Apple scab is the most economically important disease of apples in the world. Fungal scab infections cause cracks in apples. Infected leaves fall off the tree which can result in reduced tree growth for one to three years. Apple growers worldwide have been spraying fungicides for over 100 years to control scab. And in New Zealand…..
“New Zealand apple industry spray programmes for control of black spot (scab), caused by Venturia inaequalis, typically use 16-20 fungicide applications each season, including dodine and fungicides in the demethylation inhibitor (DMI) group. These fungicides are particularly important to orchardists because their systemic activity prevents black spot development when they are applied after infection has occurred.”
Authors: R.M. Beresford1, P.J. Wright2, P.N. Wood3 and N.M. Park3
Affiliation: 1The New Zealand Institute for Plant & Food Research, Auckland, New Zealand; 2The New Zealand Institute for Plant & Food Research, Pukekohe, New Zealand; 3The New Zealand Institute for Plant & Food Research, Hawke’s Bay Centre, Hastings, New Zealand.
Title: Sensitivity of Venturia inaequalis to myclobutanil, penconazole and dodine in relation to fungicide use in Hawke’s Bay apple orchard.
Publication: New Zealand Plant Protection. 2012. 65:106-113.
Organic apple production in the Eastern US is very difficult because of the presence of insects and disease pests. The moist climate is perfect for mold, rots and other fungi. Recently, a couple in New Hampshire felled their organic apple trees. They explained their reasons in an article for the Concord Monitor.
“In 10 years of organic apple production we had yet to turn a profit. Additionally, the trees in our organic block were the least healthy on the farm and were a source of pestilence for our other apple trees. After harvest, the trees were cut down and will serve their last purpose: keeping us warm next winter.”
“Apple scab – which appears with the springtime rain in New England – was the toughest problem. In an organic orchard sulfur and copper are the pesticides used to combat scab. Trouble is, they wash off and are at best poor fungicides. At a recommended rate of 12 pounds per acre and their propensity to was off, I was spraying this block every time it rained, over and over again.”
“Last June we came to the realization that the organic block was not only a net financial drain on the farm but, more important, an environmental drain. I was spraying it more, using more fuel, more pounds of pesticides, more precious time, and it was serving as the source of pestilence for the rest of the farm.”
Author: Chuck Souther
Headline: Organic apple farming just didn’t work: Trees became a source of pestilence
Publication: New Hampshire Concord Monitor. 10 January 2010.