My journey in the garden has been wonderful but not without its challenges. As a master gardener, I’ve faced the onslaught of many garden pests, each with its own unique way of testing my patience and skill. Yet, every encounter has only deepened my resolve and enriched my understanding of the delicate balance in our ecosystems.
I’m passionate about organic gardening and seek natural ways to address pests on my plants. So, whether you’re a seasoned gardener or just starting out, join me as we delve into the world of these tiny troublemakers and discover sustainable strategies to keep them at bay.
Introduction to common garden pests
While garden pests can vary by region and climate, there certainly are a few usual suspects that cause trouble in gardens near and far. Dealing with garden pests can be challenging, but it’s crucial to remember that nature often has a balance. By encouraging natural predators and using non-chemical solutions, you can maintain a healthy garden ecosystem while protecting your precious plants.
Many of these pests can be quite irritating for gardeners, not just because of the visible plant damage they cause but also due to the potential for these pests to spread diseases or attract more pests. Effective management of most common garden pests often requires a combination of cultural practices and targeted treatments. Integrated Pest Management (IPM) is a comprehensive approach that can help gardeners tackle these challenges in an environmentally friendly manner.
Aphids
Aphids are tiny, pear-shaped insects known for their sap-sucking behavior, which leads to plant stress by causing leaves to curl, wilt, or turn yellow. These pests can be found in various colors, including green, black, brown, yellow, or red. Beyond the direct harm from feeding, aphids can transmit diseases, sometimes injure plants with their toxic saliva, and excrete a sticky substance called honeydew that attracts other pests and can promote mold growth.
To combat aphid infestations organically, gardeners can use a strong water spray to dislodge them or apply soapy water pesticide sprays. Additionally, attracting beneficial insects such as lady beetles, aphid midges, syrphid flies, and lacewings can help manage aphid populations. To attract these beneficial insects, try companion planting with attractive flowers such as sweet alyssum.
For preventive measures, utilizing floating row covers can be effective in keeping aphids at bay. Aphids are also much less likely to attack plants that are well-watered. On the other hand, overfertilizing with nitrogen can cause lots of fresh, succulent growth that is vulnerable to aphid attack. Most species of aphids only feed on a particular group of plants and therefore don’t easily spread between different plants in the yard. If aphids are a recurring problem, horticultural oil may help control overwintering eggs.
Slugs and snails
Slugs and snails are notorious for their voracious appetite. These land mollusks are recognized by their soft bodies that leave trails of slime behind them. Snails and slugs flourish in cool, moist environments, especially during seasons of consistent rain or irrigation. These pests primarily emerge at night or during overcast, humid days, feeding on garden plants (sometimes the entire plant), leaving a tell-tale silvery trail behind them. They reproduce by laying eggs in damp places under debris.
To minimize damage from slugs and snails, I my garden during the morning hours so that the soil surface can dry by evening. Be cautious about over-mulching or maintaining dense plantings, which provide ideal hiding places.
Another preventative measure is to introduce barriers like diatomaceous earth to deter these pests due to their sharp edges. Additionally, some garden predators, such as frogs and toads, can naturally control slug and snail populations. Lastly, homemade bait such as beer traps (or another fermenting, yeast-containing liquid) can catch them (especially during wet evenings). Even a wet piece of newspaper can attract these pests as they leave shiny slime trails all over your plants. Peel the newspaper back in the morning and destroy any interlopers.
Japanese beetles
Japanese beetles, often identified by their metallic blue-green head and copper-colored wings, are notorious insect pests in many gardens. They feed on many types of plants, leaving behind skeletonized leaves and flowers. Their larvae, known as white grubs, can be equally destructive, feeding on the roots of lawn grasses and garden plants, leading to patches of dead or dying plants.
Controlling Japanese beetles requires a multi-pronged approach. One of the most immediate methods is hand-picking the beetles off plants, preferably early in the morning when they are less active, and dropping them in soapy water to kill them. Additionally, attracting natural predators such as birds and parasitic wasps can help in reducing their numbers. Using pheromone traps can help, but place them away from the plants you want to protect to avoid attracting more beetles. While there are pesticides available to combat these pests, it’s essential to prevent harm to beneficial insects and the environment.
