Pest Prevention

Whilst we can do a lot to keep pests off our veggies in the safety of the polytunnel, when it comes to our outdoor crops it gets a bit trickier. As all gardeners know only too well, the damage caused by pests can be devastating, sometimes destroying a whole crop in one fell swoop.

So we’ve done a bit of research and put together a cheat sheet of everything we have learnt and what we are doing to keep our plot pest free so you can benefit too.

Hated by gardeners universally these slimy lumberjacks can take down a whole chilli plant in one night by selfishly chomping through the main stem. Fortunately we have a multipronged attack plan!
Firstly our natural deterrents:
Eggshells around the base of the plants will ensure a scratchy journey for the slug who will probably give up and look for less painful to reach treats.
Mint will deter slugs so we have some growing near the doors and around our outdoor crops. Make sure it’s potted or well contained though as it will easily spread.
We also have slug traps dotted throughout the tunnel. These are made from the bottom half of a plastic bottle, partially sunk into the ground and filled with beer/lager. The slugs are attracted to the lager, climb in and then cannot get out and drown. (*evil laugh*)

If all that doesn’t sort your problem then the last defence against the slugs is some conservation slug pellets, as these will kill off anything that dares to slime its way onto your patch! BUT make sure they are conservation grade pellets like ours so none of the stuff in them will harm any secondary consumers such as hedgehogs and frogs.
Which brings me to thanking Freddo and Freddette, our current resident amphibians who we spotted in a shady corner of our tunnel, guarding the courgettes. If you can attract predators such as frogs and hedgehogs to your garden, they will do half the pest control for you!
Other options which we haven’t tried yet are:
Copper tape – A natural repellent you can stick around doorways/plantpots which is good for indoor/patio plants but a bit pricey so probably just an option to be used for your favourite flowers.
Sharp sand – This works in the same scratchy way as the eggshells mentioned earlier.
Pine needles – Again, Ouch! These make an uncomfortable journey for the slug but they will also alter the acidity of your soil so watch out how much and how often you use them, especially if you have any pH temperamental plants.

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Furry and Feathered Friends (or foes!)
Fencing off or covering your precious crops with netting is about the only way to keep these creatures away from your cabbages. Rather than spending hundreds (or thousands!) of pounds on a fruit cage from a garden centre, here’s what we managed to make good use of…

Bamboo canes
Old plastic bottles
Tent pegs
Netting (bought fairly cheaply by the square metre online)

We have an area approx. 11m2 and wanted to cover the whole thing with a giant cage we could work under, weeding and watering etc.
We used 2.5m bamboo canes buried approx. 50cm into the ground. (Making a pilot hole with a metal rod will make pushing them in easier). These were spaced at 1m intervals around the perimeter and 2m intervals inside for support.
On top of each bamboo cane place an upturned plastic bottle, the bigger the better, as these will hold the netting over your poles.
Then throw the netting over the top and pull taut. (You might want to ask some friends to help with this)
Secure each side with tent pegs at 1m intervals. (This may take a bit of to and fro, two people working on opposite sides make it much easier)

If you are creating a smaller cage, you won’t need to bury the canes quite so deep but if you are on a particularly exposed/windy site we would also recommend some U shaped pegs rather than a standard tent pegs. They are available quite cheaply online as astro turf/ground cover pegs and will be a more secure fastening.

TIP: If you are considering using this type of cage in your garden and think it will look a bit unsightly with all those bottles bobbing around try to collect lots of the same type of bottle or paint the bottles with fun colours/patterns. I’m sure most of you have a few tester pots knocking around in the shed that need using and this is a great activity to get the kids involved with the garden. The bright colours may even attract some pollinators to your plot!


Creepy Crawlies
So what else will plague British gardens this summer? The list is endless but the main ones we think our crops will attract are aphids and caterpillars and we want to keep them and any other hungry blighters from getting their tiny teeth into our veg!

One trick we are very keen to utilize is companion planting. This is an organic method of repelling certain pests and/or attracting predators to the garden by growing certain plants in close proximity to each other.

Companion Plants we hope will protect our plot:
– These really brighten up the polytunnel with their cheerful blooms but they serve a much more important purpose. Predatory hoverflies like the look of them too and will guard nearby plants against attacking pests. The scent of French Marigolds will also deter the tomato munching aphids as well as cabbage maggots (who love all brassicas), and asparagus beetles (who obviously love asparagus).

hoverfly on marigold
A hoverfly on our English marigolds by the polytunnel doors

Basil – Not only does basil help liven up a tomato soup, this herb complements your tomato plants from the get go. Growing basil among your tomatoes will help prevent whitefly, thunder flies (thrips), hornworm, aphids and also acts as a natural fungicide. This magical pairing is also said to boost the yield of tomatoes and improve the flavour of fruits. Bonus!

tomato truss basil and marigolds
Stripy tomatoes, guarded by French Marigolds and Basil

Nasturtiums – These are a great sacrificial plant and Cabbage White caterpillars love them! Simply put a pot of them near your cabbages, wait until they have a load of creepy crawlies on them and then chuck the whole plant in the compost, pests and all. Job done.

Peppermint – A few leaves of peppermint ripped up and scattered about will soon have any ants marching off your turf as well as repelling the kale and cabbage munching ‘flea beetle’. We have planted peppermint (in a pot!) near the entrances of our tunnel so it can both deter them entering and be a source for fresh leaves to be used elsewhere. Although a lot of those tasty tips end up in my teacup!

Chives – These fast growing herbs will deter aphids and make a great dip for summer BBQs too. The flowers are edible as well so when those lovely purple buds appear, pop them on your canapé trays or in the salad.

Strong smelling plants such as Lavender or Coriander – these will attract lacewings and ladybugs to your plot, which in turn will create larvae who eat enormous amounts of aphids! Lavender planted around the edge of your plot will also deter pests such as carrot fly as they can’t smell the carrots through the lavender.

lady bug larvae
Lady bug larvae – very good at eating aphids.


As always, we are happy to answer any questions about our methods, if you have tried any of these or have some of your own, please leave them below in the comments.

Theo and Pippa


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