Fresh green beans straight from the garden are one of the best parts about growing plants at home. So it can be extremely irritating to find out that bugs are invading and eating your hard work.
Several insects and bugs love to eat bean plants, including aphids, Japanese beetles, armyworms, leafminers, corn earworms, slugs, bean leaf beetles, thrips, leafhoppers, and cutworms. You can treat these pests by picking them off by hand, making barriers with cheesecloth, or using insecticidal soap.
With the right arsenal of products, you can get rid of and prevent more bugs from eating your bean seedlings. Keep reading as we go over 10 bugs and insects that want to eat your beans and how to treat and prevent them.
Bean Leaf Beetles Love To Eat Bean Seedlings
Bean leaf beetles are small insects that somewhat resemble ladybugs. These beetles are more elongated, though, and have a more visible head. According to Minnesota University Extension, most bean leaf beetles have four black spots on their backs, a black marking along the margins, and a black triangle at the top of the wing covers.
Some bean leaf beetles are a dingy yellow-green color, while others can be red and lack black spots. They will all have the tell-tale black triangle on the back section of their segmented bodies.
Bean leaf beetles cut holes into the leaves of bean plants making them look like leafy Swiss cheese. These pests prefer newer, younger leaves and enough beetles can strip new seedlings bare. Older plants can usually withstand a moderate amount of damage from these beetles.
Bean leaf beetles feed on the plants after they emerge from the soil. The larvae hang out in the ground and will feed on bean roots, though they rarely do a lot of damage in the ground. In warmer climates, you can go through two generations in one season which can be troublesome.
In later months, these beetles can feed on the bean pods. This damage looks like small divots carved out of the pods. While this damage doesn’t ruin the pods, it can look unsightly and unappetizing.
These beetles can sometimes pass along plant infections, though most hybrid bean seeds sold in stores are pretty resilient to these illnesses. If you see bean leaf beetle damage to the pods, wash them before preparing, and you can cut away the holes.
How You Can Treat And Repel Bean Leaf Beetles
One way to minimize damage from these insects is to delay planting your beans for a few weeks. Most beans are ready for harvest after 60 days, so you should have plenty of time to get a strong harvest.
Bean leaf beetles typically start to emerge from the soil in spring, so if there are no bean plants for them to eat, they most likely won’t invade your garden.
Pick Them Off By Hand
Another way to treat these pesky beetles is to pick them off by hand. Early in the morning before the sun has had time to warm them up, you can usually grab them before they take flight. Just drop them into a container of dish soap-laden water and watch them sink to the bottom.
Plant Trap Crops
Plant trap crops to lure the bean beetles away. They tend to like zinnias and marigolds even more than green beans, so plant these away from your bean plants. When the insects invade those plants, dispose of the beetles as you see fit.
Plant Smelly Herbs
These beetles don’t care for the smell of garlic, chives, or onions. Assault their olfactory senses by planting those fragrant ingredients near your beans. This will help to deter them. Plus, you have more seasonings for your beans!
Remove Weeds and Garden Debris
Regular maintenance of your garden will help deter these pests. Before you start planting, during, and after you harvest, be sure to remove weeds and garden debris. These beetles like to lay eggs under leaves and among weeds, so ridding your garden of these hiding spaces will help deter next year’s infestation.
Utilize Nematode And Bacillus Forces
The use of beneficial nematodes and bacillus thuringiensis (BT) will get rid of bean leaf beetle larvae. These microscopic organisms are natural predators of beetle grubs. Adding nematodes or BT will help to get rid of the bean leaf beetle worms but won’t do anything against adults.
Bonide Thuricide (BT) Liquid Concentrate is a spray to keep bugs from eating your garden plants. This naturally occurring bacteria is a great, all-natural way to get rid of most plant-eating insects. It prevents the feeling of hunger, so beetles stop eating.
Use Diatomaceous Earth
Sprinkling your plants with diatomaceous earth is another way to get rid of these beetles. This is a microscopic, granule that will cause tiny cuts in insect carapaces. The insects soon dry out because they can’t heal the cuts.
