Wednesday 26 August 2015

Control of box caterpillar

A defoliated box hedge in France.
Healthy last year all the box hedges are devastated. Note all the other plants are completely unaffected
News filtered home in May that Peter's garden box hedge was looking sick. My first thought was that it was the dreaded box fungus disease known as box blight. Normally thought to be the kiss of death to buxus in a garden, research on the net suggested that repeated spraying with fungicide might bring a revival. Probably not for Peter.

It was therefore good news when in June we heard the hedge was being defoliated by caterpillars! Good news in that caterpillars can be killed relatively easily by a caterpillar spray. I am not familiar with popular French pesticides but informed Brenda's son that many common insecticides are systemic and he should not use them as they are more effective against sucking insects such as aphids rather than biters. This is particularly true on woody plants. I suggested he might seek out a spray of Bacillus thuringiensis, an extremely effective biological control available in France but not in the UK.
In the event he bought a contact killer that killed the caterpillars within 24 hours. Pete needed a full fifteen litre knapsack sprayer to thoroughly drench his eighty meters of hedges. Unfortunately it was too late to reverse the damage and the hedge turned completely yellow and all the remaining uneaten leaves died.
I felt fairly certain that the culprit would be the ermine moth. It sounded to have all the classic symptoms with vast numbers of caterpillars devouring the leaves and producing copious webbing.

Peter later confessed that the more out of the way boxes had not been sprayed. Their hoped for recovery will take longer
I am now writing this in France at the end of July. We are here for a party and the hedge is yellow and brown! What a disaster! It is only the box that has died. Other hedge plants are completely unaffected even where growth intermingles.
I turned to the RHS website and found that it was not ermine moth but a pest newly reported in the UK specific to box and now dubbed the box caterpillar. It looks as if it might be a future problem at home in the UK. Here in Toulouse it is extremely hot in Summer. No surprise that hot London gardens are now starting to suffer.
The hedge is now weakly starting to sprout new green shoots.

Unfortunately this recovery is exceptional and most of the hedges are still completely brown
Optimistically I am hoping in the next few weeks it will green up again. For this to happen Peter must re-spray at the first sign of a new generation of caterpillars reappearing. I did today find half a dozen caterpillars he had missed. It was enough to just squash them.
It is extremely important that in late Spring next year he keeps his eyes peeled and at the very first sign of caterpillars emerging from within the protection of leaves webbed together he resprays. It is likely the hedge will survive being defoliated once, but twice I don't know.
I have done all that can be done at the moment. In the more obvious places I have brushed off some of the dead leaves that still clung to the plant. Not only is the hedge visually improved exposing the few delicate new shoots it might help in a very small way to speed recovery because the new leaves are more open to sunshine. I noticed some of the twigs contain chlorophyll and this will enable them to photosynthesise.

Green twigs have a small photosynthetic capacity
I have emphasised to Peter that unless the hedge improves substantially he should not clip any new green shoots this year.

Three days later and already a change of plan! The new shoots are coming quite quickly in this warm Summer weather helped no doubt by Brenda's generous irrigation. Unfortunately more caterpillars are apparent. No doubt some that Peter missed (although I now read that there can be three generations a year). I was going to spot spray but decided it would be wise to spray all the hedges again.
I checked on his spray. It was delta methrin. A very safe and effective spray. Chemically it is related to natural pyrethrum. Why it's almost organic! I was quite disappointed when I saw he had spent twenty five euros on a small 250ml bottle. I quickly changed my mind. We were in France after all. He had gone to his rural supplier - he has two horses - and bought professional product. I needed to dilute 10ml for a full fifteen litre knapsack sprayer. A cost of one euro!

I only needed 10ml of this deltamethrin to make up a full sprayer
It was great that he had a professional Berthoud sprayer that I had previously ordered, cost £130, for the spraying of weeds I do on our visits. I think in my life I must have emptied fifteen thousand full knapsacks spraying weeds but I have never sprayed a hedge! What a delight not to have to bend down. With the long lance it was very easy to spray and on the taller hedges to reach the top. Fortunately his nozzle was a cone one designed for such spraying.

