October, 1910.] 



315 



Plant Sanitation. 



ing this amount of blistered leaf was 

 Bs, 657. At Jukvar the loss this year is 

 about 30 maunds of tea. These are 

 average examples of loss, but some 

 gardens have lost much more and others 

 much less. No account has been taken 

 of the damage due to lowering of tone 

 and weakening of the bushes. 



How the blight came to the tea plant 

 in this district is not definitely known. 

 It may have been imported into the 

 district from Assam or have come from 

 the jungle. Every year small quantities 

 of seed are imported into the Dibrugarh 

 and the surrounding tea-area where some 

 of the best tea seed is grown. It is 

 possible that the blight may have been 

 introduced with the seed or the earth 

 in which it is usually packed. Though 

 many spotted leaves from weeds and 

 trees among the tea bushes and on the 

 edge of the jungle were examined, none 

 were found to have been caused by the 

 same fungus (Exobasidium iwxans) as 

 causes blister blight on tea. On Kharaui 

 (Symplocos Thecefolia) a very similar 

 blister occurs caused by an Exobasidium 

 nearly related tc that on tea. There 

 are microscopic differences between the 

 two fungi and probably they are 

 different species. Preliminary inocul- 

 ations made to see if spores from the 

 Kharani blister would attack tea, were 

 not successful. 



Methods that have been tried for 

 keeping the disease in check resolve 

 themselves into (1) picking off diseased 

 material, (2) pruning, and (3) spraying 

 with fungicides. The first and second 

 aim at lessening the spread of the disease 

 by removing, and destroying the mate- 

 rial containing the spores of the parasite 

 which cause new infection. The third 

 aims at killing the fungus and at pre- 

 venting the growth of spores that may 

 tall on the sprayed leaves, 



On Dooteriah Division ever since the 

 blight was first seen the Manager had 

 the blistered leaves picked off destroyed, 

 and it was hoped that this would have 

 been enough to keep the disease in 

 check. The coolies who picked the 

 blistered leaves were not allowed to 



Eick leaf for tea and the baskets were 

 ept separate. The diseased leaf was 

 burned in the factory furnace when the 

 coolies happened to be within reach, 

 otherwise it was buried in trenches. 

 This saved the risk of infection while 

 the baskets were being carried long dis- 

 tances through the tea or sent down 

 the wire rope. The tea near these 

 trenches did not become more affected 

 by the blight than anywhere else. In 

 all 620 maunds of blistored leaves were 



destroyed this season, yet in September 

 the blight spread more rapidly than it 

 could be dealt with and got beycnd the 

 available labour for treating it in this 

 way. Thus, though the blight was kept 

 in check for a time the result was not 

 satisfactory. 



The Manager of Pussimbing tried to 

 check the blight by close picking. 

 All blistered leaves, young shoots and 

 sprouting buds were removed whether 

 affected with blister blight or not, and 

 then the coolies got round the garden 

 once every eight to ten days- They 

 took a bud and two leaves as usual but 

 removed most of the third leaf as well. 

 The idea was to take all the leaves on 

 which the blight grows before it had 

 time to bring its new spores to maturity. 

 By thus continually preventing the pro- 

 duction of spores, it was hoped that, 

 after a time the young shoots would 

 grow up free from blight. So far as the 

 absence of blister blight is concerned, 

 the result on Pussimbing, and especially 

 on Pubong, was very satisfactory. In 

 July, blight was prevalent on both 

 gardens and severe on part of the latter, 

 but by the middle of September there 

 was not much blight on either. 



The drawback planters urge against 

 this method is that it takes a strong 

 labour force to pick over a garden in 

 the tima and in most gardens in the 

 Darjeeling district at the present time 

 this is said not to be available in the 

 busy season. If a garden was in vigorous 

 health and flushing well, it could not be 

 overtaken in time, for even with the 

 ordinary way of picking it is sometimes 

 v difficult to get round. Then, again, this 

 method of close picking is practicable 

 only in the latter part of the season 

 after good growth has been made in the 

 earlier part of the year, but would be 

 dangerous after a period of unfavour- 

 able growth at the opening of the grow- 

 ing season. Some modification in the 

 style of leaf picking along the lines of 

 this method seems, however, the most 

 likely way of doing with the blight in 

 the rains, and the details will have to 

 be worked out by a practical man on 

 the infected gardens. 



Spraying.— It was demonstrated at 

 Tukvar in a number of small experi- 

 ments, that spraying with Bordeaux 

 mixture kills the spores and filaments 

 of the fungus where the liquid comes in 

 contact with them. It also does much 

 good on young green twigs affected with 

 blight. In the usual course of the 

 disease when a twig becomes " blistered" 

 the swelling extends gradually round 

 and through the twig, and ultimately 

 causes the part above the spot to 



