1030 DISEASES XOT DUE TO I'ARxVSlTES, OR OF UKKXOWN ORIGIN 



Of the eighteen infected areas examined at the time the observations 

 were begun, eight appeared already cured, while in the ten others the infec- 

 tion was in full course of development. Five of these latter always con- 

 tinued active, two recovered and then became active again, and finally three 

 seemed fully healed at the end of the thirteenth month. 



With regard to the eight other areas, healthy in appearance, four re- 

 mained so for some time, in two the disease became active for some length 

 of time, and the last two, with the disease in active progress, continued in 

 this condition with extensive mortification of the tissues and abundant 

 secretion of gum. 



As will be seen, the development of the disease is verj' slow, with al- 

 ternating active and passive phases, which may be related to variations 

 in the degree of resistance of the plant attacked. When healing takes 

 place, the whole of the infection has not been eliminated through the 

 tissues of the host, but the pathological process appears to be arrested, 

 perhaps owing to the formation of new tissues which react with more 

 intensity against the disease. This is the period of greatest resistance of 

 the plant. Afterwards the continuation of the attacks, excessive production 

 of fruit, and other factors also, weaken and exhaust the plant, lowering its 

 resisting powers so that the infected area reverts to the active stage, and 

 the disease spreads to the surrounding tissues. 



The writer also carried out inoculation experiments with diseased tissue, 

 with cultures of Diplodia natalensis and with cultures of Phomopsis Cilri, 

 both on young orange trees in pots and on adult plantation trees. No defi- 

 nite conclusions can be drawn from the results obtained, as it was not poss- 

 ible in any case to produce the formation of the characteristic infected 

 areas. In the adult trees there was, it is true, a slight secretion of gum, with 

 partial mortification of the tissues, but it was only for a very short time, 

 and over very limited extents of the bark. The results are still more 

 negative in relation to young plants, which are undoubtedly endowed with 

 a higher degree of resistance. 



In the control experiments the best results were obtained by means of 

 cupric paste and carbolineum : 



(i) Cupric paste : solution of sulphate of copper and milk of lime in 

 equal parts ; mix thoroughl^^ then add lime until the mixture acquires 

 a certain consistency. The infected areas were cured in the proportion 

 of 64 %. 



(2) Carbolineum diluted in soap water : cures 60 %. 



Before applying the antiseptic, it is necessary to cut away unstinting- 

 ly all the infected wood and the adjacent parts, and not to confine oneself 

 to simply sci aping and removal of the bark, as is usually done in the majorit}' 

 of cases. 



804 - Citrus Barkrot in the Philippines. -/erbst c, 11. in Jiu- FhHippinc Aiincuituud 



Review, Vol. \'1I1, No. 2, pp. 'i5-y7, MaiiiUu, it>i5. 



The appearance of the disease known as " citrus barkrot " has caused 

 serious injury to the cultivation of citrus trees in the province of Batangas, 

 Philippine Islands. This disease having broken out with special severity 



