BULLETIN 192. 



INSECTS INJURIOUS TO THE VINE. 



137 



over the world, and attacks a large variety of plants. In the Argentine 

 Republic it is said to be the most destructive disease of the vine occur- 

 ring in that country.* In the United States, outside of greenhouses, 

 nematodes are chiefly injurious in the Southern States and in California. 



This parasitic species is an exceedingly small wormlike creature 

 about one seventy-fifth of an inch long, and of a transparent whitish 

 color. It has a sharp slender organ on the head that enables it to make 

 its way into the more tender portions of the roots, where it embeds itself 

 in the tissues. Here it develops, and lays the eggs from which succeed- 

 ing generations arise. These may scatter through the soil and attack 

 other portions of the root. By means of 

 this sharp lancelike organ they are able to 

 draw nourishment from the roots. It is not M 

 so much this direct drain on the roots, how- 

 ever, that causes the damage as it is in the 

 decay of the hypertrophied tissue due to the 

 irritation caused by the work of the worms. 

 They make conditions favorable for the 

 attack of wood-rot fungi, which hasten the 

 decay. The roots of vines infested with 

 this worm show numerous swellings, some- 

 what like that due to phylloxera. The 

 nodosities or swellings caused by phyllox- 

 era, however, are most conspicuous and are 

 larger on the smaller roots, while those of 

 nematodes are largest on the larger roots. 

 The swellings are also of firmer consistency 

 than those of phylloxera. 



The general effect on the vine is not very different from that of the 

 phylloxera. The distribution of the affected vines will, however, gener- 

 ally distinguish the two. Vineyards infested with phylloxera show the 

 characteristic oil-spots, the interior vines being worst affected and grad- 

 ually diminishing in injury toward the periphery of the affected spot. 

 The amount of injury is said to vary with the soil conditions, but the 

 authorities apparently are not agreed, some claiming less injury in 

 light, sandy soil and others the reverse. Moisture is, no doubt, the 

 most important factor in favoring their development. In California 

 this pest seems to be most common on vines in the Fresno section, and, 

 in general, this is a section of sandy soil. 



Control. No satisfactory remedy has yet been found for controlling 

 parasitic nematodes. In greenhouses the usual procedure is to sterilize 

 the soil, but this, obviously, is not applicable to a vineyard. However, 



*Boletin del Ministerio de Agricultura, Buenos Ayres, Mayo de 1906. 



FIG. 24. N. Swellings on the roots 

 of vine caused by the Nematode 

 root gall. M, M. Eggs of the 

 Nematodes found in these galls. 



