Studies were conducted to determine the effects of iron and zinc chelates on these deficiencies . Soil treatments, and foliar treatments with and without urea were used . It was found that in soil treatments at least one pound chelate per tree must be used to significantly increase the iron content of the leaves. The soil treatments did not re~lt in as high a concentration in the leaves early in the season, but they had a residual effect that lasted throughout the entire growing season. Foliar treatments with iron did not effect the foliage that developed after the final application was made . In the conditions of this experiment the application of iron and/or zinc chelates resulted in increased peach size, soluble solids and sugar content.

No description available.

Crop load management of fruit trees is a challenge for producers. For this experiment apple, peach, and sweet cherry trees were thinned using mechanical blossom thinning (MBT), and hand blossom thinning (HBT) to mimic MBT. Apple bloom was reduced by MBT, but only one treatment consistently reduced fruit set. Marketable yield, fruit weight, and quality were unaffected by thinning treatments. An apple spur leaf study found that damage from MBT was negligible. Mechanical blossom thinning of peach significantly reduced fruit set and hand thinning requirements at ‘June drop’. Marketable yield, fruit firmness, and soluble solids concentration were largely unaffected by thinning treatments, but fruit weight and size increased in one year. The two highest rates of sweet cherry MBT and HBT reduced fruit set but total yield, fruit weight, and quality were unaffected. Overall, MBT may be a viable option for tree fruit producers, especially peach growers. / The University of Guelph/OMAFRA Sustainable Production Systems Research Programme, the Niagara Peninsula Fruit and Vegetable Growers' Association, NSERC.

Threshold and non-threshold linear models that govern toxicology are challenged by an alternative model, hormesis. It is defined as low-dose stimulation and high-dose inhibition from a stressor. Insecticide-induced hormesis has been studied in a plethora of insect-insecticide models at biochemical, individual and population levels. This research focuses on the effects of sublethal concentrations of insecticides on reproductive responses of green peach aphid, Myzus persicae (Sulzer), at individual and population level besides regulation of stress, dispersal and developmental genes during hormesis. In laboratory studies, irrespective of the duration and route of exposure, sublethal concentrations of imidacloprid induced stimulations in fecundity of M. persicae but the nature of response differed intra- and trans-generationally. Fitness tradeoffs could be rendered due to declined fecundity in successive generations. However, continuous exposure to sublethal concentrations does not compromise overall fitness trans-generationally, considering recovered levels of fecundity as controls in successive generations and the total reproduction after four generations. Greenhouse experiments affirmed uncompromised fitness where reproductive stimulations were noted in aphids exposed to imidacloprid treated potato plants. Up- and down- regulation of stress, dispersal and developmental genes was noted during imidacloprid-induced hormesis in M. persicae that mirrored the reproductive responses in few instances. Global DNA methylation results emphasized the heritability of adapted traits trans-generationally via hypermethylation. Dispersal related genes (OSD, TOL and ANT) that are predominantly expressed in alates (about 2- to 5-fold) were affected in apterous aphids continuously exposed to sublethal concentrations of imidacloprid. No direct relation with the previously noted fecundity was established implying adaptive cellular stress response pathways might be triggered rather than normal regulatory processes due to low-dose imidacloprid exposure. At a biochemical level, a study noted that imidacloprid-induced hormesis concurrently stimulated juvenile hormone III (JH) production and fecundity in M. persicae. Precocene, an anti-JH, at sublethal concentrations induced reproductive stimulations in M. persicae. Gene regulation during precocene-induced hormesis mirrored imidacloprid results for few genes including FPPS, a JH precursor gene, with a higher magnitude of regulation. Considering these stimulatory effects that insecticide-induced hormesis at various biological hierarchies, causes for pest resurgence, hormesis could have ramifications from declines in natural enemy population.

Thesis (Ph. D.)--Ohio state University, 1928. / Autobiography. Bulletin 460 of the New Jersey agricultural experiment station (23 cm) with 2 prelim. leaves (t.-p. and preface) and 1 leaf containing autobiography added. Bibliography: p. 24.

Studies were conducted to better understand the effect of temperature, photoperiod, cultural practices, and growth regulators on the hardening and dehardening of peach tree wood. Greenhouses were constructed to control temperatures to which peach trees were exposed. It was noted that hardening and dehardening usually followed the temperature fluctuation fairly closely. However, trees exposed to temperatures above 60 F (15. 6 C) became hardy to 0 F (-17. 8 C). A photoperiodic response in regard to an increase or decrease in hardiness was not definitely observed in peach wood. Extended photoperiod did not produce any significant effect on hardiness. Defoliation, bloom date, and fruit set were all the same as the controls. The cultural practices of fall pruning and heavy late summer fertilization with nitrogen did not result in a change in the hardiness level of the trees when compared with the controls. Likewise gibberellic acid spray had no effect. Defoliation produced serious physiological damage when done in mid-August, while defoliation in mid-September was not nearly so damaging, Defoliated trees were less hardy than the controls until mid winter.

Many deciduous trees enter a stage each year when their visible growth ceases. This is not always associated with cold weather or lack of water, and may occur with many species in mid-to-late summer. Trees entering this phase are said to be in rest. Rest is caused when internal factors are unfavorable for growth, while dormancy is defined as external factors being adverse for growth.

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No description available.

Several photosynthetic inhibitors were screened for relative photosynthetic reduction on leaves of greenhouse-grown peach trees. The most effective were 8% Vapor Gard, 10M diurcn, 10⁻³M ABA, and 10⁻³M terbacil, all of which reduced net photosynthesis (Pn) rates by 50% or more by 1 day after treatment without causing excessive phytotoxicity. Of these 4 treatments, terbacil at 10⁻³M gave the most consistent effects; treated leaves re-established near normal Pn rates within a week of treatment. At 1, 3, and 7 days after treatment with terbacil at 10⁻³M, Pn rates were 1.1, 9.0, and 16.6 mgCO₂ dm⁻² hr⁻¹ , respectively, compared with a pretreatment rate of 19.7. Terbacil was applied as limb treatments to bearing peach trees in the field to determine fruit thinning activity. Treatments were: single applications of 1000 or 2000 ppm, double applications a week apart of 1000 ppm, or 2000 followed by 1000 ppm. All treatments significantly reduced fruit number. Fruit drop was 73 to 90% on treated limbs compared to 20% on non-thinned check limbs. Only the single 1000 ppm treatment resulted in fruit size similar to the hand-thinned check, however, all treatments increased fruit size over the non-thinned checks. / M.S.