135 



various species that they encounter, nor of distinguishing beneficial from 

 noxious species. This information is given in a simple and concise 

 form and the author has produced an essentially practical handbook, 

 illustrated with numerous figures. It is hoped that the present volume, 

 which forms one of a series on these lines, will refute the frequently 

 expressed opinion that scientific agronomic knowledge has no place 

 in the domain of practical experience. 



The volume is supplied with adequate indices, both general and 

 classified, as well as a plant index. 



ScHOEVERs (T. A. C). Het Stengelaaltje als Tabaksvijand. [The 

 Eelworm as a Pest of Tobacco.] — Tijdschr. over Plantenziekten, 

 Wageningen, xxiii, no. 5, November 1917, pp. 167-180, 2 plates. 



In 1916 tobacco at Deest was injured by Tylenchus devastatrix, 

 Kiihn, and the attack was repeated in 1917. The bast of the affected 

 plants rotted away completely, just above the ground, while higher up 

 it was dark brown in colour and in a decaying condition. Above this 

 the stem was green and vigorous, but covered with excrescences. The 

 shoots in infested plants were much hypertrophied and deformed, and 

 most of their leaves were small, while even those of normal size were 

 marked with yellow-green spots. The atrophy of the valuable shoots, 

 the breaking of the stem near the ground and the reduced value 

 of the spotted foliage constitute the damage done to tobacco by 

 T. devastatrix. 



At Deest the cultivation of tobacco has been given up in consequence 

 in many plots, though adjacent ones have been unaffected. Crop 

 rotation provides the best remedy, but it is one that tobacco growers 

 are naturally reluctant to adopt. At present no measures have been 

 found that will check the pest without interfering with the tobacco. 

 After harvesting the stems are usually left in the fields until the spring, 

 thus permitting the Nematodes to migrate to the ground. The stems 

 must be stored under conditions that render them harmless or burnt 

 without delay. Infested leaves and shoots must be immediately burnt. 

 If the conditions permit, the upper layer of soil may be buried at a 

 depth where the presence of sufficient moisture will cause the eelworms 

 to starve by preventing them from passing into a latent condition. 

 The application of large quantities of potash as a manure also appears 

 to be useful. Earthing up the infested plants may enable them to put 

 forth roots above the diseased point and thus obtain the sap necessary 

 for development of the shoots. 



VAN PoETEREN (N.). Bestrijding van Dopluis op Perzik en Druif. 



[The Control of Scale-Insects on Peach and Vine.] — ■ Tijdschr. 

 over Plantenziekten, Wageningen, xxiii, no. 6, December 1917, 

 pp. 195-203, 1 plate. 



This paper strongly recommends water-soluble carbolineum against 

 Eulecanium corni and Pulvinaria betulae infesting peaches and vines 

 grown under glass. The solutions must be of 2-5|- per cent, strength 

 for the peach and 4-S per cent, for the vine. . 



