When I was a kid, I hated picking beans. It was hot, humid, and eventually, I was sunburned from picking them. My sister and I put off picking them until the harvest was big and the heat was high, which made the work very hard. Learn from my mistake: Don’t wait to harvest.
Beans also will stop producing if you don’t pick them. After all the picking was done, I had to trim the ends off. I heard it once said that green beans were a country kid’s worst nightmare. I knew it was mine! I had mostly eaten canned beans my whole life, so I didn’t see why I should grow them.
Since then, I have become an adult and can now say homegrown garden beans are much tastier. Bush and pole beans are a couple of my contributions to our MOTHER EARTH NEWS garden. Thanks to my friend Benedict Vanheems for the idea for the pole beans. As my friend and former Mother Earth Living Editor Hannah Kincaid once said, “Try something new!” The pole beans are my something new. We haven’t planted them in a circle yet, but since our garden is in Zone 6a, we might be able to.
I care about these beans, so when I saw a lot of holes in them, I felt like a mother bear! I took pictures and walked back into the Ogden Publications office to ask Hank Will, our Editorial Director, what to do. With Hank’s insight, we discovered the issue to be bean leaf beetles munching away to their hearts’ delight.
Growing green beans can be a rewarding experience. The satisfaction of picking fresh, crisp beans right from your own garden is hard to beat. However, your bean crop can quickly become a frustrating disappointment when bugs move in and start feasting on the leaves. Chewed up, holey leaves don’t just look bad – they can stunt your plants’ growth and reduce your yields. Getting rid of the bugs eating your bean leaves is crucial for a healthy, productive crop.
The most common pests that attack green bean leaves include aphids, bean leaf beetles, Mexican bean beetles, leafhoppers, mites, caterpillars, and thrips. These bugs can appear seemingly overnight and spread rapidly, destroying leaves, flowers, pods, and even the entire plant if left unchecked. Don’t let them take over and ruin your bean harvest! Here are effective organic and chemical methods to get rid of bugs eating your green bean leaves.
Identify the Culprits
The first step is to properly identify the insects that are damaging your bean plants. Different bugs can cause similar types of injury, so careful inspection and identification ensures you use the right control methods.
Aphids are soft-bodied pear-shaped insects that cluster on the undersides of leaves. They use piercing-sucking mouthparts to feed, which distorts leaves and stunts growth. Aphids secrete sticky honeydew that attracts sooty mold.
Bean leaf beetles are tiny spotted beetles that chew irregular holes in leaves They can also damage pods and stems, Adults overwinter and reinfest plants in spring
Mexican bean beetles are copper-colored ladybugs lookalikes. Both adults and spiny larvae feed on leaves, skeletonizing them by eating just the green tissue and leaving a lace-like network of veins.
Leafhoppers are wedge-shaped fast moving insects that pierce leaf veins and stems to feed. This causes yellow stippling and curling of leaves.Nymphs and adults can quickly spread plant viruses.
Mites are tiny arachnids, not insects. They are usually found on the undersides of leaves and feed by sucking plant juices. This causes yellow speckling and bronzing of leaves. Mites thrive in hot, dry conditions.
Caterpillars are the larvae of butterflies and moths. Species like corn earworms, loopers, and cutworms eat ragged holes in bean leaves. Some are camouflaged to blend in with the leaves.
Thrips are tiny winged insects that rasp and suck juices from leaves, resulting in silver-white streaks and spots. Leaves turn brown and die back from the edges. Thrips hide in flowers and leaf crevices.
Remove Bugs by Hand
Manually picking pests off plants is an effective organic control for minor infestations. It allows you to selectively target the specific bugs eating your bean leaves.
Carefully check the tops and undersides of leaves and flatten them to expose insects hiding in crevices. Knock pests into a container of soapy water to kill them. Pay special attention to the undersides of leaves and new growth, as these are favorite feeding sites.
Hand removal works best for large, slow pests like caterpillars and adult beetles. Use tweezers to grab small, fast bugs like thrips and mites before they escape. Check plants daily to catch early infestations before they multiply.
Combine handpicking with other organic methods like insecticidal soap or neem oil spray for more stubborn pests like aphids that rapidly reproduce. Manual removal is safe for beneficial insects like ladybugs that eat pests.
Use Organic Insecticidal Soaps
Insecticidal soaps are highly effective at controlling soft-bodied insects like aphids, thrips, leafhoppers, and mites on contact. The soap disrupts cell membranes and causes insects to desiccate and die, without harming plants.
Look for concentrated formulas labeled for use on edible plants. Mix according to label directions and spray plants, including the undersides of leaves, until completely coated with solution. Spray in the evening to avoid leaf burn. Repeat every 5-7 days as needed.
Soaps primarily kill nymphs and adults, so repeat applications are needed to control newly hatched generations. But they provide quick knockdown of pests compared to other organic options. Soaps also help repel and deter future infestations.
Apply Neem Oil for Long-Lasting Control
Extracted from the neem tree, neem oil is an effective natural pesticide for a wide range of chewing and sucking insects. It contains azadirachtin, which repels and disrupts growth and reproduction of pests.
Neem oil is absorbed into plant tissues, so it keeps working for up to 3 weeks after spraying. It’s less harsh than synthetic pesticides and safe for beneficial species. Look for 70% cold-pressed formulations to use on edible plants.
