Gardening: 10 Beneficial And Harmful Insects You Should Know

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When it comes to gardening, beneficial and harmful insects are the top concerns of nature loving people. However, the truth is that the best gardens are full of bugs!

These little critters play a vital role in maintaining the health and beauty of our gardens. For instance, bugs such as bees, butterflies, and beetles help to pollinate flowers, while others like earthworms improve soil quality.

Moreover, some bugs even keep harmful insect pests at bay. But how can we tell the difference between beneficial and harmful insects?

Let’s find out more in the article below.

Beneficial and harmful insects
A beautiful garden depends on you knowing the difference between beneficial and harmful Insects.

CONTENTS – In this article, you learn the difference between beneficial and harmful insects (and how to get rid of the bad guys), including;

What’s Eating You? Recognize Insect Damage to Your Garden

The best Gardens are full of bugs.

Bugs pollinate flowers.

They improve soil quality.

And they keep other insect pests at bay.

But it only takes a few bad ones to spoil the garden for all of them.

That’s why it’s important to know the difference between beneficial and harmful insects. Once you recognize signs of the bad bugs and what the good bugs look like, you’ll be one step closer to a beautiful garden that thrives!

Recognizing Garden Damage Caused by Harmful Insects

When gaping holes appear overnight in the foliage of a prize perennial, you need to act fast.

But instead of reaching for chemicals that kill all insect life, you’ll want to target only the offenders.

To do this, you must first recognize the tell-tale signs of damage caused by harmful insects.

Here are 5 indications of trouble and how to rid yourself of the likely insect culprits.

1.   “Skeletonized” Leaves

Beneficial and harmful insects

When all that remains of leaves is an intricate “skeleton” of veins, it is the handiwork of a beetle.

While many kinds of beetles are responsible for ornamental damage, the Japanese Beetle is perhaps the most notorious.

Oval bodied with spiny black legs, they have an unmistakable metallic blue green body with bronze wing covers.

Adult Japanese Beetles skeletonize a wide range of plants in early summer. If you don’t intervene, they can completely defoliate your prized possessions.

Also responsible for leaf skeletonizing and lawn damage is the Chafer Beetle. This harmful insect looks similar to the Japanese beetle, but is more oblong in shape and is entirely bronze-colored.

Before either of these beetles begin doing damage in your garden, they’re causing problems underground.

The grubs of both beetles emerge in spring to feed on tender grassroots. You’ll recognize their handiwork by the large masses of dead lawn.

Effective treatment depends upon you interrupting the beetles reproductive life cycle.

So, you’ll want to hand-pick and drown those beetles you do find in soapy water. This minimizes the egg-laying populations.

In Spring, apply milky spore to treat Japanese beetles larvae.

Or, you can apply these beneficial nematodes as a biological control to destroy both Japanese beetle and chafer beetle larvae before they emerge.

2.   Leaf Holes and Notches

Beneficial and harmful insects

Any number of pests eat holes in leaves, flowers and buds.

But a closer look at the size and shape of the holes may reveal important clues.

When the leaves on your plants begin to look like Alpine Swiss Cheese, it is often the damage of the Flea Beetle.

Flea Beetles are small, round, dark beetles that jump when disturbed — hence their name.

They make tiny, round holes in leaves and also spread viral diseases.

For Flea Beetles, apply benefitcial nematodes, or Neem Oil. This oil is derived from plant materials and can help control heavy infestation.

Medium to large holes in leaves that pierce through leaf veins may indicate that some kind of caterpillar is to blame. Seeing droppings will be the evidence you need.

Next are the Cabbage Looper, also known as the inchworm. This small green caterpillar with two white stripes along the back.

Similar to the inchworm is the Cabbage worm, which is velvety green with a single thin yellow stripe across the back.

You may need to hand pick and destroy these damaging pests several times a week to keep up.

Another option is to attract natural predators, like Parasitic Wasps, to the garden by planting flowers high in pollen and nectar.

For heavy infestation, spray the bacterium Btk (Bacillus thuringiensis var. kustaki), which kills most common pests caterpillars.

Slugs rasp large holes in your foliage and often completely demolish seedlings.

These brown or gray, fleshy blobs are night feeders, taking cover and moist shady areas, like beneath hosta plants, and daylight.

