Bad Bugs For Gardens? | bugs and grubs you NEED TO KNOW about

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As a gardener you will quickly come to learn that there are bad bugs for gardens.

Before you get totally put off let’s put those bad bugs into perspective…

There are about a million known insect species on the planet and of those, less than 1% are classified as ‘agricultural pests’. 

The vast majority of bugs in your garden will either come with several benefits, from improving soil to eating pests…or they’ll just be there, chilling out!

For the purpose of this post I’m using the term ‘bugs’ incredibly loosely to mean anything small, creepy, crawley or slimy.

Before I get into which bugs are “good” or “bad” I want to share with you something that my mum always says…

No-one would ever plant anything if they worried about all the pests that could destroy it.”

My Mum

She’s grown an acre of fruit and vegetables for almost 40 years and although she’s lost a few plants (sometimes several), she takes it in her stride and never resorts to chemicals to prevent or treat any gardening issue.

It is totally possible to produce an abundance of food 100% organically.

Organic gardening pests

Permaculture is all about working with nature and understanding that all native bugs have a place in your garden (often they are food for the good bugs!). It is not a gardeners job to wipe out an entire population of insects…

That said, infestations of problematic bugs are a nuisance and can sometimes destroy crops.

As organic gardeners, using pesticides to combat damage from pests is not something we would consider so preventing infestation is the best way to avoid issues.

How to prevent pest damage:

There are some practices that are easy to implement that will reduce the likelihood of pest damage and help to keep any problems under control:

  • Rotate disease and pest prone plants to avoid build up in one area e.g brassicas, onions.
  • Use companion plants to deter or distract nuisance bugs and attract beneficial bugs to areas of your garden.
  • Avoid planting too much too close together so that air can circulate between plants.
  • Keep greenhouses and polytunnels well-ventilated.
  • Use insect netting to protect pest prone vegetables like carrots (carrot fly) and brassicas (cabbage white butterfly).
  • Instead of buying ‘good bugs’ (yes that really is a thing!) first focus your energy on creating a habitat where they can thrive. e.g. build a pond to attract slug-eating frogs and toads.
  • Probably the most important practice is to observe your garden regularly. Check for damage and remove any pests that you see. What you choose to do with them is your choice. Throw them in the hedge, in the duck pen or squish themthat bit is up to you!
  • Choose resistant varieties of the vegetables that you have trouble growing.
  • Confuse bugs by inter-cropping different vegetables, flowers and herbs together.
  • Transplant when seedlings are strong and maintain their good health by feeding them with homemade organic natural fertilizers.

Learning to recognise bugs and the role they play is important knowledge to have as a gardener. You can then begin to dispose of or distract the destructive ones while encouraging the beneficial ones.

So, let’s take a look at which bugs are ‘bad’ for gardens and what you can do to prevent damage…

1. Cabbage White Butterfly

I’ll start with the prettiest pest so I don’t scare you off!

Various butterflies and moths will try to lay their eggs on your brassicas. Their caterpillars will happily munch their way through the leaves or cabbage hearts leaving them unsightly.

The offenders should be pretty easy to spot as there will be caterpillars and their excrement on the plants.

How to prevent and deal with Cabbage White Caterpillars:

Covering plants with a net will prevent butterflies from laying eggs on your plants.

If your cabbages become covered in caterpillars then you can pick them off.

You can also soak some rhubarb leaves or garlic in water and pour it over plants where pests are a problem.

2. Gooseberry Sawfly

If you’re growing gooseberries or currants then you’ll want to look out for sawfly larvae who will eat their way through leaves from the edges working inwards.

If there are lots present they can strip your bush of its leaves which will slow it’s growth.

How to prevent and deal with gooseberry sawflies…

Keep a lookout for telltale leaf damage and remove any wrigglers and eggs.

Keep plants well pruned as Sawfly caterpillars don’t like breezy bushes!

If your plants develop a problem you can sprinkle wood ash round the base and shake the bush. The fallen caterpillars won’t be able to climb back up.

Using rhubarb or garlic infused water on the plants (as suggested for Cabbage White Caterpillars) should help with Sawfly Caterpillars too.

