BROWN ROT REMEDIES.

New Zealand Herald, Volume LXII, Issue 18945, 17 February 1925, Page 13

BROWN ROT REMEDIES.

PERCHLORIDE OF MERCURY. EXPERIMENTS AT HENDERSON. Dr. K. H. Makgill, who has carried out several interesting experiments afc the Garth orchard, Henderson, sends us the following regarding brown rot,: Soma mention having been made of the possible value, of perchloride of mercury as a remedy for brown rot, the writer decided to make some trials on peach trees at The Garth orchard, Henderson. As doubtless many orchardists have observed, not only are certain varieties of peaches moro susceptible to brown rot infection than others, but Individual trees appear to suffer more extensively than do the average trees of the same variety. Trees showing this special susceptibility were selected for the experiments, namely, Paragon peach; three eleven-year-old trees bearing heavy crops of fruit; Carmen peach; twelve eleven-year-old trees bearing light crops; Delicious apple; one three-year-old treo bearing a heavy crop of fruit for it„s size. The paragons and carmens were sprayed with a solution of perchloride of mercury having a strength of one part in five thousand parts of water on October 6, when twig-blight began to appear. This twig infection, though not severe, was not checked appreciably by the spray. On November 27, the spraying with a solution of the same strength as the first, was repeated, as infection was beginning to appear in the now well-developed fruit. Despite the wet season brown rot has not been very severe on this year's crop of peaches, but the sprayed trees, as in previous years, showed more infection than the average, and there was no reason to think that the mercuric salt had protected the. fruit or twigs. On the other hand after each spraying there was a very marked fall of the more matured leaves live or six days later. The younger leaves were less affected. The delicious variety was not sprayed til! January 17, when the fruit was well coloured and almost ripe. At this time a very severe infection appeared, both twigs and fruit being attacked. All infected fruits were pricked and the tree then sprayed with a solution of a strength of one part in six thousand. This failed to protect the remaining fruit and a week later almost every peach was destroyed by the rot. In this instance, again, there was, after a few days, a marked falling of the matured leaves" despite the fact that a weaker solution was used. As a further test, some of the peaches which had been picked on January 17, on account of infection. were wetted with the solution and set aside with some of the unwetted fruits. The perchloride slightly delayed the spread of the fungus as the wetted peaches still showed some sound flesh when the others were wholly destroyed. The delay was, however, only temporary. The results seem to indicate that, perchloride of mercury in solutions so w-eak as one part in six thousand causes injury to the foliage, and at a strength of one in five thousand fails to check brown rot in peaches.