Saturday, 6 July 2019

Not quite gardening without insecticides and fungicides


In Bolton Percy churchyard for forty years I never used fertiliser, fungicide or slug killer but did use an insecticide once
My college lectures were on very diverse topics to quite separate groups of students. Some thought me a green eyed ecologist and others a raving chemical lunatic. How could that be?
In forty years managing Bolton Percy cemetery garden I only sprayed once against pest or disease. In contrast the garden would have not been created from an overgrown wilderness and maintained without the herbicide glyphosate. 
Today I have been called back by the wonderful team who now maintain the churchyard garden (You must drop in and see it if you are ever in the area - it is always open and free). I had more or less hung up my boots but Jackie reported they just cannot keep on top of the weeds. Please could I come back and spray? I am going today (written in May).


You can buy iron sulphate as a fertiliser relatively cheaply. If sold as a pesticide (in this case a mosskiller) it's rather expensive
I want today to discuss whether gardeners can manage without pest and disease control chemicals. I won’t have enough time to explain why farmers and growers cannot. 
In my own garden I sometimes use slug killer and regret that proper Provado is no longer available to control meally bug on my indoor orchids. I did eliminate Cathi’s woolly aphid on her apples with 'gentle' household chemical (safety not always a given) and pruning and scrubbing.

Now four years later the woolly aphid has never returned
In my own garden of thousands of ornamentals and not inconsequential fruits and vegetables I hardly use any plant protection chemicals at all - other than herbicides, iron sulphate as a mossklller and for my greenhouse glass cleaning fluid.

You CAN control box caterpillar with a forceful caterpillar-killer spray into the bush from a knapsack sprayer if it is spotted at the very beginning
I would on the other hand chemically troubleshoot without hesitation if such as the now notorious pest box-killer caterpillar should pay me a visit. (Except I don’t grow box - it smells too much like pee).
How to manage with little pesticide usage
When you examine lists of pest and diseases for every plant you grow it is frightening. The good news is that health is the norm and most will never appear or are of little significance. When you have a large and varied mixed planting, natural balances develop between pests and their predators and for example birds and insects will devour most of the aphids. Don’t disrupt things at first sighting by plastering  with chemicals.
The flaw in this argument is that sometimes a timely intervention such as nipping out your broad bean tops, pruning away a few tips of infested shrubs or a mere squash with a finger will solve a later problem. Or even a well timed spray - you just need to know.

If you grow your plants well you will have less pest and disease. Some gardeners are natural growers. They know  how to manage their plants. They plant in the right place and at the right time, water when needed, are alert to natural stresses and avoid creating their own. It’s not just geriatric experience, some of the best gardeners are young ones. I suggest healthy plants are more resistant to pest and disease.
And yet again their are serious exceptions. Tell it to the cabbage white caterpillar or brassica whitefly, they will still suck or munch away. 

Some diseases and pests such as lupin aphid are so virulent they can destroy their host plant however well it is grown. Just don't grow them!
Although I advocate the merits of mixed planting I do not recommend formal companion planting. Often based on false assumptions or weak plant interactions they are  rarely effective.

Aster novae-angliae is resistant to powdery mildew
One of the best ways to avoid plant pathogens is to grow plants that are resistant. Take michaelmas daisies. Many are susceptible to powdery mildew and that includes some of the most tempting new ones in the garden centre - so clean, fresh and glowing under temporary fungicide protection. Aster amellus and Aster novae anglae do not get mildew at all.

I was sucked in to a purchase of this fungicide protected aster last year. This year I am not optimistic
An important plank in the complete absence of such as glasshouse white fly, red spider mite, scale insect and meally bug from my garden is zero tolerance. If it should appear or threaten on purchased plants they are thrown away! For fear of clubroot I would never plant brassica plants grown in someone else's soil. (I have not made friends this way by refusing kind offerings). It’s called isolation and works very well. 
(Nor should you accept a herbaceous perennial infested with your friend’s ground elder). 
Do not overwinter whitefly on some half dead unwanted pelergonium left in a warm corner. For me it helps that both my greenhouses are unheated and any whitefly  or glasshouse red spider mite would freeze. (I have not suffered greenhouse whitefly - as distinct from brassica whitefly - in twenty years, nor red spider mite)

Does ‘no dig’ help reduce pest and disease?
I often wonder when I hear regular cultivators so regularly holler about soil grubs and infections. Things like flee beetle I never see. I wonder how might fluffed up soil provide a suitable pest environment and how many many pest predators cultivation deters. What are the implications of all that shredded mycorrhiza? What too are the implications of roots damaged by digging?
Of course I argue that minimum cultivation makes for healthy plants.

My top ten cultural controls
Such tricks of the trade avoid use of chemicals or in a few cases make them more efficient or less of a rolling blunderbuss. I do not personally use biological controls where pest predators and parasites are bought in. It is sometimes immensely important in commercial horticulture but for many amateurs it is an expensive (and unnatural) sop. 
Don't confuse artificial predator/parasite introduction with doing everything possible to enhance natural invasion by such as ladybirds, ground beetles and hover fly. Nor those wonderful mammals and birds that gobble aphids and slugs

1. Physical barriers such as fleece. I am particularly keen on environmesh for carrots. It can be reused every year. It is not only carrots that might be protected from winged thugs and thieves. On brassicas it will keep off pigeons, cabbage white caterpillars and brassica root fly.

