ANNUAL REPORT, 1935 33 



7. Wild bean or ground nut (Apios tuberosa Moench.) is readily killed back 

 to the ground by spraying with 7 pounds of sodium arsenate in 400 gallons of 

 water to the acre. If this spray is applied when the cranberry vines are in 

 bloom, it may burn a few of the blossoms and more tender tips. After the 

 berries are set, the injury is negligible. The continued use of this spray for 

 two or three years should eliminate this weed entirely. This is a refinement 

 of a treatment advocated heretofore. 1 



8. Green moss (Polytrichum commune L. ) can apparently be killed very 

 readily with a spray of iron sulfate, 3 pounds to the gallon of water, 800 gallons 

 to the acre. This is probably the best treatment so far found for moss. It 

 should be applied in the late fall or early spring, when the cranberry vines are 

 dormant, and should be followed by a good resanding after ten days to two 

 weeks. 



9. Violets (Viola lanceolata L.) can be killed with dry iron sulfate, 1% tons 

 to the acre. 



COOPERATIVE CRANBERRY INVESTIGATIONS 



Conducted by the Bureau of Plant Industry, United States Department 

 of Agriculture, in cooperation with the Massachusetts Agri- 

 cultural Experiment Station 



H. F. Bergman, Senior Pathologist, U. S. D. A., in Charge 



Development of Strains of Cranberry Resistant to False Blossom. 



(H. F. Bergman and W. E. Truran. ) Reciprocal crosses between Early Black 

 and McFarlin represent the larger part of the cross pollinations made during 

 the past season. Sixty fruits were secured from each of these combinations. 

 Reciprocal crosses were also made between McFarlin and Shaw's Success and 

 between Paradise Meadow and Shaw's Success. A few crosses of Early Black 

 x Shaw's Success, of Paradise Meadow x Early Black, and of Paradise Meadow 

 x McFarlin were made, tne last being a new cross. 



Seeds from crosses made in 1934 were planted this year. Germination was 

 poor in all cases. Seeds from the cross of Early Black x McFarlin gave the 

 highest percentage of germination, 32 percent. Most of the seedlings were 

 killed by damping-off fungi but some seedlings of each cross survived. These 

 have been transferred to pots and are to.be set out on the bog next spring. 



Oxygen Content of Flooding Water in Relation to Injury to Cran- 

 berry Vines. (H. F. Bergman and W. E. Truran.) Measurements of the 

 oxygen content of water and of the light intensity at various depths were made 

 on several flooded bogs to ascertain the relation between these two factors. 

 Light measurements were made by means of a photoelectric cell which could 

 be submerged to the desired depth. The light intensity as measured by this 

 method is about 25 percent less at midday on bright days at a depth of 1 foot 

 in clear water than it is above the water surface. During the early lorenoon 

 and late afternoon, on cloudy days, or in colored water the reduction in light 

 intensity at that depth may reach 50 percent of that above the water surface. 

 The oxygen content of flooding water varies with changes in light intensity, 

 but no definite relations between the two can be made at this time as the cal- 

 culations from data secured have not been made. 



iBul. 305, Mass. Agr. Expt. Sta., 1934, p. 23. 



