Public Enemy Number One: Slugs on Soybeans

Bill Cissel, Extension Agent – Integrated Pest Management,; Phillip Sylvester, Extension Agriculture Agent, Kent County,; David Owens, Extension Entomologist,

Last week, we were focused on slug injury on corn. While this is still a concern, the current weather is setting us up for another problem, possible slug injury on soybeans. Unfortunately, slugs in soybeans can be challenging to manage. The reason for this is that slugs will feed on soybeans before they emerge and kill the plants outright. In many cases, you don’t realize you have a slug problem until you return to a field, 7-14 days after planting, expecting to see a beautiful stand of soybeans, only to find that you have poor emergence or that you don’t have a stand at all.

The classic scenario where we tend to see the greatest problem is when soybeans are no-tilled into heavy crop residue and planting conditions were a little wet and the seed trench did not get closed all the way. Slugs will travel up and down the open seed furrow, using it like a “highway”, to feed on the germinating seeds. With the recent rains and stall in planting, we know many of you will be anxious to get back to planting and may be tempted to plant when conditions are a little wet. If you can relate and your fields have a history of slug problems, you might be setting yourself up for a slug problem.

Pay close attention to planter setup as there are several adjustments that may help. Row cleaners move residue away from the emerging seeds and help with uniform planting depth. Soil should cover the seed trench, not residue since it serves as a hiding place for the slugs. On the back end of the planting unit, be sure the closing wheels are completely closing the seed trench. The standard rubber-edged closing wheels that came with your planter work by down pressure to close the seed furrow. This might work in drier soil or under tilled conditions, but perform poorly under marginal conditions (think wet, clay soils) and will not properly close the seed trench. Several aftermarket closing wheels are available, commonly a variation of a spike-type wheel that collapses the seed trench from the side rather than from the top, which may provide a better close in sub-par conditions.

“Slug highway” left when the seed trench isn’t closed all the way.

Below ground slug feeding injury to cotyledons.

Once the soybean plants emerge, slugs will continue to feed on the cotyledon, unifoliate, and trifoliate leaves. Above ground slug feeding injury can be confused with bean leaf beetle damage so look for slugs and “slime trails” to make sure you accurately identify the culprit. Checking for slugs with a flashlight after dusk is another good option as they are most active during the night.

Above ground slug feeding injury. Check for slugs under residue close to the plant.

Above ground slug feeding injury. Notice heavy feeding on the cotyledons. Slugs will also feed on the unifoliates and trifoliate leaves.

Above ground feeding injury. Checking after dusk is a good time to catch the culprits in action.

Tillage is the most effective cultural control method if a field has a slug infestation, especially in re-plant situations. We have limited experience with how well “slug bait” can control slugs when they are feeding on germinating plants before they emerge and if slug bait is effective at reducing damage in a re-plant situation.

Here is a report from our 2013 Delaware Soybean Board funded project: Management of Slugs in Delaware Soybean Fields. This report has more information evaluating the effectiveness of chemical control management of slugs in soybeans:

Another tactic, aside from tillage or making sure the seed furrow is closed, is to adjust your planting date. Planting early, ahead of egg hatch allows the plants to emerge before heavy slug feeding injury occurs from juvenile slugs. Once the slugs hatch, delaying planting has been effective by allowing plants to rapidly emerge. Unfortunately, hitting the perfect planting date is difficult because it is a moving target. What is considered “early” this year isn’t what we considered “early” last year, and probably won’t be what we consider “early” next year. We have already seen healthy populations of newly hatched grey garden slugs in fields throughout the state. In general, at this point in time, anything that will promote rapid seed germination and emergence will help to get the plants out of the ground before slugs have an opportunity to kill the plants outright. In some cases, that is half the battle.

To help determine if your field has a slug infestation, you can actively sample your fields for slugs using shingle trapping methods, searching under crop residue, and sampling for slug eggs.

