Page 6 - Vol.37-No.1 issue

CROP PROTECTION

BLUEBERRY – SUPERCHARGED

CALCIUM FOR A SUPER FRUIT

with most plant breeding having been
focussed on this species. The wealth of
varieties now available covers a wide
range of cold hardiness, fruiting season,
DR. TERRY MABBETT berry size and flavour.
Recent years have seen blueberry take
Cultivated blueberry is very much a on the mantle of the world’s ‘super-fruit’
20th century phenomenon. Before the primarily due to the exceptionally high
early 1900’s the only way to enjoy the antioxidant content but more generally
North American native bush fruit was because they are rich in a range of min-
to gather them in the wild. The roots of eral nutrients and vitamins as well as be-
blueberry cultivation are firmly embed- ing a good source of fibre. Maintenance
ded in the State of New Jersey (United of this status in commercial fruit clear-
States), and were ‘put down’ by com- ly comes with a strict requirement for
bined skills and cooperation between dedicated plant and crop nutrition. This
farmer Elizabeth White Coleman and
means provision to plants of all essential Applications of soluble calcium
nutrients including the macronutrients give high yields of good
(nitrogen, phosphorous and potassium); quality fruit and remaining f rm
micronutrients including manganese, throughout storage
copper and zinc; and the so-called me- (Picture courtesy Omex)
so-nutrients like calcium and magne-
sium. blueberry bush root system is increas-
Raw blueberries are exceptional- ingly unable to absorb water and nutri-
ly rich in manganese while containing ents to support the above-ground plant
generous amounts of phosphorous, mag- parts. Foliar symptoms including wilting
nesium and calcium. However, some of with yellowing and reddening of the
these nutrients and especially calcium leaves are among the earliest indications
and phosphorous may have other im- that something is amiss below ground.
portant functions including roles in fruit Indeed these are the sort of physiolog-
quality and boosting the resilience of ical responses expected when a plant
crop plants to disease. Calcium is the fails to access sufficient water and a full
most important and intriguing in this re- complement of essential nutrients due to
spect. a malfunctioning root system.
Root rot of blueberries
Blueberry cultivation and Blueberries have only been under
production without using
chemical fungicide is now a intense cultivation for a relatively short
reality. (Picture courtesy Omex) period of time but this has not stopped a
range of plant diseases evolving with the
crop to cause potentially- serious eco-
botanist Dr Frederick Colville, and nomic levels of damage and crop loss.
based on his pioneering research work The most widespread and serious is
entitled ‘Experiments in Blueberry Cul- root rot caused by a fungus-like Phy-
ture’. First cultivated crop of blueberries tophthora pathogen called Phytophtho-
was produced in 1916. ra cinnamomi. Like other root infecting
Four types of blueberry are cultivat- pathogens this one resides on debris in
ed commercially: highbush blueber- the soil and as such is a pernicious prob-
ry (Vaccinium corymbosum), lowbush lem for perennial bush crops like blue-
blueberry (Vaccinium angustifolium), berry which by their very nature will
hybrid half-high blueberry (hybrids spend many years growing and yielding
between Vaccinium corymbosum and in the same soil.
Vaccinium angustifolium to give more In common with other Phytophthora
compact plants) and rabbit-eye blue- pathogens, which target the root systems
berry (Vaccinium virgatum). The most of plants, Phytophthora cinnamomi is es- Blueberry bush in full f ower
widely-grown is highbush blueberry sentially terminal because the infected (Pictures courtesy Omex)

4 Vol. 37 No. 1