The long hose and lance enabled very easy and rapid spraying
There was more box hedge than I thought with a total surface area of seven hundred square meters. Unlike Peter I emptied two knapsack sprayers. It took nearly two hours.
Peter might have to re-spray later this year, or perhaps not. He will certainly need to spray next Spring or early Summer. (It later emerged that Peter had only sprayed half the hedges – those in prominent places hence the discrepancy in the amount of spray needed. These hedges are regenerating much more slowly!)

I have mentioned before gardeners who falsely economize buying cheap amateur sprayers. The large area of mature box hedging is worth infinitely more than the cost of the sprayer. Without a decent sprayer that is safe, accurate and rapid to use I doubt if the hedges would be booked for future healthy survival.

Organic control?
What about folk who do not use pesticides?
I rarely spray insecticide or fungicide in the ornamental garden but this was force majeur. There were far too many caterpillars for hand picking. How about biological control?

A packet of biological powder
A very effective biological control is Bacillus thuringiensis. For reasons I fail to understand it is unavailable in the UK. It is a bacterial disease of caterpillars and the packeted powder in addition to millions of bacterial spores contains the disease's natural toxins that immediately kill caterpillars on contact. They recoil on contact and immediately die! The disease is completely harmless to other than caterpillars and usually maintains its infection of future caterpillar generations for the rest of the season. It is actually applied as a spray. As mentioned Peter can chose to use it in France as it is sold at the amateur store.
The RHS site lamely and unconvincingly mentions a parasitic nematode. Is this practical or just pie in the sky? Why is one biological control approved and not a better one?
I wondered if the caterpillars might be washed off with a forceful hose. If so would they climb back to return? When I picked off a caterpillar to get a picture it jerked away on what appeared to be an immediately spun thread. As I watched it, it gently threaded its way back. I doubt success but for a no-chemical gardener washing off might be worth trying.
By the time I got out my camera the caterpillar was almost returned

And a parallel story.

In my first teaching post, Lancashire Agricultural College provided a garden advisory service. For several years there were numerous phone calls every Spring when ermine moth caterpillars ravaged local hawthorn hedges. It is etched on my heart the chemical control we recommended. It is not available now.
The fascinating thing was that the phone calls in the first year were very close to Preston. Each year the radius of infection increased by ten miles. I left four years later and moved to York. Ermine moth should have arrived there by now!
I jest, nature does not work like this. Numbers of pests might explode in population for several years but eventually a balance is restored. Pests and parasites increase in numbers and maybe change their habits of feeding. Sources of nutrition might be depleted, vagaries of the weather might bring massive destruction and geographical barriers might get in the way.
I might mention that Peter's box caterpillar similarly appeared out of nowhere with no apparent infection in the previous year.
I wonder what will happen to the box caterpillar if it really establishes at home in the UK.

A box hedge in a London park. Box caterpillar has not yet arrived in Colliers Wood. I hope it never will.

The culprit and the damage it causes

A hungry box caterpillar eating a new green shoot. Note the webbing and the completely eaten portions of leaf

I suspect that if I left the caterpillar here on the ground it would find its way home

A typical skeletonized leaf. Smaller caterpillars have not completely eaten through the epidermis

We only found a single pupae. Does this mean that Peter caught most of the caterpillars in time?

There was lots of webbing
It was interesting that all the original foliage was completely killed even if not obviously eaten. The whole plant had gone yellow, then the leaves dead and brown. I wondered whether this was the plants’ defence mechanism to deprive the caterpillars of green food or perhaps in contrast it was the result of a toxin that made the leaf more palatable. Whatever the explanation it was an absolute mess

Link to what happened over the next two years

Tuesday 25 August 2015

Horse chestnut leaf miner

Peter’s pests
Horse chestnut leaf miner
At the beginning of July we visited Peter’s family in France. He had two alien invaders. Both now also found in the UK, they are recent arrivals. The cause of greatest concern was that of box caterpillar which I will post on tomorrow.

A contrast between Autumn tints and early Summer growth.

