96 THE AGRICULTURAL PESTS OF INDIA. 



Peronospora arborescens is a most serious parasitic 

 foe of the opium poppy. It is a blight-mould confined 

 to the leaves, and is more or less common on the plant 

 in one or other of its modes of development. Differ- 

 ences in the degree of oxygenation of the juices promote,, 

 suppress, or impede the development of this mould. 



Phelipea Inclica, one of the broom-rapes, is a phoeno- 

 gamic root parasite, frequently causing much damage to 

 the poppy. Where it is of frequent occurrence, mustard 

 seeds should be sown along with the poppy seeds. The 

 growth of the poppy is not checked, but it never yields 

 the full amount of opium. It is in many districts a 

 serious pest to the poppy ; is very prevalent in parts of 

 the Patna Division. Orobranche cernua and 0. Indica. 

 two species of broom-rapes in Bengal, are parasites of the 

 tobacco plant. 



Sun -burning is the 'moorka' or 'joorka' of the 

 natives, due to the sun scorching the plant. The leaves 

 are dry and withered, with more or less discoloured 

 purply-black or brownish veins. It occurs in hot seasons,. 

 with a deficiency of moisture in the soil. 



Eoot canker occurs in stiff clayey soils, with an excess 

 of the oxides of iron or manganese, or with an excess of 

 any of the alkaline salts. The tap-root becomes corroded, 

 and the leaves wither from below upwards. 



Petechia. The leaves first acquire a pale yellow tinge,, 

 and subsequently the whole surface becomes gradually 

 studded with specks and patches of a pale purply-black 

 colour, but confined chiefly to the leaves. It is due to 

 overcrowding in damp soils. 



Gangrene occurs on all the affected plants ; juices 

 exude, forming small black specks, or even large black 

 tears, all over the plant. 