2. As mentioned resistant plants. Heritage tomatoes might for you be quite wonderful. Give me modern F1 hybrid tomato seed which has been bred with all manor of resistance. They taste better too if you choose such as Albenga and Sweet Million

3. Avoid creating disease prone atmospheres such as early season heating of greenhouses when light levels are poor

4. On the above theme ensure plants have sufficient light both inside and out. Optimum levels will vary with the nature of the plant

Who would believe drought stress and heat would make rhubarb vulnerable to this leaf curling pest?
5. Do not create excessive humidity by such as covering seed trays with plastic - ugh

6. You would be surprised at the rewards of skilled ventilation in growing structures

7. Sometimes aphids accumulate early around plant growing points. Just snipping the worse ones out will restore control to its natural predators.


Last year I completely halted an infection of black fly on my dahlias by snipping out several infected shoots. I looked hard this year to just find this one
8. Avoiding drought or water logging works wonders

9. In very small gardens just squash pests or hose them away

10. Many gardeners find isolation by growing in pots hides hostas away from the slugs. I find quite a few plants get started better in tubs rather than in open ground. Difficult shrubs such as cut leaf maples (watering, wind and wilts) and small hollies (rabbits love them) are good examples. Enjoy outdoor display for a year or two before popping them in.

And what about my escapade with insecticide in Bolton Percy churchyard…….?

In the early days I found drought and shade tolerant Solomon’s seal suitable for difficult corners. One evening I found a precious clump hosting the dreaded sawfly caterpillars and knew if left they would next year take over the churchyard.
There were just a hundred or so caterpillars and rather than squash them I hand pulled them and flung them far away over my shoulder. After all they would only survive on the said host.
I came back an hour later to find if I had missed any. They had all returned and some were still climbing.
I rushed home and got a hand sprayer. 
I still feel guilty at killing those itinerant caterpillars.
PS I now just live with the defoliation of Solomon's Seal by this caterpillar. Although unsightly when skeletonised I just trim them back with my strimmer. By July I have already had the pleasure of their Spring flowers and foliage. They do not suffer in their next year performance. 
I have a vague theory that it is not in their interest to defend themselves after flowering and the turning of their tough tissues to mush by devouring caterpillars recycles the nutrients.
My variegated Solomon is admired every year. Now in July I have finished off the job done by the sawfly caterpillars

Links
I described how to use slug pellets safely

First of two posts describing my encounter with box caterpillar in France

My previous attempt at describing cultural control

My encounter with Cathi's woolly aphid

My very early posts were so different

I found this discoloration on Choisya ternata 'Sundance'. Was it die back or disease or a sport? Should I prune it out or propagate it?

I just left it alone

11 comments:

  1. Funny how fashionable it is to have pollinator plants, and do our bit for the bees and the butterflies, but heaven forbid that any invertebrates want to dine on the plants themselves. Like you, I don't mind seeing some damage, as long as the plant survives.
    We have slugs by the thousand, and a few snails, and unfortunately if they target a new plant it often doesn't survive. There isn't much point in putting up a fight, they always win in the end. I wish there was a nursery that supplied slug proof plants, as I would be their best customer. Trial and error results in a lot of expensive slug dinners!

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    1. Sounds if your site is a wet one, or you have very high rainfall Sarah.
      I find hardly any of my plants get slug damage - and I only use pellets on the hostas (well Brenda doesa

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    2. Sorry I got called away whilst answering your post Sarah.
      I think I probably overlook slug damage by fretting about the rabbit damage.
      Not growing veg these days I am not planting much soft material which so susceptable to slugs. And as you say I don't worry about things so much!
      Hope your garden is thriving despite the slugs and snails

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  2. We find the wool pellets deter slugs but they ate expensive so we use them selectively.

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    1. Slugs are ovinophobic...



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    2. This is what it says on the bucket
      Slug Gone wool slug pellets are composed of 100% natural materials including phosphorous, nitrogen and potassium. As soon as water is added the fibres swell to form a barrier or insulation blanket. When slugs climb onto the fibres it irritates the foot and causes it to seek easier feeding elsewhere. We have used poodle wool with similar effect but didn’t make pellets so it was messier.

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    3. I haven't tried wool pellets. Do the birds take them or chuck them about? I have tried coffee grounds (works slightly for a day or two), garlic spray (ditto), beer traps (catches a few), bran (works quite well as a decoy, but attracted mice) and going out after 10pm with a torch. It was the last one that made me realise I was fighting a losing battle. By the time I'd gone around the garden the first plant was under siege again.
      RHS didn't find wool very useful, but perhaps a hungry slug will do anything for a lettuce!
      http://press.rhs.org.uk/RHS-Science-and-Advice/Press-releases/RHS-slug-study-busts-home-remedy-myths.aspx

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    4. ovinophobia - irrational fear of sheep - you girls are having me on!

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    5. As In that immortal phrase 'you cannot be serious'

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    6. Hey, I never said that - don’t blame me. The birds don’t touch them.

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