Compared with box caterpillar his horse chestnut leaf miner was a minor distraction! Perhaps it ought not to have been because in the UK it has been the matter of some concern as from first sightings in London in 2002 it has spread almost everywhere. It has been subject of ‘citizen research’ where gardeners and schools have participated in recording its spread.
Please forgive me if I observe that in the UK an alien invader has been attacked by an alien invader. To me the irony is that the horse chestnut is not native to the UK. It was introduced from the Balkans four hundred years ago and of course has spread everywhere. Most people now regard it as native. How long must an immigrant stay to be thought one of our own? Most of you will know that the concept of alien plants is foreign to me!

Horse chestnut premature leaf fall 

On the first of July Peter’s yard looked as if it was Autumn. The ground was covered with golden brown leaves from his two large trees. The trees were almost completely denuded. There will be no conkers this year.

Leaf miners on chestnut are small moth-caterpillars that tunnel under the leaf surface. In some cases thousands have been recorded on a single leaf. The good news from intensive investigation is that they do little long term harm to the tree and each year fresh new leaves appear in Spring. I find it difficult to believe that loss of Summer photosynthesis will do no harm at all. There must be some loss of vigour? Not necessarily a bad thing.
I find it of great interest that some plants such as Solomons’s Seal can be completely defoliated – in that case by sawfly – and suffer zero long term harm. I wonder in terms of natural selection what’s going on!

Autumn in July

Although the pest is primarily one of horse chestnut other members of the same genus aesculus can be infected – but not all. It has been recorded on sycamores growing near to large primary infection on chestnuts but would seem to be of no present concern.

The citizen recordings seem to show that it takes three or four years for an infection to build up to a maximum. If the maximum is as much as that on Peter’s trees that’s a lot.
It is impractical to spray large horse chestnut trees. The citizen research observed that the rate of establishment of natural predators and parasites at the present time is not very significant. Blue tits do make a very small contribution.

The caterpillar tit-bits might be very tasty but bluetits do not provide control

If there are no near horse chestnuts in your neighbourhood it might reduce future infections on your tree if fallen leaves are swept up and burned or covered and composted.

I discuss alien invaders here
About the citizen science horse chestnut project

Wednesday 19 August 2015

Seaton Ross village plot in July

Although garden seats are not for me, whenever anyone passes as they walk to the village shop they give me a smile, a friendly wave or a jovial comment
We had lived in the village for several years when a piece in the village magazine appealed for help with various communal activities. The request to which I might contribute was the one asking for help growing ‘wild flowers’ and I duly volunteered.
That’s when we first met Peggy who we privately call ‘Mrs Seaton Ross’. At that time any good works in the village and indeed any village activity at all was inspired, worked and organized by that lovely old lady. I wondered what the project might involve and fantasized as to whether I might grow UK wild flowers from any public source or restrict myself to just those of East Yorkshire provenance.
It was then that I learnt about the village plot. About an acre it had been the site of two cottages which I can only think of as ‘alms houses’ for the poor. How such a plot came to be owned by the village, I don’t really know. Only the hard foundations of the cottages remain. Several very old apple trees survive. The plot  when viewed in July 2007 had become the most luxuriant stand of ground elder you can imagine.

It transpired that what Peggy really wanted was someone to clear the plot and plant some flowers! There had been half hearted attempts before but without glyphosate they had always failed. Someone had tried spraying but had merely succeeded in providing a haven for the ground elder!
It was with a mixture of pleasure and disappointment that I realized that what Peggy wanted was nothing about growing wild flowers but more a matter of getting rid of unwanted ones. Many wild flowers are specific to special ecological niches and my original vision was probably unachievable. En passant I might add that with my methods a great number of wild flowers do establish in my gardens.

That was eight years ago. Peggy was still fit enough to cut the Hawthorn hedge, two cuts a year, for the first four years. A lovely hermaphrodite holly berried each year but had blown horizontal and new trunks were making a large thicket. Peter brought his chain saw and there is now a nice tall single stem tree. Peggy sowed grass under the fruit trees much to my consternation. She had the silly idea that it would provide a route for village children to see the chickens in the garden beyond! I never saw a child and the young man who kept the chickens left home. I love the grass now because it has provided a lovely ecological opportunity and it buffers the windfall fruits.
I won’t mention the unfortunate incident when for a season the grass was mown by sheep! The fruit has now recovered but it was a very close run thing. Now the grass is just cut once a year. Thank you two volunteers who have cut the grass and the kind gentleman who cut the hawthorn last year. I missed your help this time.
I maintain the plot in about three hours a month. It is easier to manage than my cemetery gardens because I can pop in when I go down to the village to visit the farm shop. ‘Little and often maintenance’ is much better than a huge infrequent crusade.
Last month I walked round with my camera. Warts and all here are the pictures.
All the agapanthus needs to thrive is a light position and weed free undisturbed soil

