Abstract
Melon cultivation is frequently heavily reliant on synthetic fungicides, including products used to control gummy stem blight caused by Stagonosporopsis cucurbitacearum. The essential oils used in controlling plant pathogens may offer an alternative to chemical pesticides. This study evaluated the effectiveness of essential oils to control the gummy stem blight in melon plants. In vitro tests were carried out using essential oils obtained from ripe noni fruit (Morinda citrifolia) and dehydrated leaves of the following plants: lemon grass (Cymbopogon citratus), citronella grass (Cymbopogon nardus), basil (Ocimum basilicum) and Mexican tea (Chenopodium ambrosioides) at different concentrations. A synthetic fungicide was used as control treatment. Results showed that the essential oils from noni and lemongrass had the highest effect on mycelial growth inhibition in S. cucurbitacearum. When applied on melon plants as a preventive measure, the essential oils from noni and lemongrass controlled gummy stem blight at the following concentrations: 0.03, 0.05, 0.1 and 0.3%. These results highlight the potential of essential oils to manage melon fungal diseases, which may result in reduction of pesticide application. Key words: Cucumis melo, Stagonosporopsis cucurbitacearum. Didymella bryoniae, alternative control, plant disease.
Highlights
Gummy stem blight (GSB) is a major disease that strikes several cucurbit species and is caused by Stagonosporopsis cucurbitacearum (Fr.) Aveskamp, Gruyter & Verkley, known as Didymella bryoniae (Auersw.) Rehm (Steward et al, 2015)
This study describes the effectiveness of the application of essential oils of noni fruit (Morinda citrifolia L.), lemon grass, citronella, basil and mastruz (Chenopodium ambrosioides L.) in the control of S. cucurbitacearum and of the gummy stem blight disease in melon plants
Starting at the 0.5% dosage level, there was inhibition of mycelial growth by noni fruit essential oil, rising to total inhibition of fungus growth at concentrations of 1% and above (Table 1)
Summary
Gummy stem blight (GSB) is a major disease that strikes several cucurbit species and is caused by Stagonosporopsis cucurbitacearum (Fr.) Aveskamp, Gruyter & Verkley, known as Didymella bryoniae (Auersw.) Rehm (Steward et al, 2015). The fungus causes seedling damping-off, foliar lesions, as well as, stalk and stems cankers. It can be universally found in every continent and attacks at least 12 genera and 23. Growers have considered synthetic fungicides to control cucurbit diseases. In addition to environmental pollution and contamination of consumable products, several cases of resistance to the main active fungicides on the market have been reported for GSB (Thomas et al, 2012; Keinath, 2013). Other methods of reducing the damage caused by GSB, include the use of partial genetic resistance (Santos et al, 2009) and biocontrol (Zhao et al, 2012)
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