Last week I attended a talk by the delightful and entertaining Paul West, from River Cottage Australia, as part of the Sydney's Writers' Festival. He mentioned some of the non-toxic strategies he uses to outwit pests that attack his vegetable garden. Having heard lots of great tips readers had for non-toxic weed control in response to last week's blog, I decided to turn my attention this week to non-toxic organic solutions to garden pests and diseases. Chemical sprays are scary and kill good insects as well as bad ones; and who really wants to eat home-grown food that has been sprayed with them?
One of Paul's favourites is an 'exclusion' method, mainly for his Brassica vegetables (such as cabbages, broccoli etc) that are targeted by the white cabbage moth - the caterpillars of which can destroy the vegetables. Fine netting is tented over the crops in a way that precludes the insects from getting to the crops, but still allowing sun, air and water to get through. Though most of my vegies are grown in tubs, I have used the same approach for rocket and kale, both martyrs to the white cabbage moth, as they are also in the Brassica family. I created large wooden frames, rather like playpens, over which I stapled fine netting. The vegie tubs are placed inside, protected from pests. I also place my tubs of mint and basil inside the frame, as in recent years, I have a plague proportions of the horrid flea beetle, which is attracted to members of the Lamiaceae family such as these herbs (also all my Salvia plants) and disfigures the foliage quickly and ruthlessly. It is possible to buy kits to make a tunnel with netting that can be placed over tubs or garden beds, or else simply throw a length of fine netting over crops. This netting method is only suited to crops that don't need to be pollinated to set fruit - because bees and other 'good' insects are excluded along with the baddies. However, exclusion can also be practised after crops have been formed, and can be used - for example - to prevent fruit fly in figs and stone fruit, by putting bags or sleeves over single fruit or bunches of them.
Snails are another annoying garden pest - and these days many of us feel wary of using snail pellets, because they can present a hazard to other garden creatures that eat the snails killed by the poison. My father's method (circa 1965) was to pay his four daughters to find and kill snails in a bucket of salt - we were paid 1 cent for every 10 snails. I think that modern children would probably expect a higher salary than that but the scheme worked with gullible us! Other tactics can include surrounding vulnerable seedlings with crushed eggshells or grit; or creating beer traps from jam jars half-filled with beer and sunk into the soil. I have also used coffee grounds around seedlings, having read that coffee is lethal to slugs and snails. Copper tape made into collars around seedlings and pots are also supposed to be useful - like an electric fence when the snail touches the copper! It is possible to buy a product based on copper that can be sprayed around plants (and even on letterboxes, for those of us who have had our snail mail actually eaten by snails!) that creates a long-lasting barrier - I haven't tried this myself but it sounds intriguing. There are also now snail baits based on ferric phosphate, which breaks down to a harmless soil nutrient, and don't contain the scary traditional chemicals.
I use white oil a lot for scale, aphids, mealy bugs and caterpillars. It is available commercially or you can apparently make your own using vegetable oil and dishwashing liquid diluted with water. It basically suffocates the pests. It is important to only spray white oil when the weather is cool. If used in hot weather, it can be detrimental to the leaves. I have never tried chilli or garlic sprays for chewing and sucking insects but they are said to be useful. Adding a little vegetable oil and dishwashing liquid helps the mixture to stick onto the foliage.
For diseases, bicarb soda (2 teaspoons mixed with 1 litre of water and 1/4 teaspoon each of vegetable oil and dishwashing liquid) is said to combat fungal diseases such as black spot, rust and powdery mildew. My main problem with plant disease is rust on Canna and daylilies. I have heard that an application of potash is helpful in reducing rust, so I will try that one day. My current solution to the problem is simply to cut all the leaves off at this time of year and put them in the green Otto bin!
I would love to hear about organic methods you use in your garden!
The charm of vintage gardening books
28 Feb 21
A trip back in time
21 Feb 21
Cane-stemmed Begonia cultivars are summer stars for foliage and flower power in Sydney gardens.
14 Feb 21
There are some unusual flowers on my grasses now.
07 Feb 21
These plants bloom for many months in my garden - and some are in flower all year!
31 Jan 21
Many scented flowers are in bloom now.