How to Conduct an On-Farm Foliar Fungicide Test

Ground or Aerial Application?

Either ground or aerial equipment can be successfully used to apply fungicides for a SXS test. The main determining factors will usually be equipment and operator availability and cost.

Advantages of aerial application - Aerial applicators can cover acres more quickly and there is no crop damage due to equipment-crop contact. In addition to wheel traffic injury, ground equipment can also spread disease inoculum through a field if the boom or vehicle contacts wet foliage.

Advantages of ground application - There is less potential for spray drift with ground application due to lower boom height. In parts of North America growers may also have greater access to ground equipment which could provide more flexibility in scheduling the applications.

Setting Up the Test

In any on-farm evaluation, the individual test strips should be as close to adjacent as possible. This is to insure that differences in crop performance in the strips are due to the treatment differences and not naturally occurring spatial variation. The larger the strips or the farther apart they are, the less confident one can be that differences in performance are real. In a fungicide vs. untreated SXS comparison it is necessary to include a buffer between the two strips to protect the untreated check strip from spray drift (Figures 1 and 2).

  • With ground application use a buffer width of 50 feet (twenty 30-inch rows)
  • With aerial application use a 75 foot buffer (30 rows) for still wind conditions and up to a 150 foot buffer (60 rows) for more windy conditions.
Spray drift pattern falling outside the effective swath width for an aerial application.

Figure 1. Spray drift pattern falling outside the effective swath width for an aerial application. Source: Univ. of Wisconsin.

Recommended layout for an on-farm fungicide vs. untreated SXS comparison.

Figure 2. Recommended layout for an on-farm fungicide vs. untreated SXS comparison (not drawn to scale).

Applying the Fungicide

  • Make the fungicide applications according to the label instructions. This is typically between tasseling (VT growth stage) and 50% brown silk for corn and early pod stage (R3) and later for soybean.
  • Communicate in advance with the applicator to verify the pass width of the aircraft or ground rig to be used. This typically varies from 50 to 69 feet for aerial and 40 to 80 feet for ground application.
  • Clearly mark the spray passes using flags or other suitable markers to visually guide the pilot or sprayer driver.
  • Permanently identify every treated and untreated strip using GPS or physical markers such as flags or stakes. This will help the combine operator note the exact location of all strips during harvest.
  • Note wind speed and direction and other environmental conditions at the time of application plus flight direction.

How to Minimize Spray Drift*

How to Minimize Spray Drift

Source: Spray Drift Task Force, and Terry Sharp, custom applicator, Indianola, IA.

In-Season Monitoring

  • Begin monitoring the treated and untreated strips for foliar diseases and overall plant health beginning at about the tasseling stage in corn and first bloom (R1 stage) in soybean. Record disease and severity four weeks after application.
  • Within one week before corn harvest, note differences in stalk lodging among strips. Count the number of lodged plants in four row lengths containing 25-consecutive plants for each strip. Total the counts to give percent stalk lodging.

Harvesting the Test

  • Harvest all of the end rows and any areas that did not receive a full rate of fungicide.
  • Measure and record the length of the treated and untreated strips with a tape or measuring wheel.
  • Harvest the same number of rows in all strips.
  • If possible, make harvest passes in the two fungicide passes and the two untreated strips as diagramed in Figure 2.
  • Use a well-calibrated yield monitor, weigh wagon or elevator scale to determine the grain yields produced in the different test strips. Test a grain sub-sample for moisture content if a weigh wagon or scale is used.
  • Correct yields to 15% moisture for corn, 13% for soybean.
  • Submit data as an "Agronomic" Trial Type to the Pioneer Field Information System (FIS) - Trial Data Entry (TDE).

Pesticide and Application Safety

Pesticide usage should follow all label instructions provided by the manufacturer. Likewise, field application should be conducted by skilled professionals with adequate training and safe, well-maintained equipment (including protective clothing and swath-marking devices).

Arial field application

Do's and Don'ts for Conducting an On-Farm Fungicide Side-by-Side Test


  • Select fields that contain a single hybrid or variety.
  • Spray a full round in the field rather than a single pass, especially with aerial application. Apply parallel to rows.
  • Use spray volume minimums of 2-5 for aerial and 15 gal./acre for ground applications or as noted on label.
  • Use adjuvants according to label instructions for specific products and crops. Crop oil can increase the potential for drift with aerial applications due to smaller droplets.
  • Request geo-referenced flight maps from the aerial applicator to verify plot location.
  • Install replicates of the SXS strips within the same field or in different fields to increase reliability of the test.


  • Split larger fields, spraying half and leaving half untreated. Spatial variability can mask real differences.
  • Spray when winds are >12 m.p.h. Try to minimize drift.
  • Spray corn too early. Early treatment may increase risk of crop injury. Verify proper timing from the product label.
  • Make repeat fungicide applications to the SXS test.
  • Combine fungicides with other pesticides, surfactants or fertilizers unless compatibility and crop safety is well documented. If in doubt, conduct a jar test (see label).

Additional Information