What are corn rootworms?

Corn rootworms are destructive pests that pose a significant threat to corn crops worldwide. These insects belong to the Diabrotica genus and are particularly notorious for their feeding habits, which target the roots of corn plants. In this article, we will delve into the life cycle, identification, damage caused, economic impact, and management strategies for corn rootworms.

Life Cycle of Corn Rootworms

The life cycle of corn rootworms consists of four stages: egg, larva, pupa, and adult. The adult female corn rootworm beetle lays her eggs in the soil near corn plants during the summer months. These eggs hatch into small larvae, commonly known as rootworms. The rootworm larvae feed on the roots of corn plants, causing substantial damage. After completing their larval stage, the rootworms enter the pupal stage, where they undergo metamorphosis before emerging as adult beetles.

Identification of Corn Rootworms

Identifying corn rootworms is crucial for implementing effective management strategies. The adult beetles are approximately 0.25 to 0.5 inches long and can vary in color, ranging from yellowish-green to tan. They have distinct stripes on their wings and a black head and thorax. The larvae, on the other hand, are small, white worms with brown heads and six legs.

Damage Caused by Corn Rootworms

Corn rootworms are voracious feeders, and their feeding activity primarily targets the roots of corn plants. This feeding can lead to reduced nutrient uptake, stunted growth, and weakened plant health. Severely affected plants may lodge or topple, resulting in significant yield losses. In addition to direct root damage, corn rootworm feeding can also make the plants more susceptible to diseases and secondary pests.

Economic Impact of Corn Rootworms

The economic impact of corn rootworms can be substantial. Yield losses caused by these pests can result in significant financial setbacks for farmers. Additionally, the costs associated with implementing management strategies and potential damage to soil health further contribute to the economic burden. It is estimated that corn rootworms cost the agricultural industry millions of dollars annually.

Management Strategies for Corn Rootworms

To mitigate the damage caused by corn rootworms, various management strategies can be employed. These strategies include cultural control, crop rotation, chemical control, biological control, integrated pest management (IPM), resistant varieties, and monitoring and scouting.

Cultural Control

Cultural control practices aim to create unfavorable conditions for corn rootworms. These practices include the removal of crop residue, deep tillage, and field sanitation. Removing crop residue eliminates potential overwintering sites for rootworms, while deep tillage disrupts their life cycle by burying eggs and larvae. Field sanitation involves removing volunteer corn plants or other potential hosts that can serve as breeding grounds for rootworms.

Crop Rotation

Crop rotation is an effective strategy for managing corn rootworm populations. By alternating corn crops with non-host crops, such as soybeans or small grains, the rootworms are deprived of their preferred food source. This practice reduces the population of rootworms and disrupts their life cycle, ultimately decreasing their impact on corn crops. It is essential to carefully plan crop rotations to ensure that the non-host crops effectively break the rootworm cycle.

Chemical Control

Chemical control involves the application of insecticides to manage corn rootworms. Insecticides can be applied to the soil during planting or as foliar sprays. It is crucial to follow label instructions and use insecticides judiciously to minimize environmental impact and avoid the development of resistance in the pest population. Integrated pest management (IPM) strategies often combine chemical control with other management approaches for optimal results.

Biological Control

Biological control methods utilize natural enemies of corn rootworms to reduce their populations. One of the most common biological control agents is the parasitic wasp, which lays its eggs inside rootworm eggs. When the wasp larvae hatch, they consume the rootworm eggs, effectively reducing the pest population. Nematodes and entomopathogenic fungi are also used as biological control agents against corn rootworms.

Integrated Pest Management (IPM)

Integrated pest management is an approach that combines multiple strategies to manage pests effectively. In the case of corn rootworms, IPM integrates cultural practices, crop rotation, chemical control, biological control, and monitoring techniques. By using a combination of methods, farmers can reduce reliance on insecticides and minimize the risk of resistance development.

Resistant Varieties

Planting corn varieties with resistance to corn rootworms is another valuable tool in pest management. Some corn hybrids have genetic traits that make them less susceptible to rootworm damage. These resistant varieties can withstand root feeding and have been shown to reduce yield losses. However, it is essential to monitor the effectiveness of resistance traits as rootworm populations can evolve and overcome these defenses.

Monitoring and Scouting

Regular monitoring and scouting are crucial for the early detection of corn rootworm populations and for assessing their impact. By conducting field inspections, farmers can identify signs of root damage, such as root pruning and lodging. Monitoring techniques include using pheromone traps to capture adult beetles and sampling soil for larval presence. Monitoring allows for timely intervention and adjustment of management strategies as needed.


Corn rootworms pose a significant threat to corn crops, causing damage and economic losses. Understanding their life cycle, identification, and the damage they cause is crucial for implementing effective management strategies. By employing a combination of cultural control, crop rotation, chemical control, biological control, integrated pest management, and planting resistant varieties, farmers can mitigate the impact of corn rootworms and protect their corn crops.


  1. Are corn rootworms only a problem for corn crops?
    • Corn rootworms primarily target corn crops, but they can also infest other related plants, such as sorghum and wheat.
  2. How long does the life cycle of corn rootworms typically last?
    • The life cycle of corn rootworms can range from one to two years, depending on environmental conditions and the availability of food sources.
  3. Can corn rootworms be controlled without using insecticides?
    • Yes, cultural practices such as crop rotation and field sanitation, as well as biological control methods, can help manage corn rootworm populations without relying solely on insecticides.
  4. Are there any natural predators of corn rootworms?
    • Corn rootworms have natural predators such as birds, spiders, and other insects that can help control their population. Additionally, parasitic wasps and nematodes are commonly used as biological control agents.
  5. How often should I monitor my corn fields for corn rootworms?
    • Regular monitoring and scouting should be conducted throughout the growing season,

FAQs (contd.)

  1. How often should I monitor my corn fields for corn rootworms?
    • Regular monitoring and scouting should be conducted throughout the growing season, starting from early stages until harvest. It is recommended to check for signs of root damage, adult beetles, and larvae presence at least once every two weeks.
  2. Can corn rootworms develop resistance to insecticides?
    • Yes, corn rootworms have the ability to develop resistance to insecticides if they are overused or used improperly. It is essential to follow proper insecticide rotation and resistance management strategies to minimize the risk of resistance development.
  3. Are there any cultural practices I can implement to prevent corn rootworm infestations?
    • Yes, cultural practices such as removing crop residue, deep tillage, and field sanitation can create unfavorable conditions for corn rootworms. These practices help disrupt their life cycle and reduce their population.
  4. How can I determine if my corn crop has been affected by corn rootworms?
    • Look for signs such as stunted growth, wilting, lodging (falling over), and poor nutrient uptake in the corn plants. Digging up plants and examining the roots for feeding damage and presence of larvae can also confirm corn rootworm infestations.
  5. Can corn rootworms survive in the soil during the winter?
    • Corn rootworm eggs can survive in the soil during the winter months. They remain dormant until the following spring when they hatch into larvae and start feeding on corn roots.
  6. Are there any genetic engineering methods used to control corn rootworms?
    • Yes, genetic engineering techniques have been utilized to develop corn varieties with built-in resistance to corn rootworms. These genetically modified crops express toxins that are lethal to the rootworms, reducing their impact on the plants.

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