Pests & Pest Management

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At some point, you will have to deal with pests on your plants. However, you can do a few things to limit a full-blown infestation.
Inspect Often – Prevention is the key to limiting the spread of pests. Inspect leaves and stems every time you water. Thoroughly inspect any plant you purchase as well. The earlier you identify a pest, the easier it is to spot-treat and save your plant.
Isolate New Arrivals – Nurseries grow plants close to each other. Because of their growing environment, it’s easy for pests to hop from one plant to another. When you get a new plant, it’s a good idea to isolate it from the rest of your collection for a few days to ensure it doesn’t have pests.
Quarantine – If you spot any pests on your houseplants, quarantine them immediately. Pests quickly spread from plant to plant. Isolate the plant and treat until there is no sign of an infestation, then you can put it back among your collection.

Most Common Houseplant Pest Infestations:

Click a pest image to see details & care

Aphids

Common Whitefly

Fungus Gnats

Mealybugs

Red spider mites

Scale

Thrips

Pest Details

Scale (Coccus hesperidum

Most common scale is brown scale.  These inconspicuous little soft-bodied pests resemble flat brown slugs. Like other houseplant pests, brown scale feeds off the plant’s sap. They are small and hard to detect, especially if you have a small infestation. However, the pests will look like strange brown bumps on top of or underneath a leaf upon closer inspection. Scale can be treated by wiping or washing leaves and stems to remove the insects and the honeydew they leave behind. This method works well for small infestations. You can even pick or rub them off one by one. You will need to use neem or horticultural oils for larger infestations.

Pest Details

Mealybugs (Pseudococcidae family)

Mealybugs are an unarmored scale insect.  Mealybugs are soft-bodied insects that appear as white cottony masses on your plant’s leaves and stems. Depending on the species, adult mealybugs are an oval shape with a white or gray mealy wax on their surface. Wash or wipe off any cottony mass you see on the leaves or stem. You can also spot-treat an area using a cotton swab and isopropyl alcohol. Dab the alcohol directly onto the mealybugs to kill them instantly. Check your plant every couple of days to make sure you destroy any visible adult.

Pest Details

Aphids (Family Aphididae)

Most commonly seen in the garden on food crops and less common on tropical house plants. Aphids are soft, pear-shaped insects with long antennae that destroy plants by using their piercing mouthparts to feed on the plant’s sap. Aphids produce a sugary liquid waste called “honeydew,” which causes a fungus called sooty mold to grow on the honeydew deposits, turning leaves and branches black. It’s at this point that most aphid infestations are noticed. Aphids live in colonies on the undersides of leaves. They are under 1/4-inch long when mature, and they are often nearly invisible to the naked eye. Depending on the species, they can be white, black, brown, gray, yellow, light green, or pink. How to Get Rid of Aphids: The best way to treat an aphid infestation is to catch it early. “Examine the opening of leaves and flower buds carefully,” says Clark. “Many aphids prefer to feed on soft new growth.” She also says you can dislodge aphids and eggs from the leaf or bud by squirting them off with a spray bottle or rinsing the plant leaves in the sink. If the infestation is partially bad, follow up with an application of neem oil or insecticidal soap for several weeks to ensure you have killed all eggs.

Pest Details

Common Whitefly (Trialeurodes vaporariorum)

Drawn to food crops. Eggs will hatch in less than a week and then their nymphs, similarly to scale, will crawl a short distance, plant themselves, and suck the plant until they go into a resting stage at about the 3 week point. In about four, maybe five weeks, they begin to emerge as adults and the process repeats.  Whiteflies are sap-sucking insects that are often en masse on the undersides of leaves. They are small, so most houseplant owners don’t notice them until they see great clouds of tiny flies take flight when they disturb the plant. Both nymphs and adult flies can cause damage to plants. Getting rid of whiteflies starts with suppressing the adult population. Blasting the flies with a strong water stream or using yellow sticky traps helps reduce pest numbers. For heavy infestations, apply insecticidal soap or neem oil. Your plant may need several applications to kill off any remaining whitefly eggs on the plant.