Hydrangea and hosta - I tend to forget the names of my cultivars. I do know the holly is the monoeccious self fertile cultivar Ilex ‘J C Van Tol’ which is covered with berries every Christmas

My hugelkultur heap gets mistaken for a rubbish dump. I can live with that but fret that people imagine the plants are discarded too. In another year it will look lovely...or perhaps the year after...

Although Peggy originally sowed a rye grass mixture (yuk) I have been bringing it round to a finer grass sward
The old cottage foundation is a good place for the seat. The rowan tree is self sown

The old trees still give delicious apples. I have made the mistake to tell everyone to help themselves - they belong to the village. Unfortunately last year there were none left for me

Several plants were lost in the wet winter two years ago when the adjacent blocked ditch overflowed. It did not harm these bog plants! 

Sometimes people give me plants that I cannot use at home

Honeysuckle seed was brought in by the birds and the climber now straddles the trunk of the old pear tree
The popular image of impatiens is as an alien invader. To me it is the delightful bee bum plant

Peggy was very keen to have a log pile as a home for the beetles

Piptanthus is a most undervalued yellow flowered shrub. Anyone can help themselves to these seeds and grow it at home 

Phlox takes two or three years to achieve its finest on our sandy soil

Ten years ago the ground elder infiltrated the hedge right to the road. My fine fescue grass now gets regularly mown  by the council when they cut the grass verge on the otherside of the path. I worry each year that my daffodils will be beheaded too soon! Although I leave my hedge clippings on the surface of the plot I need to tidy them up here!
The notice board shows a map of the village

This fine birch sowed itself in the rubble ten years ago

In this post I described eliminating the groundelder. It is completely gone now!
In this post I mentioned  my effort at hugelkultur

Tuesday 11 August 2015

The glyphosate posts

 Review of past posts
A great supporter and former neighbour, professor John Taylor used to nag me that I ought to make a record of my naturalistic and labour saving methods in maintaining Bolton Percy cemetery.

My basic philosophy is that if I take care of the weeds the plants will grow themselves. Nature abhors a vacuum.
There is obviously more to it than this whether in a cemetery or in a garden. Not only does one need to know how to recognise and understand your plants but you need a speedy and effective way to control weeds. There are no good public accounts about how to use glyphosate in the way I do and one of the reasons I blog is to tell anyone who will listen!

Is this pretty ragwort a weed? It is classified as a noxious weed and is a problem that when dead this toxic plant is palatable to grazing animals. I do not allow it in my cemetery gardens. My normal strength glyphosate is not quite strong enough and at the end of my day I return to give it a second dose.

What my blog lacks at the moment is bringing my glyphosate posts coherently together.
Today I try to point a way through the thicket.
The thicket? If you don’t like using glyphosate this creeping thistle is quite vulnerable to mowing or strimming at this stage of growth
Summaries of past posts
In ‘batting for glyphosate’ I make out a case for using this herbicide. I have not changed my mind that for me it is very safe and effective. In my own case maintaining over six acres of mainly naturalistic gardens I could not garden without it. There is much doubting comment on the net about this wonderful material. I intend in the future to write a more forthright post as to why I think such comment is misguided and wrong.

In this post I make some introductory comments about some of the basics of using glyphosate. In particular I emphasize that for anyone with other than the smallest garden they ought to invest in a decent knapsack sprayer. A good knapsack with the appropriate nozzle can be much more accurate than even a hand sprayer. I use a yellow cone nozzle, rather than the type often advised in the literature written for farmers by agricultural engineers!

