389 



Plant Sanitation, 



complete their transformations, emerging as moths which will disperse themselves 

 over the surrounding fields to give still greater trouble in the next generation. We 

 have had experience of what ' nettle-grubs ' can do, in the outbreak of 1899 which 

 created quite a scare in the Morawak Korale district. On that occasion TJiosea 

 recta was the culprit. The plague was only stayed by wholesale pruning and 

 burning. 



I have received a sample of Eri cocoons damaged by the larvse of a beetle,— 

 probably Dermestes vulpinus. They were part of a small parcel that had been 

 left exposed for several months. It should act, however, as a warning to silk 

 growers. Places where cocoons arc stored should be kept scrupulously clean. 

 The cocoons should not be exposed for long periods, but should be stitched up 

 in bags — preferably with a few lumps of napthalin. This beetle is a well known 

 pest of silkworm rearers in India. The larva will also attack and devour the 

 young worms. 



On some Castilloa plants sent to the Mycologist as attacked by root 

 fungus, the stems and branches were thickly infested by a scale insect) Aspidiotus 

 camelliae). The severity of the attack was probably due to the previously 

 unhealthy condition of the plants. 



An attempt has been made to destroy 'white-ant' nests by filling up the 

 shafts with a mixture of Paris green and sawdust. It was hoped that the 

 termites might eat the sawdust and be poisoned by the arsenic. The experiment 

 at first appeared to be successful. The insects, which were in full activity at the 

 time of application, disappeared, and no fresh work was observed for a space 

 of a fortnight. Then, in one night, a fresh series of shafts was opened up beside 

 the old deserted mounds, and the colony appeared to be as vigorous as ever. 

 The Carbon-bisulphide treatment remains the only satisfactory method of dealing 

 with this pest. 



THE PHYSIOLOGICAL EFFECTS OF BORDEAUX MIXTURE. 

 The physiological effects of Bordeaux mixture, R. Schander, (Landw, Jahrb., 

 33 (1904), No. 4-5, pp. 517-584 ; abs. in Jour. Bd. Agi\ London 12 (1905), No 7, pp. 413- 

 416). — After discussing the effect of copper on plants and the use of Bordeaux mixture 

 as a fungicide, the author gives an account of an extended series of experiments to 

 test the effect of Bordeaux mixture upon the host plant, wholly aside from its action 

 as a fungicide. 



The various theories regarding the supposed stinitdating effect of Bordeaux 

 mixture are reviewed, and the author rejects the idea of stimulating effect acting 

 through the epidermis of the leaves, stating that wherever the copper penetrates 

 the cuticle it acts injuriously upon the protoplasm of the leaf cells. The copper left 

 in the soil as a result of repeated sprayiugs cannot be other than injurious to the 

 plant, especially if present in appreciable quantity. 



The beneficial action of this fungicide is attributed to a number of factors, the 

 principal of which are the action of the lime, the repression of many insects by 

 spraying, and the influence of a thin coating of copper on the assimilation and trans- 

 piration of the plant. The latter of these factors is believed to be the most 

 important, and to it much space is given. The author considers that the thin coating 

 of copper hydrate on the leaves protects the chlorophyll against the injurious action 

 of too intense light and diminishes the transpiration of the leaves. No chemical 

 action takes place, the beneficial results being due solely to the physical action of the 

 thin layer of copper in reducing the intensity of light. As a practical application of 

 this theory, it is suggested that the strength of Bordeaux mixture might be 

 regulated to suit the character of the season, exposure, etc. 



