The overall goal of this project is to enhance soybean productivity, profitability and environmental sustainability by using nano-encapsulated biopesticides (plant essential oils), alone or in combination with fungicide seed treatments, to manage soybean SDS. Our project goal fits into ISA’s research focus of ‘Soybean disease, nematode, insect pest and abiotic stress biology, management, and yield loss mitigation.
Plant essential oils are a type of biopesticide that has shown effectiveness against several plant pathogens and pests. For example, lemongrass oil and thymol oil effectively inhibited Fusarium solani growth in vitro (Eke et al. 2020, Kong et al. 2021). In addition, lemongrass and thymol reduced disease caused by several other plant pathogens, including Phytophthora root rot in curcubits (Amini et al. 2016) and bacterial pustule in soybean (Kumari et al., 2018). Plant essential oils are promising crop protection options because they are safer and more environmentally friendly than their chemical counterparts.
Nanotechnology is being explored as a pesticide delivery system that can enhance the efficacy of pesticides and reduce pesticide use. With this technology, pesticides are encapsulated in nano-emulsions which have droplet size within ranges of 1~100 nanometers. These nano-emulsions provide many advantages, including increased stability, controlled release, and higher absorption rates of the encapsulated active compounds.
Nano-encapsulation of biopesticides can increase their efficacy by up to ~20% (Kah et al., 2018), reduce their cost, protect them from adverse environmental conditions (Blanco-Padilla et al., 2014) and allow better control of their release (Mossa et al., 2018). Nanocellulose is an organic nanomaterial that is nontoxic, biodegradable, and an effective nanoencapsulation agent. Soybean and corn residues have high cellulose content and are therefore great, low-cost sources of nanocellulose.
Our goal is to use nano-encapsulated plant essential oils as a seed treatment for management of soybean sudden death syndrome (SDS). This is an economically important disease of soybean that has limited treatment options. Two fungicide seed treatments are currently available to manage SDS: ILeVO (fluopyram) and Saltro (pydiflumetofen). However, these treatments are expensive and may not result in economic profit to growers when weather conditions are not conducive to SDS. In addition, ILeVO treatments are known to cause phytotoxicity in soybean seedlings, which can negatively impact root growth and sometimes reduce yield (Budi, 2020). A combination of nanoencapsulated plant essential oils and ILeVO at a reduced rate has the potential to effectively suppress SDS without phytotoxicity.
With ISA funding over the last two years, we have been testing nanocellulose derived from soybean residues to encapsulate plant essential oils with activity against the SDS pathogen, Fusarium virguliforme. In this proposal (year 3), we are requesting a third year of funding to continue our work to deliver a novel SDS management tool for soybean growers. Since corn residue is more widely available and is a more sustainable source of nanocellulose for agricultural uses than soybean residue, we propose to encapsulate selected essential oils in nanocellulose obtained from corn for year 3 studies.
In addition, we propose to focus our efforts on optimizing the delivery system for the essential oils as this will make our findings more immediately transferable to soybean growers. We will determine the optimum rate to treat soybean seeds that allows for effective suppressions of SDS while avoiding phytotoxicity to soybean. We will also test different combination seed treatments, including mixtures of essential oils and combinations of essential oils with reduced rates of IlEVO, for their effectiveness against SDS.
Opportunity for farmers and the soybean industry:
Farmers and the soybean industry will benefit from increased value of soybean by-products from the utilization of crop (soybean and corn) residues to obtain safe, inexpensive cellulose for use in a variety of nanotechnology applications. Industry will also be provided with a novel technology to explore in their pesticide and biopesticide formulations. Although in this proposal we are focusing on SDS, the nanotechnology developed can be tested in the future against other pathogens and pests, and as a way to deliver micronutrients and plant health products to soybean.