Pest Profile

Photo credit: Kansas Department of Agriculture, Bugwood.org

Common Name: Bean Leaf

Scientific Name: Ceratoma trifucata

Order and Family: Coleoptera, Chrysomelidae

Size and Appearance: The larva is white in color and is shaped cylindrically. The head is dark brown and on the end of the abdomen there is a brown patch. The adults are about 5 to 6 mm in length and can be a variety of colors from yellow to tan or orange to red. They are an oval-shaped and are distinguished by a distinct black triangular mark behind the thorax on the wing covers. The wing covers each have two black spots and a black band that goes around the edges. The black spots may be absent sometimes, leaving the triangle the only black color on the wing covers.

Length (mm) Appearance Egg 0.8mm Orange to red in color; oval shaped with tapered end; females can lay 250-350 eggs; eggs laid in soil near host plant; hatch in 4-14 days. Larva/Nymph 9mm White; cylindrical shaped; brown head; brown patch on end of abdomen; three instars. Adult 5-6mm Can be yellow, tan, orange or red in color; oval shaped; have distinct black triangular mark behind thorax on wing covers; wing covers with two black spots and black band around the edge; black head. Pupa (if applicable) White; immobile; resembles adult in shape; pupate in earthen cell in soil.

Type of feeder (Chewing, sucking, etc.): Larvae and adults: Chewing

Host plant/s: A wide variety of legumes serve as host plants. The bean is most damaging to the soybean, but it will also damage garden beans. Other hosts include snap beans, peas, and dry beans.

Description of Damage (larvae and adults): Adult bean leaf chew small holes in young plant tissue and feed primarily on the undersides of leaves. Adults can defoliate young plants, especially if there is a high population of them. The vigor and yields of bean plants can be reduced due to high feeding damage. The adults primarily damage leaves and pods on soybean plants with their chewing mouthparts. Larvae are root feeders and feed on root nodules and girdle roots; however, the damage is not significant. The bean leaf beetle can vector to soybeans.

References:

Bean Leaf Beetle. (2009). Purdue University Extension. Retrieved January 10, 2016, from: https://extension.entm.purdue.edu/fieldcropsipm/insects/bean-leaf-beetle.php

Bean Leaf Beetle. (2011). Iowa State University Department of Entomology. Retrieved January 10, 2016, from: https://www.ent.iastate.edu/soybeaninsects/bean_leaf_beetle

Bean Leaf Beetle Identification. (n.d.). Cropwatch. University of Nebraska-Lincoln. Retrieved April 2, 2017 from: http://cropwatch.unl.edu/insect/beanleafbeetleid

Bennett, K., Hahn, J. (n.d.). Bean Leaf Beetles in Home Gardens. University of Minnesota Extension. Retrieved January 10, 2016, from: http://www.extension.umn.edu/garden/insects/find/bean-leaf-beetles/

Cassel, M. E., Kuhar, T. P. (2009). Bean Leaf Beetle Biology and Management in Snap Beans. Virginia Tech Cooperative Extension. Retrieved March 31, 2017 from: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/444/444-009/444-009_pdf.pdf

Cranshaw, W. (2004). Chapter Three: Leaf Chewers - Bean leaf beetle. Garden Insects of North America: The Ultimate Guide To Backyard Bugs. (pp. 190). Princeton, New Jersey: Princeton University Press.