lit:; 



PLANT SANITATION. 



Entomological Notes. 



By E. Ernest Green, Government Entomologist. 



Specimens of a Longicorn beetle (Moechotypa verrucicollis, Gahan.) have 

 been sent in from the Matale district, together with examples of young rubber 

 stumps said to have been killed by them. The bark of these plants has 

 been nibbled off, in large irregular patches, exposing the bare wood. Similar 

 specimens, under identical conditions, were received from the same district 

 exactly a year ago. Examination of the roots prove that they have previously 

 been attacked by the parasitic fungus, Botryodiplodia elasticae, Petch. This 

 fungus attacks the collar of the plant ; kills the upper parts by cutting off the 

 supply of nourishment; and works down into the root. It has always 

 seemed to me extremely doubtful that a healthy rubber plant, protected by the 

 natural Bow of latex, could be successfully invaded by bark-eating and boring 

 insects, and the following experiments have strongly corroborated my theory t 

 Several of the living beetles were confined in a large cage together with a healthy 

 living plant of Hevea of the same age and stage of growth as those which were 

 the objects of attack in the Matale district. The beetles crawled up the stem and 

 presently tried their jaws on the bark. The puncture resulted in an instantaneous 

 exudation of latex which adhered to the mouth parts of the beetles and was 

 evidently very distasteful to them. They immediately abandoned the attack and 

 spent some time in endeavouring to remove the sticky fluid. After the first 

 rebuff no further attempt was made, even under stress of starvation. After 

 seven days' confinement, with no other food, I then removed the beetles to another 

 cage and provided them with some small branches of Cassia and tea. They com- 

 menced to feed greedily upon the bark of the Cassia, but the tea branches are not 

 altogether to their taste. They have fed only sparingly upon the outer layers 

 of the bark. These experiments clearly show that a healthy rubber plant is immune 

 from attack. But should the latex tubes become dry, from disease or any other 

 cause, the plants will fall an easy prey to boring and bark-eating insects. Stumped 

 plants that have been despatched by rail for long distances and have become 

 withered during transit, will be especially liable to attack. 



Further specimens of young rubber stumps, the ends of which have been 

 tunnelled to form a receptacle for the nests of a small Hymenopteron, have been 

 received. (See note in February number of this journal.) The present specimens 

 come from the Badulla district, and contain the nests of a tiny bee (Ceratina sp.). A 

 considerable number of small wasps and bees have this habit of boring into the pith 

 of dead parts of plants. The wasps usually store their nests with insects, while the 

 bees provision theirs with ' bee-bread' Ca mixture of pollen and honey). The follow- 

 ing species have been observed to infest young rubber plants : — Trypoxylon intrudens 

 and T. pileatum (provisioning their nests with spiders), Stigmus niger (with Aphides), 

 Odynurus sichelii (with small caterpillars), Ceratina simillima, C. viridissima, 

 and C. propinqua (with ' bee-breed '). Though none of these insects will attack 

 the living parts of the plant, it is possible that the tunnel in the dried ends of the 

 stump may form a lodgement for water and subsequently for injurious fungi. It is 

 advisable therefore to cut off the dead ends of the plants, care being taken that the 

 cut should be just above nodes (or knots) of the plant. If the cut is made 

 through or just below the node, it is probable that a further section of the stem will 

 die back. 