Beneficial nematodes can be introduced into the soil to target the white grub stage of the beetle’s life cycle. These microscopic worms infect and kill the larvae, breaking the life cycle of the beetle. Floating row covers can also be effective, especially during the 6-8 week period when the beetles are most active.
Cabbage worms
Cabbage worms are caterpillars that primarily target the Brassicaceae family, including cabbage, kale, broccoli, and Brussels sprouts. These smooth, pale green caterpillars have a faint yellow stripe along their back. Adult cabbageworms are small white butterflies.
From late spring to September, both the adult butterflies and the caterpillars can be found in gardens. There can be three or more overlapping generations of these pests each year. As colder months approach, they enter a dormant state, overwintering as pupae.
Cabbageworms are notorious for their appetite, feeding primarily on cabbage, broccoli, and other members of the mustard/cabbage plant family. As a cabbage maggot grows, the holes it creates in the leaves increase in size. A distinct sign of their presence is the green, crumbly pellets of excrement, known as frass, that they leave behind.
Covering young plants with floating row covers is an effective way to prevent adult butterflies from laying their eggs on the leaves of your plants. Naturally derived BTK sprays can also be effective when timed correctly.
Tomato hornworms
Tomato hornworms are large caterpillars that feed on tomatoes, peppers, eggplants, and potatoes, often causing extensive defoliation. Recognizable by their bright green coloring, these (awfully disgusting) caterpillars can grow up to 3-4 inches long (8-10 cm). Their most distinguishing features include a series of eight V-shaped marks that line their sides and a pronounced horn located at their tail end.
Adult moths lay their eggs on the undersides of plant leaves. These eggs hatch within a few days, giving birth to the caterpillar larvae. These larvae then feed on various plants for a month or two during the summer season and can completely defoliate plants. Once they’ve completed this feeding phase, they burrow into the soil to undergo pupation, transforming into moths and awaiting the next cycle.
Tomato Hornworms cause significant damage to gardens. They are voracious eaters, consuming leaves, shoots, and occasionally the fruits of plants like tomatoes, peppers, and potatoes. In severe infestations, a large number of these caterpillars can completely strip plants of their foliage. As a control measure, these pests are notably vulnerable to sprays containing BTK.
Squash bugs
Squash bugs are notorious pests that suck the sap out of squash and pumpkin plants. Adult squash bugs are easily identifiable by their brownish or dark gray bodies and flat, shield-like shape. They can measure up to half an inch in length. The younger nymphs vary in color, starting as a bright red when they first hatch and transitioning to gray or brown as they mature. Both adults and nymphs are known to have a piercing-sucking mouthpart which they use to extract sap from the plants.
Females lay clusters of bronze or reddish eggs on the undersides of leaves. These eggs hatch into nymphs that suck nutrients from plants, leading to the yellowing and wilting of the leaves. One of the hallmarks of squash bug damage is the wilting of squash plants, despite adequate soil moisture, a condition that can be mistakenly attributed to insufficient watering. If left unchecked, a significant infestation can severely weaken plants and reduce crop yields.
Early detection is key, so regular inspection of plants, especially the undersides of leaves, is essential. If found, egg clusters should be removed and destroyed. Physical barriers, such as floating row covers, can prevent the bugs from reaching the plants, although they must be removed during flowering to allow pollination. Neem oil and insecticidal soaps can deter squash bugs when applied regularly. Furthermore, encouraging natural predators like spiders, ladybugs, and lacewing larvae in the garden can help keep the squash bug population in check.
Scale insects
Scale insects are small, flat disc-shaped bugs that live on the leaves and stems of plants. Unlike typical insects, these scales appear as small oval brown or tan bumps on plant stems and foliage, measuring up to 4 mm in length. They suck plant sap, weakening the plants. Their presence becomes evident when there’s sticky honeydew residue on leaves.
