ASK THE AGRONOMIST BLOG

Stine’s Ask the Agronomist blog is your source to the latest information from our expert team, including advice and insight on field practices, product recommendations, planting and harvest updates, new technologies, crop management, innovative research and information about how to keep your farm operation running smoothly year round. 

  • Aaron Stockton Image

    Extra Moisture? Watch for Waterhemp

    July 24, 2019

    Posted by Aaron Stockton in Crop Management

    As the name of the weed suggests, waterhemp — a member of the pigweed family that affects soybean fields — thrives in areas where there’s been a lot of moisture. This year, that’s pretty much the entire country. Flooding exacerbates the spread of waterhemp, which a few years ago used to be a problem only in the South but has gradually made its way up to the northern United States. Now, to make matters worse for growers, scientists have discovered another strain of herbicide-resistant waterhemp.

    According to the University of Illinois Extension, certain strains of waterhemp are now resistant to the Group 15 herbicide family. Extension experts note this includes herbicides with the following active ingredients: acetochlor, dimethenamid, metolachlor, pyroxasulfone and S-metolachlor. Waterhemp has also shown resistance to six other herbicide groups, including Group 2 (ALS inhibitors), Group 5 (triazines), Group 14 (PPO inhibitors), Group 9 (glyphosate), Group 27 (HPPD inhibitors) and Group 4 (2,4-D).

    What does this mean for soybean growers? Growers will need to use multiple herbicide families, mixing up different modes of action. If they have a weed that’s resistant to whatever herbicide they’re using, multiple chemical families within your chemical program are a must. Start with clean fields and then come back with a post-emerge after the crop is up and weeds are within the legal range. You can even come back and spray a different family within the post-emerge, adding additional residual into the mix.

    Growers who are using the Stine® Enlist E3soybean system this growing season will be at an advantage. Waterhemp shows itself to be increasingly problematic when it comes to single-mode or glyphosate-based soybean platforms. This reason is why we are so excited to see the Enlist E3 soybeans finally hit the market. So far, we have seen it in burndown scenarios, and the weed control of not just waterhemp but also marestail and other significant weeds has been absolutely fantastic! My expectation with all the rain we are receiving is that weed pressure will continue to be tremendous, and those weeds, especially waterhemp, will be very robust and tough to kill this year. Having a platform like Enlist E3 is a lifesaver because it offers three modes of action to tackle these weeds.

    Experts note waterhemp can reduce yields by up to 44 percent. Each waterhemp plant has the ability to produce up to one million seeds, making it extremely problematic to control. At Stine, we’re working diligently to test different traits and herbicide modes of action in our test plots. Our goal with these plots, located in Adel, Iowa; Edgerton, Kansas; Cedar Rapids, Iowa; Windom, Minnesota; and Reynolds, Indiana, is to test what works best against weeds in general. We’re looking at different types of applications and chemistries to see what’s going to do a better job this year in controlling all weeds. And with the wet condition this year, it’s going to be interesting to see which herbicide combination really works the best and how the weeds affect yield.

    Talk to your local Stine sales agronomist if you’re experiencing problems with waterhemp and other weeds this growing season.

     

  •  Image

    Part Three: Herbicide Issues to Look for in a Late Planting Year (Like This One)

    July 17, 2019

    Posted by Stine Seed in Crop Management

    Next up in our series of what to be on the lookout for in a late planting year (like this one), we discuss why plants are growing slowly and what chemicals are showing a greater crop response this year.

    Why are plants growing slowly? And why are chemicals showing a greater crop response this year?
    In reality, these are two separate issues that are closely related. Slow-growing plants in many areas of the country are not a result of subpar seed, fertility or any other input but rather poor environmental conditions. Many areas of the country are too wet, which causes saturated soils.  Water drives out the air in the pores of the soil and, in turn, leads to a lack of oxygen. Oxygen is required for photosynthesis and for microbial activity, such as nitrobacteria, which make nitrogen available for soybean nodulation. 

    Some areas are too dry, and this leads to a lack of soil solution bringing nutrients to plants through mass diffusion, so plants may show signs of nutrient deficiency. Adding nutrients is not necessary, as these plants will either grow to interact with available nutrients or soil moisture (from rain) will bring the nutrients to the plants. In both cases, this can lead to slow-growing, chlorotic plants.

    The second issue has to do with why we are seeing a greater crop response from traditional chemistries that are used annually. As plants grow at a slower pace, all the functions of life (metabolic) are slowed as well. We might think of this in terms of when we are sick with the flu, we tend to have less energy and have less of an appetite than when we feel 100 percent. Some of the chemistries that we have seen issues with are listed below.

    *Note: Cool and wet early-season growth conditions will favor slow plant metabolism of the pre-emerge herbicides. Warmth and humidity with fast-growing conditions in early summer will affect the plants when applying post-emerge herbicides. We have seen herbicide injury in corn and soybeans that have shown up in the following:

    Photosynthesis inhibitors or Group 5 mode-of-action herbicides. Active ingredients include Metribuzin and Atrazine, which have been applied in slow, cool-growing conditions. The soils that have been most affected are high pH or sandy soils. Leaves or the whole plant may turn yellow and stunted, with the veins remaining green.

    Pigment inhibitors and mainly the Group 27 site of action. Consists of products like Balance Flex®, Callisto®, Impact® and Laudis®. Leaves will become chlorotic or have a bleached white banded appearance and can become necrotic. Usually seen on the older leaves, and most plants grow out of it, but slow-growing conditions could lead to yield loss or even death of individual plants or field areas.

