ORCHARD LOSSES

New Zealand Herald, Volume LXXV, Issue 22955, 5 February 1938, Page 17

ORCHARD LOSSES

BEOWN KOT INFECTION NECTARINES AND PEACHES 70 PER CENT DESTROYED The havoc wrought in the orchards of the Auckland Province this season by brown rot is causing.grave concern. Since it was, first noticed in 1915, this disease has spread so rapidly that it threatens to become the most destructive enemy of the orchardist. According to latest estimates, it has destroyed 70 per cent of the nectarines and peaches grown this season for tho city markets. However, the cause of the disease is known and effective measures for its control have been devised. Ten days of humid heat last October while the trees were in blossom was the main cause of the exceptionally severe incidence of brown rot this year, said Mr. L. Paynter, orchard instructor for the Department of Agriculture in Auckland, yesterday. The sudden, onset of hot, moist weather at that time rapidly matured the spores of the fungus to their most harmful stage. In this condition they rose into" the air like smoke and infected the blossoms and finally the wood of the tree. Process oi Infection When the fruit developed, tho fungus settled on the skin, but could do no injury unless the skin got punctured. Especially when the fruit hud ripened during a prolonged spell of humid weather, as this season, the skin was easily punctured by insects or developed Aveak spots owing to pressure from rapid growth. The slightest injury even to picked fruit jvhich had reached market without trace of disease would allow the rot to develop in a few hours.

Orchards in the Auckland district were especially liable to attacks of brown rot, not only on account of the climate, but ajso because of the lack of attention to orchard sanitation, added Mr. Mummified fruit, which was usually infested with the fungus, was allowed to drop on the ground, so that spores accumulated a few inches below the surface and the soil became a large-scale incubator from which the matured spores emerged at blossom time to fill the air and broadcast the infection. Fungus bearing dead wood was also allowed to remain on trees until the disease was firmly established. Combating the Menace Mr. Paynter said he considered that brown rot could be reasonably controlled if proper precautions were taken. All mummified fruit and dead wood should be removed and destroyed to prevent ground iufection. When trees were about to blossom it was necessary to cultivate the soil to destroy the spores before they matured. Further danger of infection could be lessened by the use of surphur sprays during the blossom season and again when the fruit commenced to swell.