Bean Leaf Beetle

• The bean leaf beetle (Cerotoma trifurcata) is a pest of green bean plant leaves. According to the University of Minnesota Extension, symptoms of infestation consist of visible yellow-green or red quarter-inch-long beetles, small holes on the undersides of foliage and reduced plant vigor. The beetles emerge in late spring and can infect bean plants throughout the summer growing season.
  
  

Aphids

• Aphids are small insects that affect a variety of garden plants including green beans. According to Penn State University, aphids suck the nectar out of plant leaves and stems and often transmit the deadly bean mosaic virus.
  
  

Control

• Leaf beetle infections hardly cause serious harm to bean plants, but severe infections are controlled with esfenvalerate, permethrin, or carbaryl-based insecticides, according to the University of Minnesota Extension. They can also be controlled by hand picking. Control aphid infestations with traps, insecticides or natural predators such as ladybugs and green lacewings.