554 EXPERIMENT STATION RECORD. [Vol.35 



brood and that the second cutting will take off most of the second brood pupae. 

 Fall pasturage will destroy many of the third brood. Plowing old clover stubble 

 in the spring preparatory to planting corn practically exterminates all larvae 

 in the field. The present well-established customs for harvesting and pastur- 

 ing clover furnish a logical and effective program of control." 



Effect of Roentgen rays on the tobacco, or cigarette, beetle and the results 

 of experiments with a new form of Roentgen tube, G. A. Runner {U. S. 

 Dept. Agr., Jour. Agr. Research, 6 {1916), No. 11, pp. 383-388 ) .—This is a 

 report of studies conducted in continuation of those previously noted (E. S. R., 

 29, p. 359). 



" Under laboratory conditions, tests made with a Roentgen-ray tube permit- 

 ting a high-energy input and giving an intense and powerful radiation gave 

 results which promise that the X-ray process may be successfully used in treat- 

 ment of cigars or tobacco infested with the tobacco, or cigarette, beetle. Heavy 

 dosages mu.st be given, as is indicated by the exposure given in the series of 

 experiments tabulated in this paper. In treatment of the egg stage, heavier 

 exposures are required to sterilize eggs which are near the hatching point than 

 are required to sterilize eggs newly laid. In experiments performed by the 

 writer a dosage equivalent to 150 milliampere minutes exposure with a spark 

 gap of 5.5 in. gave satisfactory results with eggs in tobacco placed 7.5 in. from 

 the focal spot of the tube. With this exposure the eggs in which embryonic 

 development was well advanced hatched, but in all cases where these larvae 

 were kept under observation they failed to reach the adult stage. The minimum 

 lethal dosage at a given distance from the focal spot of the Roentgen tube used 

 has not been determined. 



" In two separate experiments adults were given an exposure of 600 milli- 

 ampere minutes (amperage X time), with a spark gap of 5.5 in., giving an 

 approximate voltage of 65,000, with humidity at 57. The distance from the 

 focal spot of the Roentgen tube was 7.5 in. The results are as follows : 



"(1) No effect on length of life was apparent, as the beetles died at about 

 the same rate as the same number of beetles kept as a check. (2) Large num- 

 bers of eggs were deposited after exposure. These eggs were infertile. Eggs 

 laid by the check beetles hatched normally. 



" Larvae were given an exposure of 600 milliampere minutes, other conditions 

 of the experiment being the same as in the experiments with adults given above. 

 While no immediate effect was apparent, the treatment had the effect of stop- 

 ping activity and development, the larvae remaining in a dormant condition 

 for a prolonged period. All treated larvae died before reaching the pupal stage." 



Tlie alfalfa weevil and methods of controlling it, G. I. Reeves, P. B. Miles, 

 T. R. Chambeelin, S. J. Snow, and L. J. Bower {U. S. Dept. Agr., Farmers' 

 Bui. 741 {1916), pp. 16, figs. 7). — A popular summary of knowledge of this 

 insect and means for its control. 



Cotton boll weevil control in the Mississippi Delta, with special reference 

 to square picking and weevil picking, B. R. Goad {U. S. Dept. Agr. Bill. 382 

 {1916), pp. 12). — In plat tests of five square pickings at 7-day time intervals 

 an increase of 23 per cent over the check was obtained. Tests of seven weevil 

 pickings with the bag-and-hoop indicated similar results. Comparative obser- 

 vations on different methods of collecting weevils demonstrated the great supe- 

 riority of the bag-and-hoop over hand picking so definitely that there should 

 be no question as to which method to follow. The margin of profit to be 

 derived from these two control measures seems to be too slight to allow their 

 operation on a wage basis. For this reason the only condition under which 

 they should be attempted is on tenant cotton where the work can be performed 

 without any direct outlay for labor. 



