Field Performance Assessment

Field Performance Assessment - Eastern Canada

I. Performance Expectations
II. Assessing Control

I. Performance Expectations

If label directions and Dow AgroSciences recommended practices are followed, satisfactory control can be expected in most situations. If label rates and application instructions are not followed, control can diminish to unsatisfactory levels. Remember, an untreated area is the best measure for an objective evaluation of herbicide performance. Protect your herbicide investment by following label directions and Dow AgroSciences recommended practices. If you do not follow the label and Dow AgroSciences recommended practices, you should lower your expectations accordingly.

Infestation Levels
The number of weeds in a field will influence your visual expectations. If weed densities are low, for example, 10 per square foot, then 90% control would leave one weed per square foot. If weed densities are 100 per square foot, 90% control would leave 10 weeds per square foot and weed control would not look as effective. In fields with very heavy infestation levels, be prepared to spray those areas with weed escapes. While a few escapes can have a visual impact on the look of the crop, they do not provide much competition to a healthy crop, after the crop has grown past the critical weed free period.

Weather Conditions
Herbicide performance may be influenced by weather conditions. For example, with Broadstrike* Dual' Magnum' applied pre, adequate soil moisture is required for optimum herbicide activity. Rainfall that moistens the top two inches of soil is generally enough. If adequate rainfall is not received within seven to 10 days of pre-emergent applications of Broadstrike Dual Magnum, a shallow cultivation or rotary hoeing will control established weeds and move the herbicide into the weed germination zone.

Broadstrike Dual Magnum works best when the weeds are actively growing and taking up the herbicide. Weed control may be reduced due to adverse conditions (dry or very cold) when the weeds are stressed resulting in suppression only.

Application Rates
Recommended label rates must be used for good weed control. If you reduce rates, expect inconsistent or lower levels of weed control. Higher than recommended rates may result in reduced crop safety.

How Well the Label is Followed Affects Results
Protect your investment by following label directions and, where your use does not follow the label, lower your expectations accordingly.

When you cut corners on the label, you assume the risk of non-performance. Application (or incorporation) instructions should be followed because they have been proven to give the most consistent weed control.

Weed Resistance
Manage your weed resistance by rotating your crops and herbicide. Using herbicides with more than one mode of action is also recommended. For example, Broadstrike Dual Magnum has more than one mode of action which contributes to the improved management of weed resistance. Both products also control triazine resistant pigweed and lamb's-quarters.

FirstRate* is a Group 2 herbicide. Any weed population may contain plants naturally resistant to FirstRate and other Group 2 herbicides. These resistant individuals can eventually dominate a weed population if Group 2 herbicides are used repeatedly. These resistant weeds will not be controlled by FirstRate, or any other Group 2 herbicide.

To delay resistance:

avoid the exclusive, repeated use of FirstRate or any other herbicides in the same herbicide group
rotate with herbicides from a different herbicide groups that control the same weed spectrum as FirstRate
use tank mixes with herbicides from different groups when a use is permitted; integrate tillage or other mechanical cultural control methods into weed control programs wherever practical
prevent movement of resistant weeds to other fields by cleaning harvesting and tillage equipment and planting clean seed and keep accurate records of crop rotations and herbicides used in each of your fields.

For further information, contact your local Dow AgroSciences representative or call our Solutions Center at 1-800-667-3852.

Proper Application/Incorporation Equipment
Preplant Incorporated
The correct equipment must be used to ensure thorough mixing of the herbicide and effective incorporation of the herbicide into the top layer of soil. Improper mixing of product and incorporation is often the cause of poor herbicide performance.

Research has shown that accurate application for effective weed control can be accomplished when spray volume is uniform and spray nozzles are properly calibrated.

Equipment should be clean to ensure even coverage or incorporation of the field. It is important to have your sprayer properly calibrated to prevent uneven application. An uneven application could result in erratic weed control or crop damage.

Broadstrike Dual Magnum can be applied in a total spray volume of 100 to 400 L/ha (8.9 to 35.6 gallons/acre) using pressure between 135 and 270 kPa (20 to 40 psi).

Weed Species
Make sure you properly identify the weeds before spraying and double-check to ensure that your herbicide program controls the spectrum of weeds present in your field.

Field Conditions
Field conditions have a large impact on weed control. Many field conditions like flooding, trash cover and soil pH can negatively affect performance, but can be managed to help maintain a high level of weed control.

Crop Residue
The flumetsulam component of Broadstrike Dual Magnum binds weakly to crop residue and is easily moved into the soil with minimal rainfall.

Soil pH and Organic Matter
Soil conditions may affect the product fit in a grower's weed management plan as well as product performance. For example, Broadstrike Dual Magnum has use restrictions related to soil pH and organic matter. Do not apply Broadstrike Dual Magnum to areas where the soil pH is greater than 7.8 and organic matter is less than 2% as this could result in decreased crop tolerance. Also, do not apply to peat or muck soils or any soil containing more than 5% organic matter because this could result in decreased weed control.

II. Assessing Control

To help determine the level of performance that a herbicide delivers, it is important to leave an untreated area as a comparison to treated acres.

To determine the level of control, compare weed control in the treated area with the number of weeds in an untreated area. The percentage of control can be determined as follows.

Place a one-foot square measure on the ground in a representative treated area of the field, and count the number of live weeds (i.e. weed escapes) in the square (Value A).
Place the one-foot square measure on the ground in a representative location of the untreated area and count the number of live weeds in the square (Value B).
Determine the level of control using the following formula:

Percentage level of control = [1–(A/B)] x 100

For example, if you counted 10 live weeds (weed escapes) in a square foot section of the treated area and 82 live weeds in a square foot section of the untreated area, you would have the following level of control:

10 weed escapes / 82 live weeds = 0.12195

(1 – 0.12195) x 100 = 87.8% control
Monitor the field starting two weeks after spraying and look for herbicide activity on labelled weeds.