1918.] DISEASES OF PLANTS. 759 



ville, Cookstown, Lindsay, Bowmanville, and Ottawa. At present only 

 two points of infection are linown in Quebec, namely, at Oka and St. Anne de 

 Bellevue. 



Diseases of the leaves and stem of Hevea brasiliensis in the Malay Penin- 

 sula, R. M. Richards (Agr. Bui. Fed. Malay States, 5 (1917), No. 8-9, pp. S07- 

 317; Proc. Agr. Conf. Malaxja, 1 (1917), pp. U-54)-—^t is stated that though 

 the Para rubber tree has shown itself to be a particularly healthy plant in the 

 Malay Penin.sula, losses have occurred following improper or inadequate man- 

 agement. A species of Phytophthora which is said to cause an abnormal leaf 

 cast from July to September in Ceylon has not been observed here. The most 

 serious stem diseases discussed are those caused by Corticmm salmonicolor 

 (pink disease), Phytophthora faberi (bark canker), Phytophthora sp. (decay 

 of tapped areas), and Botryodiplodia theobronuE (die-back). The less harmful 

 troubles are due to Phyllosticta ramicola, GlCBOsponum albo-rubrum, Cyphella 

 heveoe (thread blight), and burs in the tapped areas. 



Clean clearing, pests, and disease, W. R. Shelton-Agab (Agr. Bui. Fed. 

 Malay States, 5 (1917), No. S-9, pp. 300-306; Proc. Agr. Conf. Malaya, 1 (1917), 

 pp. 37-43). — This is a di.scussion of rubber tree pests and diseases. The dis- 

 eases are classed as those that are fatal (requiring prevention) and those 

 amenable to treatment. The fatal class include such diseases as Fomes. Hy- 

 menoch^ete, Ustulina, and Poria, and the amenable class stem and bark diseases 

 such as Diplodia, pink disease, thread blight, and cankers. 



The author gives results of experience in the control of Termes gestroi, and 

 observations on the various seasons of fungus attack and on the control of 

 disease. 



Preventive measures ag-ainst black thread (Phytophthora faberi), H. C. 

 Pbatt (Agr. Bui. Fed. Malay States, 5 (1917), No. 5-6, pp. 180-182).— This is 

 a preliminary note on the causation, progress, and treatment of black thread of 

 rubber trees in Sumatra. 



The disease is favored by light rains and an overcast sky, but ceases in dry 

 weather. It is more prevalent on flat land and on densely shaded areas. The 

 attack is limited mainly to the first 20 in. of basal bark. The results of tests 

 with fungicides are tabulated. Daily disinfection is considered necessary. For 

 this purpose izal is not so satisfactory as carbolineum. A 20 per cent strength 

 izal burns the delicate tissue of the tapped surface, but a 10 per cent strength 

 has proved quite satisfactory. 



Note on the development of chromogenic org'anisms in dry raw rubber 

 allowed to become damp, B. J. Eaton (Agr. Bui. Fed. Malay States, 5 (1917), 

 No. 5-6, pp. 177-179). — The author has experimented in order to ascertain 

 whether or not sheet rubber may develop spot diseases after being shipped in a 

 perfectly dry and clean condition, owing to splashing or absorption of water. 

 He claims to have found that such a change is possible, and that consequently 

 carelessness or accidents at the shipping port may in this way injure sheet 

 rubber in transit It is stated that dry well-smoked sheet rubber may develop 

 mildew, while low-grade rubber may ferment and become tacky. Thickness 

 also appears to be a factor in susceptibility. 



It appears that the presence of air Is necessary for the development of the 

 organisms or for the formation of pigments. Excessive moisture may retard 

 or prevent the formation of the pigments which may develop after the mois- 

 ture content is somewhat reduced, or it may be removed so quickly that the 

 formation of the pigment may be prevented. These organisms may act on the 

 protein or its decomposition products and destroy the accelerating agent, or may 

 produce furthe;* cleavage. 