Diatomaceous earth is an all-natural, organic way to treat many insects and pests. You will have to add more after rain showers, though, because the water can wash the powder off surfaces.
Cover Seedlings With Cheesecloth
Covering your bean seedlings in a fine cloth or garden screen can help to completely prevent the beetles from getting to your plants. You can use a gauze-like material, or cheesecloth to cover your seedlings when they start to sprout.
Simply cover your seedlings with the fine cloth, then anchor it to the ground somehow. You can use rocks, landscape stakes, lawn staples, or whatever other means you have to keep the cloth over your seedlings and keep beetles out. Be sure to leave enough space and slack in the covering for the beans to grow.
A word of caution when utilizing the cloth to cover your beans: remove the covering when the growing season reaches very hot temperatures. When the days start peaking in the high 90s, a cloth covering could retain too much heat for the plants and burn them up.
Slugs Love Eating Bean Plants And Seedlings
Slugs love gardens because there are plenty of soft, succulent plants for them to gorge on. They especially love seedlings and can ruin new plantings in a heartbeat. Don’t get discouraged though because there are plenty of ways to battle these slimy pests.
You probably won’t see slugs in your garden because they like to come out at night away from the sun, but you’ll see tell-tale signs they were eating your plants. They leave iridescent slime trails wherever they go, and leave behind ragged-looking leaves where they have been feeding.
How To Repel Slugs From Your Bean Plants
Wait A Little Longer to Plant In The Garden
Slugs will attack new growth first as they love the tender leaves and shoots. Help prevent damage by keeping your beans in pots until they are larger and more able to withstand slug damage.
Wait until your beans have matured a little beyond the seedling stage before planting them in your garden.
Create a welcoming predator habitat. Birds such as robins, blackbirds, thrushes, and starlings will eat slugs. Set up birdbaths, and birdhouses, and set out feeders to attract avian slug predators to help you battle these legless intruders.
Toads are another slug-eating machine, and they’re typically nocturnal as well. Put out toad houses, and offer clean, chlorine-free water dishes to attract toads who will happily gobble up snails and plenty of other garden pests for you.
Pick Slugs Off By Hand
Another way to take care of the slug menace is to pick them off yourself. Slugs are very slow-moving gastropods so you will be able to yank them right off your plants without having to break a sweat. You might want to wear gloves when you do this though.
The slime coating on slugs will get all over your fingers and sometimes touching or grabbing them can be a disconcerting experience – so we recommend wearing gloves!
You’ll want to wait until after dark and bring a flashlight, because slugs will hide in moist, dark places during the heat of the day. Bring a small pail of soapy and/or salty water to drop them in after you pluck them off your bean plants.
Use Copper Barriers
Repel slugs by using copper. It is thought that when slugs or snails touch anything with copper, they receive an electric shock and can’t pass over the metal. This probably has something to do with their slime coating. (It may also remind you of what it feels like to chew aluminum foil when you have metal fillings in your teeth.)
Placing copper rings, copper tape, or even a tight line of pennies can create a proper slug barrier. If your plants are in pots or raised beds, copper tape will prevent them from climbing in and munching on your tender bean plants.
Powder Barriers to the rescue
Stop slugs short by applying a barrier of diatomaceous earth, sharp mulch, or egg shells. Diatomaceous earth works to dehydrate slugs very fast, and when they touch the powder, if for some reason they aren’t turned away by it, they will dehydrate and expire before doing much damage.
Mulch and egg shells work in a similar manner except that the slugs have very soft and sensitive bodies. When they touch something sharp like egg shells or prickly mulch, they won’t be able to pass through the barrier.
If you use a lot of eggs, just crack them into small pieces and surround your garden or plants with them. You’ll have to replace them on occasion because they will degrade and work into the soil which is a good thing. After all, they add nutrients to the ground.
Diatomaceous earth will need to be reapplied occasionally too. Rain and watering will wash it away.
Grab More Odiferous Herbs
Garlic again! Strongly scented plants like garlic, chives, rosemary, and mint work to repel slugs. Plant these around your bean plants to keep slugs away.
