330 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



Tarsonemidae. Those interested in this malady of peach nursery trees, 

 are referred to the above mentioned bulletin by Prof. Quaintance 

 which contains besides valuable observations, excellent descriptions 

 and illustrations, a reference to previously published articles and a 

 resume of their more important statements. 



The purpose of this article is to give what the writers consider defi- 

 nite proof that Stop-back of peach in Virginia, at least, is not caused 

 by the tarnished plant-bug, Lygus pratensis L. So far as is known, no 

 reliable data has been given to fix the responsibility on either Tarsone- 

 mus waitei Banks or Lygus 'pratensis L. To quote from Prof. Quaintance. 



"Prof. Waite's careful observations, and those of Messrs. Johnson, 

 Phillips, and others, indicate clearly that the Tarsonemus waitei is the 

 cause of the so-called "stop-back" affection of peach nursery stock. 

 It may also be true that injury practically identical in effect on the trees 

 is caused by thrips, as stated by Dr. Smith and Prof. Alwood. Young 

 thrips, principally Euthrips tritici, are very commonly found in the 

 tender growing tips of various kinds of vegetation, and are especially 

 common on peach nursery trees. In blocks of trees infested with the 

 mite, the thrips larvae have been found by the writer in great abun- 

 dance, but never, so far as could be determined, killing the tips of the 

 shoots. The wi-iter is inclined to the belief that the injury in Ohio, 

 New Jersey, and Virginia (as shown by Phillips) is due to the Tar- 

 sonemus, its small size, agility, and habits contributing to its oversight. 

 Any injury to the growing tip of a peach shoot, as by plant-bugs, would 

 naturally produce a similar effect in causing the cessation of gro^^'th 

 and the development of lateral shoots, but the comparative scarcity 

 of such insects in injured blocks in the territory under consideration 

 does not warrant their association with the trouble." 



To be considered with the above statements, the following are offered : 

 In early May, 1911, the senior writer was notified that "Stop-back" 

 was at work in a nursery near Richmond. He was not able to make an 

 examination until about June 10th, at which time he was told that the 

 trouble was not spreading much. A very large percentage of the peach 

 trees were affected. No insect was sufficiently abundant to attract 

 special attention, but tiny mites, thrips and Lygus pratensis were 

 collected. Lygus pratensis was observed sucking the juices from termi- 

 nal buds, but was not in sufficient numbers to appear to be responsible 

 for the wholesale injury. All things considered, mites, from their 

 abundance, were thought most likely to have caused the injury. No 

 further observations were made during 1911. 



On May 8, 1912, infol-mation was received that Stop-back was be- 

 ginning to appear in blocks of peach trees near Richmond. On May 

 21st, the writers visited the nursery in question and found that Lygus 

 pratensis was abundant in sufficient numbers to warrant the belief 



