ARS | Publication request: Fungicide Application Technology

Submitted to: National Soybean Rust Symposium
Publication Type: Proceedings/Symposium
Publication Acceptance Date: November 7, 2007
Publication Date: December 11, 2007
Citation: Derksen, R.C., Ozkan, H.E., Zhu, H., Hammond, R., Dorrance, A. 2007. Fungicide Application Technology. National Soybean Rust Symposium.

Technical Abstract: Asian Soybean Rust (ASR) posses a significant risk to soybean production in the U.S. and currently fungicides are the only means for managing infection. It is difficult to protect soybeans against ASR infection since it usually develops low in the mature canopy. Infection is most likely to occur once the canopy is nearly fully developed and most difficult to treat. The objective of this research was to study the effect different application strategies had on the fate of fungicides in a mature and dense soybean canopy. Field trials were conducted in 2005 and 2006. Fluorescent tracers, water sensitive paper, and fungicide residue analysis were used to evaluate all of the application strategies. Factors evaluated included droplet size, spray pattern, spray volume, and the use of air-assisted spray delivery. Much more residue was found on leaf tissue sampled from the middle canopy section than the lower canopy section. Much more fungicide residue was also found on leaf tissue compared to stem tissue. Coverage and spray deposit measurements showed that medium spray quality nozzles performed better than nozzles producing coarse or fine sprays. Air-assisted delivery performed better than conventional flat fan treatment across both years. Twin-fan pattern nozzles that had 60 degrees of separation between spray patterns than the twin-fan pattern nozzles that had 60 degrees of separation between spray patterns. There was some indication that spray volume was not a good predictor of the amount of spray residue found on plant tissue and artificial targets. However, high spray volume produced higher spray coverage. This research demonstrates strategies growers can use to improve spray penetration into narrow-row soybean canopies which will help put fungicides where they will be most effective.