NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. 



9 



potato beetles (Leptinotarsa decemlineata L.) and tussock moths 

 (Hemerocampa leucostigma S. & A.). 



Fifteen potato-plant leaves, each bearing a cluster of potato- 

 beetle eggs (1 and 2 days old), were collected in a potato patch, and 

 after the petiole of each leaf had been inserted into a bottle of water 

 in the laboratory, 11 of the leaves were sprayed with solutions of 

 nicotine sulphate 1 : 400 and 1 : 800 and the other four leaves were 

 used as controls. The eggs thereafter were observed daily ; prac- 

 tically all of them hatched, and the newly hatched larvae were ap- 

 parently not affected by remaining on the wilted leaves 1 or 2 days, 

 after which they thrived when fed fresh and unsprayed leaves. Rela- 

 tive to the time of hatching there seemed to be little, if any, differ- 

 ence between the sprayed and unsprayed eggs. Similar results were 

 obtained by spraying eight clusters of potato-beetle eggs in a potato 

 patch with a solution 1 : 400 containing soap (2 pounds to 100 gallons 

 water). 



In order to obtain tussock-moth eggs of known ages, many large 

 caterpillars of this moth were collected and were put in wire-screen 

 cages, in which the remainder of the life history was completed. On 

 various dates eggs from these cages and some from trees in the field 

 were collected, placed in open pasteboard boxes, and then sprayed 

 with four solutions of nicotine sulphate. Two of the solutions con- 

 tained soap in the proportion of 2 pounds per 100 gallons of water. 

 Some of the control eggs were not sprayed, while the others were 

 sprayed with tap water ; no difference in hatching between these was 

 observed. The details of these experiments are summarized in 

 Table III: 



Table III. — Effects of nicotine sulphate on eggs of tussock moth in laboratory. 





Eggs collected in cages. 



Eggs collected in field . Age 

 probably from freshly- 



Strength of 



nicotine- 

 . sulphate 

 solution 

 used, and 

 control. 



Eggs 1 and 2 days old. 



Eggs 2 and 3 days old. 



laid eggs to those ready to 

 hatch. 



Num- 

 ber of 



egg 

 masses 

 tested. 



Egg 

 masses 



that 

 hatched. 



Egg 

 masses 



that 

 did not 

 hatch. 



Num- 

 ber of 



egg 

 masses 

 tested. 



Egg 

 masses 



that 

 hatched. 



Egg 

 masses 



that 

 did not 

 hatch. 



Num- 

 ber of 



egg 



masses 

 tested. 



Egg 

 masses 



that 

 hatched. 



Egg 

 masses 



that 

 did not 

 hatch. 



1:400 





Per cent. 



Per cent. 



4 

 4 

 4 



Per cent. 

 25.0 

 62.5 

 25.0 



Per cent. 

 75.0 

 37.5 



75.0 



12 



Per cent. 

 83.3 



Per cent. 

 16.7 



1:800 











l:800+soap 



l:1000+soap. 



4 

 4 

 3 



25.0 

 37.5 

 83.4 



75.0 

 62.5 

 16.6 



33 



45 

 45 



87.9 

 82.2 

 93.3 



12.1 



17.8 



4 



87.5 



12.5 



0.7 







It is seen from Table III that nicotine sulphate is not efficient 

 against the eggs of the tussock moth ; the percentages given for the 

 masses of eggs that did not hatch, however, are too low, because the 

 final examination showed that as a rule when a control and a sprayed 



22660°— 21— Bull. 938 2 



