ANNUAL REPORT, 1939 39 



COOPERATIVE CRANBERRY INVESTIGATIONS 



Conducted by the Bureau of Plant Industry, United States Department of Agri- 

 culture, in cooperation with the Massachusetts Agricultural 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 \V. E. Truran.) Berries from crosses made in 1938 were sent to 

 the U. S. Horticultural Station, Beltsville, Md., where the seeds were germinated 

 and the seedlings grown. From a total of 353 fruits 8,233 seeds were obtained 

 which produced 6,337 seedlings. In July 1939 there were 6,291 plants. These 

 will be taken to New Jersey and set out on a bog in 1940. Because of the lack 

 of bog area for use in testing hybrid seedlings no crosses were made in 1939. 



Studies on Flower and Fruit Production. (H. F. Bergman and W. E. Truran.) 

 Studies to determine the effect of oxygen content of winter flooding water on 

 flower and fruit production have previously been made. Previous observations 

 have shown that the average flower production in the Early Black, Howes, and 

 McFarlin varieties, under favorable conditions, is about four flowers per upright. 

 Flower production in liarly Black on section 14 of the State Bog, in 1939, was 

 about the normal average. In Early Black on the Star Bog and in McFarlin on 

 the State Bog flower production was less than the average by one flower per 

 upright. Elsewhere on the State Bog the difference was greater, amounting to 

 about one and a half flowers per upright in Howes on section 13 and to about two 

 flowers per upright in Early Black on section 4 and in Howes on section 7. A 

 correlation with weather conditions could not be determined from available data. 



The average percentage of fruit set in any of the three varieties, under favorable 

 conditions, varies from 30 to 35. The set in Early Black on section 14 in 1939 

 was less than half this average. The highest percentage of fruit set, on the State 

 Bog, was 18.6 in McFarlin, the lowest 7.6 in Howes, both on section 13. The low 

 percentage of fruit set appears not to be correlated with the oxygen content of 

 the winter flooding water. It seems possible that the low rainfall during July 

 1939 may have had an efi^ect on the setting of fruit and may partly explain the 

 variation in set in difi^erent locations on the State Bog. The Howes vines on 

 section 13 were on higher ground than elsewhere and might be expected to have 

 had the least water supply; the McFarlin vines were in one of the lowest spots 

 on the bog and probably had the best water supply. The water supply of vines 

 in other locations on the State Bog was intermediate. This is in agreement with 

 the observed set on vines in the dilTerent locations. Furthermore, the percentage 

 of fruit set by flowers on uprights from large terminal buds was less than on 

 uprights from medium or small terminal buds in all locations on the State Bog 

 except in McFarlin on section 13. This is in conformity with the suggestion that 

 the reduction in the percentage of fruit set may have been due to a lack of water. 

 The proportion of uprights with three or more flowers per upright is greater in 

 uprights from large terminal buds than in uprights from medium or small terminal 

 buds and a lack of water would affect the set of fruit on uprights with three or 

 more flowers more seriously than on uprights with only one or two flowers. 



Spraying Experiments for the Control of Rosebloom. (H. F. Bergman and 

 W. E. Truran.) Bordeaux 4-1-50 and 5-2-50, a red copper oxide-bentonite 

 mixture 2-2-50, and yellow copper oxide 1^-50 were each applied once (June 

 12) on duplicate plots on a bog badly infected with rosebloom. Bordeaux 5-2-50 

 gave the best control. Within three days after the spray was applied diseased 

 shoots had turned black and shriveled, and no unaff'ected or only partly killed 

 diseased shoots couid be found. Bordeaux 4-1-50 was only a little less effective 



