50 REPORT OF THE AGRICULTURAL RESEARCH INSTITUTE 



supposed to result from climatic conditions. In South 

 India the same fungus is believed to be responsible for 

 considerable damage and it is at present under study by the 

 Madras Department. 



The fungus is found both in the diseased bark and also 

 on the fruits. It has been grown in pure culture and an 

 extensive series of inoculations carried out both on rubber 

 and on numerous other plants known to be attacked by 

 species of Phytophthora. On rubber it is a wound para- 

 site, being unable to infect the undamaged bark; through 

 wounds it infects readily and produces the characteristic 

 symptoms of the disease. Of the other plants tried, the 

 ordinary hosts of Phytophthora infestans, Ph. parasitica 

 and Ph. Colocasiw, the three species most commonly found 

 iv. Northern India, are immune, as also is cacao, one of the 

 chief hosts of Ph. Faberi, and many other plants known to 

 be liable to Phytophthora attack. Only on seedlings of the 

 garden plants, Gilia -and Salpiglossus, were successful 

 infections secured. 



The disease is favoured by excessive humidity and 

 shade and is, therefore, worst in thickly planted rubber 

 estates. The free admission of sunlight and air checks its 

 progress, and good results may be obtained from judicious 

 pruning and thinning. The chief source of infection 

 seems to be the fruits, and as these have practically no value, 

 and develop in the rains a copious growth of the parasite, 

 from which spores are shed on the bark, it is recommended 

 that all fruits be carefully picked and destroyed before the 

 monsoon breaks, in infected plantations. 



In continuation of the studies on allied species of this 

 genus which have been carried on at Pusa in recent years, 

 an account of a form of Phytophthora parasitica found on 

 Vinca rosea has been recently submitted for publication. 

 Germination of the durable type of spore (the oospore) has 

 been obtained and was found to correspond in essentials 

 with that described for Ph. erythroseptica in Ireland. 



(4) Opium poppy blight. The investigation of this 

 disease has led to the conclusion that while Peronospora 



