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Limit Garden Pest Damage Organically | Pest Control Without Chemicals | The Old Farmer's Almanac

How We Keep Pests Out of the Garden (Naturally!)

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Tomato hornworms can seriously damage tomato plants, but allowing parasitic wasps to live in your garden will limit the damage.

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University of Minnesota
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Natural garden pest control!

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Every garden faces pests. But that doesn’t mean we can’t keep pests in check. You don’t need chemicals, which affect beneficial bugs. All our methods to keep pests out of the garden are organic so you can manage pests in step with nature.

As gardeners, we often find that various insects can be found eating our crops. This is disturbing and frustrating. Broccoli looks disgusting when it is covered by small worms along with their poop. Cucumber beetles eat holes in the leaves of the plants and spread disease from one to the next. Cutworms strike at night, taking one bite of a plant right where it goes into the ground killing it.

See how to identify which pests are eating your garden.

There are, however, things that we can do to minimize insect destruction in our gardens.

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1. Start Using Covers!

The very simplest way to avoid pest problems is to simply cover your crops so nothing can get at them. For example, cover young beets or beetroot to stop leaf miners! Getting this on while the plants are still young hopefully stops them from ever being discovered in the first place, so they’re protected right from the start.

Use a really fine gauge mesh netting, also sold as insect barrier mesh or under brand names such as Enviromesh. This stuff is super fine, so there’s no way any flying insect can penetrate it. In most cases it’s just a matter of laying this over your beds – but take meticulous care to secure it at the edges so nothing can get in at the sides. Pin mesh down with bricks or stones to ensure this. Insect mesh is both breathable and permeable, so the sun and rain can pass through and reach your veggies. 

Insect mesh is our go-to cover during the growing season. It stops everything in its tracks – from the neighborhood cats to flying insect pests, and it’s lot more durable than fleece covers, which inevitably snag and tear. As well as deploying them to prevent leaf miners, use insect mesh to stop carrot flies from landing on carrots and burrowing down into the roots. It’s also a lifeline for keeping the butterflies and moths responsible for caterpillar damage off brassicas.

If squash bugs or squash vine borers are a problem where you garden then covers can be really helpful early on in the lifecycle of your squash plants. Cover plants the moment they’re planted and keep them covered until your plants are well-established and have begun flowering, at which point you’ll need to remove covers to let the pollinators in. At least by then you will have given your squash a fighting chance.

Other crop covers include wider gauge netting. Use to keep birds off! Then as we move into summer, switch to insect mesh. 

You’ll also find butterfly netting which does as the name implies – keeps butterflies and moths off. It’s a finer gauge than the bird netting. It’s good stuff, but because the holes are clearly bigger than the insect mesh, it’s essential to support the netting so it’s lifted off your plants otherwise, if it touches, there’s a chance that the butterflies could still get at the foliage by simply laying their eggs through the netting. And it’s for that reason, use insect mesh almost exclusively during the summer months, because it really is an all-purpose cover.

See the video below. Ben demonstrates different types of netting.


2. Remove Pests

But we can’t cover everything all of the time. Some vegetables are just too tall for that or need to be out in the open so they can be pollinated. Like green beans, which predictably for this time of year, have black bean aphid on them. Aphids are just part of the lifecycle of beans, and pest predators like ladybugs or ladybirds do seem to eventually find them and snaffle them up.

Early aphid infestations – whether black bean aphid, cabbage aphids or whatever – can, however, be set back, buying you time till those pest predators arrive – if you act fast the very moment you spot them. Either cut off affected foliage or squish small clusters between your finger and thumb.

Another option is to blast them off with your hose. Choose a setting on your spray gun that gets the strongest jet of water… then just work over the foliage, holding leaves in one hand if necessary, to blast the aphids off onto the ground where they’ll likely perish.

If you see tunneling on your leaves, it’s those leaf miners, grubs that literally devour their way within the leaf. In a bad infestation they’ll join up to create this kind of papery appearance. If the infestation isn’t too far along you can try to squash the leaf miners within the leaf, or just pinch off and remove the leaves and then hopefully the leaves that grow to replace them will be leaf miner-free.

Slugs can be a nuisance in wet weather or earlier on in the season. And the best way to deal with them is to set traps that will make them easy to collect up. You can set up shady escapes for them – luring them beneath the cool of a grapefruit shell for example, or a few strategically placed larger leaves like this rhubarb. Then from time to time check under your shady refuges and collect them all up. Learn more about controlling slugs.
 

3. Attract Beneficial Bugs

Insects are everywhere. Many are feared while some should be encouraged. We sometimes lump all of these creatures into one nasty category that we would rather do without. However, we do so at our peril. Pollinators like bees do vast amounts of work for us, and we would find ourselves in dire circumstances if they were all eliminated; this is why it’s important not to use chemicals.