To control bugs eating bean leaves, thoroughly coat all leaf surfaces with neem oil according to label directions. For heavy infestations, make two applications spaced 7-10 days apart. Neem oil is most effective against young, immature insect stages.
Combine neem oil with insecticidal soap or horticultural oil for improved coverage and pest control. The oil’s residual activity and repellency provides long term protection of bean plants against future damage.
Apply Diatomaceous Earth to Deter Small Pests
Diatomaceous earth (DE) is a natural mineral dust that can help control small soft-bodied insects and mites on contact. The microscopic sharp edges cut into insect bodies, causing injury and death from dehydration.
DE is safe for humans and plants, but avoid breathing in the dust. Wear a respirator and protective clothing when applying. Lightly coat leaf tops and undersides, stems, and soil around plants. Reapply after rain or watering.
For best results, use DE early before pests multiply. It kills adults but is less effective against eggs and larvae. Combine DE with neem oil for enhanced control of mites, thrips, and other small pests that infest bean plants.
Attract Beneficial Predators to Your Garden
Encourage natural biological control by attracting beneficial predators like ladybugs, lacewings, and syrphid flies to your garden. These “good bugs” feed on pests and help keep populations in check.
Plant small flowering plants like sweet alyssum, dill, and fennel to provide pollen and nectar. Put up bird and bat houses for insect-eating species. Avoid broad-spectrum insecticides that kill beneficials along with pests.
You can also purchase live ladybugs, lacewing larvae, parasitic wasps, and predatory mites from garden centers or online sellers. Carefully follow release instructions for best results. Time releases to early infestations before pests multiply.
Combining biological control with selective organic pesticides like soaps, oils, Bt, and spinosad will support a healthy population of beneficial insects that thrive and keep bean plants free of leaf-eating pests.
Apply Targeted Bt (Bacillus thuringiensis) for Caterpillars
Bt is a natural bacterium that effectively controls caterpillars infesting bean plants, while sparing other insects. Look for Bt varieties like Dipel, Thuricide, etc. specifically formulated and labeled for vegetable use.
The Bt bacteria produce toxins that are activated in caterpillar’s alkaline guts, paralyzing their digestive system. Death occurs from starvation within a few days. It is very specific to caterpillars and safe for humans, animals, plants, and beneficial insects like bees.
Strictly follow label instructions for mixing and applying Bt as a foliar spray to bean plants. Thoroughly coat the leaves, including the undersides, for best results. Depending on formulation, reapply every 1-2 weeks as needed.
For best results, treat young caterpillar stages. Bt degrades quickly in sunlight, so repeated applications are needed, especially after rain or watering washes residues from leaves.
Apply Horticultural Oils to Smother Eggs and Mites
Highly refined horticultural oils and petroleum oils (like dormant or superior oils) control a range of soft-bodied pests by smothering and asphyxiating insects and mite eggs before they hatch. The oils coat all plant surfaces and prevent pests from breathing.
Only use plant-based oils specifically formulated for vegetables. Mix according to label rates and spray plants, covering the tops and bottoms of leaves, stems and branches. Repeat applications every 7-14 days if needed.
Oils are effective against young nymphs and adults of aphids, leafhoppers, mites, and other pests, but immature stages inside unhatched eggs will be protected. Therefore, repeated applications are required to control newly emerged generations.
Use Spinosad-Based Products
Spinosad is a natural insecticide derived from the actinobacteria Saccharopolyspora spinosa. It affects the nervous system of insects, causing paralysis and death within 1-2 days of ingest
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Identify the Treacherous Bean Leaf Beetle
Bean leaf beetles are 1/4-inch long and display many colors. They have a triangle behind their head and four black spots on their backs. Without chemicals, they are hard to track down. They thrive in moist climates such as ours and emerge in mid- to late-spring. Adults eat from under the leaf, while larvae eat the roots, nodules, and stems that are below the ground. Luckily the beetles have not done much damage below the surface. We continue to see new growth, but the same shotholes are appearing on those as well.
Photo by Tonya Olson
The bush beans are doing much better than the pole beans. This might be because they were planted in different places. Along the edges of the garden, our pole beans are planted in rows so that they can climb something, which we haven’t decided what yet. Because bean leaf beetles like to hang out on the edges of fields, it’s best to keep the area around the garden trimmed or plant beans in the middle of the garden.
Photo by Ingrid Butler
As a Great Plains country kid, I was not raised in an organic environment (were you?). My first thought typically would be to sprinkle some insect bug killer on the beans, but this is blasphemy in the MOTHER EARTH NEWS garden. I knew that wasn’t going to fly. I want to learn organic agriculture principles so that I can do it and share it! We found that the University of Wisconsin-Madison page directs organic growers to use rotenone, pyrethrum, or neem. Hank pointed me towards neem, so neem it is!
Neem is natural toxin that causes insects to lose their appetite, stunting their growth. Farmers in India also have harnessed the medicinal properties of neem for years. Read more in How to Use Neem Oil to Prevent Garden Pests. For such a small bottle, it really does work! Neem smells familiar to me, maybe because it comes from an evergreen tree.
How to Stop Insects From Eating Green Bean Plants
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