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The search for an organic apple thinner

The search for an organic apple thinner

The search is on in Nova Scotia’s Annapolis Valley for an organic blossom thinner for apple orchards.

“The big driver on this is Honeycrisp,” explains Charles Embree, a tree fruit scientist with the Agriculture and Agri-Food Canada’s Atlantic Food and Horticulture Research Centre.

Honeycrisp, a highly desirable and premium-priced apple, is notorious for its bi-seasonality, bearing an overabundance of blooms with a resulting crop of undersized apples in one year, and, in the second year, blooming sparsely due to diminished tree vigour before coming back the next year with a vengeance.

Blossom thinning in the spring can help Honeycrisp trees produce a consistent harvest year after year of the much sought-after large fruit. But Dinitro, a chemical thinner, can no longer be used after it was decertified due to environmental sustainability issues. The product’s decertification has “created quite a problem,” says Embree.

AFHRC was already working on blossom thinning trials using organic products when Dr. Sara Avila-Good of nearby Acadia University, an expert on pollination-related issues, suggested joint collaboration on organic blossom thinners.

“We thought it would be a good match,” recalls Embree.

In May of 2007, Dr. Miriam Ferrer, who is doing postdoctoral research fellowship on organic growth regulators for apples, began her research internship with Dr. Avila-Good.

Before beginning her research internship, Dr. Ferrer says she met with apple growers. She has two organic producers, Craig and Doug Nichols, on her research team.

The apple producers provided her with data on what sort of products they were using for crop load management, application techniques and what they thought could be useful as blossom thinners.

During 2007, Dr. Ferrer examined about 40 products commonly available in grocery and farm supply stores, including mayonnaise, egg whites, vinegar, cream of tartar, soap, table salt, lime sulphur, calcium chloride, corn oil, citric extracts, clove oil and even sea water.

The AFHRC then screened the potential organic blossom thinning agents, taking samples of twigs from the centre’s organic trial plots from so Dr. Ferrer could remove the pollen for analysis in the laboratory and greenhouse at Acadia University.

As a result, Dr. Ferrer identified five potential organic thinners. The naturally occurring minerals were applied this season to the branches of Honeycrisp trees planted in AFHRC’s experimental organic plot. What was used cannot yet be disclosed.

“We want to make sure first they will work in the field trials,” says Dr. Ferrer.

The potential thinners were applied at various concentrations in the AFHRC orchard to mimic the different conditions possible in the field.

Dr. Ferrer’s research internship concludes with this year’s apple harvest. She will then do a technical analysis and a final report for presentation to the Nova Scotia Fruit Growers Association (NSFGA)  in December.

Although Honeycrisp was the focus variety of her research, Dr. Ferrer also examined the pollination process in Macintosh, Jonagold and Gala.

As a plant breeder, Dr. Ferrer is particularly interested in the “self-incompatibility” system of hermaphroditic fruit trees that prevent them from self-pollinating. It is this professional interest that originally brought her to Acadia to work with Dr. Avila-Good, an expert on self-incompatibility.

The organic thinners research is Dr. Ferrer’s first scientific research project on fruit trees. She previously completed her honours thesis on medicinal plants back home in Mexico. Dr. Ferrer’s research is funded jointly by the Mathematics of Information Technology and Complex Systems (MITACS) and the NSFGA.