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THE AGRICULTURAL NEWS. 



April 15, 191L 



Even then the position may appear almost hopeless, ami 

 may only be saved by the intervention of some unfore- 

 seen external circmnstance. A good iihistration ofwhat 

 is meant is afforded by thi' outbreak of canker on the 

 chestnut, trees of tiie United States,* which only 

 attracrted attention in the year 1904. and has now 

 become a serious efiidomie, so far impossible to control. 



The disease is due to a wound fiinefus identified as 

 Diaporthe parasitica, Murrill, which lives in the inner 

 bark and cambium of the stem and all woody branches 

 of the chestnut. On limbs with smooth bark, the para- 

 site produces pale brown, sunken patches on the outer 

 bark. These become more or less thickly covered with 

 theyellow orange or reddish brown pustules of the fungus, 

 which break through the lenticels. In a damp atmos- 

 phere, the summer form of spore is extruded in a yellow 

 or greenish tendril, which becomes brown as it grows 

 older. The fungus grows so fast that it can completely 

 girdle a branch or small trunk, and thus kill it, in from 

 one to two years. Even large trunks are girdled as 

 a rule in four years 



The native American chi'stnut (Castanea den- 

 tate ) is the plant most subject to attack, but the 

 chinquapin {Ca.stanea puinikh), found native from 

 New Jersey to Florida, is also affected, while the 

 disease has been found, as well, on the Japanese chest- 

 nut {Castanea crenata.) Indeed, it is suggested that 

 imported plants of this foreign variety growing at Long 

 Island may well have served as the original source of 

 the disease. This point has not, however, been definitely 

 established. 



Instances of a disease which may have been this 

 were noted as early as 1902, but it was not until 1904 

 that it attracted attention; while it did not receive 

 full^investigation by a mycologist until 190.5. At that 

 time it had assumed serious proportions, and by 1909 

 over fifty per cint. of the trees within a radius of 

 twenty-five miles of New York had been completely 

 killed out. In addition to this, the disease had appc,-ir- 

 ed at various points in a number of states, and its ra])id 

 spread throughout the whole of the chestnut and 

 chinquapin-growing area of the United States appeared 

 imminent. Another very serious consideration was 

 that all the preventive measures tried within the area 

 of serious infection had failed absolutely to produce 

 any effect, though these had been cai-ried out on a fair- 

 ly extensive scale by trained men, and though support 

 was^given to the work by the United States Depart- 



' *A popular account of this disease is given in an article in 

 Mmiseij's MiKja-ine, for September IHIO, l)y B. Millard. 



ment of Agriculture. There was, moreover, no lack of 

 co-operation on the part of individuals, and no want of 

 money. Everything possible was done in many in- 

 stances, but absolutely no result was achieved. At the 

 present time, pr.ietically every tree within the inftcted 

 area is doomed, while the possibility of the complete 

 destruction of the native American chestnut and of the 

 chinquapin must be faced. It is needless to state that 

 this destruction represents a loss of economic products 

 aggregating in value several hundred million dollars. 



Metcalf and Collinsf, writing in 1909, took a less 

 gloomy view of the situation. They believed that the 

 spread of the disease could be restricted to the badly 

 infected area, if stringent measures were adopted with 

 this object. These measures included the most careful 

 inspection of all nursery stock, and the passing of very 

 thorough quarantine laws in all districts at that time 

 free from the disease. Furthermore, they stated that 

 the Department of Agriculture was ])repared to give all 

 possible assistance, particularly in educating the public 

 to recognize the disease, so that trees recently infected 

 in a previously healthy area could be removed, and 

 diseased parts burned. In such an area, where the 

 sources of reinfection were small, very careful excision 

 of di.seased parts might also prove effective. Even then, 

 they advised that constant vigilance would be neces- 

 sary. Spraying experiments with infected trees were 

 inconclusive. In the badly infected area, the complete 

 destruction of diseased trees was recommended as the 

 only course to be adopted, since the sources of reinfection 

 were so numerous as to preclude the possibility of suc- 

 cessful treatment. It was also suggested that, subse- 

 quently, )-eplanting with a partially immune variety, 

 such as the Japanese chestnut, or with a cross between 

 this and the native species, might be found possible, 

 though the Japanese tree does not yield such good nuts, 

 and does not a]ipear to be nearly as useful as lumber. 



No disease as destructive as this has ever yet been 

 experienced in the West Indies. The sugar industry was 

 fortunately saved by the discovery of compai-atively 

 immune varieties of cane, giving returns as good as, 

 or even better than, the variety destroyed. Neverthe- 

 less, the experience of the United States in the instance 

 quoted indicates that an outbreak of disease might 

 occur on any crop, which could not be checked by the 

 most skilful treatment or the most thorough co-opera- 

 tion, and that nothing would remain but to face the 

 consequences and to adopt the cultivation of some 

 different plant. 



tBulletin No. 141, Part V. Bureau nf Plant Inilu.stry, 

 United Slates Department of Agriculture. 



