BURfeAU OF ENTOMOLOGY. 255 



rience confirms the conclusion reported last year that arsenate of 

 lime may be used in all situations as a substitute for Paris green, 

 and that it will also, for poniaceous fruits, prove a satisfactory sub- 

 stitute for arsenate of lead when used with lime or fungicides con- 

 taining lime. 



It has been shown that nicotine sulphate is an unsatisfactory sub- 

 stance to use against the eggs of the codling moth in the field. Nico- 

 tine is, however, coming rapidly into use as an insecticide in other 

 ways, and the bureau has been trying to find a less expensive substi- 

 tute. The results already obtained ai-e promising. Basic studies in 

 connection with this work have been made on the physiology of 

 injurious insects, especially on their olfactory organs, and a number 

 of publications have been issued on this subject. 



NATURAL CONTROL. 



Under this head, studies of insect-destroying fungi have been con- 

 tinued, especially a fungous disease of cutworms. An obscure dis- 

 ease of the so-called seventeen-year locust, or periodical Cicada, has 

 also been studied. 



AVork with the ladybird known as Ilippodamia convergens, in tho 

 Imperial Valley of California, has been continued in cooperation 

 with the California State Horticultural Commission, especially in 

 regard to certain nee<led changes in the method of handling tho 

 insects. This work will be contmued. 



An especial study has been begun of the natural enemies of the 

 plant-lice which are injurious to walnuts in southern California. 



INVESTIGATIONS OF INSECTS INJURIOUS TO VEGETABLE AND 



TRUCK CROPS. 



Work upon this group of insects has been continued as heretofore 

 under the direction of Dr. F. H. Chittenden. Under the necessity 

 for stimulation of food production much of the research conducted 

 on the less important subjects under this head was temporarily dis- 

 continued, and attention was especially directed to the important 

 staple crops. 



SWEET POTATO WEEVIL ERADICATION AND CONTROL. 



Continuing the policy of the fisciil year 1918, under a $50,000 allot- 

 ment for the eradication and control of this insect, intensive work 

 was done. The definite boundaries of infestation were established in 

 Florida, Georgia, Alabama, Mississippi, Louisiana, and Texas. More 

 than 30,000 farms were inspected during planting and harvest (since 

 at these times the presence of the weevil is most apparent) , and the 

 infested properties were listed and mapped. Large-scale experiments 

 in control have been continued. In one large eradication project in 

 Florida, selected for demonstration since it embodies most of the 

 serious difficulties to be encountered, material progress has been made. 

 All of the infested estates have been subjected to continuous super- 

 vision, contracts have been made with the growers for the destruction 

 of all seed potatoes grown on infe^sted land, and the scrupulous execu- 

 tion of these contracts has been rigidly enforced. More than 1 ,000,000 

 weevil-free sweet-potato draws have been distributed to growers by 



