Objective 1: Laboratory studies showed that the EC50 values ranged from 211 µg/ml to 703 µg/ml Indicating higher dosages of silver nano particles are required to manage the disease white mold and the efficacy is isolate dependent.

Objective 2: There were no significant differences were obtained among the laboratory prepared and commercial grade silver nano-particles in the efficacy of white mold pathogen. Commercial silver nano-particles at the dosage of 1000 µg/ml applied at R4 stage has lowest white mold disease severity index and on par with the standard Endura. However, there were no differences among the yields obtained between the treatments (Table 1).

Objective 3: Seed samples were submitted to Dr. Achintya Bezbaruah, Professor at Civil Engineering, NDSU. Laboratory results are due.

Updated July 4, 2018:

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Use of Silver nanoparticles as an alternative to conventional fungicides to manage white mold in soybeans

Principal Investigators: Dr. Venkat Chapara, and Amanda Arens, NDSU Langdon Research Extension Center and Dr. Achintya Bezbaruah, NDSU Civil and Environmental Engineering

The goal of this project is to determine the fungicidal properties of silver nanoparticles prepared in the laboratory to manage white mold (caused by Scelrotinia sclerotiorum) on soybeans in field condition and to use as an alternative to conventional fungicides in managing white mold.

Research conducted: The effective concentration of silver nanoparticles on Scelrotinia sclerotiorum isolates were determined in the laboratory and the appropriate concentration and application timing of silver nanoparticles were tested in field condition at Langdon Research Extension Center (LREC) alone and in combination with biological fungicide (Ballard Plus®). Silver nanoparticles were prepared in the laboratory by research group of Co-PI Dr. Bezbaruah at the Department of Civil Engineering/NDSU, Fargo. S. sclerotiorum isolates have been recovered from sclerotia collected in the previous year from infected soybean stems. Out of twenty three S. sclerotiorum isolates, five isolates have been randomly picked and were tested for efficacy by determining the EC50 values (the effective concentration at which 50% of fungal growth reduction occurs) at LREC/ Plant Pathology Lab. The concentrations of silver nanoparticles used in the sensitivity test were 0, 1, 10, 100, 500 and 1000 µg/ml.

Further, the efficacy of laboratory prepared and commercial silver nanoparticles were tested in field condition using concentrations of 500 and 1000 µg/ml. Foliar applications of silver nanoparticles alone and in combination with Ballard Plus were compared with standard dose of conventional fungicide “Endura” and a biological fungicide “Ballard Plus” at R1 and R4 stage of soybean. Supplemental irrigation was provided to enhance disease incidence during flowering season.

Findings of the research:
Laboratory results: Silver nanoparticles at very high concentrations showed response of growth reduction on S. sclerotiorum isolates when grown on silver nanoparticle amended potato dextrose agar (PDA) culture media Petri plates. The EC50 values ranged from 211 µg/ml to 703 µg/ml indicating silver nanoparticles as of alone do not have fungicidal properties (Figure 1).

Field research results: indicate mean white mold incidence was high (9.5%) in non-treated control with a mean severity of 2.5% and has higher index (percent white mold incidence x severity/100) when compared with the other treatments of the current research trial. Whereas, the lowest incidence of white mold was observed in the combination treatment of commercial grade silver nanoparticle at 1000 µg/ml with standard dose of Ballard Plus when applied at R1 stage of soybean (Figure 2).

Benefits/Recommendations to North Dakota soybean farmers and industry: In general, research with low diseases incidence and of only one year is often difficult to draw conclusions from.

The objective of silver nanoparticle residue determination in soybean seed is under progress.

Acknowledgements: The author acknowledge the financial support from North Dakota Soybean Council (NDSC) in conducting this research.