Container Gardening: Bugs: Friends or Foes?

The Bad Bugs

“Tomato Lover” by Distant Hill Gardens is licensed under CC BY-NC-SA 2.0 


Caterpillars eat leaves of fruits, vegetables, and ornamentals. Some even tunnel right into the fruits. Tomato hornworm, one of the most insidious, targets the upper portions of host plants like tomatoes, eggplants, peppers, tobacco, moonflowers, and potatoes 

Signs of infestation: Other than the caterpillars themselves, look for bites taken out of leaves and tiny pellets of frass (caterpillar poop) on top of leaves.  

Treatment: Encourage native predators. Tomato hornworms can be eradicated with insecticides, manual removal, and parasitic wasps. Safer Brand, a line of organic gardening products, offers insectkilling soap, garden dust and caterpillar killer. The garden dust and caterpillar killer incorporate bacteria that attacks the caterpillars from the inside out. Lepidoptera species of caterpillars can be controlled with Bt, an insecticidal bacterium. Bt is nontoxic to humans, pets, bees, and beneficial insects.  

“Snail taking a walk” by arievergreen is licensed under CC BY-NC-SA 2.0 


What they do: Snails climb flowering plants and eat flower buds. They can climb fruit trees and eat the newly ripened fruit. Snails will strip bark off young trees and chew holes through leaves 

Signs of infestation: Look for the classic slime trails that come from the mucus that snails secrete as they move, as well as white, spherical eggs in the soil. Snails are most active at night and on cloudy days. They typically seek shade on sunny days.  

Treatment: Apply a product called Sluggo monthly. Sluggo is a nontoxic, organic compound that when ingested by slugs and snails, stops them from feeding. After use, Sluggo breaks down into an iron phosphate fertilizer, so it is completely safe for your soil 

“File:Mealy Bugs.jpg” by Mokkie is licensed under CC BY-SA 3.0 

Mealy Bugs 

What they do: Mealybugs are soft-bodied, wingless insects that look like white, cottony masses on the leaves, stems, and fruits of plants. Mealy bugs use their stylets, or sucking mouthparts, to draw sap out of the tissue of plants, causing leaf yellowing and curling as the plant weakens. As mealybugs feed, they produce honeydew, which makes the plant sticky and encourages the growth of sooty molds and the presence of ants 

Signs of infestation: Check your plant’s leaves for yellowing and curling. If you see molding on your plants, this is another sign you may have mealy bugs. A third sign of mealybugs is the presence of ants. The ants are attracted to the honeydew secreted by the mealybugs.  

Treatment: Spray plants with soapy water. A good ratio is 1 tablespoon of dish soap per quart of water. You can also hose plants down with a strong stream of hose water. Another option is to use neem oil to disrupt the growth and development of mealybugs. Heavy infestations may require an insecticidal soap. For a short-lived, natural pesticidal soap, look for Safer Brand’s insecticidal soap. 


“APHIDS-oleander” by Plant pests and diseases is licensed under CC PDM 1.0 


What they do: Aphids suck plant sap, causing foliage to distort and leaves to drop. They also secrete honeydew, which leads to the growth of sooty mold that will blacken leaves and the attract ants 

Signs of infestation: Aphids are incredibly small and hard to spot. Sometimes the first sign of their presence is the sudden arrival of ants on your plants. The ants are after the honeydew that aphids secrete. Other signs of aphids are plants that look limp or are dropping leaves or are covered in sooty mold.  

Treatment: Wash plants with a strong stream of water. You can also spray soapy water on the plants. A good ratio is 1 tablespoon of dish soap per quart of water. Encourage the presence of native predators like lacewings and ladybugs. For heavy infestations, you can use hot-pepper spray, garlic repellent spray, horticultural oil, insecticidal soap, or neem oil.  

“Tomato (Solanum lycopersicum): Root-knot nematodes” by Plant pests and diseases is licensed under CC PDM 1.0 


What they do: Nematodes are parasitic worms that thrive in the sandy soils of Southwest Florida. Nematodes burrow into roots, inhibiting them from being able to absorb water and nutrients.  

