Root and stem rot, and wilting of olive tree caused by Dematophora necatrix and associated with Emmia lacerata in Central Italy

Abstract

Lethal wilting was observed on young olive trees cv Favolosa in a grove in central Italy. White mycelial strands wrapped the basal portion of the stems that had been buried during planting. The bark was rotted and the xylem was discoloured. A fungal morphotype was strictly associated with symptomatic plants and identified as Dematophora (ex Rosellinia ) necatrix. Pathogenicity tests on cvs Favolosa, Leccino and Ogliarola demonstrated that D. necatrix was the causal agent of the disease. Our investigations revealed that infections occurring during autumn and winter greatly favour the disease. By applying a marcottage to the inoculation point, we accelerated the course of the disease and mimicked the lethal outcome observed in the field. In in vitro tests, seven systemic (potential) fungicides strongly inhibited D. necatrix . Dentamet, Al-phosphite and Thiophanate methyl were selected to be tested in planta with a curative and preventive modality . Only Thiophanate methyl, in preventive modality, fully protected the plants from disease progression throughout the observation period. An additional fungal species was strictly associated with both diseased and apparently healthy plants. Morphological and molecular features identified the fungus as Emmia lacerata, a polypore species within the Irpicaceae, which is the agent of white rot on dead woody substrates. To our knowledge, this is the first time that E. lacerata has been reported in Italy and worldwide on olive trees. Inoculation of ‛Favolosa’ trees revealed that it colonizes the xylem without causing visible alterations. The possible role of E. lacerata in the olive tree- D. necatrix pathosystem is discussed. Supplementary Information The online version contains supplementary material available at 10.1007/s10658-022-02458-1.

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“…P. richardsiae causes twig and branch dieback in olives, with extensive discoloration phenotypes starting at the roots and extending into the trunk when opening the trees. Other fungal species that were recently surprisingly detected on olives are Dematophora (ex Rosellinia ) necatrix , and Emmia lacerate ( Fusco et al., 2022 ). These were identified in young olive trees suffering lethal wilting in central Italy, while being diagnosed for X. fastidiosa .…”

“…The presence of E. lacerate , normally a wood decaying fungus, has not been reported before in olive trees. Although apparently growing symptomless in olives ( Fusco et al., 2022 ), the saprophytic fungus may have a biological role in modifying natural decomposition processes in olive trees which may affect other biotic stresses.…”

Exploring Bacterial and Fungal Biodiversity in Eight Mediterranean Olive Orchards (Olea europaea L.) in Tunisia

“…These impacts include nutrient pesticide contamination characterized by variable effectiveness and damaging effects on the ecosystems [11] and human health [12], as well as increased resistance to insects and diseases. The management of the olive pest and diseases are based on appropriate agronomical practices, such as the use of certified healthy material, solarization, balanced pruning, improvement of soil management, irrigation, and fertilization control [13]; and preventive chemicals, such as the use of cupric salts [14], dimethoate [15], thiophanate methyl [16], fosetyl-aluminum and benomyl [17]. Other control approaches include biological control, trapping methods, the release of sterile insects, and integrated control.…”