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  • Author or Editor: C. G. Lyons Jr. x
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Abstract

Strong winds during periods of heavy rainfall in August and Septem ber 1979 either blew over or loosened m any 3- to 5-year-old peach (Prunus persica(L.) Batsch) trees in Northern Virginia. In the spring of 1980, many of these trees grew poorly, failed to produce normal leaves, and in some cases, died.

Open Access

Abstract

Limb applications of 5% or 10% alkaryl polyoxyethylene alcohols (X-77 or X- 45) caused flower bud removal when applied to peach trees [Prunus persica (L.) Batsch] with a hand pump sprayer from first pink to 90% bloom. Applications made in late pink or bloom period caused a greater reduction in fruit set than earlier treatments. Applications made at 90% bloom caused some phytotoxicity to the tips of the first small leaves but did not affect the growth of the terminal vegetative primorida or of larger leaves produced on later terminals. Thinning appeared to be commercially acceptable when applied between 30% and 90% bloom. Fruit size at harvest was greater than the unthinned control. Airblast applications of 10% X-77 on the ‘Loring’ cultivar reduced fruit set about 40%.

Open Access

Abstract

Airblast applications of ammonium nitrate, ammonium thiosulfate, an oxylated alcohol surfactant (SN-50), or 7-oxabicyclo-(2,2,1) heptane-2,3-dicarboxylic acid (endothall) to peaches [Prunus persica (L.) Batsch] in bloom reduced fruit set and increased fruit size on several cultivars. Foliage injury was minimal when applied at bloom. Applications of these chemicals 6 days post-bloom to ‘Redhaven’ trees caused unacceptable foliage injury and did not cause fruit abscission. Several other surfactants and fertilizers were found to have caustic action in laboratory trials, but fruit set on ‘Redhaven’ was not reduced in field airblast trials.

Open Access

Abstract

Airblast application of fertilizers, desiccating herbicides, or surfactants reduced fruit set and increased fruit size of ‘Redhaven’ peach [Prunus persica (L.) Batch]. The addition of the surfactant, aikylaryl polyoxyethylene glyco phosphate ester (Spray Aide), to ammonium thiosulfate (ATS) at rates from 0 ml/liter to 5 ml/liter did not increase thinning. When rates of ATS/ha remained constant, water volumes from 2338 Iiter/ha to 420 liter/ha did not affect thinning. Forty-six percent to 62% more flower buds developed on twigs from chemically thinned trees than on hand thinned trees. Most of this flower bud increase was on the 5 basipetal nodes of current season shoots. Treatment of the stigma, petals + anthers, peduncle, or calyx with ATS reduced fruit-set. Necrotic regions in the peduncle of some flowers could be seen under a microscope 48 hr after treatment. Flowers sprayed with DuPont WK or NH4NO3 + X-77, plus methylene blue (added as a tracer) had blue dye in the veins of the calyx, pedicle, and peduncle of some flowers after 24 hr.

Open Access

Abstract

High-budded trees of nectarine [Prunus persica (L.) Batsch] that were mechanically planted with the bud union as a depth guide resulted in poorer growth when compared to those planted with the crown roots within 5 cm of the surface. Deeper-planted trees had smaller leaves and less total increase in trunk cross-sectional area, and were more susceptible to the formation of air pockets around their bases.

Open Access

Abstract

Shallow-planted trees of ‘Delicious’ apple (Malus domestica Borkh.) on Mailing (M) 7A and Mailing Merton (MM) 111 rootstock had increased frequency of burr-knots and were less likely to be loosened in the soil by wind than were deep-planted trees. Deep-planted trees on seedling roots were more likely to be loosened by handshaking; however, burrknots were not a problem. Leaf size was larger significantly for all shallow-planted trees. Growth differences were related to soil type, rootstock, and planting depth.

Open Access

Abstract

Vydate (oxamyl; methyl N’, N’ dimethyl-N[methylcarbamoyl) oxy]-l-thioox-amimidate) and Sevin (carbaryl; 1 napthyl-N-methyl carbamate) did not give significant thinning of ‘Starkrimson Delicious’ apples (Malus domestica Borkh.) when applied as airblast treatments in 3 years of tests. Neither multiple applications nor the addition of a 70-sec superior spray oil gave significant thinning compared to untreated controls. Airblast treatments of these materials on ‘Golden Delicious’ were effective but were inadequate to reduce crop load to the desired level. The data suggest that Vydate and Sevin are inadequate as thinners if applied with airblast machines. Ethephon treatments caused erratic responses at the rates and timings used. Sevin applied for thinning caused an increase of European red mites and their eggs.

Open Access

Abstract

Airblast spray applications of ammonium thiosulfate (ATS) were made to individual peach trees in a single row or to small blocks 5 rows wide and 10 trees long to determine if drift from adjacent rows increased bloom thinning. Increased flower thinning was found in the center row of the 5-row-wide-block when compared by regression analysis to applications made to trees in a single row. Ethylene-bisdithio-carbamate (Zineb 78WP) was used to determine the amount of spray deposit contributed by airblast sprays to adjacent rows. Airblast spraying of peach trees in full bloom contributed chemical deposits to peach flowers in the adjacent row equal to 43% of that deposited on the sprayed row, and 26% to the second row removed.

Open Access

Abstract

Foliar copper deposits varied by a factor of 5-fold when copper was applied with an airblast sprayer at a rate of 935 liters/ha (100 gallons/acre) to trees of apple (Malus domestica Borkh.). Higher deposits were recorded as tree size decreased. Chemical deposit was related inversely to percentage of light penetration through the canopy.

Open Access

Abstract

Shading of nectarine [Prunus persica (L.) Batsch] scaffold limbs 45-58 days after full bloom caused seed discoloration and fruit abscission. Shading of peach [Prunus persica (L.) Batsch] scaffold limbs from 31-41 days after full bloom caused greater fruit adscisson than shading from 11-21 or 21-31 days after bloom. The photosynthetic inhibitor, 3-tert-butyl-5-chloro-6-methyluracil (terbacil), applied to whole trees 35 days after full bloom induced fruit abscission. Terbacil at 500 ppm or higher caused excessive thinning. Fruit size was larger than hand thinned fruit, since overthinning occurred. Fruit color, soluble solids, and firmness of fruit from the 500 ppm treated trees were similar to fruit from hand thinned trees. No leaves abscissed, but marginal chlorosis occurred on less than 30% of the leaves at harvest. Flower bud numbers per cm of terminal length were similar to the hand thinned trees, but much greater than unthinned trees. Residue analysis of fruit at harvest from the 500 ppm terbacil treatment revealed 0.07 ppm in the fruit.

Open Access