DiFlexx DUO — A New Corn Herbicide

Apr 12, 2016

By Amit Jhala - Extension Weed Management Specialist

DiFlexx™ DUO is a herbicide for control of annual broadleaf and grass weeds in field corn, corn grown for silage, popcorn, and seed corn and for post-harvest burndown weed control. It is a premix of DiFlexx (dicamba: 19.73%) and Laudis (tembotrione: 2.83%). DiFlexx DUO has Crop Safety Innovation (CSI™) Safener technology, which enables corn plants to better withstand herbicidal activity and provides better crop safety. DiFlexx is a growth regulator herbicide and Laudis is a pigment inhibitor. Therefore, this herbicide has two modes of action: Group 4 and 27.

Field photo of weed trial with Roundup Powermax

Figure 1a. Non-treated control in UNL weed management trial.

DiFlexx DUO is a selective pre-emergence and post-emergence herbicide for

control of annual broadleaf weeds;

control and/or suppression of many biennial/perennial broadleaf weeds; and

control of annual grasses in corn.

Weed control ceases within hours after DiFlexx DUO is applied. Symptoms on susceptible weed species include epinastic-like symptoms such as the stems and leaves facing outward or downward and tissues turning yellow and bleached in color and soon becoming necrotic. Plant death generally occurs within 7 to 14 days after application.

Do not apply DiFlexx DUO by air or through any type of irrigation system. Use application equipment that will provide uniform, thorough spray coverage of weed foliage to achieve consistent weed control. DiFlexx DUO mixtures should be sprayed within 24 hours of mixing to avoid product degradation. DiFlexx DUO is rain-fast within four hours after application to most weed species.

Field photo of weed trial with Diflex DUO and Roundup Powermax

Figure 1b. Weed control with DiFlexx DUO applied early post-emergence at 32 fl oz/acre in corn.

Weed Control Information

DiFlexx DUO applied post-emergence at recommended rates of 24 to 40 fl oz per acre will effectively control a broad array of important annual broadleaf weeds and grasses. Best control of annual broadleaf weeds is achieved when weeds are less than 6 inches in height and actively growing. Best control of annual grasses is achieved prior to tillering when grasses are actively growing. In corn, adding atrazine at a minimum of 0.5 lb active ingredient per acre will improve control of annual broadleaf weeds and increase the speed, spectrum, and consistency of grass control. DiFlexx DUO applied post-emergence at 24 to 40 fl oz/acre will also control or suppress many biennial/perennial broadleaf weeds.

Field photo of weed trial in corn with resistant Palmer amaranth

Figure 2a (above). Atrazine + HPPD inhibitors-resistant Palmer amaranth in corn field near Shickley before application of DiFlexx DUO. Figure 2b (below). Control of resistant Palmer amaranth 14 days after application of DiFlexx Duo at 32 fl oz/acre in Roundup Ready corn.

As a pre-emergence application, DiFlexx DUO will provide suppression/control of certain annual broadleaf and grass weeds but will generally not provide season-long weed control. Pre-emergence applications of DiFlexx DUO should always be either tank-mixed with additional registered residual pre-emergence herbicides or be followed by a planned post-emergence herbicide for improved weed control. Always follow the most restrictive use rates and use instructions listed on the labeling of all tank-mix partners.

Application Method, Timing, and Number of Sprays

Broadcast Application: DiFlexx DUO may be applied to corn as a broadcast spray application from emergence up to, but not including, the V7 stage of growth (seventh leaf collar) or 36 inches tall, whichever comes first.

Directed Application: DiFlexx DUO should be applied as a directed spray application when corn is from the V7 through V10 growth stages (7-10 collars), up to 36 inches tall, or up to 15 days prior to tassel, whichever occurs first. Directed sprays should also be used if corn leaves prevent proper spray coverage, sensitive crops are grown nearby, or when tank-mixing with 2,4-D.

Sequential Application: A maximum of two (2) applications of DiFlexx DUO may be applied per growing season. Sequential applications must be separated by a minimum of two (2) weeks.

Postharvest Burndown Treatment: DiFlexx DUO may be used as a postharvest burndown treatment to control broadleaf weeds at any time of the year following harvest of corn or planting of the next rotational crop. Specific rotational crop intervals must be observed between the postharvest application of DiFlexx DUO and planting of the next crop (Table 1).