Pest Details

Fungus Gnats (Bradysia sp.)

Fungus gnats look similar to fruit flies and are often mistaken as such. Their larvae, which are really the more cause for concern here, prefer to feed on fungi in the soil, which you can only get in moist conditions. They technically can eat plant material, but if the fungi levels are high, they often won’t. Adult gnats are harmless, but they can become a flying nuisance. Their larvae, however, can cause damage to tender plant roots. Getting rid of the gnats requires a change in watering habits. Only water once the top two inches of soil are dry and infrequently during the cold months. It is essential to catch the adult gnats so they won’t lay new eggs in the soil. A yellow sticky trap is the most effective way to catch them.

Pest Details

Red spider mites (Tetranychus sp.) (Panoychus ulmi)

Mites are technically not insects but they, like insects, are Arthropods. They are probably some of the most feared of the common household insect pests, largely because they are so difficult to eradicate. Spider mites are nearly naked to the eye. You often need a magnifying lens to spot them, or you may just notice a reddish film across the bottom of the leaves, some webbing, or even some leaf damage, which usually results in reddish-brown spots on the leaf. Panmychus ulmi is the European red mite which causes damage on fruit trees. Similar to aphids, spider mites cause damage by sucking the sap from leaves. Initially, the damage looks like a stippling of light dots on the leaves. As they feed on, the leaves turn yellowish or reddish and drop off. Examine undersides of leaves carefully. Look for small bits of detritus near the leaf veins. How to Get Rid of Spider Mites: You can thoroughly wipe or wash the leaves with water in the early stages of infestation on a smooth leaf-plant like ficus, stromanthe, or monstera. Repeat this process every few days for a few weeks to eliminate any remaining mites. Once that initial mite population is under control, follow up with neem oil to ensure all remaining spider mites are destroyed.

Pest Details

Thrips (Order: Thysanoptera)

Thrips are typically generalists, puncturing the outer layer of a plant and creating a silvery discoloration on the plant leaf. You’ll also notice tiny little bits of black frass, which is a nice way of saying “insect poop”. Thrips commonly enter and damage roses and other floral plants resulting in failure of the blossoms to open and damage to the appearance of the blossoms.

Most Common Outdoor Pest Infestations:

Click a pest image to see details & care

Aphids

Asparagus Beetle

Adult Vine Weevil

Bagworm

Beetle Grub

Black Carpenter Ant

Cabbage Looper Caterpillar

Cabbage White Caterpillars

Codling Moth

Colorado Potato Beetle

Corn Earworm

Cucumber Beetle

Cutworm

Earwig

European Corn Borer

Four-Lined Plant Bug

Flea Beetle

Gall Mites

Grasshopper

Japanese Beetles

Leaf Miner

Leaf Roller

Mealybugs

Mexican Bean Beetle

Red Spider Mites

RIFA-Red Imported Fire Ant

Rose Slug

Sawfly Larvae

Scale Insects

Slugs

Snails

Squash Bug

Stink Bug

Tarnished Plant Bug

Thrip

Tomato Hornworm

Tomato Moth

Viburnum Beetle

Vine Weevil Larvae

Whitefly

Winter Moth

Wireworms

Woolly Beech Aphid

Yellow Dog Tick

Pest Details

Red Spider Mites (Tetranychus urticae)

Tiny mites that live under leaves and suck sap, causing yellow mottling. Fine webs are sometimes visible.

Pest Details

Gall Mites (Eriophyidae Family)

Microscopic mites that suck sap and cause abnormal growths. In moderate numbers they cause disfigurement of the leaves but do not cause serious damage to the overall plant.

Pest Details

Bagworm (Family Psychidae)

Bagworms are the larval form of a moth that attacks evergreens and other trees. The worm inside each bag feeds on the evergreen bush or tree, building a case around itself for protection from predators. Females lay eggs in the bags in late fall.