These pests are detrimental to plants as they weaken the overall plant health, and the honeydew they excrete in abundance becomes a breeding ground for mold. Soft brown scale infestations are common in a variety of plants, including houseplants like ficus and schefflera, as well as outdoor plants like bay laurel and camellias. Their proliferation outdoors is kept in check somewhat by natural predators and colder winter temperatures, which affect their numbers.
Controlling soft brown scales is a challenging task due to their hardy nature and protective outer shells. To prevent infestations, it’s crucial to inspect new plants thoroughly before introducing them to an environment with existing plants. As for treatment, while physically removing scales is an option, it’s often labor-intensive and may not guarantee complete eradication. Natural pesticides that target younger scales can be effective, as mature scales are well-protected by their waxy exterior. Pruning heavily infested branches and using insecticidal soaps or neem-based products can also help manage these pests.
Spider mites
Spider mites are pin-point-sized insect pests on plant leaves that are difficult to see without the aid of a magnifying glass. The immature mites are even smaller than the adults. Early signs of their activity include pale stippling on the leaf surface. Many spider mite species create fine webbing on the leaves and branch tips. As the infestation progresses, the damage becomes more pronounced, manifesting as browning or bronzing on the leaves. In severe cases, plants can become so weakened that their leaves drop.
Prevention is key in managing spider mite infestations. These mites are commonly brought home on ornamental plants from nurseries and florists, so it’s essential to inspect plants thoroughly before purchase. To further reduce the risk, it’s recommended to keep newly acquired plants isolated from existing plants for several weeks to ensure they are not harboring spider mites.
Spider mites can usually be effectively controlled with an insecticidal soap spray. Spider mite populations outdoors are usually kept in check by natural predators.
Leaf miners
Leaf miners are larvae of certain flies, moths, and beetles that create winding tunnels inside leaves. The damage they inflict appears as irregular brown patches or as silver-colored, winding tunnels on the foliage. Though the destruction they cause is unsightly, it seldom poses a significant threat to the health of the host plants.
Gardeners should remove and discard newly attacked leaves during the spring or early summer when leafminers are most active. One method of prevention that gardeners with ornamental plantings can employ is to replace the plants that are prone to leafminer infestations with species that are more resilient. Another effective strategy involves attracting beneficial insects to gardens. Many predatory insects and parasitic wasps prey on leafminers, thus naturally curbing their populations.
Whiteflies
Whiteflies are small, white-winged insects that suck plant sap. They also excrete honeydew, often leading to sooty mold. This mold not only blocks sunlight, further hindering the plant’s ability to photosynthesize, but can also make the plant more susceptible to various diseases (some of which are spread by whiteflies).
To manage whitefly populations, gardeners often employ a combination of predators, traps, and insecticidal soaps. However, the key to effective whitefly management is early detection and consistent intervention, ensuring that their populations are kept in check before they become overwhelming.
Cutworms
Cutworms are caterpillars that cut young plants at the base, typically at night, causing them to topple over. Most are active predominantly in the spring, although some can be found during warm winter spells. Gardeners may find plants severed or small seedlings completely missing overnight.
Several preventative measures can be taken. Before spring planting, it’s advised to till the soil multiple times and leave it unplanted, allowing birds to feed on the pests. Gardeners should also consider planting seeds and seedlings later in the spring, during the peak cutworm activity. Additionally, using cutworm collars can protect young transplants. These collars, which can be made from thin cardstock or flexible plastic, are positioned around the plant’s stem, extending into the soil, to prevent the cutworms from accessing and damaging the plants.
For those looking to control an existing cutworm population, physical removal is one approach. This involves inspecting plants for damage during the morning hours and digging around damaged ones to locate and eliminate the cutworms. In the case of climbing cutworms, evening inspections using a flashlight can aid in finding and picking off these pests. Biological control methods, such as using specific nematodes, offer another avenue for cutworm management.
