8 



BULLETIN 686, U. S. DEPAETMENT OF AGRICULTURE. 



fallen, kept better than those picked during the hottest part of the 

 day. - 



BOTRYTIS. 



RELATION OF BOTRYTIS INFECTION TO MOISTURE CONDITIONS. 



Botrytis ^ is characteristically a cause of field rot of strawberries. 

 It is, however, by no means of uniform importance. Its abundance 

 seems to be closely correlated with moisture conditions. During 

 the past three years the writers have observed three epidemics of 

 Botrytis, all associated with abundant moisture. Tlie first occurred 

 in the early part of June, 1915, at the Arlington Experiment Farm, 

 in Virginia. Not only were green and ripe fruits affected, but fruit 

 pedicels and leaf petioles as well. 



The epidemic began during a week of almost continuous cloudy 

 weather in which over 3 inches of rain fell, as indicated by the accom- 

 panying report (Table VII) taken from the Monthly Meteorological 

 Summary for Wasliington, D. C, published by the Weather Bureau 

 of the United States Department of Agriculture. 



Table VII. — Meteorological data, Washington, D. C.,' May 28 to June 3, 1915. 



Date. 



May 28 

 May 29 

 May 30 

 May 31 

 June 1 . 

 June 2. 

 Junes. 



Temperature (° F.). 



Precipita- 

 tion 

 (inches). 



Maximum. 



Minimum. 



76 

 61 

 57 

 73 

 68 

 64 

 69 



48 

 57 

 52 

 52 

 49 

 54 

 49 





0.12 

 .10 



.11 



3.00 

 .03 



Character of day. 



Partly cloudv 



Cloudy ■. 



do 



Clearo 



Cloudv 



....do 



....do 



Percentage 

 of possiTile 

 sunshine. 



o Corrected from the published Monthly Meteorological Summary on the advice of Mr. M.C. Bennett, 

 acting chief, Climatological Division, Weather Bureau. 



This infection occurred on the experimental plats of the Office of 

 Horticultural and Pomological Investigations, in which a test was 

 being made of more than 300 varieties of strawberries. No difference 

 in the susceptibility of the different varieties could be noted. 



A strongly localized epidemic which was of special interest because 

 of its evident direct relation to moisture conditions occurred at 

 Hammond, La., following a rain on April 16, 1917. On one field 

 known for its high yields and careful culture there was great loss from 

 Botrytis. The loss was markedly greater on one side of the field 

 where a grove of tall trees shaded the plants during the early part of 

 the day and evaporation took place more slowly than elsewhere. 

 More than haK of the berries picked in this field on one day were 

 discarded as culls because of Botrytis infection. The inspection of 



1 While careful comparative studies of material from various localities have not been made, the collections 

 of Botrytis on strawberry fruits appear to belong to a single species, probably B. cinerea Pers. 



