12 Common Garden Pests (And How To Save Your Plants From Infestation)
Are pests plaguing your beautiful garden? Or are you just trying to stay ahead of the storm?
Wherever you are in your gardening journey, this is the one pest guide you need to make it through. Keep reading to learn how to identify the most common garden pests, plus tips for how to treat each infestation.
There are a lot of things you can ignore in a garden (like weeds, to a point) but pests are not one. Once you turn a blind eye to the first pest, they are sure to multiply exponentially to the point of a full-on invasion. While it’s easy to be overwhelmed by the thought (or the reality) of severe pest infestations, with the right treatment program you can take back control in your garden.
Common Garden Pests and Treatments
It’s wild that such tiny insects can become such an issue, but aphids can cause significant damage to your garden. The minuscule, green or black spider-looking insects feed on plant sap and can deplete plants of essential nutrients. One common sign of aphids are discolored and curled leaves, and if you look close enough you’ll be able to see the aphids themselves. Honeydew, the sticky substance aphids secrete, is especially attractive to ants.
When aphids infest young plants, they can hinder their growth and development, resulting in smaller undeveloped plants. Aphids multiply at an alarming rate (one adult can produce 80 offspring in a week!) but aphid populations can be controlled by regular application of insecticidal soap or the introduction of predatory insects like ladybugs.
2. Japanese beetles
Japanese beetles are voracious feeders and can cause significant damage to a wide range of plant species. They consume leaves, flowers, and fruits, which can result in defoliation, reduced crop yields, and eventual plant death.
The work of Japanese beetles is easy to see—the beetles eat away at plant foliage, leaving behind large holes in the leaves. Fortunately, Japanese beetles are large enough to see clearly and they’re slow to move, making them relatively easy to capture by hand.
Handpick the beetles off of plants and place them in a jar of soapy water, where they will eventually drown. While pheromone traps are another option, the University of Minnesota Extension recommends against it, since the pheromone traps draw more beetles to your garden but don’t necessarily kill them all.
3. Potato bugs
The aptly named Colorado potato beetle can cause extensive damage to potato plants. Potato bug larvae are a bright orange-red color and are marked with black dots, while the winged adults feature black and white alternating stripes.
If given the chance, potato bugs will damage more than just potatoes—the beetles and their larvae feed on tomatoes, peppers, eggplant, and other nightshades. They chew on the foliage, leaving behind skeletonized leaves that can no longer perform photosynthesis effectively, resulting in fewer and lesser-quality fruit production. If left uncontrolled, potato bugs can lead to substantial yield losses, plus the bugs can transmit diseases between plants.
Potato bugs are large enough to see and pick off plants, and regularly spraying an insecticidal soap or neem oil is usually enough to keep moderate infestations under control.
If you’ve ever gone to harvest a tomato and felt something slimy on the other end, you won’t be surprised to find out that slugs can take out a substantial portion of your harvest. Slugs can damage mature fruits and vegetables by nibbling on them, leaving behind unsightly holes or scars that are quick to rot. The slimy trails slugs leave behind can significantly reduce the yield and quality of the harvest.
One of the easiest ways to kill slugs is by setting out beer traps. Yep, slugs have a taste for booze! Buy a case of cheap beer (no need to buy high-dollar craft beverages) and gather a few shallow bowls. Spread the bowls around the perimeter of your garden, and fill the bowls with beer. The slugs will crawl into the bowls to get to the beer, and they won’t be able to climb out!
Copper traps have also been proven to be effective against slugs. The copper reacts with the slime that slugs produce, sending an electric shock through their body. Simply wrap planters and pots with copper foil for an effective chemical-free slug repellent.
Caterpillars are known for their bottomless appetite. As cute as caterpillars are, they can easily consume large amounts of leaves, leading to stressed plants and stunted growth.
Some caterpillar species are known to defoliate entire plants, leaving the plant and its fruit exposed to direct sunlight, which can cause sunburn, dehydration, and eventual death. Caterpillars can also act as vectors for plant diseases, transferring pathogens from infected to healthy plants.
Bacillus thuringiensis (Bt) has proven to be an effective pesticide for controlling caterpillars, but a safer and natural alternative is to plant certain caterpillar-repelling companion plants, including strong-scented marigolds, ladybug-attracting dill, lavender, and mint.
6. Spider Mites
Spider mites, which are nearly invisible to the naked eye, have the appearance of small spiders. Spider mites feed on plants, sucking out water and nutrients that the plants need. This feeding activity weakens the plants and reduces their ability to photosynthesize effectively. Continuous feeding by spider mites can lead to stunted growth in plants.
Discolored foliage with a web-like covering is a sure sign of spider mite damage.
Introducing predatory insects like ladybugs and predatory mites is very effective at controlling spider mites in the garden. Some growers also have great success by misting their plants to increase the humidity (spider mites prefer dry conditions) although this opens up the door for other moisture-loving pests and diseases.
