September, 1910.] 



223 



Plant Sanitation. 



does not usually emerge until after the 

 decay of the fruit. 



Pests' Ordinance. 

 The ' Red Coconut Beetle ' has been 

 proclaimed, under the Pests' Ordinance, 

 in the Batticaloa district. All owners or 

 superintendents of coconut trees will be 

 required to take active measures against 

 the pest. 



MISCELLANEA: CHIEFLY 

 PATHOLOGICAL. 



Bv T. Petch, B.A., B.SC 



During the last two years, tea nur- 

 series have been instituted on a large 

 scale to supply the extensions which 

 are to take the place of the tea sup- 

 posed to have been damaged by the 

 Hevea planted among it. Within the 

 last few months several consignments 

 of dead seedlings have been sent in from 

 these nurseries, and in some cases they 

 are said to have been killed off in large 

 numbers.' Where the disease was caused 

 by fungi it appears to be the same in 

 all cases. The fungus attacks the seed- 

 ling at the collar and kills the bark 

 for about an inch above the ground 

 level. This effectually rings the seed- 

 lings and prevents the passage of any 

 food from the leaves to the roots. 

 Consequently the upper part of the 

 stem becomes thickened down to about 

 an inch from the ground, while the part 

 attacked by the fungus remains the 

 size it was when first attacked. The 

 edge of the thickened part is marked 

 by a well-defined swollen ring or callus. 

 Evidently the disease is not a rapid one, 

 for the plant is able almost to double 

 the diameter of the stem between the 

 time of attack and its death. So long 

 as the bark only is attacked, the plant 

 can live on the food manufactured by 

 the leaves, since the water it requires 

 travels up the wood. It dies when the 

 fungus has attacked the wood and 

 stopped the water supply. 



The disease is readily distinguished 

 by the thickened ring or callus, about 

 an inch above the collar. It appears to 

 be caused by a species of Fusarium. 

 Fungi of this class frequently live in 

 the soil and cause root diseases, generally 

 known as "wilt," in various plants. 



I have previously quoted in the " T.A" 

 a method which has been found effi- 

 cient in lowering the percentage of coni- 

 ferous seedlings killed by " damping off," 

 and which might be adopted with ad- 

 vantage in tea nurseries. The surface 

 of the seed bed was sprinkled with sand 



immediately after the seed had germin- 

 ated. Clean sand of rather coarse tex- 

 ture should be used, and applied as hot 

 as it can be handled, sprinkled over the 

 surface to a depth of about one-sixteenth 

 of an inch. 



Sterilisation of seed beds prior to use 

 is now being extensively adooted in the 

 United States of America, especially in 

 tobacco nurseries, the sterilisation being 

 effected by steam, or by surface firing, 

 or by formalin. The most effective steam 

 treatment is the inverted pan method, 

 in which a galvanised iron pan, 6 by 10 

 feet, and inches deep, is inverted over 

 the soil and the steam admitted under 

 pressure ; the pan has sharp edges which 

 are forced into the soil to prevent the 

 escape of steam. Surface firing is done 

 either by burning straw, etc., over the 

 bed for about an hour, or by heating 

 the surface soil to a depth of 6 inches 

 in a large iron pan. Iu the Formalin 

 treatment, the soil is thoroughly pul- 

 verised and then drenched with a for- 

 malin solution composed of one part of 

 commercial formalin to 150 or 200 parts 

 of water, from three-quarters to one 

 gallon being used for each square foot. 

 The solution is applied with a watering 

 can fitted with a rose, and distributed 

 as evenly as possible, so as to thoroughly 

 wet the soil to a depth of a foot. Iu 

 most cases it is necessary to put this 

 solution on in two or three applications, 

 as the soil will not take this quantity 

 of liquid immediately. The beds are 

 then covered with sacks or tarpaulin 

 to keep in the fumes for a day or so, 

 and then aired for a week before sow- 

 ing the seed. In some cases a lower 

 percentage germination has been re- 

 corded after the formalin treatment, 

 but a greater number of plants survived 

 than in the untreated bed. 



The amount of loss sustained in tea 

 nurseries scarcely justifies the adoption 

 of any of the above methods, though 

 simple surface firing is inexpensive and 

 should be tried where old nurseries 

 are used a second time. The sand treat- 

 ment should, however, be adopted. 



When nurseries are attacked by the 

 disease referred to above, all dead plants 

 should be upi ooted and burnt, and the 

 affected patches, i.e., the bare soil, 

 watered with a solution of carbolic acid 

 or Jeyes' fluid, one ounce to a gallon of 

 water. This has been found effective in 

 checking the disease. 



On a recent visit to a rubber plantation 

 (Hevea), I was shown an old tree which 

 always yielded thick latex. It happened 

 also to be decayed on one side near the 

 base. Examination proved that a large 



I 