Click on the links below to watch several Youtube Videos about slug injury on soybeans and demonstrating each of these sampling methods:

When and Where Slugs Can Be a Problem in Soybeans:

How to Sample for Slugs in Soybeans Using Shingle Trapping and Residue Sampling Methods:

How to Sample for Slug Eggs in Soybeans:

Marl Pit Tailgate Session

Tuesday, June 5, 2018     6:00 – 8:00 p.m.
UD Cooperative Extension Research Demonstration Area
¾ Mile east of Armstrong Corner, on Marl Pit Rd. – Road 429, Middletown

Join your fellow producers and the UD Extension team for a discussion of this year’s demonstration trials and current production issues. Other topics will include nutrient management, pest management and weed management.

Bring a tailgate or a lawn chair

We will wrap up with the traditional ice cream treat.

Nutrient Management: 1.0, Pesticide: 1.0

The meeting is free and everyone interested in attending is welcome. If you have special needs in accessing this program, please call the office two weeks in advance.

To register or request more information, please call our office at (302)831-2506. Please register by Tuesday, May 29.

Welcome and Introductions
Dan Severson, University of Delaware Cooperative Extension

Overview of Small Grains Variety Trials at Marl Pit
Victor Green, University of Delaware Extension

Weed Update
Mark VanGessel, University of Delaware Cooperative Extension Weed Specialist
Discussion of early-season weed management issues. We will talk about what we have seen and been asked about in the spring of 2018. We will explain and discuss our cover crop demonstration plots at the Marl Pit site as well.

2018 Insect Pest Outlook
David Owens, University of Delaware Extension Entomologist
Perennial insect pests that need to be anticipated will be discussed along with management implications of current insect pest populations.”

Nutrient Management Update
Amy Shober, University of Delaware Extension Nutrient Management Specialist

7:10-7:30 Agronomic Crop Insect Management Update
Bill Cissell, University of Delaware Cooperative Extension
This talk will address current pest management concerns, focusing on cereal leaf beetle management in small grains and pest management issues with cover crops.

Using NDVI to Measure Wheat Populations and Spring Nitrogen Needs
Jarrod Miller, University of Delaware Extension Agronomy Specialist
UAVs can be used to scout crops as well as obtain NDVI measurements of crop health and biomass. Research on winter wheat was performed to determine whether NDVI imagery could detect wheat population, tiller counts, and nitrogen needs.

Conclusion and Evaluations
Dan Severson, University of Delaware Cooperative Extension

Crop Insurance: Claim Guidelines

Compiled by Lucas Clifton, Program Specialist, Targeted States RME,

How do I initiate a claim?
Call your crop insurance agent and follow up in writing (keep a copy for your records). Your crop insurance company will arrange for a loss adjuster to inspect your crop. It is your responsibility to call your crop insurance agent and initiate this process.

How do I know when to file a claim?
Any time you have crop damage that will adversely affect your yield, or the value of your crop, you may be eligible to file a claim. The loss adjuster will determine whether your yield falls below the yield guarantee stated in your crop insurance policy. This applies to revenue guarantee policies as well as to traditional yield protection policies.

Most policies state that you (the insured) should notify your agent within 72 hours of discovery of crop damage. As a practical matter, you should always contact your agent immediately when you discover crop damage.

In some cases, you may discover a loss while you are harvesting (a row crop for instance). Stop harvesting and contact your agent right away.

In the event of losses, you must file notice immediately after each unit is harvested (within 15 days) and before the end of the insurance period. For sweet corn and corn cut for silage, you must file notice at least 15 days before harvest begins.

How soon should I expect an adjuster?
In practice, there are different levels of urgency for crop inspectors. If you are still within the window of opportunity to replant your crop, or switch to another crop, contact your crop insurance agent immediately.

The insurance company should make every effort to get an adjuster out right away. If, later in the growing season, your crop is wiped out by a hurricane, for example, or if a severe drought has damaged your crop, you still need to contact your agent — but the urgency for an inspection depends on your intentions. If you want to destroy the crop (perhaps to plant a cover crop), then an adjuster needs to come out first — before you do anything. If, on the other hand, you intend to continue to care for the crop and harvest what you can, there is less urgency for the adjuster to make the inspection immediately. Even so, an assessment of damage should be done as soon as practical.

While you wait for the adjuster, remember these rules: Do not destroy any of your crop. Do not disk. Do not plow. Do not replant. Do nothing to destroy your crop until you have permission from a claims adjuster or an insurance company representative.

