Disease management in Hawke's Bay apple orchards converting to organic production
Disease control achieved by 10 apple growers converting to organics during the 1997-98 and 1998-99 seasons is reported. Two orchards experienced black spot outbreaks each season, while the remainder averaged 0.5% spotted fruit. Powdery mildew was severe in 1997-98 but acceptable in 1998-99. Fruit rots after cool-storage averaged 0-11% for different varieties in 1997-98 and 0-30% in 1998-99. Fungicide applications averaged 11.6 in 1997-98 and 18.4 in 1998-99, which was a net increase in chemical use. Copper use was below 3 kg/ha/year. The most-used spray programme was a green-tip copper, three pre-bloom lime-sulphurs, sulphur/copper bloom sprays and sulphur or sulphur/ copper sprays thereafter. Results showed that acceptable disease control is achievable in "organic" orchards, but summer and core rots remain a concern.