There’s a whole host of beneficial bugs such as predatory insects that love to feed on soft-bodied pests: ladybugs or ladybirds, parasitic wasps, lacewings, hoverflies and minute pirate bugs, for example. Wasps absolutely love aphids. We let them nest where they won’t bother us (high on the house, etc.) and we’ve never had an aphid problem. We can tell right away if a nursery plant comes with them as the wasps are all over it right away. Parasitic wasps are also a great help in controlling tomato hornworm populations. 

paper-wasps-control-pests

4. Start Companion Planting

They’ll find the pests eventually, but you can attract more of them to your garden by planting the flowers they love. Dill plants – along with fennel flowers – are a big pull for these sorts of beneficial bugs. In fact, many herbs, if allowed to flower, will pull in the good guys: parsley, thyme, mint, basil, oregano – they’re all powerful plants to include for this reason alone – and, of course, you can eat them!

The cabbage moth, which produces the small worms in broccoli, Brussels sprouts, cabbage and kale, can be almost entirely controlled by planting marigolds right in the beds with the plants. It’s best to put them at both ends and in the middle of very large beds. Lemon gem and tangerine gem are lovely scented varieties that can be picked and added to salads.

Then there are my go-to veggie garden flowers: poached egg plant or Limnanthes douglasii, calendula, sweet, sweet alyssum, and marigolds. Pop in these fellas here and there and you’ll up swell the ranks of your gardening allies and have them on hand… right here, where you need them!

marigold-companion-planting-pest-control

5. Use Natural Remedies

Cutworms can be deterred in a number of ways. When planting in rows or broadcasting, the addition of crushed eggshells on top of the ground makes it hard for their soft bodies to get around. When transplanting varieties into the garden, place a cutworm collar on the plant. Ideally, you want to put it an inch above the ground and an inch below (see photo). This makes it impossible for the cutworm to bite into the plants.

cutworm-collar-get-rid-of-pests

Japanese beetles are often a big problem. However, they can’t fly when it is cool, so they are easy to knock into a cup of water early in the morning or late in the evening. We bring them down to the chickens, who eat them with glee. If you don’t have chickens, a dab of dishwashing liquid in the water will also kill them.

The cucumber beetle was a problem for me one year. A friend and soil specialist said that it was an indication of a potassium deficiency. I added greensand to the cucumber bed in subsequent years and haven’t seen this beetle since. This same soil specialist also clearly states that if we give our plants everything that they need, the insects won’t be able to eat them because the sugars will be too high for them to digest.

6. Use Organic Sprays

If you have an infestation that you’re determined to be rid of, the final option is to spray using an organic, natural pesticide. Just hearing the word ‘spray’ makes us wince, and this really should be the very last option because any spray – even a ‘natural’ spray – is going to have potential side effects and may impact non-target species.

Suitable sprays include ones made with pure, cold-pressed neem oil, pyrethrin extract, Spinosad or BT, which uses the bacteria Bacillus thuringiensis. BT is especially effective against caterpillars – like those that munch on our brassicas, while others like Spinosad or pyrethrin extract are broader spectrum, which just means they tackle a wide range of pests.

Another, very simple spray can be made by just adding about a teaspoon of dish soap or washing-up liquid to about a pint or half-liter of water. Give it a good shake then use this as a contact spray where infestations are very concentrated. Liquid soap isn’t great for the garden, so please, only use it in limited amounts as a kind of break-glass-in-case-of-emergency solution.

Whatever you decide to use, please, please avoid spraying during the day when other beneficial bugs are about. Wait until the evening – till dusk – when pollinating insects and other beneficials are less likely to be about. Spray on a still evening if possible, so it doesn’t blow about, and be as targeted as you can, so you’re not just spraying willy-nilly.

We rarely use sprays, preferring other methods like barriers, beneficial bugs and variety selection to dodge the worst of the pests. If you have a longer growing season, you could also look to grow crops either side of the main danger period for their pests – for example, grow brassicas from autumn to late spring when butterflies aren’t around so much.

With the decline in bee and butterfly populations, it would behoove us to look carefully at potential bug problems before dowsing everything with poison. Explore this list of beneficial insects to see which insects you can keep around to help you control pests. 

The chemicals we often use to get rid of pests are not very good for us either. Let’s leave a clean planet to our children and grandchildren instead. 

About The Author

Celeste Longacre

Celeste is The Old Farmer's Almanac astrologer. She has also been growing virtually all of her family’s vegetables for the entire year for over 30 years. Read More from Celeste Longacre

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