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  • Author or Editor: R. P. Covey x
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Abstract

‘Golden Delicious’ apple trees (Malus domestica Borkh.) growing in gravel culture required a minimum of 0.088% P in mature leaves for continued shoot growth. Immature leaves were found to be a better index of P nutrition than mature leaves. A correlation of r = 0.959 was obtained between growth as indicated by increase in trunk circumference and percentage P over the range of 0.05 to 0.35% P in immature leaves and r = 0.84 over the range 0.055 to 0.188% P for mature leaves.

Open Access

Abstract

Zinc fertilization (5 ppm) of apple seedlings (Malus sp.) grown in chloropicrin-fumigated soil increased shoot weight slightly and Zn concentration significantly after 70 days. Inoculation of seedling with vesicular-arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, or G. fasciculatus (Thaxter) Gerd. & Trappe without Zn fertilization increased shoot weight but not plant Zn concentration. Zinc fertilization plus mycorrhizal inoculation increased shoot weight and Zn concentration. Total Zn uptake was increased 7 fold by combined Zn fertilization and G. fasciculatus inoculation. G. mosseae was slightly less effective than G. fasciculatus in promoting seedling growth.

Open Access
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Abstract

Two field experiments were conducted to evaluate the influence of rootstock (seedling, M.26, MM.106), soil fumigation (metam-sodium, methyl bromide), and planting hole substrate (original soil, non-orchard soil, organic mix) on early growth of ‘Granny Smith’ apple trees (Malus domestica Borkh.) in a Quincy sand. Application of soil fumigants in the fall before tree planting the next spring or replacement of the original soil with non-orchard planting hole substrates having greater water-holding capacity and nutrient status significantly improved tree growth. Combination of fumigation and soil replacement had a synergistic positive effect on tree growth. The size-controlling characteristics of the rootstocks were evident in the non-orchard soil and organic mix treatments, but not when the trees were planted in the original orchard soil. Chemical name used: sodium N-methyldithiocarbamate (metam-sodium).

Open Access

Abstract

Symptoms of 2,4-D injury were observed on apple and pear trees following commercial herbicide application. This was thought to be due to absorption from the soil. 2,4-D was found to move easily into orchard soils when applied to soil columns and irrigated. Concentrations in excess of 0.5 ppm occurred. Apple trees were damaged by this concentration. 2,4-D is readily inactivated in moist soil or on a moist soil surface. Less than one week is required for deactivation. Although field observations always indicated injury occurred when both 2,4-D and paraquat were applied together, laboratory and greenhouse studies indicated that paraquat did not increase 2,4-D movement or slow its deactivation.

Open Access

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.

Open Access

Abstract

The growth of apple seedlings (Malus domestica Brokh.) is negatively correlated with soil arsenic and zero growth occurs at about 450 ppm total arsenic. Soil arsenic concentrations less than 150 ppm, which are frequently found in orchard soils, contribute less to the replant problem than biological factors. Growth of apple trees was increased 50% or more by preplant soil fumigation with methyl bromide or trichloronitromethane (chloropicrin) in 87.5% of the trials in 17 apple orchard soils tested. Non-specific plant pathogens in orchard soils attack cereals as well as apple seedlings, but apple orchard soils also contain an entity that specifically affects apples. This is probably the same unknown entity that is responsible for specific apple replant disease in Europe, Australia, and elsewhere.

Open Access

Abstract

“Dead spur” is a disorder which affects the spurs of ‘Delicious’ apple (Malus domestica Borkh.). The spurs die on 2-year-old and older sections of the tree. A survey of ‘Delicious’ sports showed Royal Red, Earlistripe and Sharp have a higher incidence of dead spur than the other sports. There was no relationship of the disorder to rootstock, but the interstock Ottawa 292 increased the severity of dead spur.

Open Access

Abstract

Growth of seedlings of apple (Malus sp.) and pear (Pyrus sp.) was significantly greater in 14 out of 19 chloropicrin-fumigated-pear sous as compared to the nonfumigated check soils. Increase in seedling growth in the 14 soils varied from 50% to more than 400% with both apple and pear. The lack of response of pear and apple seedlings to soil fumigation in 5 soils may be due to low soil pH, high soil arsenic levels and high soil phosphorous fixing capacity. Counts of plant parasitic nematodes (primarily Pratylenchus spp.) were generally low in all but one soil.

Open Access

Abstract

Incorporation of phosphorous into fumigated soil at planting increased the height, dry weight, and P level in seedlings of apple (Malus domestica Borkh.). Non-mycorrhizal plants exhibited a twenty-fivefold growth response to P and obtained maximum size at 200 mg additional P/kg soil. Mycorrhizal plants exhibited less growth response to P (3.2 × increase) but had greater maximum growth (78.0 vs. 67.9 cm) than nonmycorrhizal plants. Maximum growth of mycorrhizal plants occurred with the addition of 100-200 mg P/kg soil.

Open Access

Abstract

Apple trees (Malus domestica Borkh.) grown in soil fumigated with methyl bromide showed a significant increase in growth as measured by trunk circumference. The increase in trunk circumference from fumigation varied from 33 to 49% after 6 to 8 years. Fruit production increased from 2- to 4-fold during the same period. Soil pH, soil arsenic and nematode counts were not considered to be major factors in the lack of growth and fruit production for trees grown in unfumigated soil.

Open Access