220 FRUIT INSECTS 



the leaf. The adults of the summer generations differ from 

 the hibernating forms in being J smaller, in their brighter color- 

 ing and in the markings of the front wings. The two forms are 

 so unlike that they were formerly considered as distinct species. 



Methods of control. 



Pear orchards subject to attack should be kept clean of trash 

 under which the hibernating psyllas might find shelter. Dur- 

 ing the fall or winter the rough bark should be scraped from 

 the trunks and larger branches to render them less attractive 

 as hibernating quarters, and to make it easier to reach the insects 

 by spraying during the dormant season. The scraping can be 

 done with a dull hoe, taking care not to injure the living wood. 

 This work can be done to best advantage during damp weather, 

 when the rough bark comes off the easiest. When the psyllas 

 are abundant great numbers are scraped off with the bark; 

 in such case it might pay to collect and burn the scrapings. 

 During warm days in November and December, or in March 

 and early April, many of the hibernating adults crawl from their 

 hiding places in crevices of the bark. At such times they are 

 sluggish in their movements and do not readily take flight. 

 A large proportion of them can be destroyed by a thorough 

 spraying of the trees with " Black Leaf 40 " tobacco extract, 

 1 pint in 100 gallons of water, adding three to five pounds of 

 soap. The application should be made on days when there is 

 no danger of the liquid freezing on the trees. It is important 

 to spray both sides of a tree before proceeding to the next be- 

 cause the flies often dodge to the opposite side of a branch, 

 and thus escape being hit by the spray. Effective work against 

 the hibernating flies can also be done by using kerosene emul- 

 sion diluted with 10 parts of water, miscible oil diluted with 

 12 or 15 parts of water, or whale-oil soap 1 pound in 4 to 6 

 gallons of water. These mixtures are, on the whole, not so 

 satisfactory as the tobacco extract from the standpoint of safety 

 and efficiency. 