Signs of infestation: If your plants are doing poorly in otherwise ideal conditions and show no other physical signs of pests, pull one plant from the ground or its container to check the roots for little balls or knots 

Treatment: After harvesting crops, you can till the soil to expose roots to the sun. Direct sunlight will kill nematodes. Plant French marigold (Tagetes patula): its roots release a chemical that is toxic to nematodes. Improve the overall health of your soil by adding compost, manure, and mulch. Healthy soil is a great buffer to nematodes.  

“File:Coccoidea – 8661.jpg” by Amada44 is licensed under CC BY-SA 3.0 


What they do: Scales suck plant sap which weakens plants causing them to turn yellow, drop leaves, and die. Scales produce honeydew as they suck on fluid that attracts ants and invites the development of black sooty mold 

Signs of infestation: Scales are usually off-white, tan, or brown. Most have a smooth, flat covering, but some look cottony or fluffy. The adults do not move. The young scales are typically orange and move slowly. Plants with scale may look unhealthy due to the loss of sap. If you see black sooty mold on your plants, you may have scale. Another sign of scales is the presence of ants. The ants are attracted to the honeydew secreted by the scales.  

Treatment: Prune infested plant parts. Encourage native predators. Spray plants with soapy water. A good ratio is 1 tablespoon of dish soap per quart of water. You can also hose plants down with a strong stream of hose water or apply neem oil.  

“Endemic Hawaiian hibiscus: Whiteflies” by Plant pests and diseases is licensed under CC PDM 1.0 


What they do: Whiteflies are sapsucking insects like aphids, scale, and mealybugs. They target ornamentals and vegetables and look just like their name implies, like white flies. Whiteflies produce honeydew which leaves plants susceptible to sooty black mold and ant infestations.  

Signs of infestation: Your plants may have yellow leaves, stunted growth, or sticky honeydew on the leaves. Check under the leaves of your plants for tiny, white ovals. These are whitefly eggs. If your plants have a lot of ants or develop black sooty moldyou may have whiteflies.  

Treatment: Create a garden that is hospitable for whitefly predators such as ladybugs and lacewings. You can also spray your plants with a pressurized stream of water to knock the whiteflies off the plants and subsequently treat the plants with insecticidal soap. For a homemade soap remedy try 1 tablespoon of dish soap per quart of water.  

“Weevil” by nutmeg66 is licensed under CC BY-NC-ND 2.0 


What they do: Weevils are a group of beetles that have long snouts and legless larvae. Adults eat notches in the edges of leaves and the larvae eat plant roots. There are several kinds of weevils, and they will attack everything from vegetables to fruits to grasses to ornamentals.  

Signs of infestation: Look for notches cut in plant leaves 

Treatment: An organic pest solution for weevils is diatomaceous earth, or D.E. This powdery substance is composed of razor-sharp shards of fossilized remains of ancient algae that are deadly to soft-bodied insects.  


The Good Bugs 

“Garden spider yellow black” by watts_photos is licensed under CC BY 2.0 


Spiders eat aphids, caterpillars, grasshoppers, and fruit flies. Spiders need a place to spin their webs, and taller plants like corn or mammoth sunflowers serve as great attractants for spiders.  

“feeding frenzy” by ClareSnow is licensed under CC BY-NC-SA 2.0 


Earthworms aerate and fertilize soil. They are great at breaking down organic materials, which returns nutrients to the soil. Earthworms are so great for soil quality that some people use them to create compost in what is known as a vermiculture system.  

“Tomato Hornworm with Parasitic Wasp Eggs” by mindwhisperings is licensed under CC BY-NC-ND 2.0 

Parasitic Wasps  

There are a range of species of parasitic wasps. Some, like the trichogramma wasp, lay their eggs in moth and butterfly eggs and then prey on the caterpillars once they hatch. Others, like the braconid, chalcid and ichneumid wasps parasitize caterpillars directly by laying eggs in or on caterpillars. The hatched larvae will eventually kill the host caterpillar or disrupt its activities enough to keep it from eating your plants. The braconid wasp specifically targets aphids and tomato hornwormsBraconids are attracted to plants will small flowers like dill, parsley, and wild carrots.  

