ECONOMIC ZOOLOGY ENTOMOLOGY. 651 



experiments show, would iudicate that it is caused by feeding punctures. Tlie 

 fact tliat injury was not produced by needle punctures would suggest that in 

 feeding the insect injects some substance poisonous to plant tissue. 



The losses occasioned to peach nursery stock are very great. The trees are 

 stunted and bushy and do not have a strong leader and must therefore be sold 

 as second or third class stock. It is stated that while these trees do not have 

 proper form nevertheless they are perfectly thrifty and in many cases are as 

 good for planting as those having a large, fully developed leader, if not better. 



Control measures are discussed at length. It is stated, however, that the 

 control of this plant bug is still an unsolved problem. Most of the remedies 

 suggested are either inadequate to meet the demands of practical growers, un- 

 suited to the conditions under which the crop is grown, or impracticable in other 

 ways. 



An extensive bibliography is appended. 



Susceptibility to spraying' mixtures of hibernating- pear psylla adults and 

 their eggs, H. E. Hodgkiss {Xciv York State Sta. Bui. 381 (1914), pp. 389-418, 

 pis. 3, figs. 2). — Investigations of failures to control the psylla in pear orchards 

 led the station to inquire into the susceptibilities of hibernating adults and 

 their eggs to spray mixtures. 



Studies of its seasonal history and habits have shown that the pear psylla 

 passes the winter as an adult and that it deposits its eggs in the spring within 

 a short period after its emergence from hibernating quarters. It was ob- 

 served to winter over on various fruit trees, such as apple, cherry, plum, and 

 peach, but the largest number was found to hibernate in the rough bark of 

 the pear tree. When mild weather prevailed the eggs were found to be largely 

 deposited within a few days after the emergence of the hibernating adults in 

 the spring. Oviposition continued for several weeks, especially if the weather 

 was variable, but usually most of the eggs were deposited before the last of 

 April. Some of the eggs were deposited on foliage, but it appeared that these 

 normally are comparatively few in numbers and result in little or no serious 

 infestation of the foliage. 



The practice of clean culture and removal and destruction of the rough bark 

 left the psylla with few opportunities of escape from application of contact 

 mixtures. " Miscible oils, nicotin preparations, and soapy solutions were 

 effective sprays against the psylla adults. Homemade oil emulsions were less 

 satisfactory, which may have been owing to varying percentages of oil in the 

 mixtures, caused by im]>erfectly prepared emulsions. 



" The best means of killing the flies is spraying during a period of warm 

 weather, preferably in November or December, or during March or early in 

 April. The most satisfactory mixture, from the standpoints of safety to fruit 

 and leaf buds and effectiveness against the insect, is 0.75 pt. of tobacco extract 

 (40 per cent nicotin) in 100 gal. of water to Avhich are added from 3 to 5 lbs. 

 of soap. 



" Eggs about to hatch and newly emerged nymphs succumb to an application 

 of the lime-sulphur solution. By postponing the dormant treatment for the San 

 Jose scale until the blossom cluster-buds are beginning to separate at the tips, 

 very effective work can be done against the eggs. The lime-sulphur should 

 be used in the proportion of 1 gal. of the concentrate, 32° B., to 8 gal. of water. 

 In some tests of other contact sprays the miscible oils, oil emulsions, weak 

 dilutions of nicotin, and soapy solutions were of small value for the destruc- 

 tion of the eggs. Ova deposited on the twigs after the wood was thoroughly 

 sprayed with the lime-sulphur solution hatched, and the young nymphs were 

 not harmed through contact with the mateiMal on the bark of the trees. On 

 the other hand, the wash having considerable amounts of sediment (15:20:50 



