RESEARCH & EVENTS
From page 36 It is unlikely that pathogens are the only cause of LLD . No single species was consistently isolated from the affected samples , and 50 % yielded no microorganisms at all . Scale infestations were not reported during the surveys , also eliminating them as a potential cause of LLD in the assessed orchards . Less dieback was observed in trees on the margins of the block . This “ edge effect ” suggests that light could be a contributing factor to LLD in these blocks . However , within the orchards , LLD branches with chlorotic leaves were sometimes located higher up in the canopy where there was ample light , suggesting that there are likely to be other contributing factors . Furthermore , trees on the edge of the orchard have less root competition for water and nutrients . Data analysis confirmed that the severity of dieback increased with tree age . Within properties , there was little difference between blocks of similar ages , but cultivars varied in LLD severity . However , there were differences between properties among blocks of similar age and cultivar , suggesting that there are likely management or environmental differences that affect LLD severity . Almond trees that appeared taller than the rows were wide had more severe LLD than blocks with trees with smaller canopies . International research has indicated that LLD is more prevalent in orchards with high inputs and intensive production systems . The increase of LLD in the Australian almond industry over the last decade might also be attributed to the intensification of the industry .
Greater nutrient and water inputs would likely increase the size of the trees , resulting in lower canopies of trees being shaded out by adjacent trees . Fluctuations in LLD were recorded over the three-year study , and dieback ratings even decreased in some cases . Activities such as hedging may ameliorate the effects of LLD , as hedging stimulates new growth in previously shaded parts of the canopy ( Doll , 2016 , Bright et al ., 2016 ). The “ rise ” of LLD in the Australian almond industry over the last decade may be attributed to the intensification of orchards , increased inputs , and the greater mean age of trees .
Innovation , not imitation
A . Twenty-three-year-old trees in the Riverland with low severity of lower limb dieback ( LLD ) and little shading . B . Thirty-eight-year-old trees in the Adelaide Plains with low severity LLD symptoms and little shading . C . Twenty-two-year-old trees in the Riverland with high severity of LLD symptoms and heavy shading , with canopies meeting between rows and trees .
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industry . australianalmonds . com . au
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