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Abstract
Spray adjuvants alone and combined with benomyl in single and multiple applications were tested for their influence on net photosynthesis (Pn) and development of apple scab caused by Venturia inaequalis (Cke.) Wint. on trees of apple (Malus domestica Borkh.) grown in the greenhouse. Triton CS-7 increased and ×-100 and 70 second oil deceeased Pn. Nu Film 17, Triton B-1956, Regulaid and ×-77 when combined with benomyl had no influence on Pn. Addition of Biofilm, Nu Film 17 or 70 second oil to benomyl did not improve apple scab control. Three sprays of benomyl plus oil decreased Pn of fully expanded leaves, and 5 sprays decreased Pn of both expanded and newly expanding leaves with the latter showing the greatest reduction.
Abstract
The lowest survival temperatures were determined quantitatively for dormant terminal buds of ‘Newtown’, ‘Golden Delicious’ and ‘Rome Beauty’ apples (Malus domestica Borkh.) that were either healthy or infected with powdery mildew (Podosphaera leucotricha (Ell. & Ev) Salm.). Irrespective of cultivar, all mildew-infected buds were more susceptible to freezing injury than healthy buds. Survival of mildew-infected buds at about −22°C was similar to survival of healthy buds at −26°. Field data on ‘Jonathan’ showed that terminal mildew infection following winters warmer than −22° was 26.5%, but was only 4.0% following winters −24° or colder.
Abstract
Stem-end decay caused by several several fungi was less in ‘d’Anjou’ pears (Pyrus communis L.) stored in a low O2 (1% O2 + 0.05% CO2, −1.1°C) room than in ones stored in −1.1° air. Ethylene concentration in the low O2 room was about 120 times higher than in the air room hut did not cause fruit softening or peel degreening after 8 months storage at −1. 1°. The 1% O2-stored fruit softened faster than the air-stored fruit during ripening and also ripened with better dessert quality. Juice binding capacity of ripened fruit pulp from 1 % O2-stored pears was greater than that of air-stored fruit; the texture of ripe fruit from the 1% O2 storage was buttery and juicy while that of air-stored fruit was coarse and dry. The high performance liquid chromatographic analysis revealed that organic acids in 1% O2-stored and air-stored fruits were qualitatively identical.
Abstract
Spray treatment a single dormant application of high concentrations of anionic (Triton CS7) and nonionic (Triton N57 and Triton X100) surfactants caused up to 5 days delay in bud break in apple (Malus domestica Borkh.), but had less effect on grape (Vitis spp.) and peach (Prunus persica (L.) Batsch) and none on pear (Pyrus spp.). Surfactants tended to extend the bud break period but were frequently lethal to buds, particularly at concentrations of 3% and 5% active ingredient. In field studies, surfactants delayed the early stages of flower bud development but not bloom of apple or peach and did not control apple scab caused by Venturia inaequalis (Cke.) wint. or powdery mildew caused by Podosphaera leucotricha (Ell & Ev.) Salm.
Abstract
Chlorogenic acid and arbutin reduced spore germination of Penicillium expansum Lk. ex Thom, and mycelial growth of Mucor piriformis Fischer. Arbutin decreased growth of Botrytis cinerea Per ex Fr. However, chlorogenic acid increased both germination and growth of B. cinerea.
Abstract
Spring overtree misting using greenhouse mist nozzles was tested for effects on bloom delay, incidence of disease, European red mite populations, fruit size, maturity, fruit russeting and tree survival of ‘Golden Delicious’ apple (Malus domestica Borkh.) on Mailing 9 rootstock. Bloom delay of 9 and 8 days was observed in misted trees in 1975 and 1976, respectively, Apple scab was controlled with standard fungicide spray programs, but fireblight was severe in 1975 on misted trees. European red mite (Panonychus ulmi Koch.) egg hatch was delayed on misted trees but post treatment populations were not affected. Phytotoxicity occurred on calyx and foliar tissue in misted trees in 1975. Fruit set and yield were reduced in misted trees in both years. Fruit size in misted treatments in 1975 was reduced through late July, but was comparable at harvest. In 1976, misted fruit size was reduced. Fruit color, soluble solids and firmness tests indicated maturity was delayed by mist. Fruit russeting in spring misted treatments was reduced. Substantial tree losses occurred in misted treatments in 1975.