Pest Details

Japanese Beetles (Popillia japonica)

Japanese Beetles are aggressive non-native insects that aren’t particular which plants they attack. Plants which are ordinarily immune to attack such as purple cauliflower are consumed by Japanese beetles.

Pest Details

Leaf Miner

Leaf miners create discolored blotches or surface trails on leaves. Most leaf miner damage is relatively harmless and can be left untreated.

Pest Details

Codling Moth (Cydia pomonella)

To avoid maggots in apples, spray emerging caterpillars twice using bifenthrin, starting in midsummer. Also hang pheromone traps in late spring to catch male moths and prevent them from mating.

Pest Details

Winter Moth (Operophtera fagata)

In spring, the leaves of fruit trees are webbed together and hide green caterpillars inside. Holes are visible when leaves expand. Apply sticky traps to capture adult moths.

Pest Details

Aphids (Superfamily Aphidoidea)

Aphids leave a sticky substance called honeydew on plants, which can allow black fungus to grow.

Pest Details

Scale Insects (Superfamily Cocciodea)

Tiny blister or shell-like bumps on leaf backs result in poor growth. Other symptoms are sticky excretions and sooty mold on evergreens. Wash off mold, and spray with horticultural oil.

Pest Details

Whitefly (Superfamily Aleyrodiodea)

Under glass, hang yellow sticky pads to trap the tiny white flying adults, which suck sap from plants; use a biological control (Encarsia wasp) on larvae or spray with organic chemical controls.

Pest Details

Viburnum Beetle (Pyrrhalta viburni)

Both the adults and larvae eat holes in the leaves, mainly on Viburnum tinus and V. opulus; this can slow growth and looks unsightly. Spray badly affected plants in spring with bifenthrin or thiacloprid.

Pest Details

Thrip (Order Thysanoptera)

This tiny black sap-sucker, known as “thunder fly,” causes white patches on the petals and leaves of indoor plants, and also peas, leeks, onions and gladioli. Use biological controls.

Pest Details

Vine Weevil Larvae:

Small cream grubs with a brown head feed on plant roots, especially those growing in containers or with fleshy roots. This can cause plants to suddenly collapse.

Pest Details

Adult Vine Weevil (Otiorhynchus sulcatus)

The adult beetle is nocturnal, flightless and makes notches in leaves. Use a biological control (nematodes).

Pest Details

Cabbage White Caterpillars (Pieris rapae):

These voracious eaters decimate brassicas and nasturtiums. Rub off egg clusters and pick off any caterpillars you find.

Pest Details

Tomato Moth (Lacanobia oleracea)

The tomato moth damages fruits. Pick off any caterpillars you find.

Pest Details

Rose Slug (Arge ochropus)

A rose slug is the larvae or immature stage of a rose sawfly. It’s easy to overlook on roses, until its feeding begins to damage leaves. Rose slugs feed on leaf undersides, out of sight, nibbling on leaf tissue — the part between the veins. When they’re done eating, leaves resemble skeletons. Usually when gardeners spot rose slug damage, they think their roses have a disease because leaves are speckled and have holes in them. Sawfly larvae are not slugs or caterpillars, but a different type of critter. Blast them off roses with a spray of water, or spray them with spinosad, a bioinsecticide made from soil bacteria.

Pest Details

Grasshopper (Suborder Caelifera)

When grasshoppers hit your garden, nothing is safe. These insects chew their way through leaves, flowers and fruits without stopping, eating up to half their body weight per day. Kill grasshoppers when they’re young anytime you can. Create a garden where bluebirds feel at home, because they’ll help eat these pests, as will toads, snakes and shrews. Explore the world of grasshopper baits to discover bioinsecticides that kill these insects using various strains of fungi or bacteria. Don’t just ignore grasshoppers, because if you have a severe problem one year, you will continue to have issues in the future.