Root-knot nematodes
Root knot nematodes are microscopic, worm-like organisms that primarily thrive in the soil and target plant roots, obstructing the plant’s ability to absorb water and nutrients. These nematodes thrive in sandy soils and warm climates, with their populations dramatically increasing during hot seasons. They can infect virtually all cultivated plants, including vegetables, fruits, and ornamentals. Infected plants display reduced vigor, stunted growth, yellowing or wilting of leaves, decreased plant growth, and decreased crop yield.
Juveniles penetrate the plant roots and establish feeding sites, leading to the formation of distinctive root knots or galls. These galls disrupt the normal functioning of the root system, enlarging and forming characteristic knots. Over time, the female nematodes lay eggs within these galls, which hatch to release more juveniles, continuing the cycle.
Crop rotation can disrupt their life cycle, while soil solarization, a process where the soil is covered with transparent plastic to trap solar heat, can reduce their numbers. Biological control agents, like certain fungi and bacteria, have also shown potential in suppressing nematode populations. Another approach is the use of resistant plant varieties, which are less susceptible to nematode attacks.
Colorado potato beetle
The Colorado potato beetle is a notable pest characterized by their hard oval bodies, measuring about 1 cm, with a yellowish-orange hue and black stripes running lengthwise on their wing covers. They lay their bright orange eggs on the undersides of leaves, which subsequently hatch within a week to ten days. The larvae feed on the plants until the next stage of their life cycle occurs in the soil.
These beetles, both in their adult and larval stages, are voracious feeders, targeting plants like potatoes, peppers, eggplants, and more. Their feeding can result in severe defoliation, where only the mid-ribs of leaves are left untouched. This intense feeding can drastically reduce or even eliminate potato yields.
To manage these pests, it’s crucial to deploy preventative measures. Attracting natural enemies of the beetles, such as predatory bugs, can be an effective strategy. Direct interventions, like hand removal of larvae and egg masses or the use of pesticides like insecticidal soap or organic insecticides in the early stages, can also help control the population and mitigate damage.
Flea beetle
Flea beetles are small, jumping insects known for the damage they cause to various plants (especially certain vegetable plants) by chewing tiny holes in the leaves, giving them a characteristic “shothole” appearance. They have the unique ability to jump long distances, similar to fleas, due to their enlarged hind legs. When plants are heavily infested, they can suffer significant defoliation. Flea beetle damage can reduce photosynthesis, stunt growth, transmit disease, and in severe cases, kill the plant.
Cabbage flea beetles are a specific type of flea beetle that primarily targets plants in the Brassicaceae family, including cabbage, broccoli, radish, and mustard. They are particularly problematic in the early spring when young seedlings are emerging, as their tender leaves are most susceptible to damage. Potato flea beetles, on the other hand, are drawn to potato plants, although they can also attack other vegetable crops like tomatoes and eggplants.
Management of flea beetles often involves a combination of strategies. This includes using row covers, encouraging natural insect pest predators like parasitic wasps, and timely application of natural insecticides. Crop rotation and the use of resistant varieties can also be effective in reducing the impact of these pesky beetles.
Deer
Deer are often admired in natural settings, but in the garden, they can quickly transform from majestic creatures to formidable pests. These herbivores have an expansive palate and are known to feed on a variety of garden plants, from tender shoots and leaves to fruits and flowers. Their feeding can result in significant aesthetic and economic damage, turning meticulously cared-for gardens into barren spaces within a short span.
The challenge with deer is that traditional deterrents, like fences, need to be sufficiently tall and sturdy to be effective. Many gardeners resort to a combination of strategies to keep deer at bay, including deer-resistant plants, repellents, and motion-activated sprinklers. Yet, as adaptable creatures, deer often require homeowners to employ a rotating approach to pest control, frequently revisiting and adjusting strategies to protect their gardens effectively.
