In Vitro Control of Phytophthora infestans and Alternaria solani Using Crude Extracts and Essential Oils from Selected Plants

Abstract

<jats:p>Tomato production is constrained by fungal diseases especially the early and late blight caused by <jats:italic>Alternaria solani</jats:italic> and <jats:italic>Phytophthora infestans</jats:italic>, respectively. Control of the two diseases is usually by use of synthetic fungicides which have a long residue effect and also contribute to environmental pollution. Innovative use of biocontrols may offer an eco-friendly and more sustainable solution. This study tested the in vitro efficacy of crude extracts and essential oils of ginger, garlic, tick berry, and Mexican marigold in inhibition of radial growth of <jats:italic>A. solani</jats:italic> and <jats:italic>P. infestans</jats:italic>. Extraction of the crude extracts was done using distilled water, ethanol, and methanol solvents, while essential oils were extracted using the dry steam distillation method. The extracts and essential oils were used to amend the growth media of the test pathogens before introducing the precultured pathogens. Sterile distilled water and synthetic fungicide, Ridomil Gold®, were used as positive and negative controls, respectively. Fungal growth inhibition was determined by measuring the radial growth of the test pathogens. Both the crude extracts and the essential oils portrayed some efficacy against the test pathogens. Garlic crude extracts were found to be the most effective, while ethanol was the most suitable extraction solvent. Essential oils were more effective in restricting the pathogen growth than crude extracts. Ginger and garlic oil was found to be as effective as the synthetic fungicide, and thus it was concluded that the two plants have strong antifungal properties with high potential of being utilized as biofungicides. However, effective utilization of these products in farmers’ fields may require industrial formulation to improve their efficiency.</jats:p>

Characterization of the Volatile Components of Essential Oils of Selected Plants in Kenya

“…Extraction of essential oils was done following a modified procedure described by Adams [ 27 ] and adopted by Mugao et al [ 28 ]. Vertical steam distillation unit, consisting of a hot plate, boiling flask, biomass flask, still head, condenser, and receiving flask (separating funnel), was used for dry steam distillation of plant material.…”

Biocontrol of Carrot Disease-Causing Pathogens Using Essential Oils

“…Many attempts have been made to discover alternative ways of controlling Alternaria spp. and reducing the use of fungicides [11,13,17,20,21]. Essential oils and plant extracts are two of the most promising groups of natural compounds for the development of safer fungicidal agents.…”

“…Essential oils and plant extracts are two of the most promising groups of natural compounds for the development of safer fungicidal agents. There are significant results with Thymus vulgaris L., Lavandula angustifolia Mill., Allium sativum L., Zingiber officinale Roscoe, and other EO efficacy to control the growth of these pathogens [17,20].…”

“…For example, essential oils extracted from the leaves, stems, bark, and various parts of the plants contain complex mixtures of secondary metabolites, which are biologically active, endowed with antioxidant, allelopathic, bioregulatory, and antimicrobial properties. Other advantages of plant-based pesticides are their wide acceptance by consumers and potential multi-purpose uses [17][18][19][20].…”

Characterization of Alternaria brassicicola isolated from tomato in Burkina Faso, and use of two essential oils for its control in vitro

“…Considering the diversity, abundance and important damage caused by species of the genus Alternaria, the main method of control of Alternaria disease and associated mycotoxins, in many tropical countries, is the use of synthetic chemical fungicides (Mugao et al, 2020), which are harmful to human and animal health, and to the environment. Also, nowadays, consumers are more and more demanding about the quality of vegetable products, which must be free of pesticide residues, microbial growth, toxins, etc.…”