3. Carrot Fly

Carrot flies lay their eggs below the surface of the soil and when their larvae hatch they will burrow into your carrots often making them inedible.

How to prevent carrot fly…

The most effective prevention method is to create a physical barrier to stop the carrot flies getting to your carrot crops. Use insect netting held off crops with metal hoops, sticks or plastic piping.

Interplant onions or leeks with your carrots as the smell will confuse the adult flies which hopefully put them off laying their eggs near your carrors.

Carrot fly larvae will also damage parsnips, celery, dill and parsley.

This bed has parsnips and carrots in as both are suseptable to damage from carrot fly larvae.

4. Leaf Miner

Leaf Miner are the larvae of non-descript black flies, moths or beetles.

They will create lines on the leaves of your current bushes, fruit trees, spinach, peas and lettuce as they burrow through.

Although they don’t usually pose a big problem to healthy plants they can destroy seedlings and restrict plant growth and hardiness.

I pulled these pea leaves from the base of my plants. Look closely and you can see the tiny grubs inside!

How to prevent Leaf Miners…

Catch them early by removing and destroying the leaves.

Most plants will do fine with some damage but you can treat leaf miners organically if needed using neem oil.

Neem oil is made by pressing the fruits and seeds of the neem tree and although it won’t immediately kill all the adult leafminers it will reduce numbers.

5. Flea Beetle

There are many species of flea beetle and they vary in colour.

They are small, shiny-coated beetles and they can jump pretty far.

If they didn’t eat my crops I’d think they were quite cute!

How to prevent and treat flea beetles?

Plant thyme, catnip, basil and mint close-by to affected crops to cover the smell of the their favourite crops e.g. cabbages, raddish.

You can also try planting nasturtiums to distract beetles from your favourite crops as they are irresistible to them instead (As is Pak Choi by the looks of my crop!)

Apparently dusting plants with a little talcum powder will repel flea beetles.

Like many pests, Flea Beetles won’t usually cause fatal damage to plants provided they are established but they can spread diseases like blight so remove them when you see them.

Watering time is a good opportunity to spot them as they don’t like getting wet and will scurry away.

6. White Fly

Whiteflies are tiny moth-like bugs that suck the plant juices out and leave a sticky substance that can cause fungal disease.

How to prevent and treat Whitefly…

Inspect plants daily and remove and destroy any infected leaves. You can also use a jet of water to blast them off.

Insects like spiders will catch loads of adult whiteflies in their webs so welcome them into your garden. Ladybirds and hoverflies too as they enjoy to feast on whiteflies.

Plant French Marigold and basil around plants like tomatoes to mask the scent and discourage whitefly from attacking plants.

7. Cabbage Root Fly

Cabbage root fly lays it’s eggs at the base of brassicas and when the maggots hatch they burrow into the soil and feast on the plants roots.

You probably won’t realise your plant has rootfly until it wilts or dies but once removed you will notice small maggots in the damaged roots.

How to prevent and treat cabbage root fly…

The best way to prevent Cabbage Root Fly is to use cabbage collars that stop flies laying eggs under plants.

You can buy them but you can also make your own by cutting a circle out of cardboard and slipping it over your plants.

8. Milipedes

Millipedes usually eat dead plants but in large numbers that can sometimes eat the roots of plants and seedlings. Finding a few is really nothing to worry about.

Millipedes are often confused with Centipedes (which are beneficial to your garden). The easiest way to tell them apart is to look at their legs. Millipedes have two legs per segment and Centipedes have one pair per segment.

How to prevent and deal with Millipedes

If you suspect Millipedes are causing damage then reduce hiding places by clearing garden litter which will mean the birds can find them.

9. Ants

Like many other garden bugs, ants aren’t usually a problem in the garden although they will eat strawberries that have been damaged by slugs.

They also collect the sticky substance I mentioned earlier that is excreted by aphids so it sometimes looks like they are the cause of your problems. Usually if you get rid of the aphids then the ants will usually go elsewhere.

10. Black Bean Aphid or Black Fly

Black fly feed on the sap of tender young plants and their excretion can cause disease.

It is a common pest on broad beans but is easily remidied if caught early.

