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A significant threat to crops, worms present serious problems for many farmers. Worm damage affects plant leaves, stems and roots, leading to reduced yields, stunted growth and even plant death. But familiarizing yourself with some of the most common types of early season worms, learning how to identify signs of the worm damage, and understanding pest treatment methods can help you develop a preventative strategy and responsive action plan against:
Corn rootworms
European corn borers
Black cutworms
Dingy cutworms
Wireworms
Corn rootworms, also known as corn rootworm beetles in later life stages, feed on and tunnel into the roots of corn plants, which can lead to stunted growth, limited nutrient and water uptake, weakened stalks and reduced yield. This weakens the plant's overall health and can result in lodging.
The University of Nebraska-Lincoln recommends the need for pest control if 2-3 larvae are found per plant.2 While scouting practices and beetle population numbers vary from region to region, rootworm larvae typically emerge as adult beetles by early July and can continue to be a pest until early October. It’s important to note that male beetles often emerge ahead of females by as many as 10-14 days, which can play a key part in your decision of whether or not to apply an insecticide.
If you do decide to move forward with chemical treatment options, consider utilizing Willowood Lambda-Cy 1EC, a broad-spectrum insecticide that affects an insect’s nervous system upon contact or ingestion. Lambda-cyhalothrin* can be applied by air or ground as a preventive measure against the pests. A powerfully effective insecticide, Lambda-cyhalothrin can be used to prevent and control a wide range of worm pests in corn and soybean crops. Because it is a restricted use pesticide, it's important to follow the instructions carefully to ensure that it is applied correctly and safely. This includes wearing protective clothing and equipment, applying the product at the recommended rate and avoiding spraying during windy conditions.
Bifenthrin, another insecticide option suitable for treating corn rootworms, functions similarly to lambda-cyhalothrin by affecting insects' nervous systems. Bifenthrin LFR 1.5 Value Pick* should be applied in-furrow at planting and can be mixed directly with water, while GCS Bifenthrin 2EC*, which can be used in the event of lambda-cyhalothrin resistance, should be applied during the growing season after seeing corn rootworms in the field.
European corn borers tunnel into the stalks and ears of the corn plant, limiting the normal flow of nutrients and water within the corn plant and reducing its yield potential. This leads to harvest issues from weakened, broken and lodged stalk as well as direct yield loss caused by unharvestable ears.
To spot European corn borers before they broadly impact your crop this season, plan to scout on a regular basis by examining 10-20 plants for eggs and larva evidence across five random locations in each field. Once you find 20-30% of plants are being affected by the pests, insecticides like Willowood Lambda-Cy 1EC and GCS Bifenthrin 2EC are generally recommended.
Black cutworms significantly damage both corn and soybeans by cutting the stems at or beneath the soil surface. To spot damage caused by black cutworms, pay special attention to areas with heavy weed growth or low-lying spots as cutworms favor these terrains. Look for signs such as irregular holes in leaves, wilting, or cut plants. Treatment is typically recommended when at least 3% of plants show signs of cutworm damage1
Insecticides containing bifenthrin or lambda cyhalothrin tend to work well in suppressing these populations, likely increasing your ROI for the season and limiting potential for heavy populations in next year’s crop.
Dingy cutworms chew through young plant stems at or just below the soil surface, which cuts or severs the plants. They also create holes in corn plant leaves by feeding on them, which reduces the plant’s photosynthetic capacity and leads to impaired growth and development. As dingy cutworms mature, they may also bore into the stalks of corn plants; this can lead to lodging, which occurs when the stalks collapse under the crop’s weight.
When scouting for dingy cutworms, keep in mind that the pests are nocturnal so scouting is best conducted at night. Using a flashlight, search for cut stems and leaves or holes and tunnels in the soil. Another option is to place pheromone traps in the field, which will attract male cutworm moths, and check them regularly to monitor for any increased pest activity.
If you do see cutworms impacting your crops, consider applying Willowood Lambda-Cy 1EC or GCS Bifenthrin 2EC.
Wireworms damage seeds and seedlings by feeding on roots or stems below the soil line, seriously weakening or even potentially killing the plants. This root and stem damage can also create easy access points for other pests or diseases to attack the plants later on, further exacerbating the impacts.
Because they affect crops underground, it can be challenging to identify wireworm damage prior to harvest. However, there are two common ways to see if wireworms are affecting your crops:
Baited Traps: Placing baited traps in your soil can attract wireworms, clueing you into their presence and enabling you to proactively treat before they can cause significant damage.
Soil Assessment: Examine a soil sample taken from your fields and check for wireworm larvae. Recognizing them prior to planting may help you avoid having to replant later in the season.
If you recognize wireworm signs in your crops later in the growing process, Willowood Lambda-Cy 1EC or GCS Bifenthrin 2EC can also be used to treat wireworms post emergence.
While worm damage is a constant threat for early season crops, a proactive scouting plan and insecticide strategy can help you defend against corn rootworms, European corn borers, black cutworms, dingy cutworms and wireworms.
Don't let worms compromise your harvest — take action now for lasting crop protection and increased profitability by exploring the insecticide products available on FBN Direct.
Estes, K. "Black cutworm feeding possible in coming weeks." Department of Crop Sciences, University of Illinois, May 17, 2023. https://farmdoc.illinois.edu/field-crop-production/black-cutworm-feeding-possible-in-coming-weeks.html
Wright, Robert J., Extension Entomologist, Corn Insects - Quick Reference Guide, University of Nebraska-Lincoln, November 2013.
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*Lambda-cyhalothrin and Bifenthrin are restricted use pesticides.
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