PHYTOPHTHORA ON VINCA ROSEA, 



BY 



JEHANGIR FARDUNJI DASTUR, B. Sc, 

 First Assistant to the Imperial Mycologist. 

 [Received for publication on the 19th July, 1916.] 



At Pusa (India) the latter part of May 1913 was wet, so also most of the 

 moiith of June. During this period the weather remained cloudy, and- the 

 atmosphere was charged with a great deal of moisture. These were ideal 

 conditions for parasitic fungi to flourish to the detriment of their host plants. 

 One of the garden plants that suffered during this period, was Vinca rosea 

 belonging to the N. 0. Apocynacew. 



Leaves, growing jjoints, tender stems just below growing points, flowers 

 and fruits were observed to damp ofi, to turn brown and then black. Micros- 

 copic examination showed the presence of a parasite of the genus Phytophthora. 

 The disease was prevalent for about a foitnight only. It disappeared soon 

 after the weather cleared up and bright sunshine once again flooded the gardens. 

 Even when the weather was wet, if diseased plants were removed to a dry 

 place, the disease made no headway and the plant dropped its diseased parts 

 and brought forth new healthy shoots. The causal parasite has never been 

 found to be of a virulent character. Healthy plants inoculated with pure 

 cultures in the laboratory invariably gave negative results, except when the 

 surrounding atmosphere was kept saturated with moisture, which condition 

 was secured by covering the inoculated plants grown in pots with bell jars 

 with an inner lining of blotting jDaper and keeping the pots in a basin of water. 

 Under these conditions the effects of the inoculations were visible in about a 

 couple of days by the inoculated parts, flowers, leaves, growing points, stem 

 just underneath the growing point, and fruits, turning brown and then black 

 as in nature. Mature stems could not be successfully inoculated even '"n such 

 an atmosphere. Follicles, sterilized by washing in corrosive sublimate (1 in 

 1 ,000) for five minutes, and unsterilized follicles were placed in six sterilized 

 tubes containing moist cotton plugs. Bits of agar medium containing living 

 mycelium from a healthy cidture were used in inoculating these follicles. 



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