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- Author or Editor: C.G. Lyons x
- HortScience x
The state of Texas suffers from a lack of chilling one out of every five years. Reduced yield in temperature fruit crops such as peach (Prunus persica) is one detrimental effect associated withinadequate chilling. Field trials with hydrogen cyanamide (Dormex) have demonstrated that a one to two percent solution applied six weeks prior to bloom will substitute for inadequate chilling of up to 150 hours. Field trials with this chemical have provided further insight into some other possible benefits associated with its use such as: increased marketable yields of fruit crops, enhanced fruit size, and an earlier more concentrated harvest. Advantages noted by the use of this product include a possible earlier crop and reduced labor costs.
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.
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%.
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.
Own-rooted `Redhaven' and `Cresthaven' peach [Prunus persica (L.) Batsch.] trees and `Redhaven' and `Cresthaven' on Lovell seedling rootstock were planted in fumigated and nonfumigated areas of a site where peach trees previously displayed peach stem-pitting (PSP) symptoms. The combined incidence of stem pitting of the `Redhaven' and `Cresthaven' peach trees was 16% on nonfumigated soil in the 10 years of the study. The combined stem-pitting incidence of own-rooted trees (9.1%) was significantly lower than on Lovell roots (22.1%). Incidence of PSP in the adjacent fumigated areas was relatively low (1% Lovell and 4% own-rooted) and, therefore, precluded a comparison of own-rooted and Lovell-rooted trees. Within affected sections of rows, 67% of the `Cresthaven'/Lovell and 64% of the `Redhaven'/Lovell trees had PSP symptoms, but only 25% of own-rooted `Cresthaven' and 18.8% of own-rooted `Redhaven' trees were symptomatic. Although these data suggest that rooted cuttings of these cultivars may be less susceptible to stem pitting, the use of rooted cuttings does not eliminate fumigation as a means of providing acceptable stem-pitting management in a heavily infested site.
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.
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.
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.
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.
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.