Just be very careful with mint, because it can quickly take over and crowd out your other garden plants. Mint works best in containers because it’s a little more difficult to escape the pots.
You can also mix up a garlic scented spray. Simply take several cloves of garlic, crush them, and boil the garlic in a few liters of water. Once it reaches a boil, let the garlic water mixture cool overnight. Here’s a full list of scents that snails hate if you’d like more options! Slugs are snails without shells, so the same list will work.
After the mixture has cooled, strain the garlic chunks out and pour the garlic water into a spray bottle. Spray the garlic “potpourri” wherever you want to repel slugs and most other pests.
You can also use French marigolds as a trap plant for slugs if you’d like!
Bring Out the Yeast
One final way to take care of pesky slugs is to leave out yeast traps. Use a few shallow containers—used, cleaned, tuna cans work great here—fill them not quite to the top with yeast, sugar water, a few tablespoons of salt and set the containers about halfway into the ground.
You can use cheap yeast for this, there’s no need to buy expensive yeast – They won’t appreciate it as much as you would! The slugs smell the yeast, are attracted to it, then drown their sorrows and themselves inside.
Where are the slugs hiding in your yard? Here are 7 places slugs come from at night and where they go.
Aphids Always Want To Eat Your Bean Plants
If there is a more prolific and annoying garden pest than aphids, I don’t want to know it. Aphids seem to pop out of thin air. They can drain your plants dry if they are left to run amok unchecked.
You will usually see their damage when you notice curling, dried up, brown leaves. Other times you’ll see the tiny green, black, yellow, or red bodies congregating on the bottoms of leaves and along the stalk of your garden plants.
When aphids show up on your bean plants, they will suck the sap out of them, and over time leave you with weak, stunted plants that eventually shrivel up and die.
If you’d like, take a look at our piece to learn more about why you have aphids in your garden!
How To Repel And Get Rid Of Aphids From Bean Plants
Aphids seem to hate catnip, so planting that around your garden may be an effective barrier against aphid infestation.
Be careful with this little plant though because it can get pretty invasive. You can leave it in containers and snip off the seed pods before they open up to keep it under control.
You can also use some of the scents that aphids hate for more options!
Apply Neem Oil
Neem oil and insecticidal soap work great on these soft-bodied insects. It has to come in contact with them though. Spray the plants wherever you find aphids and be sure to get their hiding places underneath the leaves.
Reapply as needed, up until the bean plants start flowering. Neem oil claims to be safe for bees and pollinators, but I just like to play it safe when it comes to beneficial insects.
You can view some of the best aphid repellents, including neem oil, in our guide!
Spread Diatomaceous Earth
Diatomaceous earth makes an appearance in our list again.
Sprinkle the aphids themselves or prevent them by sprinkling this dust on your beans before they take hold.
Shower Aphids With The Hose
Giving aphids on your bean plants a good spray with a hose is enough to knock them off, and most times they won’t find their way back to the original plant.
This method isn’t perfect though because it just relocates the aphids. In a garden setting, knocking aphids off with a hose could send them packing to another valuable plant.
Attract Aphid Predators
Lacewings, ladybugs, hoverflies, and predatory wasps all eat aphids, so inviting these beneficial insects is a great, natural way to tame the aphid menace.
Planting flowers such as coreopsis, dill, cosmos, yarrow, and Queen Anne’s lace is a great way to attract lacewings and ladybugs.
Hoverflies look similar to bees or wasps, but they are harmless to humans. You might have seen them floating stationary in front of your face looking quite menacing, but they have no stingers and can’t bite or sting. The adults consume nectar from flowers, but their larvae are aphid devouring machines.
You can attract these insects to your garden by planting the flowers listed above and other similar species, like coneflowers and black-eyed Susans.
When these insects find a colony of aphids they will lay their eggs nearby. When the eggs hatch, an army of hungry aphid munchers go to work.
Ladybugs and lacewing larvae eat tons of aphids as well, so having these insects in your garden will help to keep it aphid free. This is one of the best ways to stop aphids from coming back yearly.
