Evaluation of Seven Essential Oils as Seed Treatments against Seedborne Fungal Pathogens of Cucurbita maxima

Abstract

Essential oils are gaining interest as environmentally friendly alternatives to synthetic fungicides for management of seedborne pathogens. Here, seven essential oils were initially tested in vivo for disinfection of squash seeds (<i>Cucurbita maxima</i>) naturally contaminated by <i>Stagonosporopsis cucurbitacearum</i>, <i>Alternaria alternata</i>, <i>Fusarium fujikuro</i>, <i>Fusarium solani</i>, <i>Paramyrothecium roridum</i>, <i>Albifimbria verrucaria</i>, <i>Curvularia spicifera</i>, and <i>Rhizopus stolonifer</i>. The seeds were treated with essential oils from <i>Cymbopogon citratus</i>, <i>Lavandula dentata</i>, <i>Lavandula hybrida</i>, <i>Melaleuca alternifolia</i>, <i>Laurus nobilis</i>, and <i>Origanum majorana</i> (#1 and #2). Incidence of <i>S. cucurbitacearum</i> was reduced, representing a range between 67.0% in <i>L. nobilis</i> to 84.4% in <i>O. majorana</i> #2. Treatments at 0.5 mg/mL essential oils did not affect seed germination, although radicles were shorter than controls, except with <i>C. citratus</i> and <i>O</i>. <i>majorana</i> #1 essential oils. Four days after seeding, seedling emergence was 20%, 30%, and 10% for control seeds and seeds treated with <i>C. citratus</i> essential oil (0.5 mg/mL) and fungicides (25 g/L difenoconazole plus 25 g/L fludioxonil). <i>S</i>. <i>cucurbitacearum</i> incidence was reduced by ~40% for plantlets from seeds treated with <i>C. citratus</i> essential oil. These data show the effectiveness of this essential oil to control the transmission of <i>S. cucurbitacearum</i> from seeds to plantlets, and thus define their potential use for seed decontamination in integrated pest management and organic agriculture.