Pest Details

Stink Bug (Pentatomidae Family)

The brown marmorated stink bug has been in the United States 20 years, and in that time it’s spread throughout the Mid-Atlantic, Upper Midwest and along the West Coast. Stink bugs attack many home garden crops, including beans, corn, tomatoes peppers, apples and raspberries. Their feeding wounds fruits and veggies, resulting in corky spots that are inedible. Stink bugs spend winter inside, invading home voids and attics. With their stinky personalities, these bugs stir up drama indoors when they emerge from hiding in hordes, usually in winter. In the garden, knock stink bugs into soapy water to kill them. Indoors, the same method works, or you can try vacuuming up the stinkers (which might make your vac stink). Another indoor option is using a dry-mop cleaning tool (think Swiffer-type) that you cover with duct tape, sticky side out. That device gives you reach to grab stink bugs climbing curtains, walls and ceilings.

Pest Details

Sawfly Larvae (Suborder Symphyta)

The caterpillar-like larvae devour the foliage on plants such as roses, gooseberries and Solomon’s seal. Leaf rolling is usually the first sign of sawflies. Pick caterpillars off by hand or spray with bifenthrin or pyrethrum.

Pest Details

Woolly Beech Aphid (Phyllaphis grandifoliae)

Seen in early summer, these white fluffy aphids coat shoots and the undersides of leaves. They suck sap and excrete honeydew that supports black sooty mold.

Pest Details

Earwig (Order Dermaptera)

Mostly beneficial, earwigs are nocturnal and feed on dahlia, chrysanthemum and clematis flowers. Lure them into upturned flower pots filled with straw and release them elsewhere.

Pest Details

Cabbage Looper Caterpillar (Family Noctuidae)

This pest is very destructive due to its voracious consumption of plants in the cabbage family.

Pest Details

Cucumber Beetle (Family Chrysomelidae)

Striped or spotted cucumber beetles like to eat melons, squash and cucumbers and can spread disease; the bacterial wilt of cucurbits.

Pest Details

Mealybugs (Family Pseudococcidae)

Like scale, mealybugs are members of the Homoptera order (along with aphids). Mealybugs are found in cottony clusters in the nooks and crevices of plants and feed on plant juices and can spread plant diseases.

Pest Details

Tomato Hornworm (Manduca quinquemaculata)

Tomato hornworms feed on tomato plants.

Pest Details

Slugs

Small holes in tomatoes are usually caused by slugs. The problem is, once slugs open a hole, the tomato weeps juice, and soon other critters join the party, like pill bugs, fruit flies and wasps. The wound in the fruit also invites early decay and mold. Slugs attack low-hanging fruit first, but they also slime their way up tomato vines and supports. Research slug treatments and adopt several strategies to deal with them. When tomato season is done, before frost, continue to use slug treatments to kill adult slugs before they lay eggs.

Pest Details

Snails

Snails like this European brown garden snail can wreak havoc on plants.

Pest Details

Flea Beetle (Family Chrysomelidae)

Flea beetles eat edibles like brassicas but can also attack ornamental plants in the garden.

Pest Details

Colorado Potato Beetle (Lema daturaphila)

The Colorado potato beetle, also known as the Colorado beetle, is a major pest of potato crops.

Pest Details

Mexican Bean Beetle (Epilachna varivestis)

It is vital to destroy spent vegetable crops, especially those that hosted problem pests, like Mexican bean beetles. Don’t toss these plants into a compost pile unless you know it heats enough to destroy pests and eggs. It’s safer to dispose of infested plants and fallen leaves in bags you put at the curb for garbage pickup.

Pest Details

Tarnished Plant Bug (Lygus lineolaris)

This large and very diverse family of insects prefers to feed on a large number of plants including herbaceous plants, fruit trees, vegetables and flowers.

Pest Details

RIFA–Red Imported Fire Ant (Solenopsis invicta)

RIFA colonies develop quickly; a new colony can grow by as many as 10,000 ants in a single year.

