42 MASS. EXPERIMENT STATION BULLETIN 449 



scars per beetle. The greatest activity occurred between June 20 and July 15, 

 but feeding was continued to September 19, which was 99 days after the obser- 

 vations were started. 



DDT 50 percent wettable powder sprayed on canes in the insectary cages 

 killed 4 pairs of beetles in 3.12 days and permitted 0.87 feeding scars per beetle 

 during their life. Of ten different combinations and dosages of DDT, lead arse- 

 nate, and benzene hexachloride, five killed the beetles more quickly and seven 

 prevented as many feeding scars. Benzene hexachloride reduced feeding scars 

 by 57 to 86 percent and was significantly more effective in this respect than DDT 

 or lead arsenate. 



Study of Euonymus Scale and Its Control. (W. D. Whitcomb and C. N. 

 Warner, Waltham, in cooperation with the Bartlett Tree Expert Company.) 

 Studies on the Euonymus scale were started early in 1948 with dormant spraying 

 treatments. When an 83 percent white oil emulsion was used in sprays contain- 

 ing 2, 3, and 4 percent actual oil, only the 4 percent dilution was satisfactory. 



Reinfestation by crawlers following dormant sprays was reduced 100 percent 

 by Elgetol 13^ percent; 98.7 percent by Elgetol 1 percent; and 86.9 percent by 

 4 percent oil emulsion. 



In 1948 the first crawlers hatched June 14 and maximum activity was reached 

 June 28-July 2 which is considerably later than has been estimated previously. 

 Microscopic examination of female scales showed a maximum of 81 and an average 

 of 61.5 eggs per scale. 



An examination of 35 species and varieties of Euonymus growing at the Arnold 

 Arboretum showed 8 species and 8 varieties heavily infested and 5 species and 

 4 varieties uninfested. No infestation was found on E. alala and its varieties, 

 while E. europea and its varieties were all heavil}' infested. 



Sprays to Prevent Scolytid Infestation of Elm Logs. (W. B. Becker.) At 

 Springfield a number of sprays were applied once in the early spring when the 

 weather was still cool (March 13, 1947) to the entire bark surface of winter-cut 

 logs of American elm before Scolytids could attack them. Each test involved 

 20 to 22 square feet of bark with a maximum thickness between 3/8 and 3/4 

 of an inch and the quantity of spray applied was what the operator estimated to be 

 necessary to thoroughly wet the surface of the bark (66 to 155 ml. per square 

 foot). Scolytus multistriatus Marsham is abundant in the vicinity, but only 

 Hylurgopinus rufipes (Eich.) infested the unsprayed control logs exposed at this 

 season. 



One percent DDT sprays (a wettable powder, an emulsion, and solution in 

 No. 2 fuel oil), orthodichlorobenzene in No. 2 fuel oil (1 to 8 by volume), penta- 

 ■chlorophenol in No. 2 fuel oil (1 to 10 by volume), and monochloronaphthalene 

 in No. 2 fuel oil (1 to 12 by volume) all gave 100 percent prevention, based on 

 the number of exit holes found per square foot of bark in the late fall, as compared 

 with the number in unsprayed check logs. The spraying of frozen or ice-coated 

 logs, of course, may not result in such good control. 



Other logs cut at the same time were sprayed as above but during warm weather 

 (June 13, 1947). Each test involved 20 to 24 square feet of bark with a maximum 

 thickness of 3/8 to 3/4 of an inch. Between 104 and 133 ml. of spray were ap- 

 plied per square foot of bark. Apparently the logs had only recently been at- 

 tacked when the spray was applied, because boring dust was on the logs then; 

 but examination in the fall revealed that eggs had hatched in few to none ot the 

 egg galleries in the sprayed logs. While no S. multistriatus were found in any of 

 the sprayed logs, the ratio of S. multistriatus to H. rufipes brood galleries in 

 the unsprayed control logs was 1 to 8. 



