How to Control Insect Problems in Tomatoes

Tomatoes are easy to grow, but there are many pests which like to eat tomatoes and the plants. The best way to avoid either pests or disease problems when growing tomatoes or any plant is to keep the plant healthy. It has been scientifically shown that diseased plants attract insects. This is nature’s way to improve the gene pool, by eliminating species which are susceptible to disease. In addition poorly nourished plants let off excess nitrogen and insects need high nitrogen foods to thrive. Insects can smell the nitrogen and are attracted to the plants.

Attract Tomato Pest Predators

Some companion plants attract predatory insects which feed on the plant’s enemies. Having a wide variety of plant species in your garden can help to attract many species of insects and birds. In nature, plants are interspersed and there are a variety of insects, and no one specie gets out of control.

Keeping patrol of your garden for pests is the best way to know when an uninvited visitor is taking up house, so that you can get control of them before they become an infestation. Getting to know which insects are beneficial and which are not can help you to recognize pests as soon as they appear, so that you can monitor them. Hand picking and killing pests can destroy future generations, since many species complete their life cycles many times per year. Encouraging predator species with companion plants keeps pests in check naturally. has pictures to help you differentiate beneficial species from pests.

Avoid using pesticides, since they kill all insects. The use of pesticides interrupts the natural balance of your garden, and more problems will follow. A natural population of insects will keep each other in check.

How to Naturally Control Tomato Hornworms

The tomato hornworm feeds on several plants of the Solanaceae family and defoliate them. The caterpillars cling to the underside of the tomatoes stem near the main stem and are hard to see because they are green. They have a horn on their back end and closely resembles a similar species which feed on tobacco and members of the  family, but both are destructive. Tomato hornworms develop into a large moth called the five-spotted hawkmoth.

Tomato hornworms can be discouraged by planting Tagetes marigolds near tomatoes, with the stronger scented varieties being more effective. Marigold also produce a chemical that repels nematodes, Chopping up spent marigold plants and working them into the soil where you will grow Solanaceae  plants next year may be beneficial.

Borage may repel tomato hornworms. Borage blooms are edible blue flowers that can be used in salads and the leaves are used as a fresh or dried herb.

There are several species of parasitic wasps which feed on tomato hornworm larvae. Many adult beneficial parasitic wasps feed on the nectar of plants in the Umbellifer family, such as parsley, angelica, anise, carrot, chervil, fennel, and dill. Having these available in your garden can help control pest insects. Do not plant dill near tomatoes, since it draws caterpillars which also like to feed on tomatoes. But planting dill on the other side of the garden may help draw the caterpillars away while providing parasitic wasps an attractive environment. Some species of parasitic wasps lay their eggs in caterpillars. So if you see a caterpillar in your garden that is dead and swollen, this may mean that a beneficial species of parasitic wasp has laid eggs in it, so do not destroy it.

How to Naturally Control  Aphids

Aphids, or plant lice, like to feed on tomatoes and many other plants. Ladybugs, or ladybirds, feed on aphids and can be attracted into your garden with mustard plants, coreopsis, dandelions, scented pelargoniums (geraniums), legumes, coriander, dill, and many other flowering plants.

Some species of ants, called dairying ants, farm aphids. Dairying ants milk honeydew from aphids by stroking their antennae, store them in the ground for the winter, and put them on plants in spring. Ants can be controlled naturally with boric acid, commonly sold as Borax in the laundry aisle of stores. Sprinkle it widely around areas of infestation. Ants will carry it back to the queen ant as food, which will kill her.

The larvae of hoverflies, or syrphid flies, eat aphids and thrips, as well as other plant-sucking insects. They much resemble bees and wasps in appearance, and hoverfly adults feed on nectar and pollen.

Crab spiders feed on aphids, and many live on flowering plants without spinning webs. They hide or are camouflaged and ambush flying insects.

Lacewings larvae eat aphids and pests, and the adults feed on nectar.

Aphid midge larvae feed on aphids and lay shiny orange eggs among aphids on stems. When they hatch they burrow into the ground. The larvae are small and bright orange, resembling a slug, and a single larva can kill up to 60 aphids per day. The adults are small black flies resembling a fungus gnat and feed on aphid honeydew. They are only active at night.

How to Naturally Control Cutworms

Some cutworms are actually caterpillars which hide in the soil during the day and come out at night, while others stay in the soil and feed on plant roots. The ones that come above ground often wrap around the stems of plants and cut them off. They usually only attack seedlings, and can be controlled by putting snug-fitting paper collars around the stems extending two inches above and one inch below the soil. Cutworms that feed on roots can be controlled by turning the soil to expose them to freezing in winter.

