From HortScience: Managing Apple Crop Load and Diseases with Bloom Thinning Applications in an Organically Managed ‘Honeycrisp’/‘MM.111’ Orchard
Gregory M. Peck et al.

While a lot of OFGA activities are apparent and visible to all involved, even more is going on behind the scenes. The connections developed through our association bring together many players in the organic fruit-growing industry, providing important information to those who actively participate in what we do.

One such collaboration involved a team of researchers at Cornell University, the Boyce Thompson Institute, and the Penn State Extension of The Pennsylvania State University. They reached out to OFGA to see if we could support their research project, Advanced Solutions for Holistic Disease Management in Organic Apple Orchards Using Participatory Networks. OFGA President Dan Kelly responded to the follow-up questionnaire. Unfortunately, they did not get funding in the first round, but decided to fine tune the proposal and asked OFGA for feedback in order to get a higher ranking for funding. During these discussions between Gregory M. Peck project coordinator at Cornell and Dan Kelly, the conversation drifted to Dan’s SARE grant application involving methods to alleviate cedar apple rust disease. Mr. Peck told Dan about his research about apple thinning that included a component controlling cedar apple rust, and after reading it, Dan thought it could be useful information for many of you. Mr. Peck was happy to give us permission to reprint the abstract here. The whole article is available in HORTSCIENCE 52(3):377–381. 2017. doi: 10.21273/HORTSCI11412-16, and also online through ResearchGate (request full text here) or Semantic Scholar.

Managing Apple Crop Load and Diseases with Bloom Thinning Applications

in an Organically Managed ‘Honeycrisp’/‘MM.111’ Orchard

Gregory M. Peck

Horticulture Section, School of Integrative Plant Science, Cornell University, 121 Plant Science Bldg, Ithaca, NY 14853

Candace N. DeLong, Leon D. Combs, and Keith S. Yoder

Alson H. Smith, Jr. Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, 595 Laurel Grove Road, Winchester, VA 22602

Abstract. Although demand for organic produce continues to increase in the mid- Atlantic, few apple (Malus x domestica Borkh.) growers in the region have adopted organic management practices due to the considerable disease, insect, and weed pressure, as well as the lack of effective crop load management tools.

In this study, lime sulfur (LS) and Regalia® (R) were applied in different sequences (i.e., LS/LS, LS/R, R/R, and R/LS), each in a mixture with JMS Stylet-Oil, to chemically thin apple flowers in an organically managed ‘Honeycrisp’/‘MM.111’ orchard. There was also a nontreated control, a ‘‘grower standard’’ control (LS at 11 mm fruitlet diameter), and a hand-thinned control.

The treatments were evaluated for their ability to reduce crop load, as well as to control powdery mildew [Podosphaera leucotricha (Ellis & Everh.) E. S. Salmon], cedar apple rust (Gymnosporangium juniperi-virginiana Schwein.), and quince rust (Gymnosporangium clavipes Cooke & Peck). All treatments reduced crop load compared with the nontreated control, and after the first application of LS or R, the number of fertilized king blooms was reduced and fertilization was prevented in all side blooms. All bloom thinning treatments had more fruit peel russet than the control and russet was more severe when LS was one of the applications. Bloom thinning applications of LS and R did not reduce powdery mildew leaf infection compared with the nontreated control. Cedar apple rust incidence was reduced by all bloom thinning treatments, though some lesions were detected in all treatments. There were minimal quince rust infections in any of the treatments, including the nontreated control.

These results suggest that when LS and/or Regalia® are mixed with JMS Stylet-Oil and applied as bloom thinners, they can reduce crop load, and, as a secondary benefit, they can also decrease cedar apple rust incidence from infections that occur during bloom.

From: HORTSCIENCE 52(3):377–381. 2017. doi: 10.21273/HORTSCI11412

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