Non-toxic solutions

Sunday, 24 May 2015

Garlic is often used in sprays to combat pests

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?

Netting cage to exclude pests

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 annoying pests

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.

New foliage of hellebores can be attacked by aphids

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.

Hydrangea macrophylla is prone to mildew

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!

Reader Comments

  • By ronda 3058 Monday, 25 May 2015

    Hi Diedre, I have found that snails are greatly reduced since I have been sprinkling coffee grounds around the garden-an added benefit is that all my acid loving plants are loving it and thriving! I don"t have the stomach to crush snails so if there are a few who have avoided the coffee grounds, I put them in a bucket and relocate them. The coffee grounds seem to be a good deterrent for snails. Like your "relocation of snail" option! Deirdre

  • By Ian 2519 Monday, 25 May 2015

    Hi Deirdre, I think pest oil has replaced white oil as the preferred option as it contains UV components which means it does not burn foliage. Chooks and blue tongue lizards the way to go to combat snails but since I don"t have either I use the crunch underfoot method, dreadful I know! Regards Ian Thanks for that clarification re pest oil. Good to know that it does not burn the foliage. Crunching the snails underfoot is somehow quite satisfying, I find. Deirdre

  • By margaret 2122 Monday, 25 May 2015

    I have had success in using Condy"s Crystals as a spray in the garden, as a fungicide, being effective against black spot, mildew and damping off with seedlings. It also seems to keep away slugs, grubs and chewing insects. I use it on my begonias, with great success. The potassium also makes the plants strong and healthy. It is safe to use, but can stain paving, etc. Coffee seems to deter slugs (I don"t have snalis) and the plants like it. I also scatter crushed eggshells around. Thanks for those tips, Margaret. I have not ever used Condy"s Crystals. Will try. Deirdre

  • By Sue T. 2566 Monday, 25 May 2015

    This year I grew three varieties of Kale and although the cabbage moth caterpillars attacked the cavalo nero they left the curly leaved varieties alone The caterpillars really like broccoli and on these my way of keeping some control is to go out every day and pick them off and squash them. Sue Thanks, Sue. Quite satisfying to squash them! Deirdre

  • By Lesa 2445 Monday, 25 May 2015

    We use milk spray on cucurbits to minimise powdery mildew. A slurp of full cream milk in a 500ml handsprayer or a teaspoon of cheap powdered milk in the same sized sprayer spray about once a week, or if you are like us-when we have time and think of it.. The bonus is that it seems to be a bit of a tonic to the health of the plants. We spray out the whole mix each time on any plants nearby and it seems to be a pick me up for anything. Lesa Thanks for this great tip, Lesa. Will try it on my poor Hydrangea. Deirdre

  • By JAN 2130 Monday, 25 May 2015

    A quick word of warning for those who grow bromeliads - don"t use any pest treatments which contain copper as it will kill them. Thanks for that warning, Jan. Deirdre

  • By DAVID 2068 Monday, 25 May 2015

    Cabbage moth caterpillars attack my Shanghai Pak Choi. Every few days I go around the garden with a pair of long tweezers to fetch them out of the "cup" of the plant where they hide. Just look for their poo, and sure enough there"ll be a caterpillar inside. Great idea with the tweezers, David! Deirdre

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