52 THE SUGAR-BEET WIREWORM. 



EXPERIMENTS WITH DETERRENTS AGAINST THE WIREWORMS. 



A fairly exhaustive series of experiments was carried on, using 

 repellent substances against the larva. While some of these experi- 

 ments are a repetition of the work done by Corns tock and Slinger- 

 land, the greater number are rather an addition to their work. From 

 the start tliis work promised little, but was undertaken because, if 

 successful, it would afford a remedy which would give immediate 

 results, and this is most important with this insect. 



A system was adopted regarding both the nature of the experi- 

 ments and the times of application. Three tests were given each 

 experiment in the spring, when the larvae were most active, and a 

 test was given in the fall just before their hibernation period. The 

 last one was on a small scale and was carried on merely for the sake 

 of added evidence. 



Flowerjjots were the cages used in the spring experiments. It 

 was found that if the hole in the bottom was stoppered with cork, 

 none would escape in the time of the experiment. It was also 

 noted that where about half an inch of diy soil was placed on top 

 of the damp soil of the cages the wireworms would never come 

 entirely to the surface. This treatment, then, allowed the flower- 

 pots to be buried to the surface of the soil out of doors, and with the 

 exception that the larvae were a little crowded it gave outdoor 

 conditions. 



In the first test of each experiment 50 larvae were used and the 

 test covered 20 days. In the two remaining tests in the spring 25 

 larvae were used each time and the experiment was allowed to run 

 for 30 days. In the experiments with deterrents the following sub- 

 stances were tested: 



( 1 ) Carbolic acid . 



(2) Carbolic emulsion. 



(3) Turpentine. 



(4) Kerosene. 



(5) Kerosene emulsion. 



(6) Whale-oil soap. 



(7) Potassium cyanic! solution. 



(8) Potassium cyanid solid. 



(9) Copperas solution . 

 (10) Copper sulphate. 



These deterrents were used on beet and lima-bean seeds, both of 

 which are attacked by this species. It was hoped that in these ex- 

 periments a deterrent could be discovered for protecting the tender 

 roots until the plant had secured a fair start. If this could be ac- 

 complished the injury due to wireworms would be materially lessened. 



(11) Potassium sulphid solution. 



(12) Tar water. 



(13) Ash water. 



(14) Nicotine sulphate. 



(15) Free nicotine solution. 



(16) Cresol (so-called coal-tar creosote). 



(17) Salt solution. 



(18) Lead chromate. 



(19) Dry sulphur. 



