STRAWBERRY DISEASES 



1933 



STEAWBERRY DISEASES 



Autlirariiose 



Oloeosporimn fragariae Mont. 

 According to C. L. Shear, pathologist of 

 the Bureau of Plant Industry, United 

 States Department of Agriculture, this 

 disease does not occur in America. 



Black Heart or Frost lujury 



The cultivated varieties of strawberries 

 and raspberries are more or less subject 

 to frost injury, which manifests itself by 

 producing a blackened center in these 

 flowers. In severe cases, all flowers form- 

 ing a cluster may be found affected, espe- 

 cially in varieties where most of the blos- 

 soms open at one time. Night frosts are 

 capable of great injury by destroying the 

 styles of the flowers and thus preventing 

 the fruit from being formed. In some 

 instances, a few styles only may be killed 

 and the result will be a crippled, mal- 

 formed fruit, which does not recommend 

 itself by its appearance to the buyer. It 

 has been found, especially in the case of 

 strawberries, that the injury may be 

 largely prevented by covering all early- 

 flowering varieties at night with straw 

 or loose litter of some kind. The harvest 

 may thus often be increased from 10 to 20 

 per cent and more. Raspberries may be 

 planted between sheltering hedges, or 

 they may be covered over night with 

 cheesecloth. Where these suggestions 

 may not be practicable, spraying with cold 

 water early in the morning before the 

 rays of the sun take effect has been 

 proved a useful preventive. 



The lighting of smudge fires and keep- 

 ing them alive throughout cold nights 

 has also proved quite successful. 



H. T. Gussow, 

 Experiment Farms Reports, 1011. 



Black Root 



A rather indefinite trouble, character- 

 ized by the blackening and ultimate decay 

 of the roots of plants during the second 

 year after setting. It usually starts at 

 the season when new growth is beginning 

 in spring, and affected plants may put 

 forth leaves and blossoms only to die 

 later on. The trouble appears to be 

 closely associated with winter injury and 



unfavorable soil conditions, but nothing 

 definite is known about the condition at 

 the present time. 



B. 0. LONGYEAR. 

 Colorado Repnrt, 1910. 



Frost Injury. See Black Heart. 



Leap Blight. See Leaf Spot, this sec- 

 tion. 



Leaf Spot 



Mycosphaerella fragariae 



H. S. Jackson 



The only fungous disease of the straw- 

 berry occurring in Oregon that has been 

 thoroughly studied by pathologists is the 

 disease known as the strawberry leaf spot 

 or blight. This disease is nearly always 

 present to a greater or less extent in 

 every field. It is not always serious and, 

 in fact, is rarely considered by Oregon 

 growers to cause sufficient damage to need 

 special treatment. In many cases, how- 

 ever, it causes more damage than is real- 

 ized, and hence is considered of sufficient 

 interest to warrant a discussion in this 

 connection. All of the cultivated varie- 

 ties may be attacked, though many are so 

 resistant as not to be seriously affected. 



The disease affects the foliage pri- 

 marily, making its first appearance on the 

 plants as minute purplish spots more or 

 less thickly scattered. (See Fig. 1.) 

 These soon enlarge and the center be- 

 comes pale gray or nearly white in color. 

 The margin, however, remains purple, 

 shading into brown towards the lighter 

 area in the center. When numerous these 



0« Xlv S<a. 



I'lg. 1. Strawlierry Leaf Showinj; Spots Caused 

 by the I.eat Spot F^lnf,^ls. 