“Ladybug on leaf” by megan_schaub is licensed under CC BY-NC-ND 2.0 


Ladybugs prey on aphids and other soft-bodied insects. Adults can eat up to 50 aphids per day and over 5000 aphids during a lifetime. Larvae will eat up to 400 aphids before reaching their pupal stage. Ladybugs are attracted to dill and fennel.  

“Rhynocoris ventralis assassin bug” by K Schneider is licensed under CC BY-NC 2.0 

Assassin Bugs 

There are over 150 species of assassin bugs in North America. They prey on insect eggs, leafhoppers, aphids, boll weevils, and others. Most assassin bugs have no plant preferences. They can be found in vegetable gardens, orchards, or ornamental flowerbeds.  

“Green (no kiddin’) lacewing” by MarioQA is licensed under CC BY-NC 2.0 


As larvae, lacewings eat aphids, caterpillars, mealybugs, leafhoppers, insect eggs, and whiteflies. Lacewings are excellent predators and are attracted to dill, angelica, and coriander.  

“Hoverfly” by zund is licensed under CC BY-NC-ND 2.0 


Hoverflies are predator flies that move from plant to plant in search of pollen and nectar. They lay their eggs near aphids and other soft-bodied insects. The eggs hatch into larvae that can eat up to 60 aphids per day. Hoverflies also eat scale insects and caterpillars. Hoverflies are drawn to common yarrow, fern-leaf yarrow, and dill.  

How to attract the good bugs: 

Use minimal pesticides: Broad-spectrum pesticides eliminate the good guys just as effectively as they wipe out the bad guys. When you use predatory bugs instead of pesticides, you need to have a bit of patience. For instance, once ladybugs set their sights on aphids as a food source, they’ll begin to eat aphids at a decent rate, but the large payoff of ladybugs comes after they mate, lay eggs, and the eggs hatch into larvae which are prolific aphid eatersIf you do decide to use pesticides, choose one that targets the specific pest, rather than a broad-spectrum insecticide that cuts down nearly everything in its path. Also, be sure to choose products that degrade quickly and have a shorter residual impact on the insect life cycle. In most cases, botanical pesticides kill fewer beneficial insects than longer-lasting synthetic pesticides. Horticultural oils, insecticidal soaps, and botanical insecticides (such as products derived from pyrethrins or neem) will get your pest problem under control without causing long-term damage to your beneficial insect population. 


Plant insectfriendly species: Many important beneficial insects, such as hoverflies and lacewings, feed on pollen and nectar as adults. By providing flowers early in the season, you’ll be inviting these insects in time to unleash their predatory offspring on aphids and mites. Plant a section of your garden dedicated to attracting insects, known as an insectary. You can plant insectfriendly plants among your other plants. Your insectary should include plants of varying heights. Low-growing herbs such as thyme and oregano give ground beetles a place to hide. Taller flowers, such as daisies or cosmos, beckon to hoverflies and parasitic wasps looking for nectar. Praying mantids are big pesteaters that like to hide between plants that give good cover. 

Umbels and composite flowers provide the most attractive food sources for a variety of beneficial insects. Umbels are characterized by tiny umbrella-shaped clusters of flowers that offer exposed nectar and pollen to smaller pollinators like parasitic wasps. This group includes yarrow, dill, fennel, and wild carrots. Composite flowers, including garden favorites such as zinnias and sunflowers, attract larger pollinators like robber flies and predatory wasps. Plants in the aster, carrot, legume, mustard, and verbena family attract the most insects. A diversity of plants will attract a diversity of insects. Incorporate native plants in your ornamental garden. Native plants are especially proficient at attracting pollinators and bloom when pollinators are active. Pollinators provide both essential plant lifecycle and insect control services.