Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Emmanuel Byamukama

Second Advisor

Shaukat Ali


Biopesticides, essential oils, fungicide, oat, thymol, wheat


Spring wheat (Triticum aestivum L.) and oats (Avena sativa L.) are important crops due to their high consumption in our daily diet worldwide. They are the main food of consumption per capita due to the high amino-acid content as well of vitamins. However, grain production is limited due to the negative impact of the diseases that cause significant yield loss. Diseases in oats, such as crown rust caused by Puccinia coronata f. sp. avenae (Pca), and in wheat such as Fusarium head blight (FHB) caused by the fungus Fusarium graminearum. Foliar diseases such as tan spot incited by the fungi (Pyrenophora tritici-repentis), Septoria nodorum blotch (Parastagonospora nodorum), and spot blotch (Bipolaris Sorokiniana) are known to compromise grain yield and seed quality. The integrated pest management for these diseases is by using tolerant/resistant plant varieties, crop rotation, and mostly fungicide applications due to their high efficacy controlling fungal diseases. However, the overuse of synthetic fungicides has led to the development of pathogen resistance, and concerns in the environment and human health. Therefore, it is necessary to explore new products with lower toxicity and less negative impact on human health and the environment. Biopesticides such as essential oils (EOs) and pure bioactive compounds present in the EOs are substances with known antifungal properties, multiple mechanisms of action, and low toxicity in humans and environment. However, little is known about their effect on the fungal pathogens that affect small grains. The objectives of this study were: (1) To determine the potential EOs in the control of oat crown rust in vivo, (2) To determine the potential effect of EOs and bioactive compounds in the control of three important pathogens that cause foliar diseases in wheat in vitro, and (3) To determine in vitro and in vivo the potential as fungicide of two EOs, two commercial products with EOs, and two bioactive compounds presents in EOs, in the control of the fungal pathogen Fusarium graminearum. For the first objective, a two-year field study experiment, was conducted testing two EOs, neem and karanja, at two concentrations (52 and 72 %) and three rates (3.7, 7.5, 11.25 L/ha). The synthetic commercial fungicide Headline (Pyraclostrobin) and a nontreated (water) were used as checks. Applications of the above treatments were made at the flag leaf stage (Zadok’s- 37) in two oats cultivars, Horsepower and Goliath. Percentage of disease incidence (%DI), stem lodging percentage, normalized difference vegetation index (NDVI), test weight (TW), and yield were assessed for each year. In both years, the two essential oils showed a higher yield and a reduced %DI at the highest concentration and rate compared with the untreated check. The synthetic fungicide, Headline, showed a significantly higher yield (P

Library of Congress Subject Headings

Essences and essential oils.
Wheat -- Diseases and pests -- Control.
Oats -- Diseases and pests -- Control.
Grain -- Diseases and pests -- Control.
Fungal diseases of plants.
Natural pesticides.

Number of Pages



South Dakota State University



Rights Statement

In Copyright