TWENTY-SIXTH REPORT OF STATE ENTOMOLOGIST 27 



Moderate flights appeared in Rosebud, Custer, Prairie, Daw- 

 son, Richland, Broadwater, Lewis and Clark, and Teton counties. 



Heavy flights of moths were present in Sweet Grass, Fer- 

 gus, Judith Basin, Cascade, Blaine, Phillips, and Valley coun- 

 ties. 



Webworms appeared throughout all the above-named coun- 

 ties but the heaviest, though spotted, outbreaks occurred in 

 Blaine, Custer, Sweet Grass, Gallatin, Jefferson, Silver Bow, 

 Beaverhead, and Lake counties. 



Extensive spraying for webworms was carried out in Blaine, 

 Richland, and Yellowstone counties. Intensive work had to be 

 done in the vicinity of Butte to prevent migrations into the city 

 where dwelling houses were being invaded with the worms. 

 Practically all the green vegetation with the exception of cotton- 



Figure 3. — The sugar-beet webworm, (Lox- 

 ostege sticticalis L.j greatly enlarged. 



wood trees was attacked. This migration could have been 

 completely checked if the worms had been discovered before 

 they left the weedy patches out on the flat where they devel- 

 oped and from which the migrations started. 



The greatest losses to sugar beets occurred in the vicinity 

 of Chinook and Harlem. In these areas the worms got into the 

 fields when the beets were only 2 or 3 inches high and not 

 large enough to get the proper effects from spraying. Some 

 fields were completely destroyed when they were invaded early. 

 Part of this unseasonal attack was the result of drought which pre- 

 vented the growth in waste places of the early food plants (Rus- 

 sian thistle and pigweed) , thus causing the very young worms 

 to migrate to the young beets. Usually the migration does not 

 occur until the beets are much larger. Heavy damage to beets 

 was suffered also on the lower Yellowstone. 



