15 



bogs, the nearby breeding places are further reduced and the bog is 

 the more likely to remain free. 



As against the blackhead late holding will not of itself suffice, because 

 the eggs are already on the plants and will, under ordinary circum- 

 stances, hatch only under the same conditions that favor the start of 

 vines themselves. But there is a little leeway in favor of the plants, 

 and the eggs do hatch under water at a temperature not quite sufficient 

 to start the vines. To hatch the eggs the proper temperature only is 

 needed; to start the vines there must be also sun and air. If, therefore, 

 a bog is tolerably level the water may be drawn from below until it 

 just covers, and may be held there even after May 15, until the starting 

 of the vines indicates that the danger point has been reached, and then 

 it must be drawn to avoid killing the fruit buds. Runners or laterals 

 not bearing fruit buds will stand a quarter or even half an inch start 

 under water without danger unless the water is drawn on a very warm 

 day, and then there is danger of scalding. The further advanced the 

 plants the greater that danger becomes; hence great care and good 

 judgment must be exercised when this measure is adopted. Fruit- 

 bearing uprights can not be safely permitted to make more than a 

 mere start. On a sloping bog, where the water is deep at the gates 

 and becomes shallow at the edges, the water may be gradually drawn 

 from the bottom so as to leave the warmer surface water, and in this 

 way practically all the eggs will come under the influence of the moist 

 heat that favors their development. 



Carefully carried out, this measure is often verj^ efl'ective; the warmth 

 favors the development of the embryo within the egg, and when the 

 worm hatches it drowns. Occasionally a specimen ma}' bore into a 

 leaf and so maintain itself twenty-four hours or more, but usually it 

 stifles without getting even a bite. Sometimes badly infested bogs 

 are completely freed by this method without apparent injury to the 

 setting of fruit, yet at times the crop is reduced one-half by holding a 

 little too late. In the latter case, however, the crop had been destroyed 

 by the insect for several 5^ears in succession, and the owner was quite 

 willing to sacrifice 50 per cent if thereby lie got rid of the insect, as 

 he did. This method should be emploj^ed only when reflowing is not 

 possible. 



Reflowing. — When the supply of water is abundant above the bog 

 area, so that a pond or reservoir may be formed, both the yellow and 

 blackheads may be completely controlled by drawing the water early, 

 waiting until all the eggs have hatched and some of the worms are 

 nearly half grown, and then re-covering the bog with water for forty- 

 eight hours. This method is so simple and so absolutely effective that 

 the larger growers are adopting it almost universally, and f eiw new bogs 

 are laid out anywhere without considering the matter of reflowage and 



178 