Pest Details

Cutworm (Family Noctuidae)

Cutworms are the larvae of several varieties of moths and are named because they tend to feed on the stems of young plants, cutting them down.

Pest Details

Asparagus Beetle (Genus Chrysomelidae)

One of the most destructive asparagus pests, the asparagus beetle destroys garden and wild asparagus plants.

Pest Details

Wireworms (Family Elateridae)

Wireworms are the larvae form of the click beetle.  Germinating seeds, roots, bulbs and tubers are the wireworm’s favorite meals.

Pest Details

European Corn Borer (Ostrinia nubilalis)

The European corn borer has been a pest of crops in the Midwest since the Twenties and destroys a variety of crops and weeds beyond corn, including cotton, apples, soybeans, peppers and ragweed.

Pest Details

Yellow Dog Tick (Haemaphysalis leachi)

Ticks are human pests and carry a multitude of diseases, so are best kept out of the garden.

Pest Details

Squash Bug (Family Correiae)

Squash bugs are among the most common and destructive pests affecting pumpkins and squash.

Pest Details

Black Carpenter Ant (Camponotus pennsylvanicus)

Carpenter ants damage wooden structures to nest within.

Pest Details

Corn Earworm (Helicoverpa zea)

Found throughout North America, the corn earworm is a moth larva and a serious agricultural pest.

Pest Details

Leaf Roller (Family Tortricidae):

Leaf roller caterpillars often pupate inside canna leaves, damaging them as they begin to eat. Other leaf rollers attack fruits, ornamentals, and shrubs. If the infestation is light, squish the caterpillars inside the leaves, or unroll the leaves, remove the pests, and destroy them.

Pest Details

Beetle Grub (Superfamily Scarabaeoidea)

Grubs are the precursor to various types of beetles. One of the most destructive grubs is Japanese beetle, which lives in turf. These critters chew through grass roots, creating dead patches in your lawn. The best time to control grubs is in early fall, when they’re young and feeding voraciously underground near the soil surface. Treat with parasitic nematodes, a microscopic worm that attacks grubs (Heterorhabditis bacteriophora is the best), or strap on a pair of lawn aerating sandals and spike the grubs to death. Concentrate your spiking steps on brown lawn areas and the green areas just outside the brown.

Pest Details

Four-Lined Plant Bug (Poecilocapsus lineatus)

The four-lined plant bug attacks perennials, creating 1/16-inch square dead patches in leaves as they feed. These bugs create more of a cosmetic problem that plants often outgrow, but when numbers are high, the damage can lead to browned, misshapen and dying leaves, which you might mistake for disease. Four-lined plant bugs emerge about the time that forsythia leaves unfold. They’re shy and crafty hiders, so you’ll likely see the damage long before you spot one of them. The best way to control these bugs is twofold. First, in midsummer, when the insects disappear, cut back plants that have been attacked, snipping below the damage. This should remove any eggs that have been laid inside stems. Pruning in this manner delays flowering on perennials, but the plants will branch and become bushy, which means more flowers. Second, in fall, clean up all stems and leaf litter in the bed. Take care to remove all stems of plants the insect attacked during the growing season. Eggs that will hatch the following spring are typically laid inside those stems, so don’t add them to your compost pile.

About the Author: Len Nadalo - Dallas County Master Gardener
class of 2020

Originally from Chicago and currently a practicing General Diagnostic and Neuroradiology MD, Len started his career in the US Army which took him to San Antonio, Hawaii, Washington DC and eventually Texas. At each move Len developed an interest in a different type of plant unique to the region. Today Len’s home, located in Dallas Texas is a beautiful urban wildlife habitat.
Originally from Chicago and currently a practicing General Diagnostic and Neuroradiology MD, Len started his career in the US Army which took him to San Antonio, Hawaii, Washington DC and eventually Texas. At each move Len developed an interest in a different type of plant unique to the region. Today Len’s home, located in Dallas Texas is a beautiful urban wildlife habitat.