In some cases, closer examination will reveal a silver mucus trail.

One solution is to lure slugs to a shallow saucer of beer with the edge level with the soil. There, they’ll die a sudsy death.

You’ll want to replace the beer daily until slug numbers decrease.

Or, you can sprinkle diatomaceous earth around your plants. This fossilized shell remains has microscopic sharp edges to deter or kill the slugs.

Wood ashes or crushed eggshells have the similar effect of discouraging these slimy trespassers.

When you see scalloped notches in leaf edges of plant like Rhododendron, Euonymus, Astilbe, and strawberry plants maybe the work of the Black Vine Weevil.

These harmful insects are night feeders.

Black Vine Weevil adults are about half an inch long and mostly black with yellowish patches.

Their damage is usually cosmetic in nature, but root damage from them can kill your plants.

To defeat them, look at making repeated applications of foliar spray products like bifenthrin (Talstar), which will kill adults before laying eggs.

For grub control, apply parasitic nematodes.

If you’re looking for a home remedy, try using cloves or bay leaves, both of which can act as natural repellents for weevils and other insect pests.

Related: 21 Easy-Care Rhododendron Varieties That Will Beautify Your Yard

3.   Strange Winding Trails

leaf miner in leaf | Enjoy Travel Life

Curious whitish trails appearing on leaf surfaces may indicate that Leafminer larvae are tunneling within the leaves.

The larvae of these rarely-seen flies affect plants like Columbine, Joe Pye Weed, Beets, and many other plants.

Once you recognize the damage as a sign of Leafminers, remove and destroy infected leaves before they drop to the ground to pupate.

Alternatively, apply nicotine tea or Neem Oil to infected plants.

There are mixed reviews on whether it’s a good idea to apply nicotine tea to the garden; It can introduce Tobacco Mosaic Virus can be harmful to both good and bad bugs. To do this, heat a spoonful of natural chewing tobacco in a gallon of water for 45 minutes, then spray your plants with it.

If you decide to go for the nicotine tea, do so judiciously.

You’ll also want to consider removing any nearby Lambsquarters, an annual weed which serves as a host for some Leafminers.

4.   Leaf Deformation

Beneficial and harmful insects

Aphids, tiny pear-shaped insects range in color from green to black, can be winged or wingless, and often go unnoticed until their damage is done.

Their sap-sucking distorts plant leaves, buds, and flowers. And, they produce a sticky substance, called “Honey Dew,” that can cause fungal problems.

In fact, the first indication of problems you notice may be the presence of ants. That’s because ants are known fend off aphid creditors while “farming” the aphids for the honey.

You can spray a strong stream of water to knock aphids from your plants.

But, inviting aphid-eating predators is a long-term solution. Lady Beetles, Lace Wings, and Parasitic wasps feed on aphids, and you can attract them by planting pollen and nectar plants.

You might also purchase these beneficial ladybug insects on Amazon or through mail order catalogs like Gardens alive!.

Also effective at treating aphid infestations are applications of pyrethrin, nicotine, or rotenone, toxins derived from plant materials.

Thrips are another sap-sucking insect you’ll want to erradicate.

You’ll notice their presence from stunted plant growth and damaged flowers accompanied by silvery speckling or streaked leaves.

These tiny, fast-moving insects are best controlled by applying dormant oils and encouraging natural predators, like lace wings or lady beetles.

You can also place blue or yellow sticky traps to catch adult thrips.

Finally, insecticidal soap and Pyrethrin are also effective controls for Thrips.

5.   Strange Substances On Your Plants

spittle bug on stem | Enjoy Travel Life

Spittlebugs are most easily recognized as nymphs that surround themselves with a white, foamy spittle. “Spit Bugs” also deform leaves by sucking sap from plants.

Keep their numbers to a minimum by hand-picking and destroying them. It’s also helpful to keep the garden free of debris and weedy grasses where they like to hide.

If you find webbing on leaf undersides accompanied by pale or yellow leaves, it is more likely the work of Spider Mites.

For mild infestations, apply dormant oil, insecticidal soap, Pyrethrin, or Neem. You can also release predatory mites or Rotenone for heavy infestations.

Leaves rolled in a webby substance are the calling card of the aptly named Leafroller, a green caterpillar with a brown or black head.

