ASCOMYCETES 261 



after one or two generations. In general, the conditions under 

 which growth takes place do not seem to affect to any great ex- 

 tent production of fruiting stages. It is believed also that after 

 the fungus has penetrated the host it may remain under favorable 

 conditions inactive for some time, and that therefore the period of 

 incubation may be long or short, depending upon conditions. The 

 ascogenous form has not been found abundantly in nature, and 

 may not be very important in the distribution of the fungus. 



Control. Prevention should concern itself particularly with 

 sanitation, including the renovation of the cranberry bog, proper 

 regulation of the water supply, and the development of disease- 

 resistant strains. Spraying with Bordeaux mixture has also proved 

 of value. In spraying, however, the addition of substances ren- 

 dering the mixture more adhesive is necessary. 



XLII. LEAF SPOT OF STRAWBERRY 

 Mycosphcerella Fragarice (Tul.) Lindau 



DUDLEY, W. R. On the Strawberry Leaf-Spot. Cornell Agl. Exp. Sta. Built. 



14: 171-184. 1889. 

 SCRIBNER, F. L. Strawberry Leaf Blight. U. S. Dept. Agl. Rept. (1887): 



334-341. pi. i, 



One of the diseases of the strawberry most frequently met with 

 is that commonly known as the strawberry leaf spot. The disease 

 makes its appearance in the form of small, discolored spots, ap- 

 pearing upon the leaves most abundantly about the time of flower- 

 ing (Fig. 114). At first these spots are of a reddish or purplish 

 tint, but as they increase in size the center becomes pale and may 

 be quite white when the death of the. tissues has ensued. This 

 white central area is ordinarily bordered by a zone of red and 

 purple in different shades. These spots are irregularly distributed 

 over the leaves, and when numerous they may coalesce. All of 

 the cultivated varieties of strawberries may be affected, although 

 there is considerable difference in the degree of susceptibility. 

 Among some of the berries most susceptible in the northeastern 

 United States may be mentioned the Hunn and the Beeder 

 Wood. Susceptibility of a variety varies, however, when culti- 

 vated under different conditions. Marshall and Brandywine have 

 often proved very resistant. 



