632 RUBBER 



Mytilaspis rubro-vittatus, on foliage. (Ceylon.) 



Parlatoria proteus, on foliage. (Java.) 



Chionaspis dilatata, on foliage. (Java.) 



Lecanium nigrum, on young stems and foliage. 

 (Ceylon, Java, Seychelles, British Guiana, Hawaii.) 



V'msonia stellifera, on foliage. (British Guiana.) 



Asterolecanium pustulans, on stems. (British Guiana.) 

 ,, pustulans seychellarum, on stems. 



(Seychelles.) 



Pseudococcus virgatus, on foliage. (Hawaii.) 



All Coccidse are potential pests. Any species, though 

 at first of only casual occurrence, may suddenly increase 

 beyond the normal and become formidable. But of tho<se 

 known to occur upon Hevea, Asterolecanium pustulans 

 and Lecanium nlgrum are the only species of any present 

 importance. The former is responsible for an unhealthy 

 condition of the stem. The insects occupy small depres- 

 sions on the bark. When they occur in considerable 

 numbers the bark assumes an unhealthy hidebound and 

 nodular condition that must greatly interfere with the 

 processes of tapping, and may even check the elaboration 

 of latex. Lecanium nigrum sometimes encrusts the 

 young stems and branches to an extent that seriously 

 checks the growth of the plant. Mr. Dupont informs me 

 that, in Seychelles, this species is held in partial check 

 by a parasitic fungus (Hypocrella sp.), which attacks it 

 wherever it occurs. 



With such a large area of plantation rubber now in 

 cultivation it may be considered astonishing that the 

 catalogue of pests is so small. The increased attention 

 that is now being given to the diseases of plants renders 

 it more difficult for any pest to gain a foothold. It is 

 quickly observed, and measures are taken to check it 

 before it has had time to establish itself firmly. 



It should be remembered, however, that large un- 

 broken areas of a single cultivation must always afford 

 the best opportunity for the increase and spread of any 

 pest, and will render attempts at remedial treatment the 

 more difficult. It is sound policy to break up such areas 

 by interposing belts of other trees, which will tend to 

 confine any enemy within practicable limits. 