Remember: Don’t destroy the evidence.

What should I expect from the adjuster?
The adjuster should contact you to schedule an inspection. He or she will expect and welcome your presence and help during the inspection. The adjuster will be interested in what you have to say.

You can expect the adjuster to be familiar with your policy and to explain your options.

You should have your Farm Service Agency (FSA) documents ready to show the number of acres and locations of your insured crops. The adjuster should have copies of your crop insurance policy documents and your Actual Production History (APH).

How is my crop yield calculated?
For some crops, counting plants within a sample area at various locations in the field is a part of the process. For other crops, determining the weight of ears of corn per bucket or numbers of soybeans in a beaker is part of the process. Adjusters may take pictures of your fields. They may check with your neighbors on the condition of their crops and they may check with the local elevator operator for average yields in the area. They may even consult local weather data.

Calculating crop yield is not guesswork. It is a disciplined process. Your adjuster has extensive classroom and field training and is constantly studying to maintain his or her certification.

Your responsibilities

Report crop damage promptly:

  • Before replanting (many policies have replanting payments),
  • Within 72 hours of discovery of damage,
  • 15 days before harvest begins (if loss is possible),
  • Within 15 days after harvesting is completed (by insurance unit) or the end of the insurance period.

Caution: Do not destroy evidence that is needed to support your claim without clear direction from the insurance company, preferably in writing.

For more information:
Contact a crop insurance agent. To find an agent, visit our online locator at: 

Guess the Pest! Week #7

Bill Cissel, Extension Agent – Integrated Pest Management;

Test your pest management knowledge by clicking on the GUESS THE PEST logo and submitting your best guess. For the 2018 season, we will have an “end of season” raffle for a $100.00 gift card. Each week, one lucky winner will also be selected for a prize and have their name entered not once but five times into the end of season raffle.

This week, one lucky participant will also win A Farmer’s Guide To Corn Diseases ($29.95 value).

You can’t win if you don’t play!

What is this disease?

Guess the Pest! Week #6 Answer: True Armyworm

Bill Cissel, Extension Agent – Integrated Pest Management;

Congratulations to John Swaine, III for correctly identifying the moths as true armyworms and for being selected to be entered into the end of season raffle for $100 not once but five times. Everyone else who guessed correctly will also have their name entered into the raffle. Click on the Guess the Pest logo to participate in this week’s Guess the Pest challenge!

Guess the Pest Week #6 Answers: True Armyworm
By Bill Cissel, Extension Agent, IPM and David Owens, Extension Entomologist

The correct answer to this past week’s Guess the Pest is True Armyworm (TAW). Adult TAW moths do not cause any direct injury to small grains; however, they can be seen in your fields making sure there is another generation. True armyworm (TAW) larvae damage small grains by clipping flag leaves and small grain heads. It is important to be able to accurately identify true armyworms because there is another “worm” that is also considered a pest of small grains, the grass sawfly. The grass sawfly is in the Order Hymenoptera, meaning it is more closely related to bees and wasps than moths, which are in the Order Lepidoptera. Even though grass sawflies cause similar damage to small grains, management differs between these two species of insects.

There are several reasons why it is important to be able to distinguish between grass sawflies and true armyworms:

1) Grass sawflies are more damaging than true armyworms because they prefer to feed on small grain stems as opposed to true armyworms that typically will feed on leaves before clipping heads. Also, grass sawfly damage usually occurs before the peak of armyworm damage.

2) The threshold for grass sawflies (wheat and barley – 0.4 linear ft of row) is lower than the threshold for true armyworms (barley – 1 per linear ft of row/ wheat-1- 2 –per linear ft of row).

3) Not all products that are labeled for true armyworm control will provide control of grass sawflies.

4) Insecticide rates also differ between the two species for some products.

There are several features that can be used to distinguish grass sawflies from true armyworm.

Grass sawflies larvae are active during the day and can often be found on the plants so “shaking” plants to dislodge larvae is necessary when sampling. They can be identified by their green color, large amber head, and 5-7 pairs of fleshy prolegs legs. Counting the number of prolegs is the most reliable way to determine if the “worm” is a grass sawfly or true armyworm.

