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Soybean Dicamba - Yield Loss Prediction (SoyD-YeLP)

Matthew R. Foster, James L. Griffin, and Josh T. Copes

The SoyD-YeLP app was developed to predict percent yield loss for non dicamba-resistant soybeans exposed to dicamba. Data used to develop the app were collected in Louisiana 15 days after indeterminate, maturity group 4.8 to 5.1 soybeans were treated with dicamba herbicide at V3/V4 (plants with 3/4 nodes and 2/3 fully expanded trifoliates) or at R1/R2 (plants with open flower at any node on the main stem/open flower at one of the two uppermost nodes).

Six injury variables are used to calculate percent yield reduction. For V3/V4, variables include lower stem base lesions/cracking, plant height reduction, terminal leaf epinasty, leaf petiole droop, leaf petiole base swelling, and stem epinasty. For R1/R2, variables include lower stem base lesions/cracking, terminal leaf chlorosis, leaf petiole base swelling, stem epinasty, terminal leaf necrosis, and terminal leaf cupping.

Terminology for Injury Variables:

  • Chlorosis - yellowing
  • Cupping – outer margins of leaflets are rolled inward resulting in upward or downward cupping
  • Droop – angle between leaf petiole and main stem greater than 45 degrees
  • Epinasty – twisting or curling of a leaf or stem
  • Leaf petiole - slender stalk by which a leaf is attached to the stem
  • Necrosis – terminal bud kill/death
  • Terminal – uppermost growing point on the main stem where new leaves are produced

Using This App

Using This App

You will be prompted to select when exposure to dicamba occurred (V3/V4 or R1/R2) by clicking on the Growth Stage at Exposure link below. For all variables except plant height reduction, enter injury level based on 0 to 5 where:

  • 0 = No injury
  • 1 = Slight
  • 2 = Slight to moderate
  • 3 = Moderate
  • 4 = Moderate to severe
  • 5 = Severe

Clicking on the icon next to each variable will provide photos showing representative ratings for 1, 3, and 5.

For plant height reduction, injury level is based on 0 to 100%. As an example, if plant height of affected soybean plants is 10 inches and non-affected plants are 20 inches, height reduction is 50%.

It is important that if injury or height reduction is not observed that “0” be entered. If injury level or plant height reduction varies across the field, an average value representative of the entire field can be entered or the field can be sub-divided with values entered for each area of the field to obtain an average yield loss for the entire field.

After data is entered, click on the Yield Loss Calculation link.

Soybean Growth Stage
at Dicamba Exposure

(0 to 5)

(0 to 5)

(0 to 5)

(0 to 5)

(0 to 5)

Back

Based on the information entered for soybeans 15 days after exposure, yield loss may be as high as . Yield loss prediction is only as accurate as the data entered.
Data Entered

Lower Stem Base Lesions/Cracking

0

Terminal Leaf Chlorosis

0

Leaf Petiole Base Swelling

0

Stem Epinasty

0

Terminal Leaf Necrosis

0

Terminal Leaf Cupping

0

Authors

  • Matthew R. Foster, Graduate Research Assistant, School of Plant, Environmental, and Soil Sciences, Baton Rouge, LA
  • James L. Griffin, Professor Emeritus, School of Plant, Environmental, and Soil Sciences, Baton Rouge, LA
  • Josh T. Copes, Assistant Professor, Northeast Research Station, St. Joseph, LA

Photos courtesy of James L. Griffin and Matthew R. Foster

Comments concerning this app can be sent to jgriffin@agcenter.lsu.edu

Disclaimer

The effects of initial injury, persistence of injury, and effect on crop yield loss from a herbicide will be dependent on receiving timely rainfall or irrigation during the growing season and on the effective management of insects, diseases, and weeds to maximize crop yield potential.

The data used to develop this app were based on indeterminate, maturity group 4.8 to 5.1 soybeans grown in Louisiana and the models were validated in Louisiana. The ability of the models to accurately predict yield loss in other soybean producing areas has not been evaluated.