How to Naturally Control Spider Mites

Red spider mites or two spotted spider mites (Tetranychus urticae) are so small that you can barely see them, but are a pest to many garden plants. To detect them, shake the leaves over a white piece of paper and watch for them to scurry towards the edge. They can be either green or red and spin fine webs underneath older lower leaves, and spend their lives on lower leaves of plants. They pierce leaves cell by cell and extract juices, leaving a white scar. If you discover a problem, a strong blast from a garden hose every 2 to 3 days will normally control spider mites.

How to Naturally Control Grasshoppers and Soft-bodied Insects

Soft-bodied insects like grasshoppers do not have a pancreas. Mix one cup of milk with a gallon of water and spray your plants. When soft-bodied insects eat your plants, they will soon die because they cannot digest the natural sugars in milk. Milk also make an excellent nutrient for your soil by adding minerals, and will feed the microbes which loosen up the texture of your soil. Apply it at a 1:3 ratio to your soil. Three gallons of milk will treat an entire acre, so you will not need much for a small area.

How to Naturally Control Stink Bugs

Stink bugs (Acrosternum hilare) should not be confused with shield bugs (Acanthosomatidae, Pentatomoidea), or assassin bugs (Reduviidae) since they look very similar. Even the names are confusing because people in different regions have different common names for them. Shield bugs have a distinctive shield on their back with upturned points on their shoulders. Assassin bugs have a distinct wheel on their back. Shield bugs and assassin bugs are a gardener’s friend since they feed on many pests including grasshopper eggs, caterpillars, aphids, Mexican bean beetles, and Japanese beetles. Shield bugs like to hang out on nasturtium leaves and other plants, hiding on the undersides or barely camouflaged. They can bite, but are not poisonous.

There are many varieties of stink bug that wreak havoc on all sorts of plants, and they are difficult to control. They emit a terrible odor when threatened, so most predator insects will not eat them, and makes them unpleasant for gardeners to hunt. The brown marmorated stink bug is the worst pest in most regions. Some species of the parasitic wasps may attack stink bug eggs. Some spiders and praying mantises will attack adult stink bugs. (1)

Some companion plant may help to repel stink bugs. The stronger-smelling types of Tagetes marigolds may be beneficial. Stink bugs usually do not bother garlic. Mints are strong smelling but tend to be invasive, so make sure to keep them in a container and keep the container on a stone if you do not want mints to take over your garden. Chrysanthemums and lavender are beautiful perennials that stink bugs tend to stay away from. Thyme can be planted as a low-growing carpet.

If the tomato plants will dry quickly, a strong blast with a garden hose every day may encourage them to go away. It is best not to wet tomato foliage, as it makes them susceptible to disease. Hand picking stink bugs and throwing them in soapy water will help if you notice the infestation in time. Diatomaceous earth kills stink bugs, but will also kill beneficial insects, so make sure to follow label directions. Spraying your plants with a mixture of 1:2 ratio of milk to water kills soft-bodied insects. Soft-bodied insects do not have a pancreas and are unable to digest the sugars found in milk, so it kills them after they eat sprayed plants. Be sure to test this on a few leaves to make sure it does not harm the tomato plant before spraying an entire plant.

How to Naturally Control Colorado Potato Beetle

The Colorado potato beetle has ten stripes as an adult and the larvae are dark orange with a black head. They lay about 30 yellow to orange eggs underneath plant leaves. They feed on plants and make them look like a skeleton of veins.

Hand picking is the best early control, since they can have several generations in a single year. Some ground beetles feed on their pupae. The pathogenic fungus Beauveria bassiana is available for sale and has shown to be an effective Colorado potato beetle control. (2)

Nasturtiums, coriander and Tagetes marigold may repel Colorado potato beetles.

Working with nature to encourage a healthy balance of insects is the best way to control insect infestations in your garden. Sometimes this is a challenge when your neighbor loves to nuke his yard with pesticides and herbicides, but organic gardeners can triumph even with these challenges.

  1., Oct. 21, 2011
  2., Oct. 21, 2011

About Olympia

My name is Olympia Paz, and I am a graduate of Kansas State University.with extensive studies in soil science (agronomy), horticultural science, and biology. I have continued my own studies in these areas, especially soil science, and applied my knowledge to growing nutritious organic food in my home gardens, containers, and inside.

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