Grass Sawfly Larva

True armyworms are active at night and can often be found curled around the base of plants or under crop residue during the day. Larvae have four pairs of fleshy abdominal prolegs not including the pair of legs at the very end of the abdomen. There also appears to be a large gap between the 3 pairs of true legs and the start of the fleshy prolegs.

True Armyworm Larva

If your field is at threshold for grass sawflies or armyworms, there are several things to keep in when selecting which product to apply. Is the insecticide labeled for the correct pest, i.e. if you have grass sawflies, make sure you are using a product labeled for grass sawfly control? What is the days to harvest restriction (this varies among products)? Is the insecticide labeled for the crop (not all products are labeled for all small grains)?

Here is a link with sampling guidelines, thresholds, and insecticide recommendations for true armyworm and grass sawfly:

Water is Needed to “Activate” Soil-Applied Herbicides

Mark VanGessel, Extension Weed Specialist;

Herbicides applied to the soil surface require rainfall or irrigation to move them into the soil where the plants will absorb them; or to be mechanically incorporated (field cultivator). Some areas have not received much rainfall since herbicides were applied. Weed control will start to decline if water is not received within 5 to 7 days after applications. Some products, like those that contain atrazine, mesotrione (Callisto), or isoxaflutole (Balance) may be taken up by the roots and provide some control of seedlings after they have emerged. However, Dual, Harness, and Zidua are absorbed by emerging shoots, so once weeds have emerged these products will not provide control. If you have irrigation and your corn herbicides have been applied but you have not received water, you should consider irrigating to activate those herbicides. Another caveat is that early-season competition from grass can reduce yield.

Considerations for Palmer Amaranth Control in Soybeans

Mark VanGessel, Extension Weed Specialist; and Kurt M. Vollmer, Postdoctoral Researcher, University of Delaware;

Control of Palmer amaranth in soybeans requires the right product, at the right rate, at the right time. Residual herbicides are important to slow the growth of Palmer amaranth and provide a wider application window. Since soybeans are planted later than corn, and soybeans are trying to get established when daily temperatures are consistently above 85°F, the Palmer amaranth is growing rapidly. Using a preemergence herbicide applied at planting is important. Our research has shown consistently better control with applications made at planting compared to applications two weeks prior to planting. An herbicide combination has also provided better control than a single active ingredient, and helps reduce the risk of developing resistance to additional herbicide modes of action. Tankmixing Valor or Authority products with metribuzin or a Group 15 herbicide provided more consistent control than either product alone. Remember most of the Palmer amaranth in this region is also resistant to Group 2 herbicides, so those products will not help with Palmer amaranth control (but may improve control of other species).

Using an active ingredient from 2 of the 3 groups will provide better Palmer amaranth control than a single active ingredient.

Group 15
(Inhibits long chain fatty acids)
pyroxasulfone: Zidua
pyroxasulfone: Anthem* or Anthem Maxx*
Dual Magnum
Group 14
(PPO inhibitors)
Sulfentrazone (Authority)
Group 5

*Anthem and Anthem Maxx are prepackaged mixtures, but the other components do not provide any residual weed control

**Valor should not be tankmixed with Dual or Warrant when used at planting

Partial list of prepackaged mixtures with two effective herbicides for Palmer amaranth:

  • Authority Elite / BroadAxe: sulfentrazone plus s-metolachlor
  • Authority MTZ: sulfentrazone plus metribuzin
  • Fierce: Valor plus Zidua
  • Trivence: Valor plus metribuzin plus chlorimuron

Other prepackaged mixtures may contain more than one of the active ingredients in the table above, but the mixtures may not provide the right rate. Refer to table 4-2 in the Mid-Atlantic Field Crop Weed Management Guide for more information on the components of premixes.

Use the full-labeled rates; but as noted, be sure that a prepackaged mixture provides the right ratios to allow the key herbicide active ingredients to be at the right rate. Reducing herbicide rates will not provide as long of residual control, and using reduced rates could be setting yourself up for developing herbicide resistance due to the weed increasing its ability to metabolize the herbicide (deactivate the herbicide with plant enzymes).

