334 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



have been found several weeks after the injury is first evident, indi- 

 cates that the mites are either secondary or breeding only in the tissues 

 killed by the bug. 



Prof. Quaintance records the failure to discover any difference in 

 affection during the summer of 1906 between peach stock sprayed with 

 lime sulphur before the buds opened and unsprayed trees. He also 

 states that notwithstanding the fact that one large nursery firm has 

 sprayed peach trees for some years during the dormant period with a 

 miscible oil used at full winter strength, its trees have suffered seriously 

 from Stop-back. Rather than ascribe the failure of these sprays to the 

 hibernation of the mites elsewhere, it would seem more likely to dis- 

 regard the mites and attribute the failure of sprays mentioned to the 

 presence of Lygus qoratensis which is known to exist from Canada to 

 Mexico, to be especially fond of tender peach growth, and on account 

 of the ease with which it migrates from place to place, entirely 

 unaffected by winter sprays. 



No attempt was made to control Lygus pratensis on ti ees near Rich- 

 mond during May, 1912, by the writers. Certain rows were sprayed 

 with self-boiled lime sulphur by the grower but 'no difference could be 

 observed in the abundance of bugs or of diseased trees several weeks 

 later. Judicious pruning, advocated by Mr. Phillips, was found to be 

 worthless during the period of greatest activity of pratensis, for as 

 fast as a new shoot was formed, the terminal bud was at once killed. 

 Some method of driving the bugs from the blocks of peach should 

 first be tried, and be followed later by pruning after the majority of 

 the bugs have disappeared. 



Summary 



Stop-back of peach in Virginia is caused principally by the tarnished 

 plant bug, Lygus pratensis. This insect is present on peach stock in 

 largest numbers only for a comparatively short time, although it 

 causes some injury throughout the season. Unless one is present in 

 the nursery when injury is taking place most rapidly instead of making 

 examinations several weeks later, Lygus pratensis is easily overlooked 

 as the causative agent. Mites in Virginia, presumably Tarse7iomus 

 waitei, but not determined, are absent from freshly killed terminal 

 buds, but later may be found in numbers in the blackened decaying 

 tips. In the nursery, the extent of injury from Stop-back was found, 

 in general terms, to be in proportion to the abundance of Lygus pra- 

 tensis. In eleven cage experiments carried on in the field, no Stop-back 

 developed in any cage from which Lygus pratensis was excluded, but 

 all or many shoots developed Stop-back in cages into which specimens 

 of this bug had been introduced. 



