Articles
USING A POLLEN TUBE GROWTH MODEL TO IMPROVE APPLE BLOOM THINNING FOR ORGANIC PRODUCTION
Article number
1001_23
Pages
207 – 214
Language
English
Abstract
In apple production, crop thinning during bloom produces the largest fruit, the greatest return bloom in the following year, and reduces biennial bearing.
There are a limited number of fruit thinning chemicals approved for use under USDA organic standards, and many organic apple growers rely on a combination of liquid lime sulfur and fish oil applied during the bloom period.
The application timing for this spray has been subjective, and is usually based upon the percent of full bloom that is present (e.g., an application at 20 and 80% full bloom). While this approach has become a standard practice in some growing regions, more precise application timing can be achieved through modeling the fertilization of the desired percent of king bloom needed to achieve a full crop at the desired fruit size.
When this target is achieved, a bloom thinner can be applied so that later blooming flowers are prevented from setting fruit.
By measuring pollen tube growth rates under controlled atmospheric conditions using growth chambers, we have developed a model that calculates the time required to fertilize the king bloom after pollination.
We have found that cultivar differences and temperatures affect pollen tube growth and the time required for fertilization, and can offer explanations for inconsistent bloom thinning results.
The model is now being tested on a limited basis in commercial orchards with the goal to assemble specific modeling data for each commercially important apple cultivar.
We believe that this model has the potential to improve crop load management when using liquid lime sulfur and fish oil for bloom thinning in organic apple orchards.
There are a limited number of fruit thinning chemicals approved for use under USDA organic standards, and many organic apple growers rely on a combination of liquid lime sulfur and fish oil applied during the bloom period.
The application timing for this spray has been subjective, and is usually based upon the percent of full bloom that is present (e.g., an application at 20 and 80% full bloom). While this approach has become a standard practice in some growing regions, more precise application timing can be achieved through modeling the fertilization of the desired percent of king bloom needed to achieve a full crop at the desired fruit size.
When this target is achieved, a bloom thinner can be applied so that later blooming flowers are prevented from setting fruit.
By measuring pollen tube growth rates under controlled atmospheric conditions using growth chambers, we have developed a model that calculates the time required to fertilize the king bloom after pollination.
We have found that cultivar differences and temperatures affect pollen tube growth and the time required for fertilization, and can offer explanations for inconsistent bloom thinning results.
The model is now being tested on a limited basis in commercial orchards with the goal to assemble specific modeling data for each commercially important apple cultivar.
We believe that this model has the potential to improve crop load management when using liquid lime sulfur and fish oil for bloom thinning in organic apple orchards.
Publication
Authors
K.S. Yoder, G.M. Peck, L.D. Combs, R.E. Byers
Keywords
Malus ×domestica, lime sulfur, fish oil, pollination, fertilization, crop load management, flower morphology
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