10 MASS. EXPERIMENT STATION BULLETIN 239 



Treatment. 



Cessation of Flooding. 



If a badly infested bog is not flooded at all for three years it generally 

 becomes free of this pest, and sometimes it M'ill do so in a year. This treat- 

 ment is not advocated because of the danger of winterkilling and of a great 

 increase of fruit-worm infestation. 



ReffoiciiK/. 



Complete flooding early in June has been long the standard control for the 

 first brood. It also cleans bogs of several other pests. It is often very sat- 

 isfactory, but it nuist be done with a careful allowance for the factors that 

 cause the injury which often attends it and may destroy all prospects of a 

 crop. The vines are less likely to be hurt if the weather and water are clear 

 while the water is on, for strong sunlight is necessary to the process of photo- 

 synthesis by which the plants tend to maintain a normal supply of oxygen in 

 the water. A too-prolonged lack of sufficient oxygen is the main cause of 

 flooding injury. Cloudiness with a high water temperature is especially dan- 

 gerous, for the warmer the water the faster the plants respire and the greater 

 their need of oxygen. A ri.se in temi^erature of 18° F. doubles their rate of 

 respiration. The floral parts and growing tips respire much faster than other 

 parts of the vines and so are hurt most easily by flooding. Water from swamp 

 reservoirs is more likely to do harm than that from ponds or streams, for it 

 usually has much less oxygen to begin with. The conditions of weather and 

 water which injure the vines quickest also kill fireworms most readily. 



The factors aifecting the results of this flooding vary so that it is hard to 

 make rules for the operation. The following table may be a fair guide in 

 clear weather witii water from a clean pond or stream. 



Highest Temperature reached Time Complete Flood 



by Water at Tops of Vines should be held 



During Flood (degrees F.). (liours). 



6.5 50 



70 44 



7.5 38 



80 31 



8.5 24 



If it gets cloudv or the water is dark and from a swamp reservoir, the time 

 should be 8 to 24 hours according to circumstances. If the weather is very 

 warm, this reflow should be put on in the night if possible and als-o taken off 

 at night, for if tender, growing vines stand in water under a hot sun long 

 they may scald. This flooding must be done before the blossoms begin to open 

 much. If the winter water has been let ofl" before May 8, June 7 is usually 

 about the right date. 



It has been found lately that tliis early sununer reflow iimch promotes the 

 infection of the new growth with the fungi of some of the worst putrefactive 

 cranberry diseases. Because of this and of the danger of injury attending its 

 application, the treatment is less approved than formerly. However, as it 

 "•reatlv checks^ the spread of the false blossom disease, while it is not certain 

 that any spray will do this, it seems advisable where this disease is present. 



8. Probably indirectly. 



