16 BULLETIN" 833, IT. S. DEPARTMENT OF AGRICULTURE. 



EXPERIMENT 2.— CONTROL OF EGGS BY MEANS OF DIPPING ENTIRE PLANT. 



The object of this experiment was practically synonymous with 

 that of experiment 1 except that entire plants were used instead of 

 cuttings as was the case in the previous test. 



Twelve plants on which newly laid eggs were present were divided 

 into three lots, (a), (b), and (c), of four plants each. They were then 

 treated as follows: 



(a) Four plants dipped in 40 per cent nicotine sulphate (1-500) plus laundry 



soap 1 ounce to 1 gallon of solution. 



(b) Four plants dipped in 40 per cent nicotine sulphate (1-800) plus laundry 



soap 1 ounce to 1 gallon of solution. 



(c) Four plants as check; no treatment. 



In each case the plants were constantly protected by covering them 

 with an ordinary lantern globe, the free end of which was screened 

 with a double layer of cheesecloth. The first dipping was done on 

 March 29, while subsequent dippings were done on March 31 and April 

 1, 3, and 8. The plan was to treat them at least every 2 or 3 days for a 

 week or 10 days. Observations were taken frequently on the effect 

 of the treatment both on the plants and on the eggs. These obser- 

 vations were continued until the close of the experiment, April 30, at 

 which time the plants were uncovered and placed in the open green- 

 house. 



Results. — (a) Effect on plants: Slight burning was encountered 

 with the 1-500 strength solution, but with the 1-800 solution no such 

 trouble was evident. The check plants showed some sooty fungus 

 which was probably due to the presence of honeydew secreted by 

 aphids. (b) Effect on eggs : During the first few days the eggs showed 

 normal development within the shell on the treated plants, but larvae 

 failed to hatch from them, and no galls developed. On the check 

 plants all of the eggs hatched successfully and many galls developed 

 to maturity. 



Conclusions. — -The expectations were fully confirmed by the re- 

 sults obtained, as was the case in experiment 1. The checks devel- 

 oped healthy and normal galls while in the treated plants further 

 development was promptly arrested. From the economical point of 

 view it is safe to say that nicotine sulphate (1-800) plus the soap will 

 control the egg stage effectively if property applied. 



TREATMENT OF BOTH CLEAN AND INFESTED CUTTINGS. 



The importance of having all new stock free and clean from the 

 immature stages of the midge and of having the control at all times 

 closely related to the propagation of stock has already been referred 

 to. The above points were tested by the following experiment. 



This test consisted of three parts. Lots 1 and 2 were clean cut- 

 tings, while lot 3 consisted of infested cuttings. Each lot was sub- 



