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Manufacturers of biostimulants derived from ­seaweed, or algae, say the products can provide multiple benefits when applied to crops.

Purported benefits include better root growth, resistance to weather-related stress, increased plant vigor, and better uptake of micronutrients. Some products are said to improve flower bud formation or fruit set, leading to better quality fruit and higher yields, while others are said to stimulate cell division, thus improving fruit size.

However, Austrian researcher Dr. Thomas Rühmer, who began a multiyear trial with Golden Delicious apples in 2010 to investigate the effects of algae-based products on production levels, fruit size, and russeting, has found inconsistent results so far. The products he is testing are:

•    Wuxul Ascofol (Aschophyllum nodosum seaweed extracts with boron, manganese, and zinc) from Aglukon
•    Goëmar Florea (containing A. nodosum) from Belchim Crop Protection
•    Alga Mix B Mg (containing an algae mixture with magnesium and boron) from L. Gobbi
•     PhytoAS (containing pure seaweed sap) from ERB-agrar
•    Phytoamin (containing marine algae liquid) from Lebosol-Dünger GmBH.

All products were applied in 2010 and 2011 according to the manufacturer’s recommendations: four times at 10-to-14-day intervals starting at bloom.

Some of the products had a positive influence on production levels, resulting in larger apples or a smoother skin. However, the effects differed strongly in 2010 and 2011, reported Rühmer, who is based at the Haidegg ­Agriculture Research Center in Graz.

In 2010, Phytoamin and Wuxal Ascofol had a small, but not statistically significant, influence on the ­production level but not in 2011 (see Figure 1).

In both 2010 and 2011, use of all the products resulted in more apples in the 80 mm ((3-1/8 inch) and larger size range than the control (see Figure 2). In 2010, Wuxal Ascofol had the greatest effect, but in 2011, Alga Mix had the greatest effect.

In 2010, applications of Wuxal Ascofol and Phytoamin resulted in fewer russeted apples, and the other products had no influence on russeting. In 2011, none of the products reduced russeting (see Figure 3). The research is being continued in 2012.