114 



THEAGRICULTURAL SEWS. 



April 20, 1916. 



after the Franco- Piussiau war. By using hardy American 

 varieties of the vine as stocks, this pest has been 

 controlled to a great extent. 



In the West Indies the sugar-cane cultivation 

 towards the end of the last century seemed doomed, 

 owing to the wide-spread infestation of the Bourbon 

 cane with the fun,gus of red rot, the so-called rind 

 disease. Here again the substitution of canes of a more 

 hardy type has replaced the sugar-cane cultivation in 

 these islands on a tirm basis. The strains at first 

 available- were much inferior to the Bourbon, but the 

 widening of the area of selection by raising large 

 numbers of seedlings has enablerl types to be found 

 which, if not equal to the Bourbon in popular estimation, 

 at least give very satisfactory returns. Somewhat 

 similar in effect, but differing in cau.se, is the destruc- 

 tive disease of siigar-cane known in Java as 'sereh'. 

 Whereas in the case of the Bourbon cane the epidemic 

 is known to have been caused by a specific fungus 

 {Colletolrichv.m falcatum), with regard to the 'sereh' 

 disease, in spite of most patient investigation, the 

 actual cause still remains unknown. Though it 

 has not been definitely proved to be infectious 

 from cane to cane, it yet spread with great rapidity 

 over the lowlands of Java, and, once established, persists 

 in spite of the importation of planting material from 

 outside its range. But the fact that such material 

 takes a few years to become seriously infested has 

 enabled the industry to continue on the basis of a 

 carefully organized system, by which cuttings from 

 canes grown in nurseries in the hills, where the disease 

 does not occur, .are used to plant the fields in the 

 lower lands. A similar epidemic is just now causing 

 alann among sugar-cane growers in Porto Rico. 



Some of these plant epidemics, as was noticed 

 above, occur from the sudden multiplication of organ- 

 isms previously existing in the locality. Others, how- 

 ever, and these perhaps the most difficult to deal with, 

 have been carelessly introduced, and have usually 

 become well established befor-; the menace of their 

 prf^ence was realized. 



A striking instance of this is the case of 

 the gypsy "I'Jth '" ''h'^ ^'6^^' England States. This 

 pest is a native of Europe, where, pnjbably on account 

 of the pre-senci- of natural enemies sufiicient to keep it 

 in check, its ravages .are negligible. A distinguished 

 eotomologist at the University of Harvard had 

 ^>Die specimens of this moth sent him from Kurope. 

 ij^ue of the moths escaped, and could not be recap- 

 turefl. In a few years time they had so multiplied 

 that it seemed as if the larger portion "f the forest 



trees ot the neighbouring States would be des- 

 troyed by the larvae. Hundreds of thousands of 

 dollars have bein and are being spent by the 

 Federal Government and by the (Governments of 

 the various States to control this epidemic pe.st, and it 

 is only kept in check by ceasele.ss vigilance. 



I'erhaps a still more remarkable case of damage 

 caused to forest trees by an epidemic is that of 

 the chestnut bark disease in the eastern Ignited States, 

 The cultivation ot chestnut trees has been carried on 

 for centuries by the Chinese for the sake of the nuts 

 The chestnut trees in China are attacked by a disease" 

 which is somewhat similar in appearance to the canker 

 that occurs in Europe and America on apple trees. 

 The Chinese, however, have never noticed it as 

 especially harmful, nor is it conspicuous enough 

 to have attracted the attention ot travellers. This 

 disease, now known in America as the chestnut bark 

 disease, is caused by the funguS Endothia parasitica. 

 It seems to have been unwittingly introduced into 

 the United States somewhere about the year 1890, ami 

 to have been «Iistributed to various points on chestnut; 

 nursery stock. The parasite found the American 

 sweet chestnut an attractive host, and has spread and 

 assumed a virulent character which, as far as is 

 known, is totally unparallelrd in its native habitat. 

 The disease is nowgenerally distributed on native 

 chestnut trees from New Hampshire in the north 

 to Virginia in the south. It is difficult to estimate 

 the loss which the above epidemic has caused. In 

 1912 the total loss was said to be about SoO,000,000. 

 The disease has killed all the chestnut trees in the 

 localities whtre it has been present long enough. Xo 

 case is reported .if a tree or grove once attacked having 

 been saved by any method. No method has yet been 

 discovered to control it. It would seein that all 

 chestnut tre^s in the eastern Stati's are doomed. Prob- 

 ably the che-itnut forests will be to some extent 

 re-i'Stablished by the breeding and propagation of 

 immune or resistant varieties. 



Another introduced pest into the fnited States is 

 Die white tly (Ale'urotUs citri), which has been 

 a menace to citrus cultivation in Florida and California. 

 The story of the meivsures taken to combat this pest 

 was told in the Agricultural Ni'ws, Vol. .\VI, p. o8:}. 

 A still more serious ilisease, which is threatening in an 

 epidemie form the prosperity of the citrus industiy, is 

 the citrus canker, d\ie to a bacterium introduced from 

 the Far East. Were the only remedy that seems to be 

 of avail is the drastic one ot absolutely destroying by 

 fire any trees with the least trace of the disease. 



