4 MASS. EXPERIMENT STATION BULLETIN 402 



occurrence of leaf-drop, no further study of the problem was made for several 

 years. However, in the spring of 1939, winter-flooding injury severe enough to 

 cause leaf-drop and a marked reduction in yield was observed on a considerable 

 number of bogs in Massachusetts, and work on the problem was resumed. 



Determinations of the dissolved oxygen in the water on a few bogs were made 

 weekly from late in January 1940 until the ice melted in March. The severity of 

 injury to the vines on these bogs was ascertained the following summer. Again 

 during the winter of 1940-41, the dissolved oxygen content of the water on the 

 State Bog near East Wareham, Massachusetts, was determined weekly from 

 January 15 to March 20, and at the same time an experiment was carried out to 

 determine the effect on vines of depriving them of oxygen for known lengths of 

 time during the winter. The degree of injury caused by this treatment was de- 

 termined the following summer by comparing these vines with others which had 

 been deprived of oxygen for only a very short time, if at all. 



The results obtained during 1940 and 1941 yielded much information as to the 

 conditions under which oxygen deficiency occurs and the relation between known 

 degrees of injury and the dissolved oxygen content of the water during the winter. 

 Moreover, it was found that forms of injury which are known to have occurred 

 frequently and generally on bogs in Massachusetts, and which previously had 

 not been recognized as winter-flooding injury, are caused by a lack of oxygen 

 in the water during the w inter-flooding period. Since these forms of injury always 

 reduce the yield, sometimes very greatly, the problem of winter-flooding injury is 

 now known to be important to cranberry growers in Massachusetts as well as in 

 Wisconsin. The significance of various factors in bringing about an oxygen de- 

 ficiency, and the relation of these and other factors to injury to cranberry vines 

 as a result of oxygen deficiency, are discussed in this paper. 



FORMS OF INJURY 



Injury resulting from a lack of oxygen in the water during the winter-flooding 

 period varies greatly in its severity. Such injur}-, in order of decreasing severity 

 as observed on bogs in Massachusetts, causes death of a variable portion of the 

 stems with their leaves and buds; loss of leaves of the preceding season (leaf-drop) ; 

 death of the terminal (fruit) buds; death of small areas of leaf tissue in embryonic 

 leaves within the terminal bud which later causes deformation of the leaves as 

 they develop; retardation in the development of the new growth of uprights from 

 the terminal buds; death of all or some of the flower buds; failure of the flowers 

 to set fruit; failure of the fruits to grow to mature size; and reduction in the size of 

 mature fruits. Some of these forms of injury' are shown in Figure 1. The only 

 important deviation from this order is on Wisconsin bogs flooded with alkaline 

 water where leaf-drop may occur without the flower buds being killed. 



The death of stems or terminal buds and any considerable loss of leaves are 

 very obvious and, therefore, were the first forms of injury to be noticed and for 

 many years were the only ones attributed to winter flooding. The additional 

 forms of Injury listed above were thought to be due to other causes. This prob- 

 ably is the reason that winter flooding is so generally believed to have no karmful 

 effect, except possibly when the water is held late. 



Terminal buds may be killed without injury to the stems, which then develop 

 one or more branches (side shoots) on each upright from buds lower down on the 

 stem. If part of the stem is killed, the side shoots develop from buds farther 

 down on the stem. As a rule, terminal buds are more susceptible to injury than 

 the old leaves; but in some cases the terminal buds are not harmed and may de- 

 velop in the usual manner and produce one or two fruits even though the old 

 leaves are killed and drop from the stems. 



