BROWN ROT OF THE LEMON.

Gisborne Times, Volume XXVIII, Issue 2745, 25 February 1910, Page 2

BROWN ROT OF THE LEMON.

ITS CAUSE AMD TREATMENT

(By “Centigrade,” in the Auckland “Star.”)

After his return from California, some three years ago, Mr. AA r . A. Boucher, tilio assistant-director of the orchard division, in reporting the results of his visit, wrote as follows: “I trust that Brown Rot (of the lemon) will never bo introduced into New Zealand, for, with a temperature such as has been proved in California, to he most favorable to the spread of the disease, prevailing in the colony for a much longer period, and with the general humidity of our atmosphere, the results would prove much more disastrous than they have been in California.” Unfortunately this dreaded scourge of che lemon growers on the Pacific slope has been introduced into the Dominion, which leads me to place such information in the hands of growers in this country as will enable them to recognise the disease when they see it, and take effective measures to stamp it out. The outbreaks, it is true, have been limited in number, and it is not likely that infection has spread, but it would bo well for growers to be in a position to deal with it should it make its appearance in their orchards. Writing on this disease, Air. Boucher says:—“Careful experiment has proved that it differs from most other parasitic fungi in this respect; that the soil becomes infested with the dormant spores not only on the surface but even to a depth of 2ft below the surface. These spores only require the necessary conditions of temperature and moisture to become active, and, so far, observation tends io show that in California a comparatively low temperature is most favorable to the germination and spread of the fungus, for it is during the winter and spring months that it Is most destructive, gradually disappearing again as the hot weather sets in. This- makes the disease all the more troublesome for the lemon grower and packer, for it is during the winter and spring months that the main crops’ are gathered, cured, and stored, to be sold when hot summer weather has created a demand for lemons at profitable prices. Observation has convinced the investigators of this disease that infection first occurs in lemons that have fallen to the ground. The infection then passes on to the lemons growing on the lower limbs near the ground, and gradually -extends higher : but it is not so much in the ore-hard as in the curing and packing houses that the most serious trouble occurs. At one time plain water was used for the washing of the lemon, until it was noticed that an unusually high percentage of lemons became infected in the uaok-ing-house after washing, and during the curing process, from which it was inferred that infection of healthy lemons took place during the process of washing. A number of experiments were carefully carried out to determine whether this was so or not, and it has been proved beyond all doubt that the inference was correct. The nextstep war. to) determine if it was possible to use, instead of plain water, a solution which, while destroying the germs of the fungus, in the washing tank, would leave the lemons uninjured. Several solutions were tried, those of Milestone (sulphate of copper) and permanganate of potash proving the most satisfactory. At the time of my visit to the AYhittier Packinghouse, in California, a solution of permanganate of potash in the proportion of lib to 8600 gallons of water was being used, with very satisfactory results.” PREVENTION AND TREATMENT.

Owing to the Brown Rot fungus hibernating in tlie soil, treatment in this direction is advocated for partial control. This may be accomplished by topdressing with J. to 41bs. sulphate of iron per tree (according to size) and lightly working into the soil. The application should bo made in Alny or early June, the rainfall that should follow will then make it available as a soil fungicide at the season of the year best adapted for controlling this disease, which thrives best in tiie cold moist weather experienced during the winter and early spring. All orange and lemon trees should also be sprayed in Mav or early June, with the Bordeaux Mixture (summer strength). As a further preventive against this disease, all fruit that has fallen to the ground should be gathered up and burnt, and, where practicable, infected fruit on the trees should be treated in the name way.