Thrips Love To Eat Your Bean Seedlings
Thrips are minuscule insects that most people may not see until there’s already an infestation. Still, even then the tiny bugs are hard to see. Often they are noticed by the black spots of bug droppings and damaged leaves.
They drain leaves and small bean pods of moisture, leaving behind browning, shriveled up leaves. You might also see leaves dropping off the plant because of their feeding.
Ways To Repel And Get Rid Of Thrips Off Of Bean Plants
Lay On The Herbs and Spices
Garlic for the win again! Plant garlic, chives, oregano, or basil to repel thrips. These strong smelling herbs tend to repel thrips as well.
Plant the above herbs in your garden, or apply concentrated oils with a spray bottle.
Make sure you keep weeds away from your garden. Thrips like to hide out in weeds such as prickly lettuce, and other weedy plants related to the legume family.
Removing weeds is a sure way to make your garden less appealing to thrips. As a bonus, your garden will also look pristine enough to be on the cover of a magazine!
Strategically Place Sticky Traps
Setting up blue or yellow sticky traps tends to attract thrips. They will get stuck on the sticky traps and not be able to invade your bean plants.
Make sure to check your plants daily and replace traps as needed!
Leafhoppers Love To Eat Bean Plants
Adult leafhoppers are small green or multicolored insects that quickly hop and fly away when you get close to them. They will damage your bean plants by sucking the water and sap out of them.
Often these pests aren’t numerous enough to do much damage, but there are times when their numbers can ruin your crops. The damage they cause is noticed when the leaves start to become stippled and are drained of color. The veins of the plants may turn white as they are drained of moisture.
The biggest concern with leafhoppers is in what they can spread. Leafhoppers bounce from plant to plant and can quickly spread plant issues to many other plants.
Leafhopper larvae produce honeydew, a sticky waste product that ants love. So if you see ants running up and down your bean plants, they could be cultivating leafhopper larvae as they typically don’t eat bean plants.
Here’s How You Repel Leafhoppers From Bean Plants
Defense is the best offense
The best way to treat leafhoppers is to prevent them in the first place. This can be accomplished by removing any tall weeds and overgrown grass because they like to lay their eggs in tall weeds.
The eggs and nymphs often survive the winter in tall patches of weeds, so no weeds, no leafhoppers.
Keep Your Plants Healthy
Keeping your plants healthy is one of the best ways to prevent most pest infestations. Healthy, watered bean plants can fight off and withstand leafhoppers.
Water your beans in the morning—taking care not to spray the leaves—and mulch them to help keep moisture in.
Wash With Insecticidal Soap
Insecticidal soap works to control leafhoppers, especially the slow-moving nymphs and larvae. They have to be sprayed, so hitting the adults with a solid stream can be difficult.
Are Japanese Beetles Eating Your Bean Seedlings?
These bugs are hard not to see. You’ll often see them flying around or, worse, attached to your plants as they steadily devour them. They are bronze-colored, small beetles with stripes along their undersides.
They often eat the softer tissue of plant leaves while leaving behind the tough veins, leaving the leaves looking skeletonized. Japanese beetles show up in summer and can often swarm in large numbers.
How To Prevent Japanese Beetles From Eating Your Bean Plants
Use Geraniums to protect your beans
One way to prevent Japanese beetle damage to your garden is to bait them with geraniums. Plant them near your bean plants, or hang baskets of them up. Japanese beetles can’t seem to resist this plant, but it does funny things to them.
After a Japanese beetle consumes the geranium, they get dizzy and fall to the ground. There they lay in a paralyzed stupor, unable to fly away. While they are incapacitated, wild birds, chickens, or other predators can easily scoop them up.
Japanese beetles tend to eat bean leaves way more often than the pods. Healthy bean plants can easily shake off a little beetle damage and continue to produce plenty of beans.
Although they love geraniums, there are several scents that will deter Japanese beetles when used the correct way. To find out more and to find out which scents work to keep these pests away check out 9 Scents That Japanese Beetles Hate.
