Effects of Tithonia diversifolia and Allium sativum extracts on Colletotrichum gloeosporioides, the causal agent of anthracnose in avocado

Abstract

Avocado production is severely affected by anthracnose disease in the field and after harvest worldwide. This disease causes losses in the field due to fruit abortion and as post-harvest disease affecting quality and quantity during marketing and storage. The management of this disease has been through the use of chemicals that toxify human beings and contaminate the environment. So, the development of alternative bio-pesticide, which is environment-friendly, is imperative. Therefore, this study was carried out to find an alternative to fungicides currently being used in the control of Colletotrichum gloeosporioides. This was achieved by evaluating the effectiveness of plant extracts from tree marigold (Tithonia diversifolia) and garlic (Allium sativum) in the inhibition of Colletotrichum gloeosporioides in vitro. The antifungal activity of the extracts was determined by the evaluation of their effectiveness in inhibiting the fungal mycelial growth and sporulation on PDA media. Fungicide, Atracol 70WP used to control the disease, was used for comparison purposes. Data obtained were analysed by ANOVA and Fishers mean separation test using Gestart version 6 software. Concentrations of 80 g/l of Allium sativum and 120 g/l of Tithonia diversifolia were significantly effective as antracol fungicides at 2 g/l which is the recommended rate by the manufacturer in inhibiting mycelial growth and sporulation of Colletotrichum gloeosporioides. However, further studies are recommended to evaluate the effectiveness of the extracts under field conditions.

Diallyl Trisulfide, the Antifungal Component of Garlic Essential Oil and the Bioactivity of Its Nanoemulsions Formed by Spontaneous Emulsification

“…Additionally, the antifungal activity of the nanoemulsions increases with the increase of the DAT concentration in the organic phase, whereby, if the nanoemulsions contain a higher level of DAT in their lipid phase, a smaller amount of DAT is required to completely inhibit the growth of wood decay. This corresponds to the previously reported study on the effect of the concentration of active ingredients in the lipid phase of nanoemulsions on the antibacterial efficacy [ 44 , 65 ].…”

“…The results clearly showed that garlic EO has an inhibitory efficacy against two wood decay fungi ( Table 1 ). Similarly, the garlic EO was demonstrated to possess antifungal activity against the agents of anthracnose in avocado, Colletotrichum gloeosporioides [ 44 ]; of tomato diseases, Penicillium expansum and Rhizopus stolonifer [ 45 ]; Aspergillus parasiticus , A. niger [ 46 ] and A. terreus [ 47 ]; Fusarium oxysporum [ 48 ] and F. thapsinum [ 47 ]; of grapes post-harvest disease, Botrytis cinerea [ 49 ]; Penicillium citrinum [ 50 ] and P. funiculosum [ 47 ]. In addition, in the previous reports, garlic EO or extract exhibits insecticidal, antifeedant, and repellent activities against many insects and mites [ 15 , 28 , 29 , 38 , 43 ].…”

Evaluation of Pretreatments and Extraction Conditions on the Antifungal and Antioxidant Effects of Garlic (Allium sativum) Peel Extracts

“…However, garlic clove extract was assessed against C. gloeosporioides, and the results indicated that at the same concentration (1000 ppm), the mycelial inhibition was 33.78%, whereas to reach a similar inhibition to this study, 5000–10,000 ppm is required [ 31 ]. Moreover, in a recent study, garlic clove extract needed higher concentrations (30 g/L–80 g/L) to reach an inhibition percentage of 76.19–82.94% after 8 days of radial growth of C. gloeosporioides [ 32 ]. In the latter study, the authors did not provide detailed information for an adequate calculation of the concentration used.…”