First report of Lasiodiplodia theobromae on Macadamia integrifolia in Brazil

Abstract

Macadamia tree (Macadamia integrifolia Maiden & Betche) is a plant native to the rainforests of Australia. Its nut is rich in monounsaturated oils and is considered an excellent energy source. In August 2013, samples of branches and bark of the trunk of macadamia plants were received for laboratory analysis; they were from an eightyear-old commercial orchard located in São João da Boa Vista, São Paulo State, Brazil, and presented symptoms of sunken canker on the bark ( Figure 1A), while some plants had gum exudations, which culminated in dry terminal branches. At least 10 plants of the orchard were symptomatic. Fragments of diseased bark were previously surface-sterilized by immersion in 70% ethanol for 30 s and 1% sodium hypochlorite for 30 s, and then washed in sterile distilled water. Small sections (0.5 cm long) were cut from the edge of an advancing lesion on the diseased bark and placed directly on water agar medium. The developed fungal colonies were placed on potato dextrose agar (PDA) medium and, subsequently, identified based on morphologic characters. Formed cultures were dark grey colored after seven days. Pycnidia were stromatic, globose and ostiolate. Conidia were initially hyaline,

Efficacy of the biocontrol agent Trichoderma hamatum against Lasiodiplodia theobromae on macadamia

“…Lasiodiplodia theobromae can cause cankers on the trunks of macadamia tree and shoot necrosis ( Fischer et al, 2017 ). In the present study, we found that L. theobromae can also cause lesions on macadamia leaves.…”

“…( Akinsanmi and Drenth, 2017 ) and Lasiodiplodia pseudotheobromae ( Chang et al, 2019 ) are responsible for causing husk rot resulting in diffuse soft and spongy black lesions on the fruit pericarp. Lasiodiplodia theobromae can also cause trunk cankers and shoot necrosis ( Fischer et al, 2017 ). It has been reported that L. theobromae has a wide host range and geographical distribution, particularly in tropical and subtropical regions ( Salvatore et al, 2020 ).…”

“…Conidia are initially hyaline, 1-celled and subovoid. When mature, typical conidia are 1-septate, brown and measured 26–31 × 12–16 μm ( Fischer et al, 2017 ). Although macadamia cultivation still relies on the use of synthetic chemicals like carbendazim and pyraclostrobin ( Akinsanmi et al, 2008 ; Khun et al, 2021 ) to minimize disease problems, there is a broad trend to explore and develop biocontrol agents, including the use of beneficial fungal endophytes, to manage tree diseases ( Sosso et al, 2021 ).…”