EFFECT OF FUNGICIDES ON McINTOSH APPLE TREES

Abstract

A 4-year test was carried out on the effect of sprays of captan, dodine, dichlone, and phenyl mercury acetate-captan on the performance of mature McIntosh apple trees. Increases in yield of the same trees over the average yield of the previous 5 years were 40, 31, 18 and 7 per cent, respectively, for captan, dodine, mercury-captan and dichlone. The fungicides had little effect on bloom, tree growth as measured by increase in trunk cross-section, and per cent fruit color. Mercury-captan produced larger apples indicating a thinning effect. The captan sprays produced the most attractive apples. With dichlone, fruit finish was rough. Dodine injured about 3 per cent of the apples in 2 years of the test.Dodine gave the best control of apple scab (Venturia inaequalis). Dichlone was very effective for early fruit scab but did not give good control of late or pin-point scab. Mercury gave excellent control of early scab. Captan allowed some late scab to develop.

PERFORMANCE OF McINTOSH APPLE TREES SPRAYED WITH CAPTAN, DODINE OR PRE-COVER AND COVER SPRAYS OF DICHLONE

“…""ot".t schedule caused a small amount of russeting, but this iniury did not oCcur with the captan-dichlone schedule. In 196d, 0.5/" of the ipples in the dodine plots showed the type of injury already described (3).…”

“…In the earlier test (3), fruir size with dodine ^t 0.340 kg/45+ l. of water varied from year to year, but in this test at 0.227 kg there was no significant difference between treatments in fruit size in "ry "y"rt. Fungicides-had no effect on fruit color in this or the earlier test.…”