How to prevent and deal with aphids…

Use a jet of water to blast off black flies or wipe leaves with a damp cloth.

If your broad beans get blackfly then just snip off the heavily infested shoot tips.

You can also hang a bird feeder closeby to encourage birds to snack on these garden pests.

Black flies are also eaten by ladybirds and their larvae (who consume even more!). The lavae of lacewings and hoverflies enjoy munching on them too.

11. Onion fly

Onion fly damage is caused by small grubs that burrow into onions. They also effect leeks and garlic too.

How to prevent onion fly…

As with carrot fly, the best way to prevent carrot fly is to cover your crops.

Planting onions alongside carrots will also help to confuse the onion flies.

12. Woodlice

Woodlice are pretty common garden pests and although they don’t always pose a threat to you vegetables they will sometimes eat seedlings.

How to prevent and deal with woodlice…

If you have woodlouse problems then avoid mulching with anything other than compost as bark and straw will create a lovely habitat for them.

Encouraging natural predators like toads, centipedes and spiders into your garden will help keep your woodlouse population under control.

13. Red spider mites

Red spider mites are tiny insects that can actually look yellowy green at certain times of year.

They especially love hot, dry weather so greenhouses are a particular favourite.

They will slowly suck the sap out of your plants and leave their telltale web on plants.

How to prevent Spider Mite…

Because these bugs love dry heat raising humidity levels in your greenhouse or polytunnel can help to prevent infestations. You can do this simply by placing trays of water and pebbles on the floor.

If needed then you can use neem oil to deal with spider mites.

14. Slugs

No bad garden bugs post would be complete without slugs would it!

These nuisance pests will eat entire rows of seedlings overnight and are the reason we grow our lettuces in store bought and homemade slug collars!

How to prevent and deal with slugs…

The most effective ways we have found of dealing with slugs is to go out looking for them, torch in hand at around 9-10pm.

They come out late to feed when the soil is cool and damp so that is when you will find them! Dispose of them as you wish.

Watering plants in the morning will make your garden less inviting to hungry slugs s it will be dry by the time they come out in the evening.

It helps to leave a plank of wood or tempting piece of orange skin out so that slugs are easier to find.

Slugs and snails dislike the following things so you can try sprinkling them around plants:

  • Coffee grounds (free from cafes)
  • Sheep’s wool
  • Crushed eggshells
  • Seaweed
  • Seashells
  • Gorse or brambles

15. Snails

Snails do the same damage as slugs to vegetables but the slimey trail they leave behind is broken as opposed to a slugs solid line. For prevention ideas see ‘slugs’ above.

16. Chafer Grubs

Chafer grubs range in size from around 1-3cm. They look similar to Vine Weevils but have prominant legs.

These creepy little guys attack the roots of lawns and some plants, while adult chafers (beetles) feed on the leaves.

How to deal with Chafer grubs…

Dispose of any grubs you find and encourage birds that prey on beetles into your garden.

Covering with insect mesh will keep bugs off your beds.

17. Vine Weevils

The adult vine weevil is a 1cm black, wingless, beetle-like bug. It has to be one of the most destructive garden pests, especially if you plant in pots (they also love compost containing peat so there’s yet another reason to avoid it!)

Adult females lay between 500 to 1,500 eggs in the soil around plants and they hatch 15 days later into white larvae similar to Chafer Grubs.

They feed on roots as they grow to around 1.5cm and finally emerge from the soil as adult beetles.

The vine weevil beetles will die when cold weather sets in around late Autumn but the grubs will survive in the soil until Spring when the cycle begins again.

How to deal with Vine Weevils…

Inspect plants that wilt and die. If the roots look eaten then take a look in the soil for vine weevil larvae.

Centipedes and insect eating birds will eat vine weavils so welcome them into your garden.

Use netting to prevent adult vine weevils getting to your plants.

You can also replant perennial pot plants in the spring and check for vine weevil as you do so.

So, there to have it…17 bugs to watch out for in the garden. Please don’t take this as a squish them all message. Spotting a couple of bugs is not a sign of infestation.

Preventing damage with insect mesh has to be the most effective way of dealing with most of these bad bugs for the garden.

Now, to counter this post I’m off to write all about the good guys…