Be prepared to spray your postemergence herbicides in a timely fashion. I like to see Palmer amaranth sprayed by 3 inches in height. It is at this height for a very short time, so be prepared to treat. Research at UD and with Ben Beale in Maryland, clearly shows that Palmer amaranth allowed to grow for more than 4 weeks, even if a preemergence herbicide was used, are often greater than 5 inches tall. If you are not on a routine scouting schedule, then plan on spraying your postemergence herbicide by 4 weeks after the preemergence herbicide was applied. In addition, your postemergence treatment needs to include an herbicide that will provide effective residual control; and this includes Reflex, Dual, Zidua, or Anthem Maxx. Liberty or dicamba products will not provide residual control for Palmer amaranth.

For more information on the right product and right rate, use the Mid-Atlantic Field Crop Weed Management Guide (

Considerations for Irrigating Winter Wheat

Phillip Sylvester, Extension Agriculture Agent, Kent County;; Cory Whaley, Extension Agriculture Agent, Sussex County;; James Adkins, Associate Scientist-Irrigation Engineering;; Jarrod O. Miller, Extension Agronomist,

Wheat has quickly reached heading and is flowering in some parts of the state. This is an important time for Fusarium head blight management, which was discussed in the April 27 issue: click here

It is also important to pay attention to soil moisture during this critical time. Relatively warm temperatures and lack of recent rainfall may have depleted soil moisture levels. Although the forecast calls for thunderstorms, growers with the ability to irrigate should consider doing so, with the goal of keeping available water content >50%. There are a number of tools available to the grower for measuring soil moisture, ranging from electronic soil moisture sensors to a soil probe. It is probably too late to setup sensors in the field, but you can still estimate soil moisture by feel and appearance. Here is a helpful factsheet: click here

Essentially, you use a soil probe to determine your soil moisture level within the depth of the root zone. If you determine soil moisture to be less the 50%, consider irrigating.

From 2013 to 2016, we conducted research at the UD Warrington Irrigation Research Farm to evaluate the impact of various irrigation strategies on yield and to determine the optimal strategy to maximize yield (sponsored by the Delaware Crop Improvement Association). We’ll skip right to the results – irrigation resulted in significantly higher yields in three of four years compared to a non-irrigated check. On average, yields were 7-14% higher compared to the non-irrigated check. There were only slight differences between the various irrigation strategies. However, we discovered a significant trend; adequate soil moisture levels must be maintained before flower and at levels high enough to support the crop through flowering and early grain fill. Our take home message is to consider irrigating during periods of dry, warm weather a couple of weeks before and after flowering. Growers should adopt an irrigation strategy that monitors soil moisture levels early on and that provides enough water to carry the plant through flowering and early grain fill. Given the extended period of dry weather and variable soils throughout the state, plan to check your own fields now. Continue to monitor your soil moisture level after each irrigation to ensure adequate water is available within the root zone. It may take multiple passes with the irrigation to fully recharge the soil profile. Finally, there is a concern that irrigating wheat during flower may increase the risk of Fusarium head blight. This is another reason growers should fill the profile before flower and resume irrigation after flower. However, if you need to irrigate during flower to protect yield, do so during the day, allowing enough time for the heads to dry before dusk.

To Treat or Not to Treat (Slugs), That is the Question!

Bill Cissel, Extension Agent – Integrated Pest Management;

With corn starting to pop up in rows, keep an eye out for slug feeding injury. Yea, that’s right, SLUGS. Even though the current weather has been hot and dry, slugs are active at night and can still cause damage. Probably the biggest impact the weather has in helping with slugs is that corn, and soybeans for that matter, grow rapidly when we have plenty of sun and heat.

So, this brings us to the question, “To treat or not to treat”?

If the corn seedlings in your field all looked like the photo above, and given the current weather forecast, do you apply a slug bait? The answer to this is not simple and there is no substitute for experience when determining if your corn will “out compete” the slugs. I will follow the plant in the photo for several weeks and we will see together if it is able to outgrow the slug damage.

What would you do if this were your field? Given the current weather forecast, would you treat this field with a slug bait?

Click on the link below and check YES or NO: