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.

KEYWORDS:

• Allium sativum
• avocado
• anthracnose
• Colletotrichum gloeosporioides
• control
• Tithonia diversifolia

Acknowledgments

I thank the Almighty God for giving me the strength to carry on with this work. I am so grateful to my supervisor, Dr S. Kimaru, for his guidance, constructive comments and encouragement throughout the study. I am thankful to Plant Sciences Department, Kenyatta University for the chance to undertaking my research work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Public interest statement

The researcher focuses on post-harvest diseases of avocado in Kenya. The avocado has become a major fruit and economic earner for the country and at the world level. Quality and safety issues at local and export market call for research for addressing this. Post- harvest diseases being one of the major quality concerns motivated the researcher to undertake research project to study management/control options of these diseases in order to have quality, safe fruits acceptable by the consumers locally and internationally.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials. https://doi.org/10.6084/m9.figshare.13732153