    ALS inhibitors or the Group 2 site of action. Products include First Rate®, Python® and Hornet®. They usually cause the beans to have reddish veins on the underside of the leaf with some yellowing and stippled leaves. These products can lead to bottle brushed roots in both corn and soybeans. These products can carryover in the soil from one season to the next.

    As the post-applying season gets into full swing, you may see more damage from the following:

    Cell membrane inhibitors, mainly the Group 14 site of action. This includes products like Cadet®, Flexstar®, Cobra®, Sharpen®, Authority® and Valor®. Applied pre-plant, these products can expose the hypocotyl or cotyledons to high rates on soil surface or rain splashed onto the stems. This can cause plant loss or brittle stalks later in season. Post-applied herbicides cause bronzing and speckling of leaves if sprayed too late in the season. Carryover can become an issue if dry conditions persist late into the growing season.

    Finally, the one herbicide that growers especially need to be on the lookout for:

    Plant growth regulators. This is a Group 4 site of action that includes active ingredients Dicamba, 2,4-D and Clopyralid (Stinger®). Symptoms may include twisting and downward bending of stems. You may also see cupping and curling of leaves or buggy whipping of corn plants. Corn can become brittle, and green snap is definitely a concern. There has also been a lot of leaf burn lately due to certain surfactants added to post-applied herbicides. This is mainly because of spraying during the heat of the day with high humidity, so make sure you are following the label rates of surfactants. Most plants will grow out of this with a favorable extended weather forecast.

    Management Tip: In all of these instances, an improvement in growing conditions will enhance the plant’s ability to metabolize these herbicides and will, therefore, improve the appearance of the plants in question. Normal fertility practices should be maintained, so if you plan to side dress with supplemental nitrogen or micronutrients, procedures should be followed according to soil samples and plant nutrient requirement according to yield goals.

    For questions, please contact your local Stine sales agronomist.

  •  Image

    Part Two: Insects to Watch for in a Late Planting Year (Like This One)

    July 11, 2019

    Posted by Stine Seed in Crop Management

    Late planting and preventive plant acres will bring new challenges to agriculture in 2019, which is why we need to stay diligent and do our best to plan ahead. Last week we discussed diseases to scout for this growing season, this week we’re continuing our conversation but exploring insect pressure. Here are some tips for scouting symptoms of insect activity in growing crops.

    What issues will delayed planting, slow growth and development cause for the 2019 season? 
    While we covered this question in more detail last week, it’s important to remember that delayed planting will ultimately lead to delayed harvest with decreased yields. It will also lead to a greater prevalence of insect pressure.

    Why more insect pressure?
    The issue is not so much that insect pressure is necessarily higher, but there are two critical factors that will exacerbate its effects this growing season:

    1. Less margin for error from decreased yields due to the late-planted crops. Knowing the insect species, growth habit and potential damage as well as diseases they may vector to the crop will become more important this year.
    2. The second issue is having more green tissue growing throughout the “insect season” due to late planting, which may lead to more potential issues. Plants will mature at a slower pace due to cooler, wetter conditions in their growing environment, so we may have to weigh decisions on treating insects that we normally wouldn’t worry about.

    So how do we determine when to spray?  This information from Iowa State University provides guidance:

    “The most effective way to make treatments decisions for pests with chewing mouthparts (e.g., Japanese beetle, bean leaf beetle, caterpillars, and grasshoppers) is to estimate defoliation…Replicated data over multiple growing regions consistently shows economic thresholds for soybean are 30% in the vegetative stages and 20% in the reproductive stages. This threshold applies to the entire field. Sometimes these pests cause significant injury along field margins and perimeter treatments may be more cost effective if practical.”

    Determining Percentage Defoliation of Soybean Leaves
    Gather 10 to 15 trifoliates from random plants, making sure to pick the first from the bottom of the plant, the second from the middle and the third from the top, then repeat that process. Choose the worst defoliated leaf from each trifoliate. Repeat this process in three to four areas of the field and then estimate the percentage of damage for the entire field. For reproductive damage, choose and estimate pods. 

    Northern Region Insects (Corn)
    Wireworms
    White grubs
    Black and dingy cutworms
    Armyworm
    Corn earworm

    Southern Region Insects (Corn)
    Japanese beetles
    Corn earworm
    Western bean cutworm
    European corn borer (conventional hybrids)

    Management Tip
    In corn, look out for root and stalk feeding, silk clipping and grain feeding. For growers who have planted conventional hybrids, watch for boring insects and be ready to harvest early if you have damaged fields. Spraying insects can be tricky because they are able to move and find protection.

    Northern Region Insects (Soybeans)
    Aphids (leaf feeder)
    Bean leaf beetle (leaf feeder, also vectors diseases)
    Soybean gall midge (root and leaf feeder, may vector diseases)
    Thistle caterpillar (leaf feeder)
    Soybean podworm (pod feeder)

    Southern Regions Insects (Soybeans)
    Aphids (leaf feeder)
    Grasshoppers (leaf feeder)
    Stink bugs (pod feeder)
    Soybean podworm (pod feeder)

    Management Tip
    In soybeans, watch for leaf feeding and pod feeding. Leaf feeding can be deceiving to the eye when it comes to the extent of damage. Pod feeding insects will cause more significant damage and should be given priority. Utilize local extension service traps for moth flights, egg hatches, etc. Know the enemy that threatens your crop. Remember, 30 percent vegetative defoliation is the economic threshold for chewing insects damaging leaves, and 20 percent pod damage is the economic threshold from piercing and sucking insects. Presence of insects does not mean treatment is warranted. Only when the population becomes unmanageable and economically destructive is treatment necessary.

    For more information, contact your local Stine regional sales agronomist or university extension office. Stay tuned next week for Part Three of our series as we explore chemicals showing good crop response in corn and soybeans.