Unfurl and pick them from young trees weekly, and spray dormant oil in late winter to kill their eggs.

You’ll also want to attract parasitic insects or apply Btk to kill larvae before they spin webs.

6.   Severing

When an entire seedling, flower bud, or leaf is severed, Cutworms may be the problem.

To thwart this culprit, apply parasitic nematodes the week before you set out transplants.

Alternatively, protect your transplants with plant collars.

An easy way to DIY this is to cut toilet paper rolls in half and push the end into the soil around your seedlings.

For mature plants, spray with Neem oil.

Recognize that in the case of severed plants, it may instead be the nibbling of small animals, like rabbits or squirrels, or even deer.

Furry threats like these are best to discourage by placing fencing or using repellents. Liquid Fence is a great option. As with any liquid repellent, you’ll need to reapply after a deep rain.

And, when it comes to severed plants, don’t rule out the possibility of damage from well-meaning or mischievous children and the occasional ball in the flower bed.

Whoever the culprit is, with a little detective work, you can prevent a return to the crime scene.

As they say, “the best defense is a good offense.” That means when it comes to pre-empting damaging insect pests, invite the following beneficial bugs to your garden space.

10 Best Bugs for Your Garden

lacewing beneficial insects | Enjoy Travel Life
You’ll want to allow beneficial insects, like this Lacewing, to remain in your garden. They’re working to your advantage!

It’s easier to control damaging insect pests with these beneficial bugs on your side.

Attract them by planting small flowered plants, like Catmint or Dill, or allowing a few wild flowers like white clover, Queen Anne’s Lace and yarrow to grow nearby.

Just make sure you can identify them once they arrive.

Many a new gardener tries to eliminate all bugs from the garden – and that’s a big beginner mistake!

1.    Assassin Bug

Assassin Bugs are usually black or brown with a 3/4 inch long oval shaped body. The giveaway is their curved beak. This general predator includes flies and caterpillars and its diet.

2.    Bumblebee

A black and yellow striped bumblebee that’s fuzzy and plump is a welcome visitor to the garden. This is an important wild pollinator!

3.    Daddy Long Legs

Daddy Long Leg spiders have four pairs of extremely long legs and eat a variety of soft-bodied insects, including aphids, flies, leafhoppers and snails. (They also eat beneficial earthworms.)

4.    Ground Beetle

The Ground Beetle is a blue-black or brown 1-in beetle that eats slugs, cut worms, and other soil-dwelling pests.

5.    Hoverfly Cole

This yellow- or white-and-black striped fly is often found hovering over flowers. Hoverfly Cole larvae feed on many species of aphids.

6.    Ichneumon Wasp

These slender and dark wasps with long antennae sometimes have a depositor mistaken for a  stinger. But Ichneumon Wasp larvae are parasites to caterpillars, beetle larvae, and other insects. Adult females sting and feed on other pest insects, too.

7.    Lacewing

Green or brown with netted, transparent wings, Lacewings are delicate-looking behold. But don’t underestimate them: they eat aphids and are general predators!

8.    Lady Beetle

Also known as the Ladybug, Lady Beetles eat aphids, mealybugs, and stop scales and spider mites.

9.    Spined Soldier Bug

Spines Soldier Bugs are shield-shaped and about a half-inch long. They have sharp points on their shoulders and speckled with black.

These beneficials attack caterpillars and grubs, including Mexican Bean Beetle larvae.

10. Tachinid Fly

The Tachnid Fly resembles an overgrown, beefy house fly. Their larvae attack caterpillars.

Final Thoughts on Beneficial and Harmful Insects

In conclusion, bugs are not just a nuisance in the garden; they are an integral part of the ecosystem.

By understanding the different types of bugs that inhabit our gardens and their roles, you can make informed decisions about how to manage them.

Instead of reaching for harmful pesticides, consider using natural methods such as companion planting or introducing beneficial insects to control pest populations.

By working with nature instead of against it, you can create a beautiful, thriving summer garden that benefits both us and the environment.

So the next time you spot a bug in your garden, take a moment to appreciate its contribution before deciding what action to take.

Next Steps

For more about gardening tips , read the articles below, next:


This article originally appeared in The Country Gazette as “What’s Eating You? (Recognizing insect damage to your garden)” by Jackie Gately. It has been updated and modified accordingly.