4 BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE. 



EFFECTS OF NICOTINE SULPHATE ON EGGS AND NEWLY HATCHED I.ARVJE OF 



THE CODLING MOTH. 



In tests with the eggs and newly hatched larvae of the silkworm 

 moth it was determined that nicotine sulphate is efficient against 

 only the fresh eggs, but more or less retards the hatching of older 

 eggs. The exhalation from leaves which had been dipped into solu- 

 tions of nicotine sulphate from 1 to 5 days previously killed newly 

 hatched silkworms, and from the sixth to the eleventh day after 

 the foliage had been treated the newly hatched silkworms, after 

 having eaten some of these treated leaves, died, the mortality varying 

 from a high percentage on the sixth day to no mortality on the tenth 

 and eleventh days. The following pages give the results obtained 

 by using the eggs and newly hatched larva? of the codling moth : 



EFFECTS OF NICOTINE SULPHATE ON EGGS OF THE CODLING MOTH IN THE 



LABORATORY. 



Many codling-moth sticks containing wintering larvae, reared at the 

 bureau's field station in Grand Junction, Colo., were shipped to 

 Washington, D. C, where they were kept out of doors until March 1, 

 1917 ; after this date they were kept in a refrigerator, and at irregular 

 periods about 40 of them at a time were removed from the refrig- 

 erator and were placed in battery jars, which were covered with 

 cheesecloth. Each morning the moths that had emerged were re- 

 moved to other battery jars containing moist sand and either glass 

 plates or foliage of fruit trees. In these jars the moths copulated 

 and the females laid their eggs on the glass plates and foliage, which 

 after being removed were then sprayed. By this method eggs of a 

 known age were easily obtained. 



Since these experiments were started in March, when fruit-tree 

 foliage was not to be had, glass plates were put in the battery jars, 

 and whenever a'sufficient number of eggs had been deposited on these 

 plates, the latter were removed, sprayed, and then placed in other 

 battery jars also containing moist sand. 



Since the details of the four experiments performed, using eggs on 

 glass plates, are similar, only Experiment No. 1 will be described 

 fully. On April 4 the first plate, bearing 57 eggs (1 and 2 days 

 old), was sprayed with a solution of nicotine sulphate 1:400; the 

 second plate, bearing 20 eggs, with a solution 1:800; and a third 

 plate, bearing 16 eggs, was used as a control. Each plate was put 

 in a separate battery jar. On April 7 most of the eggs were in the 

 red-ring stage; the sprayed plates bore spots or a thin film as a 

 residue left after the evaporation of the solution, and these spots 

 still emitted a nicotine-like odor. On April 11 many of the eggs 

 were in the black-spot stage and the plates still emitted the nicotine- 

 like odor; two small last year's apples were put in each jar. On 



