July, 1909.] 



35 



Plant Sanitation. 



young shoots of the cotton plant, they 

 fed freely and their punctures were 

 followed by the ususal discoloration. 

 After confinement for twenty-four 

 hours, the insects died without deposit- 

 ing any eggs in the shoots. 



Other insects captured in some num- 

 bers upon the cotton plaubs were Calli- 

 cratides rama, a species of Eusarcoris> 

 Oraptostethus servus, Geocoris tri- 

 color, Lygus biseratensis, and one or 

 two small Capsids. 



Tea seedlings, killed by an 'Bel-worm', 

 have been received from the Haldum- 

 mulla district. The roots are thickened 

 and corky, and the bark is more or less 

 separated from the woody part by a 

 layer of decayed tissue of an earthy 

 consistency. In parts, the whole of the 

 tissues are decayed, and large canker- 

 ous holes appear in other parts. On 

 standing the roots in a vessel of water, 

 a few nematodes emerged ; bub the 

 plants had been dead and dry for some 

 time, and had been abandoned by most 

 of the worms, which have probably 

 migrated to the neighbouring plants. 



This is a distinctly serious pest ; but- 

 fortunately one of uncommon occur- 

 rence. Only two cases have come to my 

 notice within the last ten years. Seed- 

 lings from this nursery should on no ac- 

 count be distributed. The plants should 

 be destroyed at once. The soil should be 

 treated with a heavy dressing of either 

 quick-lime or 'Vaporite,' and the ground 

 left fallow for at least nine months. 

 The superintendent of the estate reports 

 that these plants were on the site of a 

 previous nursery in which the same 

 trouble had been noticed. The nature 

 of the disease being misunderstood, 

 manure had been applied before sow- 

 ing the secoud lob of seed, Manure has 

 no deterrent effect against eel-worms. 

 In such cases it will be a grave mistake 

 to make a fresh nursery in the same 

 soil. The ground must be left fallow, 

 or planted wibh something that is not 

 attractive to the nematodes. 



MISCELLANEA: CHIEFLY PATHO- 

 LOGICAL. 



By T. Pbtch. 



The extension of the Northway system 

 of tapping to estates in other districts 

 has produced a volume ot correspondence 

 dealing with the pathological effects 

 which have been observed to follow its 

 application. It by no means follows, 

 however, that the undesirable effects 

 noted are an inevitable consequence of 

 the employment of that system, and it 



is fairly certain that some of them 

 would have been found to exist after the 

 application of other systems, if they had 

 been looked for. 



Several planters have stripped off the 

 bark a few days after it has been 

 pricked, and have found black spots on 

 the cambium, or rather on the wood and 

 bark where the cambium has been killed, 

 round the incision made by the pricker. 

 As far as my observations go, the pricker 

 always makes a black mark, i.e., locally 

 kills the cambium, when it penetrates to 

 the wood, but with the sharp pricker 

 the mark is only small. The larger 

 marks now seen are the natural resulb of 

 the blunt pricker, both on account of its 

 greater area and the fact that it pushes 

 into the cambium pieces of bark which 

 assist the decay, In this respect the 

 difference between the effects or the two 

 prickers is one of degree ; and if the bark 

 can be pricked without injury to the 

 cambium there will be no black spots. 

 What subsequently happens on these 

 spots is shown by a specimen which has 

 been in my possession since 1906. The 

 cambium over the discoloured area is 

 killed, and for a brief period no further 



growth can take place at that spot. 

 nt in a very short time new cambium 

 grows in from the healthy cambium 

 round the spot, and this proceeds to 

 cover the discoloured area with a new 

 growth of wood. At the same time, a 

 new bark is formed underneath the old 

 bark, with the result that the original 

 bark dies and scales off. This leaves a 

 small round scar, surrounded by the 

 slightly upturned edge of the original 

 bark. The process is exactly the same 

 as if a circular patch ot bark had been 

 cut out at first ; the subsequent healing 

 processes in that case, i.e., the growth of 

 new cambium, wood, and bark from the 

 edges of the wound, follow the same 

 course as in the case of the black spots, 

 The scar which is left in the latter case 

 usually resembles a branch scar, i.e., the 

 scar which forms where a branch has 

 been broken off close to the stem, and its 

 area is roughly equal to that of the 

 underlying black patch. Though the 

 death of the cambium at these spots 

 may make it advisable to cease tapping 

 for a time, there is practically no per- 

 manent injury to the tree. The black 

 spots are ultimately buried in the wood 

 and cannot do any further harm. It 

 was suggested that, as the vessels of the 

 wood are destroyed there, they would 

 hinder the flow of water, in the wood, 

 up the tree ; but as the patches are ex- 

 tremely thin, and their breadth bears 

 only an infinitely small ratio to the total 

 area of cross section of the tree, this 

 effect is entirely negligible, 



