16 



MASS. EXPERIMENT STATION BULLETIN 317 



gray, mummied berries (Fig. 8) may be found on the ground under infected 

 bushes. Sanitary measures, such as removing wild bushes around the planting 

 and brushing the mummied berries into the middle of the spaces between the 

 rows and covering them by cultivation, will reduce the damage from this disease. 



Figure 8. Mummy Berry Disease, Caused by a Species of Sclerotinia. 



The cranberry Phomopsis usually causes the rather sudden death of more or 

 less canes during the summer. Affected canes should be cut out promptly and 

 burned. 



Crown gall, a bacterial disease caused by Bacterium iumefaciens, infects cul- 

 tivated blueberries as well as apple, pear, peach, plum, quince, raspberry, and 

 many other plants. On the blueberry it usually appears as knotty swellings on 

 the stem or branches (Fig. 9), but may appear as nodules on the roots. It is 

 spread by the use of infected propagating wood and possibly on pruning tools. 

 It may live over in the soil or in dried-up galls in the soil. The variety Cabot is 

 very susceptible to crown gall, which has been found also on Pioneer, Concord, 

 Rubel, and Rancocas. Since this is primarily a nursery disease, it need give 

 the grower little concern provided he gets clean plants. The only method of 

 control is to remove and burn infected bushes at once. 



Witches broom, which gets its name from the type of growth it induces (Fig. 

 10), is caused by the fungus Calyptospora columnaris, one of the rust fungi. It 

 is perennial on both highbush and lowbush blueberries. It does not spread 

 from blueberry to blueberry but must pass through an alternate host, the bal- 

 sam fir, from which it spreads to the blueberry. Fortunately this is not a serious 

 disease, for no control has been found. The spread of the disease in an infected 

 plant can be stopped by cutting off the diseased branch several inches below 

 the affected part. 





