U. S. D. A., B. E. Bui. 116. Part IV 



D. F. 1. 1., Issued January 17, 1913. 



PAPERS ON DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



LIME-SULPHUR AS A STOMACH POISON FOR INSECTS. 



By E. W. Scott and E. H. Siegler, 

 Entomological Assistants, Deciduous Fruit Insect Investigations. 



INTRODUCTION. 



During the season of 1912 the branch of Deciduous Fruit Insect 

 Investigations of the Bureau of Entomology, at its laboratory at 

 Benton Harbor, Mich., conducted a series of feeding experiments to 

 test the killing effect of various poisons on different species of insects. 

 In the course of the work it was soon noted that lime-sulphur, when 

 combined with certain slow-acting arsenicals and doubtful stomach 

 poisons, increased their insecticidal value. This clue was followed 

 up and a considerable series of feeding tests was made during the 

 succeeding months. These experiments indicate that lime-sulphur 

 spray alone, at the strength used in spraying orchards in foliage, 

 has a decided insecticidal action as a stomach poison. It will be 

 remembered that lime-sulphur as an insecticide has been heretofore 

 considered solely as a contact spray. In this paper are given the 

 results obtained from the use of lime-sulphur and arsenate of lead, 

 separately and hi combination. 



CONDITIONS OF THE EXPERIMENTS, 



The fall webworm {Hyphantria cunea Drury) (see Plate XI) was 

 used for most of the f eeding tests, since this insect was readily obtained 

 in large numbers. Furthermore, it was easily handled, was rather 

 resistant to poisons, and on the whole proved an ideal species for the 

 work at hand. The stock supply was collected hi the field and brought 

 to the laboratory where the tests were made. Only the very young 

 larvae, usually three or four days old, were used, and whenever pos- 

 sible those from the same nest were used for the same experiment. 

 When two or more nests of larva? were necessary for use in a given 

 experiment, care was taken to use those of as nearly the same age 

 as possible. 



The wild black cherry (Prunus serotina) was found to be a favorite 

 food plant of the fall webworm in Michigan. In addition, the foliage 

 stood up well when the branches were placed hi water, and, further, 



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