Due to the weather, a number of no-till soybean fields have not received a burndown treatment yet. As a result, many are asking about options for control. First a number of considerations:

2,4-D ester: Rate of 2,4-D may need to be adjusted. Most 2,4-D brands require a 4 week delay between application of 1 qt and planting soybeans. Rates less than 1 qt/A does not provide the same level of horseweed control. The interval between application differs with 2,4-D rates and brands. Be sure to read the label of the brand you intend to use.

Kixor products: These products have good activity on glyphosate and ALS resistant horseweed, but they have a number of restrictions due to crop safety: [Read more…]

Over the past few years, a few fields have been treated with an organo-phosphate insecticide and then with an ALS-inhibiting herbicide and significant injury has occurred. A number of corn herbicides have label precautions about use of an organo-phosphate insecticide at planting due to potential crop injury. This includes the insecticides Counter (terbufos), Lorsban (chlorpyrifos), and Fortress (chlorethoxyfos). The herbicides include both soil-applied and postemergence herbicides. Some of the common products include Callisto (Halex GT); Resolve (Steadfast, Basis); Accent; Capreno, Sharpen or Kixor. Note that the list is not only Group 2 (or ALS-inhibiting herbicides). If using an organo-phosphate insecticide, a list of herbicides that have potential interactions can be found at https://extension.udel.edu/ag/files/2014/01/CornWeedguide.pdf and go to Table 19.

Unfortunately, most corn seed companies no longer designate hybrids as either IT or IR. So if you are not sure, take the cautious approach and assume the hybrid is a “standard” hybrid (no enhanced tolerance for imidazolinone herbicides); and follow the most restrictive guidelines.

I have been asked by a few people about the differences in metolachlor (the active ingredient in Dual) products. The “old” Dual in the early 1990s was two isomers of metolachlor, R and S isomers. The Dual II included a safener to improve crop safety (improves safety to corn, not to broadleaf crops; hence Dual for broadleaf crops and Dual II for corn). [Read more…]

The weather has not been favorable for maximum effectiveness of many postemergence (or burndown) herbicides. Cool weather and overcast skies are not ideal conditions for herbicide performance. And given that many fall and early spring emerging weeds can be difficult to control once the crop is planted, it is important to scout your no-till fields to determine if a follow up treatment is necessary prior to planting.

PPO-herbicides (Group 14) used in this area include Sharpen, Valor, Authority, Reflex, Blazer, Cobra, Aim, and Cadet. In addition to the single active ingredients, there are a number of premixes containing these PPO herbicides. This group is quite varied so making generalizations about these herbicides is difficult. PPOs have gained popularity in the past few years to help combat herbicide-resistant weeds.
Here are a few points to know about these herbicides: [Read more…]

Last fall we collected seed from Palmer amaranth plants in Delaware and Wicomico County, Maryland and tested them for resistant to both glyphosate or ALS-inhibiting herbicides (Group 2). A few of the samples tested positive for resistance to both glyphosate AND ALS-herbicide. We used Pursuit in the initial trials, but past experience indicates that these biotypes are resistant to many other herbicides in this family. See the table below for list of common ALS herbicides in the region. [Read more…]