Rodents
Rodents, a category that includes mice, rats, and voles, are among the most notorious pests in garden settings. These small mammals, equipped with sharp incisors and a voracious appetite, can cause significant damage to both edible and ornamental plants. Their burrowing habits can disrupt the root systems (even of woody plants), leading to weakened or dead plants, and their propensity to nibble on fruits, vegetables, and seeds can result in diminished yields and marred produce.
The challenge in dealing with rodents lies in their rapid reproductive rate, agility, and adaptability. Traditional methods of control, like snap traps and rodenticides, can be effective if used cautiously. Natural predators, such as cats or owls, can offer some relief from rodent infestations but may not be a viable solution for all gardens, especially in dense urban settings. Many gardeners turn to integrated pest management (IPM) strategies, combining cultural, physical, and biological methods to tackle rodent problems.
White grubs
White grubs are the larval stage of various scarab beetles, including the Japanese beetle, June beetle, and European chafer. These big C-shaped, creamy-white larvae are notorious for the damage they inflict on lawns and gardens. Found just beneath the soil surface, white grubs feed on the roots of grasses and other plants, causing the turf to turn brown and die. Beyond turf, these grubs can also attack the roots of vegetables, flowers, and other ornamental plants, leading to stunted growth, wilting, and eventual death of the plants.
Controlling white grubs can be challenging due to their subterranean habitat. Cultural controls, such as maintaining a healthy lawn with deep watering and regular aeration, can reduce susceptibility to grub damage. Biological controls, like introducing beneficial nematodes or applying milky spore bacteria, target the grubs directly and offer an environmentally friendly solution. It’s essential for gardeners to correctly identify the grub species causing the damage, as control measures can vary based on the specific pest’s life cycle and habits.
Northern tent caterpillars
Northern tent caterpillars are predominantly found in southern British Columbia and the western regions of the Cascades in Washington and Oregon. Unlike the related forest tent caterpillar, it doesn’t create a tent but produces a silk trail. These caterpillars primarily feed on a variety of trees, including alder, aspen, poplar, willow, and fruit trees.
Tent caterpillar populations exhibit cyclic behaviors, with certain years seeing high infestations followed by significant population crashes. During outbreak years, they can pose a considerable threat to vegetation. They can completely defoliate plants, with deciduous trees often shedding their leaves in response. To manage and control these outbreaks, it’s advised to remove egg masses, prune out web nests, and use specific sprays, such as BTK.
Leafhoppers
Leafhoppers are small, agile insects that are frequent nuisances in gardens and on various crops. They are distinguishable by their wedge-like shape, with many species exhibiting vibrant colors. These pests feed by sucking the sap from the undersides of plant leaves, which can lead to stippling, curling, or yellowing of the foliage. Additionally, their feeding can transmit various plant diseases, making them a two-fold threat in agricultural settings.
Managing leafhoppers can be a bit challenging due to their mobility and rapid reproduction rate. Beneficial insects such as ladybugs and lacewings can act as predators, helping to reduce leafhopper populations. Moreover, neem oil and insecticidal soaps can be used as organic solutions to mitigate their presence. Regularly inspecting plants and maintaining good garden hygiene can further assist in keeping these pests at bay.
Codling moth
Codling moth is a notable pest known for targeting apples and pears. Adult moths are grey and measure approximately 1 cm in length, while their larvae are pale pink or cream-colored with a dark head. These larvae are especially damaging as they burrow into the fruit, predominantly feeding at the core, leaving behind obvious holes.
To combat these pests, preventive measures, especially on smaller trees, are recommended. Covering individual apples with exclusion bags, such as paper or tightly woven fabric bags, is an effective method to prevent moth damage, though care should be taken to properly prune and train trees for better bag application. Prune out infested plant parts and destroy them.
Leafrollers and fruit worms
Leafrollers and fruitworms are leaf-eating caterpillars that frequently appear on fruit trees during the spring season. These caterpillars vary in appearance, with some leafroller species being small, green caterpillars with dark heads.
