2019
Defoliation Soybean Response to Priaxor Application
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Contributor/Checkoff:
North Dakota Soybean Council
Category:
Sustainable Production
Keywords:
Crop protectionDiseaseField management
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Lindy Berg, North Dakota State University
Co-Principal Investigators:
Project Code:
QSSB
Contributing Organization (Checkoff):
North Dakota Soybean Council
$2,000
Institution Funded:
North Dakota State University
$2,000
Brief Project Summary:

After hail, soybean farmers may choose to mitigate the ripped leaf and broken plant carnage with a fungicide application. These fungicides are marketed to control and prevent disease and to boost plant health against stress. Priaxor is a common plant health fungicide recommended by agronomists after hail. Farmers observe darker shades of green soybean plants as an indication that the fungicide is mitigating the hail injury. But do plant health fungicides increase soybean yield production? The objective of this project is to determine plant response to Priaxor fungicide after simulated hail injury at the R2 and R5 soybean stages.

Key Benefactors:
farmers, agronomists, extension specialists

Information And Results
Final Project Results

Update:

View uploaded report Word file

A greenhouse study was conducted at the NDSU Carrington Research Extension Center during January-June, 2019. The objective of this study is to determine plant and seed yield response to Priaxor fungicide application after simulated hail injury at the R2 and R5 soybean growth stages.

Materials and methods:
The study design was a randomized complete block design with split-split plot arrangement with three replications. Soybean cultivar AG009X8 inoculated with rhizobia bacteria was planted in 10-inch diameter pots with Miracle-Gro Moisture Control potting soil on January 14.
- Untreated checks: no defoliation; no fungicide.
- 33% leaf removal: counted all leaves and removed 33% of leaves starting top to bottom of the plant.
- 66% leaf removal: counted all leaves and removed off 66% of leaves started top to bottom of the plant.
- Main stem cut-off: cut the main stem at the position that would remove half of the trifoliate notes on the main stem. 100% of the leaves were removed below the cut.
- Main stem bent over: the main stem was bent over at 135-degree angle at the same point as the cut-off treatment. One hundred percent of leaves were removed below the break and 25% of leaves were removed on the bent over portion of the stem.

Priaxor was foliar-applied three days post injury at a rate of 4oz/a with a handheld boom backpack sprayer.
Canopy coverage was recorded using the Canopeo phone app and greenness was measured using a Minolta SPAD-502 chlorophyll meter. Physiological maturity (R8 stage) was recorded and seed was hand threshed on June 6.
Data was analyzed using SAS software.

Results: The foliar fungicide applied at R2 or R5 stages did not increase seed yield of defoliated or non-defoliated soybean plants. Also, plant maturity was not affected by the fungicide. Across fungicide treatments (untreated check and Priaxor) and growth stages, plant maturity and yield was similar between the untreated check and 33% defoliation. Seed yield declined 19 to 32% with 66% defoliation, cut stem, or bent stem treatments compared to the untreated check. Also, plant maturity was delayed 5 to 11 days with 66% defoliation, cut stem or bent stem treatments compared to the untreated check.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.