18 
BULLETIN 1093, U. S. DEPARTMENT OF AGRICULTURE. 
When light infestations are present and the immediate upland 
border is clear of overhanging brush, border ditches may offer all 
necessary protection, provided they are in proper condition. To be 
effectual they should not be less than 15 inches wide and from 15 
to 20 inches deep with the bog side of the ditch perpendicular and as 
smooth as possible, in order to give little foothold to the crawling 
larvae. If not detrimental to the vines or crop, a few inches of 
water should be maintained in the ditch with a little crude oil on 
the surface. The larvae dropping from the land side into the ditch 
will become smeared with oil and suffocate. Should some larvae 
reach the bog side and attempt to crawl up the smooth surface, being 
weakened by partial suffocation they will drop back into the oil bath. 
s^^r: Earth 
Fig. 4. — Cross section of an upland trench, with board in position. 
Should the infestation prove too heavy to be controlled by the oil 
and water a board about 1 foot wide may be set against the smooth 
surface of the bo£ side of the ditch, resting on stakes driven in the 
bog at an angle of 45 degrees, care being taken to make tight joints. 
The underside of the board and stakes should be smeared with a good 
coat of commercial sticky tree-banding material. It is obvious .that 
with an infestation heavy enough to require the use of the board, the 
ditch might have to be frequently cleared of the dead bodies of the 
larvae in order to remain effective. 
