32 



SOME FUNGOUS DISEASES OF ECONOMIC IMPORTANCE. 



Experiment No. 32. 



1,250 c. c. formalin per 1,000 cubic feet of air space. 

 Temperature before mixing reagents, 80° F. 







Thielaviopsis on the fruit. 



Initial 

 growth of 

 fungus. 



Vigorous p , e / cent 

 lungus. J™ h 





Hours. 



48 

 



Hours. 



96 100 













The nonfumigated fruit was badly decayed after one hundred and 



twenty hours. The fumigated fruit remained firm and in marketable 



condition. 



Experiment No. 33. 



1,300 c. c. formalin per 1,000 cubic feet of air space. 

 Temperature before mixing reagents, 78° F. 



Thielaviopsis on the fruit. 



Initial Vigorous 

 growth of growth of 

 fungus. | fungus. 



Per cent 



of fungus 



which 



grew. 





Hours. : Hours. 

 36 j 50 

 



100 













The nonfumigated fruit was badly decayed after one hundred and 

 twenty hours. The fumigated fruit remained firm and unaffected. . 



Plate VI is a reproduction of a photograph of cultures from the 

 fruit before and after fumigation, taken one hundred and twenty 

 hours after fumigation. 



Assuming that spores of Thielaviopsis may be present on the fruit 

 after it is pulled, an attempt was made to reproduce such a condi- 

 tion. An abundant opportunity for infection was given by inserting 

 or spraying the fungous spores directly on the fruit. After this 

 treatment the pineapples were kept under conditions favorable to 

 the development of the fungus and as nearly approximating natural 

 conditions as possible. It will be observed from a comparison of the 

 tables that on the fruit inoculated by the incision method and sub- 

 mitted to the gas generated from formalin in quantities less than 

 1,300 c. c. per 1,000 cubic feet there was some development of the 

 fungus, while growth did not occur after subjection to the gas gen- 

 erated from 1,300 c. c. of formalin per 1,000 cubic feet of air space. 



171 



