![]() Common spray applications timings with visual observation method include 20%, 40%, 60%, 80%, and 100% open bloom with single or multiple applications occurring. Using the visual observation method requires growers to visually estimate the percentage of open bloom frequently during the bloom period. Currently, there are two major methods of timing blossom thinning sprays: (1) visual observation of the percentage of open blossoms and (2) model-guided spray method using the pollen tube growth model (PTGM). Timing of blossom thinning applications is critical for optimal results. However, due to phytotoxicity, variability in thinning efficacy, and spray tank mixing issues, none of these chemicals except LLS is currently labelled for chemical blossom thinning in the USA. These include dinitro-o-cresylate (DNOC), sulfcarbamide, pelargonic acid, endothall and liquid lime sulfur (LLS). Only a few chemicals obtained a label for apple blossom thinning in the USA. Unlike post-bloom chemical fruit thinning, chemical blossom thinning uses chemicals applied during bloom to reduce the crop load by preventing the fertilization of a percentage of the flowers. One alternative thinning practice is chemical blossom thinning. However, there are numerous external factors such as weather conditions that greatly impact the efficacy of post-bloom fruit thinning spray applications. Post-bloom chemical fruit thinning using plant growth regulators and carbamate insecticides are the main thinning methods to reduce crop load in apple orchards. Thinning decisions are considered to be among the most important since they directly impact yield, fruit quality, profitability, and growing habit. This study demonstrated that effective and safe blossom thinning can be obtained from applying two sprays at 20% open bloom and 48 h thereafter or using the PTGM.Ĭommercial apple growers make many important annual management decisions which directly impact the production and sustainability of their orchards. There was no conclusive evidence that lime sulfur + stylet oil blossom thinning spray timing influenced russet incidence/severity or leaf phytotoxicity. Treatments with a delayed first spray at 80% open bloom or a more extended second reapplication of 72 h were generally ineffective. Model-guided and 20% open bloom + 48-h treatments reduced fruit set and increased fruit weight, diameter, and length at both sites. 80%), and the second spray applied at a reapplication interval (48 h vs. ![]() Two main timing strategies were assessed: (1) model-guided sprays with the pollen tube growth model (PTGM), (2) fixed spray intervals with the first spray applied at a specified percentage of open bloom (20% vs. This project occurred at two locations in the USA, Winchester, Virginia, and Mills River, North Carolina, during the 2019 growing season. This study sought to evaluate how application timing of lime sulfur + stylet oil blossom thinning sprays would influence thinning efficacy and crop safety of ‘Gala’ apples. In the eastern USA and several other apple-growing regions, apple blossom thinning using lime sulfur is a relatively new crop load management strategy. ![]()
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