Rotational Crop Restrictions

The interval between application and planting rotational crops is shown in Table 1. If a corn crop has been destroyed by hail or other means soon after a DiFlexx DUO application, field corn, seed corn, popcorn, and corn grown for silage may be replanted immediately. Other crops may be replanted at the intervals specified in Table 1. Planting rotational crops at intervals less than those specified may result in crop injury. Moisture is essential for the degradation of this herbicide in soil. If dry weather prevails, use cultivation to allow herbicide contact with moist soil.

Cover Crops

Use of cover crops as a means of soil improvement, erosion control, weed and/or insect suppression, etc., following harvest of corn in the fall is increasing in the Midwest. Planting of cover crops in fields treated with DiFlexx DUO is allowed as long as these cover crops are not grazed by livestock or harvested for food. Cover crops are to be tilled under or chemically controlled with burndown herbicides in the spring. Cover crops can be planted within 90 to 120 days after application of DiFlexx DUO. However, all potential cover crops have not been evaluated for tolerance to DiFlexx DUO and significant crop injury may occur. Prior to seeding a cover crop, complete a successful seed bioassay to provide an indication of the level of tolerance to the prior DiFlexx DUO application.

Table 1. Rotational crop guidelines after application of DiFlexx DUO

IMMEDIATE	4 MONTHS	8 MONTHS	10 MONTHS	18 MONTHS
Corn (field, seed, pop, and silage)	Cereal grains (except corn and sorghum) Sweet corn Sugarcane Grass grown for seed Timothy	Soybean Onion (C)	Sorghum Peas Potatoes Canola Alfalfa Tomato Sunflower Snapbeans Sugarbeets (A,B) Dry beans (A) (types and varieties for commercial production except those listed under 18 months)	Cucurbits Dry beans (red, kidney, cranberry bean, non-commercial “garden” types and varieties) All other crops (D)
(A) Cumulative precipitation between application of DiFlexx DUO and replanting to sugar beets or dry beans must total 20 inches. Furrow or flood irrigation cannot be included in the total. The amount of cumulative precipitation required before planting a rotational crop is in addition to the required rotational interval given in months. (B) Thorough tillage should follow the crop in which DiFlexx DUO was used and precede the rotation to sugar beets. (C) This plantback interval requires that onions be grown under irrigated conditions. The plantback interval for non-irrigated onion is 18 months. (D) All other crops may be seeded only after the completion of a successful bioassay after a DiFlexx DUO application. Refer to the “Field/Small Scale Bioassay” section.

IMMEDIATE

4 MONTHS

8 MONTHS

10 MONTHS

18 MONTHS

Corn (field, seed, pop, and silage)

Cereal grains (except corn and sorghum)
Sweet corn
Sugarcane
Grass grown for seed
Timothy

Soybean Onion (C)

Sorghum
Peas
Potatoes
Canola
Alfalfa
Tomato
Sunflower
Snapbeans
Sugarbeets (A,B)
Dry beans (A) (types and varieties for commercial production except those listed under 18 months)

Cucurbits
Dry beans (red, kidney, cranberry bean, non-commercial “garden” types and varieties)

All other crops (D)

(A) Cumulative precipitation between application of DiFlexx DUO and replanting to sugar beets or dry beans must total 20 inches. Furrow or flood irrigation cannot be included in the total. The amount of cumulative precipitation required before planting a rotational crop is in addition to the required rotational interval given in months.

(B) Thorough tillage should follow the crop in which DiFlexx DUO was used and precede the rotation to sugar beets.

(C) This plantback interval requires that onions be grown under irrigated conditions. The plantback interval for non-irrigated onion is 18 months.

(D) All other crops may be seeded only after the completion of a successful bioassay after a DiFlexx DUO application. Refer to the “Field/Small Scale Bioassay” section.

Field/Small Scale Bioassay

A field/small scale bioassay trial must be completed before rotating to a cover crop other than those specified in Table 1. To conduct an effective field bioassay, grow strips of the crop(s) you intend to grow the following season in a field previously treated with DiFlexx DUO. Place the test strip in a controlled area that includes low areas and knolls, and soil variations such as type and pH. Crop response to the bioassay will determine if the crop(s) grown in the test strips can be grown safely in the areas previously treated with DiFlexx DUO.

For an effective small scale bioassay, collect uniform samples of all soil types from the DiFlexx DUO-treated field and place the soil into a sturdy container. Plant the desired crop into the soil, apply water, and place the container in a warm, sunny area to allow germination and growth of the crop. Monitor growth of the cover crop over a three- to four-week period. If the cover crop emerges and grows normally, the risk to establish and grow the cover crop in the DiFlexx DUO-treated field should be tolerable.

