Sunday, 19 October 2014

Control of woolly aphid

Scrubbing  Cathi’s trunk

Being Cathi’s head gardener it is quite a responsibility and I now find I have fallen down on the job!

My normal attitude to pest and disease in the ornamental garden is not to see pathogens and expect natural predators and parasites to keep them under control. Where possible I choose resistant varieties and grow my plants well and in doing so, do not predispose them to sickness. It does not always work out that way!


I noticed this disgusting mess on Cathi’s lovely pendulous crab apple. It must have taken woolly aphid several years to create this state of affairs. Cathi get a new gardener! She had not noticed either! None gardeners don’t see these things until it’s too late.
Very messy trunk  If you brush against it the crushed aphid stains are like cochineal! 
If not brought under control, woolly aphid brings death and destruction. It usually starts with mild stress on a susceptible variety. I remember a client whose apple tree had light infections on straggly weak shoots at the base of the trunk. The tree probably suffered from drought and the base was heavily shaded. I would annually prune the woolly aphid away and the trees continued to thrive. 

From such little beginnings, if no action is taken, over the years the infection spreads to eventually take over the tree. Each year any initial stress is magnified as the aphid sucks life from the plant. Infection accelerates and the tree becomes a write off and eventually dead! It is very difficult to spray a large tree and I know no suitable pesticides available to amateurs that will penetrate the woolly protection and control the affliction. Systemic insecticides do not work well in woody plants so no help there either.

Aphids covered with waxy protective wool. A problem on bark and buds  it can also fly to leaves and fruit.
My initial reaction was that we would lose Cathi’s tree. On closer inspection it appeared that infection was still mainly at the base of the trunk and any woolly aphid aphid higher up in the tree was at the tips of the branches. The next day I returned with my secateurs, loppers and saw. I also brought a scrubber and a secret chemical weapon!

Kitchen scrubber, sponge, soapy water and whimsical weapon.


Control

The basis of control is to cut out severely infected woody branches and scrub the bark clean. There is no guarantee that you will catch all the aphid and prevent its return but if you remove potential re-infection it will be relatively easy to manage next year. Although physical control might be sufficient a little chemical help does not go amiss. A nice soapy mixture will do. Soap will aid penetration of the waxy wool and gum up the insect’s spiracles. As I selected a kitchen scrubber and squirted hand soap into a bowl of water, my eye caught Brenda’s ‘Ecover’, the squirty sweet smelling liquid cleaner she uses to clean round the kitchen. I looked at its analysis, 10% alcohol - they will die die happy - <5% none ionic surfactants, citric and  lactic acid and perfume. It’s made with ‘natural materials, why it is virtually organic!
There was no way such a mixture would be harmful to bark and even if I were to spray the odd leaf they were already going senescent and it would do them no harm.
The work of pruning and scrubbing and squirting took no more than an hour. How I did it  in mid September is shown in the pictures.

Oh what a mess. If you carelessly brush past the trunk you cover yourself with sticky pink goo!
Woolly aphid stimulates the production of swellings and galls. My first job was to severely prune away a few lower branches, twigs and galls

I wonder if I did not clear this debris away whether the aphid would produce winged generations to fly back into the tree. Better take no chances. I think Cathi’s hens had a feast before I moved them!


Fortunately much of the canopy was not infected. 


The scale-like nymphs can crawl to fruits and leaves. 
On Cathi’s tree most of this type of infection was near the tips of the branches and the twigs could easily be pruned away.  In some cases on lower branches I gave them a squirt of Ecover and where accessible gently scrubbed them!


After scrubbing the abnormal galls stimulated to grow by the aphid can be clearly seen. I hesitated whether to completely cut them away or just leave them. I compromised and just cut out the big ones!



Now a nicer looking tree. The adjacent red weeping malus is completely uninfected, and is evidently more resistant.
The cuts will NOT be painted.  I grimace  at the very thought!


Five weeks later in October the crab apples are colouring up nicely and will last beyond Christmas

A half-hearted disclaimer
I do not consider the serendipity factor of my use of Ecover on a whim as essential to the successful control of woolly aphid! My thought was that it’s wetting power might aid penetration of the soap. I admit I got carried away merely squirting with alcohol rich ecover on a few of the higher infected branches. I made little attempt a few days later to find the aphids I sprayed. Although no aphid is apparent now, for all I know there may be some very hilarious aphids hicoughing away in happy hibernation. At least when I had finished my hands have never been cleaner! Perhaps there is scope for a project next year.

Update June 1st 2015
Its back!
Cathi noticed her cat had some white fur. It had scratched itself on the tree. Gardeners often give up at this stage. That’s fatal. The infection is now much reduced but the trunk is going to need a few more scrubbings!
Woolly aphid hibernates at the base of the trunk and on woody roots in the ground. Young crawler nymphs re-emerge to re-infect the trunk. Later - if allowed to remain  - winged generations infect higher parts of the tree. Action is required now.

I repeated the scrubbing with soapy water carried to Cathi’s in the kitchen bowl. With the convenient long firm light kitchen pan brush it took no more than a quarter of an hour. Cathi now has a lovely sweet smelling tree. I wonder how soon before I have to pop over again.

