Canopy Management of Sweet Orange, Grapefruit, Lemon, Lime and Mandarin Trees in the Tropics: Principles, Practices and Commercial Experiences

Abstract

Over the past 18 years, citrus canopy management strategies (CMS) were developed improving tree health, productivity, fruit quality and management efficiency of orchards in tropical Southern Africa and Australia. These CMS are based on understanding of knowledge of tree phenology and natural growth habit, recognition of fruiting habits of "strong" and "weak" bearing branch units (SBBU and WBBU respectively), tree physiology, floral biology, environmental physiology, effects of canopy illumination, branch sap flow patterns, and of effects on these of climate, weather, topography, altitude and local pest and disease cycles. Secondly, CMS were derived with an understanding of effects on tree physiology of specific pruning and regrowth management practices. Thirdly, cost-effective methods were developed of optimising growth, form and function of non-bearing trees, trees in full production, and old trees declining due to age and/or shading. The strategy is to create, after planting, strong, balanced tree frameworks, and to maintain these through the orchard's life by selectively pruning multiple light-and spray "channels" into the trees' canopies. As new "internal" growth arises and develops, fruiting is displaced to sheltered, well-lit and ventilated canopy interiors. Pruning specifically removes WBBU, and stimulates production of SBBU, directly subtended by scaffold branches in which sap flow is strong. These SBBU bear large, unblemished fruit of uniform high quality. Rejuvenation pruning of old trees is discussed, as is protection of leaf flush from the pests citrus leaf miner, thrips, leafhoppers and pathogens Citrus black spot (CBS), Asiatic citrus canker (ACC) and Huanglongbing (HLB). Also discussed are improvements observed to soil following additions of coarse, organic wood chip mulches derived from triturated prunings, and necessary adjustments in support of CMS to fertiliser practices, irrigation, pest-, disease-and orchard floor management.

The diversity of ‘kristal’ guava (Psidium guajava) fruit quality in response to different altitudes and cultural practices

“…Furthermore, the guava tree with less intensive cultural practice was not exposed to pruning treatment (Table 1). Pruning was a plant growth regulation technique that can improve the farmers' accessibility to do maintenance, such as fertilizing, pesticide spraying, and harvesting (Krajewski and Krajewski 2011;Gilman and Black 2011). The intensity of sunlight received by pruned plants was higher than unpruned one so that it could stimulate the growth of new productive shoots (Willaume et al 2004) and ultimately could increase fruit production and quality (Prastowo et al 2015).…”

Effect of mechanical pruning on the yield and quality of ‘Fortune’ mandarins

“…Pruning citrus trees must be a general canopy management strategy based on the understanding of specific pruning and regrowth management practices that must be combined with cost-effective methods adapted to each orchard period, growth, full production and old trees decline due to age and/or shading (Krajewski & Krajewski, 2011). Mechanical pruning can be integrated in this general strategy.…”

Technical and field evaluation of tractor operated frontal pre-pruner for Kinnow Mandarin (Citrus reticulata) and Guava (Myrtaceae) orchard

“…It is, however, not a technique that is widely accepted by growers, among other reasons due to a lack of experience. Pruning citrus trees must be a general canopy management strategy based on the understanding of specific pruning and regrowth management practices that must be combined with cost-effective methods adapted to each orchard period, growth, full production and old trees decline due to age and/or shading (Krajewski & Krajewski, 2011).…”