The Pests That Feast on Green Bean Leaves

As a green bean grower, watching your plants flourish can bring great satisfaction. But various insects and critters would love to get their paws, jaws, or mouthparts on those tender green bean leaves and ruin your hard work! Here’s an overview of the most common green bean leaf eaters, plus tips to protect your crop.

Aphids – Sap-Sucking Menaces

Tiny but destructive, aphids are some of the most troublesome pests for green bean plants. These soft-bodied insects pierce leaves and stems to suck out sap. An aphid infestation can cause leaves to curl, wilt, or become discolored. Honeydew secretions also promote mold growth. Getting rid of aphids early is key to prevent major damage.

Signs of an aphid problem:

  • Curled, wrinkled leaves
  • Sticky honeydew on leaves
  • Sooty mold fungus
  • Stunted plant growth

Spider Mites – Microscopic Leaf Damagers

You’ll need a magnifying glass to see these tiny arachnids, but spider mites can be a big nuisance in the garden. They use needle-like mouthparts to pierce plant cells and suck out the contents. This sap-feeding causes stippling, discoloration, and leaf drop. Hot, dry conditions encourage mite infestations.

Signs of spider mites

  • Stippling or speckled discoloration
  • Fine webbing on leaves
  • Drooping leaves
  • Leaf drop

Leafhoppers – Jumping Leaf Suckers

True to their name, tiny leafhoppers jump rapidly when disturbed. They puncture leaf veins to feed on plant fluids. This sap feeding stunts growth and deforms bean pods. Leafhoppers also transmit disease pathogens as they hop from plant to plant.

Signs of leafhoppers

  • Hopping bugs when leaves are disturbed
  • Curled, stunted leaves
  • Leaf yellowing or browning

Thrips – Slender Leaf Scrapers

At only 1-2 millimeters long, thrips look like tiny worms on bean leaves. They use rasping mouthparts to scrape and feed on leaf cells. This results in silvery-white spots, distortions, and eventual leaf drop. Thrips also indirectly damage plants by spreading viruses.

Signs of thrips:

  • Silvery scarring on leaves
  • Black dots of excrement on leaves
  • Stunted growth
  • Leaf curling and drop

Bean Beetles – Hungry Leaf Chewers

The aptly named bean beetle literally chews holes in bean foliage. Adult beetles are red to black oval insects about 1/4 inch long. Larvae are yellow, slug-like grubs with dark heads and tails. Heavy feeding can severely defoliate plants, leaving only the leaf veins behind. Bean beetles also transmit bacterial diseases.

Signs of bean beetles:

  • Adults and larvae on underside of leaves
  • Chewed holes in leaves
  • Skeletonized leaf veins

Slugs and Snails – Nocturnal Leaf Nibblers

These gastropods chew large, irregular holes in bean leaves, usually at night or on overcast days when they are most active. They favor moist conditions and mulched gardens. Slugs and snails can quickly defoliate young seedlings. Trails of shiny slime signal their presence.

Signs of slugs/snails:

  • Large ragged holes in leaves
  • Slime trails on leaves and ground
  • Missing seedlings

Protecting Your Green Beans

The key to thwarting these leaf eaters is vigilant monitoring along with integrated pest management. Tactics include:

  • Handpicking pests from plants
  • Applying insecticidal soap or neem oil
  • Installing row covers as physical barriers
  • Attracting beneficial insects like ladybugs
  • Crop rotation to disrupt pest life cycles

A healthy, thriving bean patch starts with nurturing your plants. Give them ample nutrition, moisture, and care for the best defense against leaf predators. Stay observant for early signs of infestation, and take prompt action to nip pests in the bud. With some diligence, you can enjoy a bountiful harvest!

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Damage caused by bean leaf beetles

  • Bean leaf beetles like to eat soft, young plant tissue as adults.
  • Large groups of adults can eat the first true leaves and kill young seedlings.
  • Extensive feeding can weaken the plant and reduce the yield.
  • Later in the season, when pods start to form, adults will also eat the outside of them. This feeding only affects the appearance of the pods.
  • Bean leaf beetles are known to carry and spread germs between plants. The good news is that this doesn’t affect vegetable growers because these diseases don’t affect snap bean varieties.

How to identify bean leaf beetles Typical bean leaf beetle

  • Adults are oval-shaped bugs that are about 1/4 inch long, and you can see their heads from above.
  • In Minnesota, most bean leaf beetles are a yellowish green color, but some can be red or orange. They have four black spots on their bodies and black lines on the edges of their wings.
  • Some may lack spots.
  • On the top of all of their wings, bean leaf beetles have a black triangle.

Q&A – What is eating holes in my green bean leaves?

FAQ

What animal is eating my green bean leaves?

The bean leaf beetle (Cerotoma trifurcata) is a pest of snap beans (also called string beans or green beans). Adult beetles feed on the undersides of leaves, creating round, 1/8 inch diameter holes. They can also feed directly on the pod. Adults are active from mid-May to early June and mid-July through September.

How do I keep bugs from eating my green bean leaves?

You can make your own pest spray with benign materials. Mix 1 tablespoon of baking soda, 1/2 teaspoon of a mild dish detergent, and 2 1/2 tablespoons of olive oil in a gallon of water to make a solution that will repel all kinds of bugs, as well as a fungicide for blight and mildew on the green bean plant leaves.

What is eating my green leaves?

If you see holes or ragged chunks of leaves disappearing and the damage has been occurring slowly, with a little feeding each night, beetles, caterpillars, earwigs or slugs may be the culprits. To distinguish among these four look for signs, or evidence, left behind.

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