Two Budworms 



Efforts to control budworms with diseases have been underway for 

 more than a decade, with partial success. The research has been focused 

 mainly on the spruce budworm, which attacks our spruce and fir stands 

 from coast to coast; and a close relative, the jack-pine budworm, which 

 in the United States is mainly in the Great Lakes area. 



Canadian scientists in 1949 found a protozoan disease at work in 

 budworms in Ontario, and in 1955 started basic studies. Since effects of 

 the chronic diseases caused by protozoa are exceptionally hard to trace, 

 results of this work have been of particular interest. The Canadians got 

 indications that the protozoan forms spores in the cells of spruce budworm 

 larvae and these spores work two ways: (1) by multiplying and robbing 

 the larvae of growth and energy; (2) by packing the mid-gut so that the 

 larvae can digest less and less food. The spores worked fast enough to 

 kill some larvae. These had no shrunken look of starvation. Laboratory 

 analyses showed a breakdown of vital organs, and this seemed the likely 

 cause of actual death. Infected female larvae that survived to adult stage 

 were weakened and produced relatively few eggs. 



A protozoan that infects the jack-pine budworm has been found also 

 in Canada. It works very much the same way as the one infecting the 

 spruce budworm, and its possibilities for use are also under study. 



In the United States and in Canada, Bacillus thuringiensis has been 

 found effective against the spruce budworm in some laboratory experi- 

 ments. 



Bark Beetles 



When the worst forest pests of this country are mentioned, three types 

 almost sure to be included are sawflies, budworms, and bark beetles. The 

 bark beetles are hard to control and even hard to study. They are tiny 

 and spend most of their lives hidden under bark. What diseases kill these 

 pests in nature is only beginning to be learned. The Forest Service has 

 begun systematic exploratory work to identify disease organisms that 

 infect bark beetles in the West. Dead beetles collected from infested trees 

 are analyzed. Pathogens found in specimens have included fungi, bacteria, 

 and spirochetes. Bacillus thuringiensis is one bacterium that has been 

 found infecting both the western pine beetle and the Engelmann spruce 

 beetle. 



Tent Caterpillars 



Microbial insecticides show great promise for protecting trees and 

 range browse from the tent caterpillars that spin tentlike webs. Experi- 

 ments in this country have progressed farthest with the Great Basin tent 

 caterpillar. This leaf-eater wrecks trees such as aspens and valuable 

 browse plants such as bitterbrush in the West. 



In one demonstration of what a virus can do, test areas of a Navajo 

 Indian reservation in New Mexico were practically rid of the Great Basin 

 tent caterpillar by spraying. To make this test, in 1957, the Forest Service 

 and the California Agricultural Experiment Station sent an entomologist to 

 the reservation. Working with the Indian tribe and the U. S. Bureau of 



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