12 CRANBERRY DISEASES. 



Ill 1901, at the urgent request of the American Cranberry Growers' 

 Association and in cooperation with the New Jersey Experiment 

 Station, a study of cranberry diseases on behalf of the Bureau of 

 Plant Industry was commenced by the writer. Both field and labo- 

 ratory investigations have been continued since as the pressure of 

 other duties would permit. Careful studies were first made of the 

 field conditions, and laboratory and greenhouse studies have been 

 made of the diseases found and the fungi producing them. 



THE MOST SERIOUS DISEASES. 



Cultures of the fungi found in diseased berries soon showed that, 

 instead of a single disease, the term " scald " as used by cranberry 

 growers includes at least three distinct diseases of the fruit scald, 

 rot, and anthracnose caused by three different fungous parasites, 

 Guignardia vaccinii Shear, Acanthorhynchus vaccinii Shear, and 

 Glomerella rufomaculans vaccinii Shear. Besides the diseases which 

 affect the more or less mature fruit there is another, commonly called 

 u blast," or sometimes " blight," by the cranberry growers, which 

 attacks the very young berries about the time the blossoms fall, 

 causing them to turn black and shrivel up. There is also a disease 

 which causes hypertrophy of the axillary leaf buds, and thus ex- 

 hausting the vitality of the plant prevents the production of fruit. 

 The most important diseases of the cranberry are those mentioned. 

 Besides these there are a number of diseases of minor importance 

 which will receive briefer consideration. 



BLAST. 



As already mentioned, the blast attacks the flowers and very young 

 fruit, which shrivels up and becomes covered with the pycnidia of 

 the parasite (PL II, figs, la, 16). It frequently happens that as 

 much as one-half of the crop on some bogs or portions of bogs is 

 destroyed in this manner. The disease is caused by the pycnidial 

 form of Guignardia vaccinii Shear. 24 The blasting of young fruit 

 had been observed for many years by cranberry growers, but appar- 

 ently the fungous nature of the disease was not known. There 

 is, of course, some blast, or blight, of blossoms and of very young 

 fruit due to other causes, as imperfect fertilization or injury by 

 storms, frost, or insects, but by far the greater part of the blasted 

 fruit on New Jersey cranberry bogs is due to the above-mentioned 

 fungus. 



Whitson, Haskins, and Malde 15 mention a cranberry "blight" 



which occurs in Wisconsin, killing the blossoms and very small fruit. 



This trouble, according to the writers mentioned, has been attributed 



by growers to hot weather. The results of their experiments were 



no 



