62 THE GRAPE ROOT-WORM. 



the soil to make its pupal cell, this plan of cultivation has been some- 

 what modified. In order to encourage the larva to come still higher 

 above the roots of the vine to pupate than it would have done under 

 ordinary cultural methods it has become customary to throw up a 

 ridge of soil beneath the trellis at the last cultivation of the preced- 

 ing summer (see Pi. V, fig. 2). Observations have shown that it is 

 highly desirable that this ridge be formed under the trellis late in the 

 summer rather than in the early spring, since in the former case the 

 soil becomes of a uniform compactness by the time the larvse are 

 ready to migrate nearer to the surface to pupate; whereas, if the 

 ridge is formed in the spring a layer of trash and leaves accumulating 

 under the trellis during the winter is sandwiched in this ridge, and in 

 no case in our examinations have we found pupal cells above this 

 layer of trash. In the operation of horse hoeing this spring-formed 

 ridge away from the vines it frequently happens that only the layer 

 above the trash is thrown away, hence the pupse, which are all 

 beneath the trash, are undisturbed. 



Undoubtedly this modification in the plan of early cultivation of 

 vineyards is an important aid in the destruction of this pest at a 

 time when it is in its most critical stage of development. Instances 

 have come directly under our observation where we have seen great 

 numbers of the pupse exposed to the air and sunlight or become the 

 immediate prey of birds and predaceous insects. The operation is 

 probably of greater value in sandy and loose gravelly soils than in 

 stiff clay soils, for in the former the earthen cells fall apart quite 

 readily with the disturbance of the soil, leaving the pupse exposed; 

 whereas in the clay the soil is more likely to turn over in lumps, leav- 

 ing many of the cells intact. In addition to this, in soils of a sandy 

 or gravelly nature the loose earth around the vines may be removed 

 by the horse hoe to a much greater depth and more pupse disturbed 

 than in the case of stiff clay soils, where it frequently happens that 

 the operation of horse hoeing amounts to little more than a scraping 

 of the weeds from the surface of the ground, especially if the season 

 be a dry one. In fact, the drying out of the soil is the chief draw- 

 back to placing reliance on this operation as a means of controlling 

 this pest. 



It not infrequently happens that a dry period may occur along the 

 Lake Erie Valley during the month of June which renders it difficult to 

 make horse hoeing as thorough and as timely as it should be to derive 

 the greatest benefit from this operation in the destruction of the 

 pupse. In the sunmaer of 1907 when the development of the pupse 

 was unusually late the operation of horse hoeing was postponed by 

 some vineyardists until the last of June and early July in order to 

 perform it at a time when the maximum number of the insects were 

 in the pupal stage, and considerable complaint was forthcoming 