While fruit trees can withstand a few of these caterpillars without a significant drop in yield, the damage they cause is evident in the way they feed on developing leaves and flower buds. To address this issue, it’s beneficial to attract insects that prey on these caterpillars by planting pollen and nectar plants near fruit trees.
Mealybugs
Mealybugs are pests known for their cottony white masses on plant stems and leaves. These tiny, pink, segmented insects, measuring about 2-3 mm in length, are most identifiable by their white fluff, which is actually a waxy substance. Typically found in indoor environments and greenhouses, mealybugs are robust pests, with some species capable of surviving year-round in temperature-controlled settings.
These pests are particularly detrimental to a wide range of indoor plants, including ficus, philodendron, and many others. As they siphon sap, especially from new growth, they can distort, weaken, or even kill plants. A telltale sign of their presence is the copious amounts of sticky honeydew they excrete, which often leads to the growth of sooty mold on leaves.
To manage and prevent mealybug infestations, it’s advised to inspect new plants thoroughly before introducing them to an indoor environment and to keep plants quarantined from others for about two months to ensure they are not infested.
Thrips
Thrips are minute insects, with most being under 1 mm in length, making them hard to notice without magnification. They come in a range of colors, from pale yellow to black, and are characteristically slender and fast-moving. Often found deep within flowers and leaf crevices, immature thrips resemble small, light-colored wingless versions of their adult counterparts.
Thrips are notorious for attacking a wide variety of plants, including onions, apples, gladiolus, and many greenhouse plants. They inflict damage in two main ways: by rasping out plant cell contents for food and by laying eggs within the plant tissues. Such actions lead to visible signs of damage, such as brown or silvery patches on flowers and streaks on leaves. Additionally, thrips are vectors for certain plant viruses, further elevating their threat to vegetation.
Carrot rust fly
The carrot rust fly is a significant garden pest known for targeting carrots and related plants (parsnips, parsley, celery, and fennel). Adult flies are sleek, shiny black with yellow legs and are not commonly seen. These adults lay their eggs in the soil next to the stems of carrot plants. Upon hatching, white maggot larvae burrow into carrot roots, leaving behind tunnels filled with crumbly, rusty-brown excrement. This infestation results in damage to the roots, damaging even stored carrots in the winter.
Gardeners are advised to delay carrot seeding in the spring, as plants sown after mid-May tend to avoid the initial generation of flies. Another recommended preventive measure is the use of barriers. Using insect netting or floating row cover fabric can deter adult flies from laying eggs on the crops. In areas with low rust fly populations, exclusion fences or even highly raised beds can be effective.
Strawberry root weevil
The strawberry root weevil is a small beetle whose large feed on strawberry plant roots throughout the summer and takes shelter in the soil to overwinter. By spring, they pupate, leading to the emergence of adults by mid-May, some of which might even overwinter in protected areas and structures. In addition to root feeding, they cause noticeable damage by clipping the leaf edges of strawberries and raspberries. For managing these pests, handpicking, organic sprays, and introducing insect parasitic nematodes are recommended.
Pillbugs
Pillbugs are small, segmented critters commonly found in many gardens. Measuring about 1 cm in length and often mistaken for insects, they are, in fact, crustaceans. They have a segmented body structure resembling a tiny armadillo. Pillbugs are usually a dark gray color, and each one lives for 1-2 years.
Pillbugs lack a waterproof exoskeleton, making them particularly susceptible to drying out. To cope with this vulnerability, they tend to inhabit damp habitats, such as underneath stones, boards, and leaf litter. These creatures are typically active during the night or on cloudy days, seeking out moist environments. This behavior helps them maintain the moisture levels vital for their survival.
While they primarily feed on decaying organic matter on top of the soil, which aids in soil enrichment, pillbugs can occasionally turn to eat living plants. They can chew on young plant stems and leaves, potentially causing damage. However, their herbivorous tendencies are generally not a significant threat to well-established garden plants. But if they are a problem, reduce their hiding places by removing debris and ensuring the soil doesn’t remain overly damp. Keep the garden tidy and dry, and let the sun in!
