Worms on Green Bean Plants

Green bean plants are susceptible to infestations of cutworms.

Home gardeners often grow green beans, along with many other vegetables. Green bean plants are generally healthy but are susceptible to infestations of damaging pests that feed on foliage. Worms are a common problem in green beans. Several species are especially damaging to the plant, such as the armyworm and the cutworm.

Types

Armyworms are a common pest for green bean plants, as well as many other vegetable crops. Armyworms are the larval stage of the miller moth and are responsible for the damage to plants. The larvae are light green while young, turning to a darker shade of green as they age. Fully grown armyworm larvae have stripes, do not have hair and measure approximately 1 to 2 inches in length.

Cutworms are another common green bean pest. Cutworms received their name for their ability to "cut off" plants at the soil line. Cutworms are pale green or light brown and reach 1 to 2 inches in length.

Effects

Armyworms feed on green beans, as well as alfalfa, clover, flax, sugar beets and millet. This worm is most active during the nighttime hours or on overcast days. During the warmer daytime hours, armyworms hide under plant debris, in cracks in the soil or under rocks. Armyworms feed on the foliage of the green bean plant, causing extensive damage.

Cutworms are also damaging to green beans, as well as other vegetable crops. Cutworms feed on the roots and foliage of the plant. This pest can completely severe host plants above ground at the soil line.

Cultural Controls

Hand-picking armyworms and cutworms from your green bean plants is one way to control light infestations. Remember, these pests rarely move during the day, so your best time to catch them is late at night or in the cool predawn hours. Scratching just beneath the soil may also reveal worms. Placing cardboard collars around the base of your green bean plants may help prevent worm damage. Collars should be at least 3 inches in height and be pushed 1 inch under the soil for best results.

Chemical Control

Chemical products are available for worm control at your local garden center. If worms are damaging the foliage above the ground, douse your plants with an insecticidal spray or dust. If worms are damaging your green beans below the soil, use a soil-drenching insecticide for best results. Be sure to follow all safety directions on the product label.

References

• Texas A&M: Beans and Vegetable Legumes
• North Dakota State University: The Armyworm and the Armycutworm: Phillip Glogoza: April 2000
• Oregon State University: Growing Your Own Vegetables -- Insect Pests