I ordered the cheaper Berthoud sprayer for delivery to Brendas’s son in France. It makes life much easier on my visits!
It has recently paid for itself several times over to kill a very large area of box caterpillar that had devastated his box hedges. (next post)

Gardeners invest huge amounts on items such as lawn mowers and other machinery but tend to buy a cheap knapsack which apart from being endlessly frustrating and inaccurate to use soon falls apart. A good professional sprayer will last ’for ever’. Myself as a frequent user who is very poor with machinery and to whom maintenance is a thing that other people do, get at least 2000 cycles of use before I think of getting a new one. Every ten years!
I am currently ordering an all singing and dancing Berthoud sprayer (illustrated in the link) for Jackie Giles who is one of the wonderful people now helping in Bolton Percy cemetery garden.  It now costs £165 already assembled. The cheaper Berthoud model (above) at about £130 is almost as good but I think you have to assemble it – so that cuts me out!
My advice to get a good sprayer for glyphosate is contradictory to my advice when spraying your cabbages or even a short hedge with insecticide when I suggest you use a very cheap two quid hand sprayer.

Shield for spray nozzle illustrated on a bottle of french glyphosate. I have never used one and never intend to!
In my post about buying glyphosate I made some very guarded comments about purchasing commercial glyphosate. I was more outspoken in last weeks post!

In this post I discussed a few points about mixing glyphosate and calculating the appropriate strength. I also wrote about spraying the over-grown village plot which was a field of ground elder spreading out under the hedge up to the public footpath and also onto neighbouring perimeter gardens. I was adamant that it was as important to eliminate the ground elder under the hedge as well as on the rest of the plot. I described how I do not spray such a plot walking in a straight line with my nozzle held at a steady height.
With my nozzle pointing downwards I more duck and weave adjusting my spray direction to the nature and contour of the patch that the nozzle hovers over.

This was a frivolous short post about brand names. It makes the important point that glyphosate is out of patent and anyone can manufacture it. Only Monsanto and any company with which they have shared the brand name can call it Roundup.
All forms of glyphosate are for practical purposes exactly the same but vary hugely in price and concentration.

All these french brands of glyphosate for practical purposes are exactly the same
In some respects a significant post that starts to tackle something that most gardeners and gardening writers shy away from - spraying amongst garden plants. Fraught with difficulties in inexperienced hands selectivity by directional spraying is perhaps best avoided by most people but without it I would find it impossible to maintain the large areas I do.
That is not to say that in most gardens there are not large weedy areas near to, but not intimate with garden plants that can easily and safely be sprayed. For example it is relatively easy to spray under a hedge or under shrubs and trees without damaging them.

Selectivity by timing is exemplified by spraying a weedy daffodil plot when the daffodils have died down dormant, or spraying couch in a herbaceous border when the herbaceous plants have completely died down.
The post also gives the traditional advice to get rid of perennial weeds before planting a new garden or garden feature.

This iris is not quite dormant but by carefully directing my nozzle down I eliminated the couch grass with a single spray in late November

Gardeners are sometimes confused because glyphosate is slower in Winter and won't kill perennial weeds that have gone dormant. It won't kill dormant garden plants either which is a huge advantage because it will kill still green weeds growing amongst them. In addition weeds mechanically controlled in Winter by such as hoeing will re-root in wet conditions whereas sprayed weeds will die.

This revolves around the fact that adverts for rival products to glyphosate portray it as slow. Good gardeners 'manage' their gardens and don't want a quick fix for the day. It is not slow to become inactive in the soil and enable replanting and will eliminate perennial weed better than any rival.

Glyphosate always gets the blame for any sick plants in a garden no matter that it may not be the cause. I review how to recognize damage and avoid it. This post ends with using glyphosate in a hand sprayer to eliminate convolvulus (bindweed).

You can hardly see the ceanothus under Steven’s bindweed! I sprayed it last July and the weed has not returned. There are just a few little corners in the garden where I had missed the odd bindweed and where a second treatment would be desirable!

This post is not strictly about glyphosate but about controlling coarse weeds in grassland

Not about glyphosate as such but about the benefits of minimum cultivations in limiting carbon dioxide pollution and efficiently producing food on a world wide scale. Glyphosate facilitates most no till or low till systems. I believe the world is a much better place for its existence.

In separate posts I write about how to use glyphosate to control these difficult weeds

There are many ways to control weeds. Here the ubiquitous epilobium needs yanking out. I would normally just throw them onto the ground but at this stage it will still set seed.

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