How To Tell If Cutworms Are Eating Your Bean Seedlings
Cutworms get their name because they cut plants—especially seedlings—down at the base of the stem. Sometimes they even eat the roots or eat through the stems just under the surface of the soil. When cutworms eat through plants at the base, it most often destroys the plant.
These devastating pests are the caterpillar form of night-flying moths. While the moths don’t do any damage to crops, the caterpillars can quickly mangle many crops in one night. They especially love seedlings and new transplants.
You probably won’t see too many of these worms during daylight hours because they hide under the soil while the sun is out. They come out at night and wreck your garden.
Ways To Prevent Cutworm Damage To Bean Seedlings
The best way to deal with cutworms is to prevent them in the first place. It’s hard to stop them after they have eaten most of your newly planted, or growing bean sprouts.
Wait It Out
If it’s possible, delay your planting by a few weeks.
Cutworms emerge from the ground in spring with their ravenous appetites.
If there are no seedlings to munch on they will still eat patches of your lawn, but this is better than them feasting on your garden.
Fix Your Collar!
No, not your shirt collar. Prevent these pests from getting to your new plants by placing plant collars around your seedlings. This can be a tedious process if you have a huge garden, so this method is easier with smaller plots.
Take empty paper towel or toilet paper tubes and place them in the ground about an inch or two deep to keep cutworms from getting to your plants.
You can cut the paper towel rolls in half. You’re looking to cover the plants with about four or five inches of a vertical surface.
If you don’t have any old paper product tubes you can use heavy paper like posterboard and shape pieces into tubes. Wrap them in aluminum foil to give your plants more protection and keep the tubes lasting longer.
Don’t Delay Clean-Up
The night-flying cutworm moths lay their eggs at the end of the season on old, decaying plant matter. Usually, after the garden has produced its last veggie, the plants are left to decay and return to the soil.
A way to prevent next season’s cutworms is to plow or till the soil and all that rotting plant matter into the ground at the end of the season. This exposes the eggs to freezing winter temperatures so cutworms won’t survive to feast next spring.
Do You Have Armyworms On Your Bean Seedlings?
Armyworms are another caterpillar that’s not really a true worm. But they can cause significant damage to crops, especially to bean seedlings.
Adult armyworms are a species of small, brown, and grey moths that like to lay eggs in tall grass.
When the eggs hatch, armyworms tend to eat grasses and grains. But if that food source isn’t available or plentiful they will turn to vegetable crops such as bean plants. In one season you could have up to three generations of armyworms.
Armyworms are another nocturnal “wriggler” that likes to hide during the day and cause damage when the sun goes down. They will skeletonize leaves and can destroy a lot of plants in one night because they march together like a platoon of army soldiers. That’s how they got their name.
Aside from the damage, you might see evidence of nightly caterpillar marches by the speckled, black feces they leave behind on your plants.
How Do You Stop Armyworms From Eating Your Beans?
Many of the strategies we’ve discussed with other insects will work when fighting against armyworms.
The first order of prevention is to keep your garden and surrounding areas clean and trimmed. The moths are attracted to tall grass, so keeping the lawn and area near your garden neat will deter moths looking to lay eggs.
Clean out any garden debris so there’s no place for armyworms to hide. Make sure you remove spent plants, clean up leaves, and any other places they can go to hide from the light.
Birds and toads will happily eat armyworms when they see them so inviting these caterpillar predators will help you keep their numbers in check if they start to march toward your garden.
If you know you have armyworms or other caterpillars for that matter, you can treat them with BT, the naturally occurring bacteria that will dismiss this army for you.
Leafminers Love Your Bean Plants
The first indication of leafminers on your beans will be small, wiggling lines patterned throughout the leaves. Leafminers create discolored “tunnels” through the leaves as they eat the soft, chlorophyll laden cells in the plant.
These pests are tiny, maggot-like insects that live inside leaves as juveniles. The adults look very similar to house flies, except they have transparent wings and small yellow lines on their sides.
While a few leafminers won’t cause extensive damage, they can quickly multiply and cause an infestation that can damage large sections of crops. The plants can lose their leaves because of the damage and eventually fade away completely.
