Abstract
Cercospora leaf spot (CLS) on sugarbeet, caused by the pathogen Cercospora beticola (Cb), is a critical biotic factor that affects sugarbeet growth and leads to the decrease of sucrose quantity and quality. Fungicide applications are a common practice to manage CLS, often informed by weather-based recommendation models and occurring up to 6 times during the growing season. Such heavy fungicide usage has led to Cb developing genetic resistance to fungicides and causes environmental pollution. Non-toxic CLS management is proposed as an innovative approach for sustainable CLS disease management. Heating water to a high temperature can be as deadly as toxic fungicides, often killing pathogens in seconds. The goal of this study is to develop an environmentally friendly way to eradicate Cb in crop residue by utilizing hot water. Application of hot water is one of the most effective energy transfer methods and has the added benefit of not harming crop plants or the climate. The cost for tap water is less than a penny per gallon, compared to up to $600 per gallon for commercial fungicide. This study uses heat transferred via water to reduce Cb prevalence, as water infiltrates into crop residues and reaches target pathogens fast and effectively. Experiments were conducted in a greenhouse on dry and fresh crop residues. Each of those samples is placed on a 15-cm diameter plate and evaluated to optimize conditions of temperature at 50-90°C, volumes between 10-100 ml, and droplet size between 100-400 microns of hot water and monitored for fungal growth or death for 3-5 days. The result indicated that boiling water can effectively kill Cb on crop residues and can facilitate sustainable management of Cb inoculum levels in sugarbeet fields. The system is scaled up for outdoor applications by deploying a UGV equipped with an on-demand water heater to heat water instantaneously through a heat exchanger. The benefit extends to applications on other biotic stresses (e.g., pest and weeds) for sustainable management of pesticides and herbicides.
