22 



MASS. EXPERIMENT STATIOxX BULLETIN 44: 



If the bog can be reflowed, the winter water should be let off about April 1 

 at least every other year. It may be held till May 23 (June 1 on the outer Cape) 

 the other years^ (except on bogs well inland, where, because of higher spring 

 temperatures, late-holding seems to be more dangerous to the crop) to control 

 the fruit worm and false arm\-worm, reduce weeds and fungous diseases, and 

 promote vine growth. It must not be held so late if it is deep over much of the 

 area or the vines are over vigorous. It may be held till about May 20 rather 

 regularly on bogs that cannot be reflowed. Holding after Ma\- 23 invites cut- 

 worm infestation. Algal scum often develops in the flood water when it is held 

 late. This sometimes dries to form paper over the vines after the water is let 

 ofif and is then harmful (Fig. 18). It can be prevented from forming b>- dissolving 

 6 pounds of copper sulfate to the acre-foot in the flowage about the first of April. 

 Coarse crystals of the chemical in a burlap sack ma\- be towed in the water be- 

 hind a canoe or fine crystals may be scattered on the bog ice late in the winter. 

 Changing the flood water early in April, exposing the bog to air a week or more 

 also usually prevents this trouble. 



Fig. 18. Cranberry Bog Covered with "Paper" from Algal Scum. 



Bogs used to be flooded regularly earh in June to check insect pests. This is 

 advisable one >ear in three but is a dubious annual practice for it carries fungous 

 infection to the new growth and sometimes reduces the crop seriously by drown- 

 ing the flower buds. This flood should go on in the night and also be taken off 

 at night if the weather is very warm, for if tender growing vines stand in water 

 long, exposed to a hot sun, they may scald. The flower buds are less likeh" to be 

 hurt by the flooding if the weather is clear while the water is on, for light is neces- 

 sary to the photosynthesis by which the plants give oxygen to the water. Cloudi- 

 ness with a high water temperature is espccialh- dangerous, for the warmer it is 

 the faster the plants respire and the greater their need of oxygen. The complete 



3 It probably is better to let the winter flowage off at the end of March, reflood about -April 20, 

 and hold the water till May 23, than to hold the winter water late. This serves all the purposes o: 

 late holding, airs the vines, and gives time to work on the bog. 



