INSTITUTE, PUSA, FOR 1916-17 59 



of the latter. The remedial measures recommended are 

 being tested on a plantation scale in Burma. The chief are 

 the free admission of light and air amongst the trees by 

 judicious thinning, and the cessation of tapping during the 

 monsoon months on all diseased trees. In South India, 

 where the same or at least a closely allied disease is under 

 investigation, good results have been obtained by the appli- 

 cation of antiseptic and waterproof smears to the cut sur- 

 face left after tapping. Tar and tallow; sulphur, cowdung 

 and clay, have been used, and no doubt other more efficient 

 mixtures will be found. It is not yet certain whether simi- 

 lar measures will be required in the relatively drier parts 

 of the Burma rubber districts and, at the time of writing, 

 Mr. Dastur is carrying out further enquiries in Burma. 



A second Memoir contains an account of a biologic 

 variety of Phytophthora parasitica, Dastur, found in Pusa 

 on Vinca. It is a weak parasite, inoculations failing as a 

 rule unless the atmosphere is almost saturated with mois- 

 ture, but succeeding in damp air on a considerable number 

 of garden plants. The fungus is, therefore, of more scien- 

 tific than economic interest. 



In a third paper, Mr. Dastur discusses the conditions 

 influencing the distribution of Phytophthora infestans, the 

 cause of the common potato blight. In India the fungus 

 is ordinarily restricted to the Himalaya, Khasi and possibly 

 Nilgiri Hills, but periodical outbreaks have been observed 

 in the Gangetic plain and the valleys of Assam and Sylhet. 

 An analysis of the conditions leading to these attacks, indi- 

 cates that temperature, moisture and source of origin of 

 the tubers are all important factors in controlling the dis- 

 tribution of the disease. Long exposure to temperatures 

 above 77°F., is already known to be fatal to the fungus and 

 such temperatures are usually found at the time of sowing 

 the plains' crop. Furthermore, damp weather at the period 

 of fructification of the fungus (January and February in 

 the plains) is necessary to permit free reproduction and 

 dissemination. And unless the tubers come from some 

 already infected area, such as the Himalaya or Khasi Hills^ 



E 



