Beneficial Insects, Harmful Insects and Scouting

The most numerous form of life on earth is the insect. Insects perform some of the most basic chores of the natural world. Our beneficial six-legged friends perform processes such as organic matter decomposition, soil aeration, and pollination.

Beneficial insects also help to control harmful insects that damage crops in a variety of ways. By employing the pest control philosophy known as IPM or Integrated Pest Management, we can identify and protect beneficial insects while controlling harmful ones.

Healthy plants = happy plants

The first step to pest control is growing healthy plants. Providing plants with good soil, proper moisture, and adequate sunlight keeps plants growing vigorously. When plants are actively growing they produce natural insecticidal chemicals and resist pest pressure. Preventing stress during transplanting is important also. When choosing plant material obtain and use insect ‘resistant’ plant material. Native plants are better suited to the southeast and will often perform better and be more pest resistant than exotics.

Scouting

Scouting is the basis of good Integrated Pest Management. Scouting, the inspection of plants for pests, should be performed weekly during the growing season. A good scout must be able to recognize the good guys from bad guys. Check the undersurface of leaves for aphids, scale insects, lacebugs, whiteflies, and spider mites. Look for signs of damage such as yellowing, chlorotic spots, curled, distorted leaves, wilting, and black sooty mold on the upper surface of leaves. Remember, good guys are often solitary while bad guys are often in groups of hundreds or thousands.

You might also employ the use of scouting devices. One type of scouting device is the white paper test. Tap flowers over a sheet of white paper to dislodge insects such as thrips.

You can also use sticky traps. These monitoring devices can be easily made from yellow and blue plastic plates. Simply coat them in some tacky substance such as spray glue or oil and hang them near your flowerbeds and shrubs.

Whiteflies, aphids, and thrips will be attracted to the traps and become lodged allowing you to count them and decide if action is needed. Sticky tape makes a good monitoring device as well. Simply wrap it around the stems of shrubs and flowers to monitor scale crawlers, spider mites, and other crawling insects.

Consider your thresholds

Set your threshold for plant damage high so you can reduce your pesticide use.

The grower decides damage thresholds. Economic and aesthetic thresholds may be different depending on plant types, the pest involved, and the use of the plants. Economic thresholds are based on the amount of monetary loss a grower can stand before control becomes necessary. Aesthetic thresholds are based on how much damage an ornamental can sustain before control measures must be implemented.

Use less toxic controls

A water hose is one of the least toxic devices you can use to get rid of pests. Aphids, lace bugs, and spider mites can all be removed with a heavy stream of water. These pests become disoriented and find it difficult to find their way back to the plants. If done several times, this can be an effective control method.

A second effective, less toxic control option is to pick insects off by hand or prune them out. This method is effective for larger pests such as bagworms, tent caterpillars, and fall webworms. Destroy the pests or bag them and place them in the trash.

The use of safer pesticides such as ‘biorational insecticides’ is another less toxic control. For instance, Soaps repel insects and irritate them, and are effective on small soft-bodied insects. Minerals such as sulphur are toxic to insects and prevent disease. Oils (Dormant, Summer, Superior, and Neem) coat and smother insects. Naturally derived botanical insecticides created from plants (ex. azadiractin) can be powerful nerve toxins to insects. Insecticides derived from naturally occurring bacteria such as Bacillus thurengiensis products (Bt, Dipel) or spinosyn (Spinosad) all provide good control without polluting the environment.

So, how do you tell the good guys from the bad? Click on the links below to see images of each pests.

The Bad Guys

Sucking insects

• Whiteflies
• Aphids
• Scale insects
• Lace bugs
• Spider mites
• Thrips

Chewing insects

–Caterpillars

• Bagworms
• Tent caterpillars
• Fall Webworms

–Beetles

• Japanese beetles
• Leaf beetles
• Flea beetles

The Good Guys

Parasites

• Parasitic wasps
• Parasitic flies

Predators

• Spiders and mites
• Lacewings
• Praying mantids
• Syrphid flies
• Ground beetles
• Lady beetles

Predatory true bugs

• Spined soldier bugs
• Damsel bugs
• Minute pirate bugs
• Assassin bugs
• Big-eyed bugs

Encourage Beneficial Insects

Beneficial insects can be encouraged in a number of ways. Start by planting alternative food sources that provide pollen and nectar. Plants such as daisies, Queen Ann’s lace, yarrow, alyssum, golden rod, alfalfa, clovers, and vetches will attract beneficial insects.

Building a bee house can be elaborate such as this one or as simple as a bundle of paper straws housed in a coffee can.

Water sources attract beneficial insects as well. Birdbaths, temporary puddles, small dishes of water, and dripping water can be easily installed in any garden. Remember to replace your water every few days to avoid mosquitoes and to keep it attractive. Place small ‘perches’ in water sources so that insects can access the water.

The final way to encourage beneficial insects is to provide them shelter. Areas that are left undisturbed benefit insects. Allow forest edges to grow wild and do not mow open areas unnecessarily. Plant perennial flowerbeds that will flower all season by staggering different species throughout the bed. Hedgerows also provide beneficial insects with shelter.

Any source of water is good for beneficial insects.

Visit the Pollinator Garden at Flat Rock Park