‘Abnormal vertical growth’: a disorder threatening the viability of the Australian macadamia industry

O'Farrell, PJ; Lagadec, M. D. Le; Searle, C.

doi:10.17660/actahortic.2016.1109.23

Cited by 8 publications

(20 citation statements)

References 3 publications

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“…AVG is a macadamia tree structure dysfunction that reduces nut production. It was originally found in Australia in the 1990s [19], and it has become a serious threat to macadamia orchards in Queensland and New South Wales in Australia. Although research on this has been done since 2002, its causes are still unknown [19].…”

Section: Discussionmentioning

confidence: 99%

“…It was originally found in Australia in the 1990s [19], and it has become a serious threat to macadamia orchards in Queensland and New South Wales in Australia. Although research on this has been done since 2002, its causes are still unknown [19]. AVG directly modifies plant structure and can reduce yield by up to 30% [19,49].…”

Section: Discussionmentioning

confidence: 99%

“…Although research on this has been done since 2002, its causes are still unknown [19]. AVG directly modifies plant structure and can reduce yield by up to 30% [19,49]. Up to 100,000 macadamia trees were affected by AVG across Queensland and New South Wales in 2016, causing an annual loss of 10.5 million Australian dollars.…”

Section: Discussionmentioning

confidence: 99%

“…Up to 100,000 macadamia trees were affected by AVG across Queensland and New South Wales in 2016, causing an annual loss of 10.5 million Australian dollars. Erect branches and poor flowering were found in macadamia trees affected with AVG [19], and these erected branches also made the macadamia trees more vulnerable to strong winds and storms. The LA and LAD results for the macadamia tree with AVG demonstrated that high spatial resolution TLS data has the potential to quantify storm damage and record where damage has occurred ( Figure 5).…”

Section: Discussionmentioning

confidence: 99%

“…Canopy structure metrics are closely related to horticultural tree growth and productivity, as well as providing strong indicators of water consumption, health condition and yield [16][17][18][19]. Leaf area (LA) calculations are essential to determine water requirements for precision irrigation and fertilisation [16].…”

Section: Introductionmentioning

confidence: 99%

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Estimating Changes in Leaf Area, Leaf Area Density, and Vertical Leaf Area Profile for Mango, Avocado, and Macadamia Tree Crowns Using Terrestrial Laser Scanning

Phinn

Johansen

et al. 2018

Remote Sensing

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Vegetation metrics, such as leaf area (LA), leaf area density (LAD), and vertical leaf area profile, are essential measures of tree-scale biophysical processes associated with photosynthetic capacity, and canopy geometry. However, there are limited published investigations of their use for horticultural tree crops. This study evaluated the ability of light detection and ranging (LiDAR) for measuring LA, LAD, and vertical leaf area profile across two mango, macadamia and avocado trees using discrete return data from a RIEGL VZ-400 Terrestrial Laser Scanning (TLS) system. These data were collected multiple times for individual trees to align with key growth stages, essential management practices, and following a severe storm. The first return of each laser pulse was extracted for each individual tree and classified as foliage or wood based on TLS point cloud geometry. LAD at a side length of 25 cm voxels, LA at the canopy level and vertical leaf area profile were calculated to analyse tree crown changes. These changes included: (1) pre-pruning vs. post-pruning for mango trees; (2) pre-pruning vs. post-pruning for macadamia trees; (3) pre-storm vs. post-storm for macadamia trees; and (4) tree leaf growth over a year for two young avocado trees. Decreases of 34.13 m2 and 8.34 m2 in LA of mango tree crowns occurred due to pruning. Pruning for the high vigour mango tree was mostly identified between 1.25 m and 3 m. Decreases of 38.03 m2 and 16.91 m2 in LA of a healthy and unhealthy macadamia tree occurred due to pruning. After flowering and spring flush of the same macadamia trees, storm effects caused a 9.65 m2 decrease in LA for the unhealthy tree, while an increase of 34.19 m2 occurred for the healthy tree. The tree height increased from 11.13 m to 11.66 m, and leaf loss was mainly observed between 1.5 m and 4.5 m for the unhealthy macadamia tree. Annual increases in LA of 82.59 m2 and 59.97 m2 were observed for two three-year-old avocado trees. Our results show that TLS is a useful tool to quantify changes in the LA, LAD, and vertical leaf area profiles of horticultural trees over time, which can be used as a general indicator of tree health, as well as assist growers with improved pruning, irrigation, and fertilisation application decisions.

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Section: Discussionmentioning

confidence: 99%