7. Flea Beetles
You might mistake flea beetles for fleas based on how they move, but the tiny black bugs are actually small beetles that prefer to feed on plant foliage.
Continuous feeding by flea beetles can stunt the growth of plants, particularly young seedlings. The damage disrupts the plant's ability to photosynthesize and allocate resources for proper growth and development. Some species of flea beetles inject toxic saliva into the leaves as they feed, causing the affected leaves to curl or become distorted.
Fortunately, flea beetles are easy to control by using floating row covers to create an impenetrable barrier. You can also place sticky traps throughout the garden to capture and kill flea beetles, reducing their population.
Like many pests, flea beetles prefer some crops over others (brassicas, nightshades, and legumes) so practicing crop rotation from season to season can interrupt flea beetles life cycles. Try rotating alliums, cucurbits, and root crops with brassicas and nightshades to manage flea beetle populations.
8. Leaf Miners
Leaf miners are more a group of pests than a specific insect—they are the larvae of various insects, such as moths, beetles, and flies—that feed on the inner tissues of leaves, creating distinctive tunnels or mines..
Leaf miners damage the chloroplasts within plant cells, which are responsible for photosynthesis. As a result, affected leaves may have reduced photosynthetic capacity, leading to diminished energy production for the plant.
The best way to manage a leaf miner infestation is by removing infested leaves. Don’t throw them in the compost pile, but take them straight to the garbage. Yellow sticky traps are also an effective method of controlling adult leaf miner populations.
Scales are small insects that look like (you guessed it, scales) that harm plants by sucking sap. Scales attach themselves to plant leaves and use specialized mouthparts to pierce the plant's tissue. These small insects consume large amounts of sap, which can lead to a decrease in nutrient availability for the plant and dehydration.
Horticultural oil or insecticidal soap are both effective products for treating scale infestations, as oils will disrupt the insects’ exoskeletons and suffocate the insects. Regular inspection and pruning of infested branches can also help manage the infestation.
Cutworms are notorious for severing the stems of young plants just above the soil line, causing them to wilt and die. These pests are capable of devouring the leaves, stems, and roots of young plants, reducing their ability to photosynthesize and their ability to absorb water and nutrients from the soil. The wounds created by cutworms provide entry points for pathogens, increasing the risk of plant diseases.
Physical barriers are among the most effective methods for minimizing cutworm damage to your garden. Since cutworms feed at the soil surface, installing a collar around your plants can prevent damage to plant stems and roots. This Red Mulch Film makes an effective barrier if you bury a few inches of the film underneath the soil.
Handpick any cutworms that you find on or around the film, and consider adding beneficial nematodes to the soil. Steinernema feltiae is one species of nematode that preys on cutworm larvae.
11. Cabbage Moths
Make no mistake—these innocent-looking white moths and their green larvae can severely damage cabbage plants and other cruciferous vegetables.
Cabbage moth larvae rapidly chew through plant foliage, creating large holes that weaken plants and result in lesser and lower-quality yields. As cabbage moths continue to feed on the leaves, the plants may struggle to produce healthy heads or develop proper size.
Regular monitoring and early intervention are key in preventing extensive garden damage by cabbage moths. First, remove any damaged leaves and destroy any cabbage worm larvae that you find. Try covering crops with floating row covers that can be used to create a physical barrier and prevent the moths from laying their eggs on the plants. Consider introducing natural predators such as parasitic wasps or spraying Bacillus thuringiensis (Bt) to help control cabbage moth populations.
You can also try intercropping moth-repellent mint and thyme plants with brassicas to deter cabbage moths.
These small and slender insects pack a punch, feeding indiscriminately on most vegetables and flowers.
Thrips create tiny, silver-colored scars on the surface of leaves and flower petals as they suck out plant sap. These scars can make the plant appear speckled or discolored. But not only do thrips damage the appearance of plants, but thrips can also transmit plant viruses from infected plants to healthy plants.
To control thrip infestations, it is important to practice good garden sanitation. Remove any infested or damaged plant parts to prevent the spread of thrips and their associated diseases. Regularly inspect plants for signs of thrips and take action at the first sight of an infestation.
Using sticky traps can help monitor and control thrip populations. These traps attract thrips and kill them. Some growers also have success with reflective mulch, which you can make by framing your plants with sheets of aluminum foil. Light-sensitive pests like thrips are confused by the reflective material and are less likely to take up residence in your garden.
For the worst thrip infestations, spray plants once a week with insecticidal soap or neem oil.
Garden pests can cause significant damage to plants, leading to stress, nutrient deficiencies, and reduced growth. And once pests take hold in your garden, they become more and more difficult to control with time.
Vigilantly monitor your garden, and be prepared to act fast at the first sign of any of these pests.
Start by removing infested leaves, and at the first opportunity introduce beneficial insects into your garden. Take preventative measures like companion planting flowers and installing physical barriers. Regular monitoring, early intervention, and good garden sanitation practices are key to preventing extensive damage and ensuring the success of your garden.