382 STATE HORTICULTURAL SOCIETY 



EXPERIMEXTS IX TREATING INFESTED NURSERY STOCK. 



DIPPING YOUNG STOCK INFESTED WITH PLANT LICE. 



As noted on a previous page, plant lice have been unusually abundant 

 during the past season. Their injurious work has been especially evident 

 in the nurseries. The greatest injury was usually caused to seedling 

 and one-year-old fruit trees. The lice attacked the tender leaves at the 

 tips of the young trees, soon causing them to curl so badly that the 

 insects could not be reached with a spray. In the nursery in which the 

 experiments were made the infested trees, principally sweet cherry, apple 

 and pear trees, showed serious injury from the effects of the lice. The 

 experiments were undertaken with a view to detrmining a practical 

 method of checking the injurious w^ork of the lice. It was evident that 

 spraying Avould not be a success and so dipping the infested trees in a 

 solution of whale oil soap and water was resorted to. It might at first 

 seem that this method would be impractical because of the time and 

 labor involved, but it should be remembered that the lice appear on com- 

 paratively few trees first, others becoming infested from these later in 

 the season, and hence if they are successfully treated more serious injury 

 by the lice may be prevented. 



All of the trees used in the experiments were seedlings, one-year-olds 

 and two-year-olds. As the lice were congregated on the leaves at the 

 tips it w^as necessary to wet only this portion of the tree. The dipping of 

 the stock w^as found to be a verv simple matter. Three or four men carrv- 

 ing pails filled with the solution passed through the blocks and, picking 

 out the infested trees, bent them over carefully and dipped their tips into 

 the solution, taking care to hold them long enough to w^et all of the 

 lice. It was found unnecessary to spend more than two minutes to a 

 tree. 



Experiments. — ^About a thousand trees were used in experiments, 

 which for convenience may be divided into six blocks. Blocks I and II 

 were sweet cherries badly infested with the black cherry apis, J/y/^ws 

 cerasi. Blocks III and IV were apples ialso badly infested, but with the 

 apple apis. Aphis mall. Blocks V and VI were standard pears infested 

 with a species of plant lice. Aphis sp. Blocks I, III, and V were treated 

 the same day, a bright, warm day about the middle of July, with a solu- 

 tion of whale oil soap, 1 pound to .3 gallons of water. Blocks II, IV, and 

 VI were treated within two days of this time, under practically the same 

 weather conditions, with a solution of whale oil soap, 1 pound to 7 gal- 

 lons of water. But one application was made in each case. 



Results. — In nearly every case where the stronger soap solution, 1 

 pound to 3 gallons, was used, the leaves were more or less injured. The 

 pears were injured most, while there was not much difference between the 

 apples and cherries. So far as could be ascertained, all of the lice on 

 these trees were killed. The weaker solution, 1 pound to 7 gallons, did 

 not injure the foliage in nny instance, but proved fully as effectual as 

 the stronger solution in killing the lice. These treated trees were not 

 seriously infested again during the season. 