How To Prevent Leafminer Infestation On Your Bean Plants
Tilling your garden in the fall after all the crops are finished is one way to reduce their numbers. Young leafminers like to pupate in the soil through the winter. Tilling the soil in the fall will expose them to freezing temperatures and prevent many of them from invading next year.
You can also lure leafminers away by planting trap crops. These pests love plants like columbines, lamb’s quarters, and radishes, so attract them to these plants, then remove the leaves as soon as you see the tell-tale tunnels.
When you see leafminer tunnels, you can also spray them with neem oil. This will take care of the worms in the leaves, and could possibly get the adults when they land on the leaves if the oil is still fresh.
Destroy The Eggs
Keeping a close eye on your garden can go a long way to stopping these pests before they become a big problem. The adult flies lay eggs inside the leaves. On the undersides of the leaves, you may see bumps that look a bit like a blister.
Smash the bumps to destroy the eggs before they can hatch, or if the plant is healthy enough, remove the leaf completely and dispose of it.
Cover Your Rows
Cover your plants with floating row covers to prevent the adult flies from laying their eggs.
Ultra Fine FARAER Plant Covers will prevent leafminer flies and many other garden pests from getting to your precious plants. It’s a great way to protect your plants while letting water and airflow get to your plants.
Corn Earworms Will Eat Your Beans
These little caterpillars don’t only eat corn, they will also invade your beans and other crops when corn isn’t available. They aren’t picky eaters.
Another moth larva, corn earworms hatch and immediately start eating. They can eat the leaves off your bean plants, but when the bean pods start to grow, they will turn on these parts of the plants.
They will cut small holes into the pods, and sometimes burrow inside and eat the tender beans. These holes can be vectors for fungus and other issues in the plant.
These caterpillars can measure up to two inches long before they pupate and morph into moths.
They can range in color from green, brown, black, to pink or maroon, or any color in between. Corn earworms often have stripes running the length of their bodies on the top and sides.
Ways To Prevent Corn Earworm From Eating Your Beans
The University of Minnesota suggests you plant your beans away from corn to help prevent these pests from invading other plants. Corn plants that have thin threads of silk attract corn earworm moths.
The moths will lay their eggs in the silks of the corn and can spread from there.
Attract predatory insects like parasitizing wasps to the garden by planting host plants. Adding herbs such as dill, fennel, cilantro, and annuals like cosmos and sunflowers will attract corn earworm predators.
Many pests want to feast on your food and hard work, but you can prevent them from wrecking your garden. Understanding these pests (and the ways to treat them) will help you get a bigger, pest-free harvest.
Natural methods like nematodes, predatory insects, and inviting insect eating birds and toads into your garden are Mother Nature’s way to keep garden eating bugs in check.
Neem oil works on many pests, as well as plucking them off by hand and dropping them into a fatal bath.
Get out there and garden, and don’t let these pests bug you anymore!
Askary, TARIQUE HASSAN, and M. M. M. Abd-Elgawad. “Beneficial nematodes in agroecosystems: a global perspective.” Biocontrol Agents: entomopathogenic and slug parasitic nematodes. CAB International (2017): 3-25.
Azizoglu, Ugur. “Bacillus thuringiensis as a biofertilizer and biostimulator: a mini-review of the little-known plant growth-promoting properties of Bt.” Current Microbiology 76.11 (2019): 1379-1385.
Sinclair, Robyn Jean, and Lesley Hughes. “Leaf miners: the hidden herbivores.” Austral Ecology 35.3 (2010): 300-313.
Singh, Shree, and Howard Schwartz. “Breeding common bean for resistance to insect pests and nematodes.” Canadian Journal of Plant Science 91.2 (2010): 239-250.
Zack is a Nature & Wildlife specialist based in Upstate, NY, and is the founder of his Tree Journey and Pest Pointers brands. He has a vast experience with nature while living and growing up on 50+ acres of fields, woodlands, and a freshwater bass pond. Zack has encountered many pest situations over the years and has spent his time maintaining and planting over 35 species of trees since his youth with his family on their property.
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