﻿STKAWBERRY EOOTWORM ON GREENHOUSE EOSES 



29 



serious retardation of the growth. For about six weeks after the 

 cut back, during which period no blooms are produced, the plants 

 may be sprayed rather than dusted with arsenates to keep the 

 foliage protected. When a solution of from 4 to 5 pounds of 

 powdered arsenate of lead or calcium arsenate to 50 gallons of 

 water, with soap added as a " sticker," was used to spray the stems 

 and swelling buds the same day, so that the beetles found them 

 covered with an arsenical, the plants in several infested rose houses 

 passed this critical stage with almost no injury. 



For several seasons one florist sprayed his plants with a Bordeaux- 

 arsenate of lead mixture which served as a repellent in protecting 

 them from the insects' voracious feeding at the time the plants 

 were making their new growth after being cut back. 



In the earlier experiments at Alexandria, Va., Paris green was 

 soon rejected as a spray because no diminution in the numbers of 

 adults was noticeable, even though the florist had been using it over 

 the entire range of infested houses prior to tests by the Bureau of 

 Entomology. No injury to the plants folloAved its application. But 

 in Indiana its use at a greater strength failed to afford any relief from 

 the work of the beetles. 

 Peterson's {23, p. 481) ob- 

 servations made eight days 

 after application indicated 

 that Paris green at the 

 rate of from 4 to 8 ounces 

 to 50 gallons of water did 

 not kill the adults in suffi- 

 cient numbers to warrant 

 its use, and that 8 ounces 

 of Paris green to 50 gallons 

 of water may burn rose 

 foliage. Furthermore, it 

 has been noticed during 



tlie last three seasons that although florists have occasionally felt cer- 

 tain that they had succeeded in controlling the strawberry leaf beetle 

 by using Paris green, they have found it later continuing its 

 ravages. From all this it is apparent that this treatment is ineffective, 



DUSTING WITH ARSENICALS 



The deposit which remains on the leaves of rose plants after 

 spraying with arsenicals is objectionable, because it impairs the 

 ornamental value of the foliage. Attention was therefore directed 

 to other means of application. A dust mixture containing 10 per 

 cent, or preferably 15 per cent, of either lead arsenate or calcium 

 arsenate and superfine sulphur or other carriers, applied Avith an 

 improved hand duster of the fan (fig. 12) or the bellows (fig. 13) 

 type, overcame this difficulty. The following formulas are recom- 

 mended and may be purchased or mixed : 



10 per cent formula : rounds 



Superfine sulphur (200 mesh) 00 



Load arsenate or calcium arsenate (powdered) 10 



15 per cent formula: 



.Superfine sulphur (200 mesh) 85 



lAud arsenate or cnlcium arsenate (powdered) 15 



Fig. 



12. — Fan type of hand duster, useful for ap- 

 plying insecticidal dusts in greenlaousGs 



