry Verbesina 



Morning-glory Currant Ambrosia 



Canna Grape Russian thistle 



Hyacinth Dock (Rumex) Spanish needle 



METHODS OF CONTROL 

 Poison 



In his work in the Arkansas Valley of Colorado, Mr. Marsh exper- 

 imented with both Paris green and arsenate of lead. It was found that 

 arsenate of lead, even where applied in quantities as high as 8 pounds to 

 100 gallons of water, was of little value in the control of the yellow-bear 

 caterpillar. Paris green used at the rate of 10 pounds to 100 gallons of 

 water to which 10 pounds of lime was added to prevent injuring the 

 leaves killed practically all caterpillars in three days. 



From the results of this work it appears that this worm is very resist- 

 ant to arsenical poisoning, the ordinary amounts being practically value- 

 less in its control. 



*H- O. Marsh. "Biologic and Economic Notes on the Yellow-bear Caterpillar." Bulletin No. 82, 

 Part V. Bureau of Entomology. U. S. Department of Agriculture (1910). 



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