314 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



nin^ the latter part of the fiscal year, when Federal funds became 

 available, a laboratory for a careful study of the camphor scale was 

 established in New Orleans. 



VEGETABLE AND TRUCK-CROP INSECT INVESTIGATIONS. 



Work on this project has continued under the direction of Dr. F. 

 H. Chittenden. The great economic importance of the Mexican bean 

 beetle, its sudden appearance, and rapid dissemination in the South- 

 ern States have caused a large portion of the work on this general 

 project to be devoted to it as a subproject. 



The Mexican bean beetle. — At the beginning of the fiscal year 

 (July 1. 1921), the Mexican bean beetle was known to be pres- 

 ent in 83 counties of the 5 States of Alabama, Georgia. Tennessee. 

 South Carolina, and Kentucky. Continued scouting during late 

 summer disclosed its presence in 111 counties in 6 States, North 

 Carolina being added to the infested list. Everything points to the 

 fact that the beetle is even more at home in its new environment 

 and is more prolific and more destructive than in the West and 

 Southwest. No scouting to follow the insect's spread during the 

 early summer of 1922 has been possible, but reports of injury indi- 

 cate that the beetle passed the winter successfully over most of 

 the territory infested last year. The largest number of complaints 

 came from the northern part of the previously infested area, indi- 

 dating that a rapid spread to the north may be expected. Growers 

 are now complaining of injury by the bean beetle in districts in 

 which the insect could be found only by careful inspection last sea- 

 son. Extensive field experiments with most available insecticides 

 have been continued in cooperation with the Alabama Agricultural 

 Experiment Station. It appears that the application of arsenicals 

 to bean plants in the southeastern United States is more hazardous 

 than in the West and Southwest. A commercial basic lead arsenate, 

 used as a dust or as a wet spray, at the rate of 1^ pounds to 50 gallons 

 of water, ranks first among arsenical applications. Standard lead 

 arsenate is too injurious to bean foliage. Calcium arsenate and zinc 

 arsenite are injurious when used as dusts undiluted. Calcium ar- 

 senate, however, can be used effectively and with relative safety as a 

 dust when diluted with 9 parts of hydrated lime. The insect is be- 

 ing carefully studied in the field. In 1921 a maximum of four gen- 

 erations was obtained and in this section the insect requires at least 

 two generations to maintain itself, while in the West and Southwest 

 one full generation and a partial, or smaller, second generation are 

 the rule. Experiments have been successfully performed to determine 

 the flight of the beetle. Marked beetles have been taken 5 miles 

 from the point of liberation within a few days. The beetle migrates 

 to woodlands and spends the winter under pine straw and leaves in 

 protected places, a high percentage of survival having been noted. 

 Of new host plants, cowpeas, beggar weed, alfalfa, and sweet clover 

 are notable, beggar weed seeming actually to be preferred to other 

 hosts than the garden bean. A substation has been established at 

 Thomasville, Ga;, in cooperation with the Georgia State Board of 

 Entomology, for the study of the insect under extreme southern con- 

 ditions. A hibernation cage containing 18,000 beetles was placed on 

 Lookout Mountain. Tenn.. and interesting comparisons have been 



