October, '21] essig: dust insecticides 393 



Mr. R. E. Campbell, Bureau of Entomology-, United States Depart- 

 ment of Agriculture has simimed up a long series of experiments on" Nic- 

 otine Sulphate in a Dust Carrier Against Truck Crop Insects" in Circu- 

 lar 154 United States Department of Agriculture issued February 21, 

 1921. 



It occurred to the writer that this material might prove satisfactory' as 

 a control for pear thrips and two seasons' experimental work has demon- 

 strated this conclusively as originally stated in Circular No. 223 of the 

 University of California, Agricultural Experiment Station, issued in 

 November 1920. 



During the past season there has been a large accumulation of data 

 obtained chiefly by entomologists relative to the different insects which 

 may be controlled b}- various strengths of nicodust. Among those re- 

 ceiving the most attention may be m.entioned : 



Aphids — ^Various aphids, excepting those which are protected l3y a 

 waxy covering like woolly apple aphis and mealy plimi louse. The 

 writer conducted a series of experiments on most of the common garden 

 species and found that practically all were easily killed with a 5% or 6% 

 "Blackleaf 40"^ mixture. Investigations conducted in Sonoma County 

 on the purple or ros}- apple aphis {Aphis malifoUae Fitch) were very 

 promising and good control was obtained on the infested plots where 

 dusting was begun as the leaf buds opened and continued until the winged 

 aphids began to migrate in from the untreated areas. Experim.ents 

 covering a period of two years in the melon aphids conducted by various 

 farm advisors and others were reported successful in all cases where a 6% 

 dust was used. 



Grape leafhopper — Some apparently successful demonstrations on the 

 control of Erythroncura comes (Say) were made by at least two different 

 distributors of nicodust in the San Joaquin Valley. These dem.onstra- 

 tions indicated that a 6% dust would kill all nymphs, but that it required 

 a 10% dust to destroy the adults. 



Hairy Caterpillars — From, many experiments conducted l^y the writer 

 and others on such hair\- caterpillars as those of the tent caterpillars 

 {Malacosoma spp.) brown day m.oth iPseudohazis eglanterina Boisd.); 

 the fall webworm {Hyphantria cttnea Drur\-); the chalcedon butterfl}^ 

 (Lemonias chalcedon D. & H.) ; the thistle butterfly (Vaucssacardmh'mn.) 

 and the West Coast Lady (\'anessa caryae Ilubn.) indicate that the 

 young readily succumb to nicodust treatment. 



False Chinch Bug — During tliis summer the false chincJi bug (Nysius 

 ericac Schilling and the small variety mimihis Uhlerj appeared in very 



'Percentages refer to the quantity of "Blackleaf 40" in all cases. / 



