Sugar-cane disease.—

In the Kew Report for 1877 the history of the various insect pests which had proved so injurious to the sugarcane in Queensland was given in some detail.

During the past year a further correspondence has taken place upon the subject between this establishment and the Colonial Office, and a large series of specimens, carefully selected and sent over to this country in various preservative fluids by Mr. J. T. Staiger, F.L.S., Government Analytical Chemist, has been received for examination.

It appears now to be placed beyond question that the "rust" is due to the punctures of a minute acarus which exists upon the diseased cane in myriads. The exact scientific determination of this parasite would be, as I am informed by Mr. McLachlan, F.R.S., who has again most obligingly assisted us in this matter, a point requiring research of some difficulty. Mr. McLachlan states, however, that "the creature looks very like a Tyro- page 49 glyphus, but the habits do not altogether accord with those of that genus."

I am glad to state that the treatment with lime suggested by Dr. Bancroft, and that with carbolic acid recommended in the Kew Report for 1877 (p. 38), promises to be quite effectual in keeping this pest under control. Mr. MacKay reports to the Legislative Council of Queensland the result of experiments upon diseased canes subjected to the following treatment directed by Dr. Bancroft, which I quote here as likely to be efficacious in other Colonies:—"I. Clean the joints entirely from all trash as carefully as possible. 2. Immerse for twenty-four hours in water and carbolic acid at a temperature to bear the hand—1 lb. of acid to 50 gallons of water. 3. Make milk of lime—2 lbs. of lime to 1 gallon of water; immerse the plants in this for a few minutes. 4. Lift out and spread in the sun, turning them over to dry for one day before planting.

"Out of twenty-four different varieties of cane so treated, I am glad to say that all except two have come up sound and healthy, and the two are but lightly touched with the disease, a few spots only showing on the outer ends of the leaves, while the heart of the cane is quite green and healthy. The old stools or roots, from which were taken the plants so treated have all come up diseased; some of them died out, so that there can be no doubt that the mixture had its effect."

The pou blanc or pou à poche blanche referred to in pp. 38, 39, of Kew Report for 1877, is reported upon by Mr. McLachlan from the specimens sent to Kew during last year as "no doubt the same as the well-known Mauritian pest" (Icerya sacchari).