Experiments with lime-sulphur and Bordeaux mixture sprays on Apple trees

Dullum, N.

Tidsskr. for Planteavl 37(4): 641-658


Accession: 013375917

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The following spray schedules were used against apple scab (Yenturia) at the Danish State Experiment Station during 1929 : (a) four applications of Bordeaux mixture (0.5 kg. copper sulfate and 1 kg. burnt lime per 1001. water); (b) one application of lime-sulphur (2 kg. lime-sulphur per 100 1. water) followed by three of Bordeaux mixture; (c) one of Bordeaux mixture followed by one of lime-sulphur and two of Bordeaux mixture; (d) in 1930 two applications of lime* sulphur followed by two of Bordeaux mixture were given instead of Bordeaux mixture only as in (a). In 1929 the percentages of perfectly clean fruit obtained under schedules (a), (b), and (c) were 14.9, ' 28.8, and 61.4 per cent., respectively, the corresponding figures for spray injury being 19.6, 14.3, and 1.8, respectively. In 1930 the percentages of perfect fruit were as follows: (b) 56, (c) 53.2, and (d) 68.9, the figures for spray injury being 2.7, 0.4, and 0.4, respectively. The fact that spray injury from the (b) and (c) schedules was more severe in 1929 than in 1930 is attributed to the unfavourable weather conditions (damp and cold) before the second application in the former season* At this critical period the fruit is highly sensitive to spray injury, which may cause considerable damage to certain varieties. In most cases this form of injury may be reduced within reasonable limits by the substitution of lime-sulphur for Bordeaux mixture in the two first summer applications.