Michigan trial links Kelpak to higher Gala apple yield and size

A 2025 Michigan field trial on mature Gale Gala trees found that four foliar applications of Kelpak boosted yield, fruit size and tree efficiency versus the grower standard. The results suggest seaweed-based support may help growers carry more crop without the usual size penalty.

Why it matters: - Apple growers have to balance yield, fruit size and tree efficiency at the same time. - A heavier crop only helps if fruit stays commercially acceptable and the tree can carry the load. - The Michigan trial suggests a seaweed extract may improve that balance during key growth stages.

What happened: - LTI Ag Research ran a 2025 trial on mature Gale Gala apple trees planted in 2014. - The study used a randomized complete block design. - Researchers compared the grower standard with four foliar applications of Kelpak at 3 pints per acre in 40 gallons of spray volume. - Trees receiving Kelpak produced 1,874 bushels per acre. - Trees under the grower standard produced 1,402 bushels per acre. - The difference was 472 bushels per acre, or 33.7%. - Using the U.S. apple industry’s 42-pound bushel standard, the yield gap equaled 19,824 pounds per acre.

The details: - Kelpak is a liquid concentrate made from fresh Ecklonia maxima, a giant brown seaweed harvested in managed strips off South Africa. - The harvest method leaves the holdfast attached for regrowth. - The product is processed with proprietary Cellburst technology. - High-pressure differentials rupture the kelp cells without heat, freezing or harsh chemicals. - The process is designed to retain naturally occurring plant compounds in the extract. - Kelpak is not intended to replace fertilizer, irrigation, thinning, pest management or other orchard basics. - The product is applied at defined phenological stages to support plant processes during fruit set, cell division and early fruit development. - Yield efficiency based on trunk cross-sectional area, or TCA, is a better apples-to-apples comparison than pounds per tree alone because trees vary in size and bearing capacity. - Kelpak increased weight-based yield efficiency from 15.8 to 19.7 pounds per square inch of TCA. - That was a 24.7% improvement and was statistically significant. - Count-based efficiency rose from 45.9 to 49.6 fruit per square inch of TCA. - That was an 8.1% increase and was statistically significant. - Average fruit weight rose from 144.1 to 163.4 grams. - That was a statistically significant gain of 13.4%. - Fruit number increased from 134 to 157 per tree. - That was a 17.2% increase. - The trial showed more fruit, larger average fruit and higher production relative to tree size. - Linda Greyling, Head of Technical Support, said growers need enough fruit to drive yield, but excessive crop load can reduce fruit size and weaken return bloom. - Greyling said the trial is notable because it combined more fruit, larger average fruit and greater production relative to tree size.

Between the lines: - The strongest result was not just higher yield, but higher efficiency after accounting for tree size. - That matters because orchard performance is shaped by crop load, tree vigor and fruit sizing together, not by output alone. - The results point to a possible role for biological inputs that are timed to the crop’s most sensitive developmental windows. - The data do not prove the same response will occur in every rootstock, soil type, season or crop-load strategy.

What's next: - Replication across production regions will be important before the findings can be generalized. - The Michigan result raises the question of whether growers can improve tree efficiency rather than simply asking trees to carry more fruit.

The bottom line: - In this Michigan Gala trial, Kelpak was associated with more yield, bigger fruit and better tree efficiency at the same time.