Spray Drift Management

Spray drift may result in injury to non-target crops or vegetation. To avoid spray drift, DO NOT apply when wind speed is greater than 10 mph or during temperature inversions. Do not apply when weather conditions, wind speed, or wind direction may cause spray drift to non-target areas. Do not apply where possible drift may occur to unprotected persons, or to food, forage, or other plantings that may then be rendered unfit for sale, use, or consumption.

Information on Droplet Size

The most effective way to reduce drift potential is to apply large droplets. The best drift management strategy is to apply the largest droplets that still provide sufficient weed coverage and control. Applying larger droplets will reduce drift potential, but will not prevent drift if applications are made improperly, or under unfavorable environmental conditions. Uniform, thorough spray coverage is important to achieve consistent weed control. Select nozzles and pressure that deliver medium spray droplets as indicated in nozzle manufacturer’s catalogs and in accordance with ASAE Standard S-572. Nozzles that deliver coarse spray droplets may be used to reduce spray drift, provided spray volume per acre (GPA) is increased to maintain coverage of weeds.

Water Volume and Nozzles

DiFlexx DUO can be applied using a minimum of 10 gallons of water per acre (unless a higher volume is specified for a tank-mix partner). For weed control in dense weed populations or under adverse growing conditions, 15 to 20 gallons of water per acre is recommended. Flat fan nozzles of 80º or 110º are recommended for optimum post-emergence coverage. Typically, flat-fan nozzles operated at 30 to 60 PSI will deliver medium spray droplets, providing optimum spray coverage and canopy penetration. Lower pressure operation and/or higher volume flat fan nozzles typically deliver coarse sprays. Refer to nozzle manufacturer’s catalogs.

Boom height should be based on the height of the crop—at least 15 inches above the crop canopy.

Air induction nozzles should be used at or near 80 psi to produce a medium droplet size.

Proper agitation should be maintained within the tank to keep the product dispersed.

Do not use nozzles that produce fine (e.g., Cone) or extra coarse (e.g., Flood jet) spray droplets.

Spray Additives

DiFlexx DUO is a suspension concentrate that requires the use of an external surfactant and a nitrogen fertilizer source to achieve optimum weed control when applied post-emergence or when applied preplant or pre-mergence if weeds are present. Agriculturally approved drift-reducing additives also may be used.

Surfactant

The use of a Methylated Seed Oil (MSO) or Crop Oil Concentrate (COC) is recommended when DiFlexx DUO is used or when alternative adjuvants are not otherwise specified. MSO or COC can improve control of weeds under stress, in high populations, in mixed grass and broadleaf weed populations, and under conditions of low humidity. Use MSO or COC at 1 gallon per 100 gallons of water (1% v/v). The MSO or COC should contain at least 80% MSO or COC and 10% or greater emulsifier.

Ammonium Nitrogen Fertilizer

Use 1.5 qt/acre of a high-quality urea ammonium nitrate (UAN) or 8.5 to 17 lb/100 gallons of spray-grade ammonium sulfate (AMS). Use UAN under conditions of low relative humidity for greater weed control.

Corn Precautions and Restrictions

Plant corn at least 1½ inches deep. Corn seed must be completely covered with soil and furrow firmed.

In rare instances, applications of DiFlexx DUO during periods of rapid growth may result in temporary leaning of the crop. Corn will usually become erect within three to seven days. Cultivation should be delayed until after the corn is growing normally to avoid potential stalk breakage.

Seed corn and popcorn only. Herbicide sensitivity in all hybrids and inbreeds of seed corn and popcorn has not been tested. Consult your seed provider for advice on hybrid/inbred tolerance before applying DiFlexx DUO. If the tolerance of a hybrid/inbred is not known, apply DiFlexx DUO to a small area to first determine if the hybrid/inbred is tolerant prior to spraying large acreages of that hybrid/inbred.

DiFlexx DUO may be applied up to 40 fl oz/acre per application.

The maximum seasonal rate of DiFlexx DUO which can be applied is 78 fl oz/acre per use season.

Do not apply DiFlexx DUO to corn that exhibits injury from previous herbicide applications.

Do not apply DiFlexx DUO with liquid fertilizers as the primary spray carrier.

Do not apply more than two applications of DiFlexx DUO per use season.

Do not graze or harvest corn forage within 45 days of the final DiFlexx DUO application. Corn grain and stover may be harvested once the crop has reached the ensilage (milk) stage.

Source: unl.edu