Beneficial Garden Insects. Gardens Are Full of Insects, But Which Ones Are Beneficial and Which Detrimental? Which Insects Are Garden Friends & Which Are Gardeners Foes? Here’s a Guide to Beneficial Garden Insects
What Is An Insect?
The reason I ask what appears a simple question is that I don’t want to confuse what some might call beneficial garden insects with detrimental insects. In fact many people would argue that all insects are beneficial in some way or other. For example wasps can be a nuisance when we picnic outside, but they are predatory insects that destroy loads of plant chomping creatures that will otherwise destroy our crops. So, arguably no insect is detrimental!
Insects are invertebrates, that’s to say they have no backbone and vertebral column. What they do have is a chitinous exoskeleton (chitin is a polysaccharide that’s also found in the cell walls of fish, and fungi) and a three-part body. That’s ahead, thorax and abdomen. And because they have a hard chitinous exoskeleton most of them lay eggs, as producing live young is difficult (though aphids and some other species do achieve it with spectacular success). Insects are a very successful group. More than 90% of all animal lifeforms on earth are insects! In some senses, insects rule the world. The Insecta classification is huge and includes beetles, flies, moths and wasps.
What Do We Mean By Beneficial Garden Insects?
These are the insects that help the gardener by things such as pollinating fruit and destroying pests.
What Do We Mean By “Detrimental” Garden Insects?
These are the insects that cause damage in the garden. They may, for example, suck sap from our plants or eat the toots leaves or flowers of our plants.
Beneficial Garden Insects
Great pollinators of all sorts of plants these are one of the insects we tend to think of when pollination is mentioned.
“And will there be honey for tea,” wrote Rupert Brooke. The honey bee is probably the most loved pollinator both for the honey it produces and the range of fruit and other plants it pollinates.
OK, so caterpillars can be a nuisance in the garden but there’s also a positive side to butterflies. Not only do they look great but they pollinate a lot of flowers.
We don’t have many butterfly species in the UK but we do have well over 2500 species of moth. Many are night flyers so we don’t get to appreciate their diversity and beauty, or the fact they pollinate numerous plants.
They may look like a beetle or bug but ladybirds are insects in every sense. The reason being that beetles are part of the Insecta group.
Ladybird larvae consume huge numbers of aphids and a true insect friend.
Many ground beetles are useful insects. These predate vine weevil larvae, slugs, snails etc. Vine weevil is a pest that infests the roots of plants and can destroy plants by attacking without being seen.
Slugs and snails need no introduction and are very destructive in gardens. So nocturnal ground beetles are a godsend when slugs and snails are a problem.
This is another big group but between them, they devour aphids and pollinate crops which makes them doubly friendly in my book.
There are many parasitic wasps and they all predate other creatures. For example, the parasitic wasp Encarsia formosa has been used since the 1920s to parasitise whitefly on greenhouse crops. You can buy Encarsia wasps in their larval form and use them in greenhouses. The larva comes on pieces of card which you hang up amongst the plants. They then disperse in search of whitefly, parasitise them and breed a new generation to keep the cycle going.
So often I see people panic when they see a wasp. And yes a sting isn’t pleasant but did you know how useful wasps are?
Wasp grubs eat huge numbers of caterpillars and other insects, which the adults capture and take back to the nest.
Solitary bees don’t have huge nests like the honey bees. They tend to nest alone in suitable locations. And with over 200 different sort of solitary bees in the UK that can mean in a wide range of locations. For example, masonry bees dig holes in mortar of soft stone, other species build their nest in disused snail shells and one species burrows holes in bramble stems. The one thing they have in common is that they are all excellent pollinators.
Lacewings are those almost transparent green flying insects that, as larvae, eat aphids.
Detrimental Garden Insects
There are thousands of aphid species and all are a potential problem to gardeners. Aphids suck the sap of plants, decreasing their vigour and often passing on diseases and viruses.
Red spider mite area pest of many commercial crops and also cause problems in domestic situations. These plant feeding mites can cause mottled leaves and subsequent early leaf loss on various indoor plants. They dislike high humidity so are less of a problem outdoors.
Vine weevil feed on plant roots and the first sign of an infestation is often the complete collapse of a plant! And if root damage caused by the grubs isn’t enough, the adults eat leaves.
Caterpillars are a huge problem pest in many situations. Organic control is via predation by Bacillus thuringiensis, a bacteria that can be sprayed on to the crop and will kill caterpillars.
Outdoor cabbage and indoor crops such as tomato can suffer whitefly problems. The parasitic wasp, Encarsia formosa is an excellent control agent.
And that’s just the start of a long list of detrimental insects!
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