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Boron: “Deficiency symptoms may be more common than you thought”

By Ben Funnekotter

Grower Solutions Magazine
Lefroy Valley Magazine
August 2004

Boron deficiencies - early stages

Brassica growers often think they have a major problem with Diamond Back Moth grub damage, and end up spraying three or four times a week to try and stop their produce looking as though a hailstorm has ripped through the crop.

However, very often, this is not grub damage at all but rather the classic symptoms of Boron deficiency. Boron deficiency is particularly prevalent in the sandy soils of WA, but that does not mean the other states in Australia are exempt from such problems. The two problems look very similar at first glance, but by taking a closer look, the differences become apparent. A technical explanation of what Boron does in the plant is not necessary, suffice to say that it is taken up in the cell wall, where one of it's major functions is to strengthen the cell wall.

When brassicas experience a Boron deficiency, the leaves become thin and are prone to tearing. Sometimes the tearing occurs on the edge of the leaves, and when the tear edge heals, the brassica leaves (particularly cabbage leaves) become heart shaped rather than round or oval. However, often a tear in the leaf of .5 - 1.5cm long takes place in the centre of the leaf. As the torn edges heal the tear changes from a line to a round or oval hole, which looks very similar to the "shot hole" symptoms of grub damage.

	Boron deficiencies - later stages

Growers should look closely at their crops to detect the symptoms at an early stage.

Often the symptoms of Boron deficiency occur despite high levels of Boron being present in the irrigation water. Ideally the first applications of Boron should be applied at seedling stage in the nursery, as a foliar spray. Thereafter the next application should be at transplant and again two weeks later.

There are many formulations of Boron on the market, some work better than others, and their application rates vary, as do their application costs. Without entering the minefield of products and costs, a rule of thumb for the grower to use is that each treatment should cost about $15 per hectare or less. Once applied, Boron will often have the effect of making the crop dark green, without the flush of new growth that Nitrogen applications would give. Yields should improve and hollow stems should significantly decrease.

So the next time you think you have grub damage but the moth numbers aren't around to warrant such large scale damage, remember to think of Boron, it could save you a fortune in spraying costs.

Quoted from AgriSupportOnline