The overall tree looks extremely healthy. The very close adjacent crab apple tree that has shown itself to be resistant to woolly aphid is still completely clear as is an eating apple ten yards away.

I rubbed off these young water-shoots on the trunk with my fingers

 
The aphids seem to gravitate to the edge of the galls
After a vigorous scrub
End of update

Further update mid October 2015
Victory proclaimed
It’s gone! I inspected very carefully and no woolly aphid could be seen. Not even in the top where at least some aphids must have escaped my attention. I expect where few pests were present natural control took over on the smaller upper branches.
As you can see the trunk is completely free but the previously raised woody galls remain but are no longer infected.

If you observed these healthy raised areas on the trunk you might wonder what they were.
The crab apples yet again brighten Cathi’s garden
Woolly aphid has been completely banished from Cathi’s garden
further update November 2016 I examined Cathi's tree for the first time this year. There is still no sign of woolly aphid returning
My holiday snaps
The very next day we went Italy to visit my son Tim who lives in Vico Equense on the Sorrento peninsula. What did we see but citrus trees infected with woolly aphid. Most of the orange tree roadside planting was in good shape but at the end  of the row it was so shady that every time I went back to take a picture, my camera flash activated. Such shade does not make for a happy tree, even shade tolerant citrus.

A holiday snap to text to my friends?


Obviously the aphid had been scrubbed away by Parks and Recreation. The galls are similar to those on the apple

A very unhappy tree in a dark garden in Sorrento

And a note about ipomoea

I recently wrote about the control of bindweed. I jested about killing bindweed in Folkestone and going home to my Morning Glory!

In Italy I was reminded what a weed ipomoea can be. Although only an annual see what it can do in a warm climate!

I found some real bindweed. In Italy in September it has almost died back from summer heat.  It would appear that it has a native predator and is not the same scourge as in England? 
I did not bother texting this picture home!

16 comments:

  1. Woolly aphid is a nuisance. One of my Camellias in the garden is prone to woolly aphid. I keep it under control by spraying and shrubbing with soapy water and spirit. When plants in the greenhouse show woolly aphids I touch them with a brush with undiluted spirit.

    ReplyDelete
    Replies
    1. Thanks for the information Janneke
      I have no experience with spirit, is it the pure form of alcohol which is not available over here? To us, spirit is paint thinner

      Delete
    2. Yes it is a pure kind of alcohol available in every super market, we use it for cleaning windows, to light the barbecue, and also as paint thinner.

      Delete
    3. I don't think we have it here in the pure form, its adulterated so we cannot drink it.
      I seem to recall that yours is pure enough to make up raspberry gin? Brenda has to use cheap gin as a base for raspberry or sloe gin.
      Wonder what would happen to a mealy bug if dabbed with gin?

      Delete
  2. I hate woolly aphid and mealy bugs which sometimes affect out old apple trees. My tool of choice for dealing with them is an old toothbrush as with that I can get into small nooks and crannies,

    I hate bindweed but have a lovely morning glory in the greenhouse - double standards? I do think bindweed is pretty flowering in wild hedgerow well away from my plants.

    ReplyDelete
  3. Poor you, mealy bug too! I can just see you brushing away!
    Yes I think bindweed is lovely in country hedgerows but not growing over clipped privet hedges!

    ReplyDelete
  4. Oh my, it seems we have both written about aphids this week, although not the same type of aphids :-) I haven’t been plagues by wolly aphids in my garden, but like Sue I have had mealy bugs, and I have successfully got rid of them, it’s a few years since last time I had them. My next door neighbour has bindweed in their garden and they do nothing to it, it creeps under the fence and I have to keep pulling it out but can never get to the source.

    Good job you did on the tree, I hope that was the end if the infestation as it is a lovely tree.
    If you head over to my blog you will see some other kind of interesting aphids, perhaps you have them in your garden? If you do, could you please let me know?

    ReplyDelete
    Replies
    1. Your post on your fascinating aphis is one of the most interesting I have read. Thank you for alerting me to it - I had noticed it on my alert to 'blogs I follow' and passed it over!
      I love your video - I hope it goes viral on u-tube.
      Its a wonderful example of a pest using the plants toxins to its advantage

      Delete
  5. As a student I spent one year in Britain. I had a room with access to a neglected garden (no one ever went in that garden). I did not know anything about gardening and had put strings to encouraged a large flower bindweed to grow on a brick wall. It looked beautiful with the large blossoms completely covering the whole wall!!! I had no clue what I was doing!
    Here we have two kinds of bindweeds one with large flowers (not common and not so invasive) and one with small flowers (which is just about impossible to get rid of).

    ReplyDelete
    Replies
    1. The innocent wisdom of youth!
      Interesting that I am getting more comments about bindweed than my original post. I think there might be a message there!

      Delete
  6. Excellent practical advice Roger, luckily I only get woolly beech aphid on my hedge so am able to cut out the affected parts, usually round the growing tips, as soon as I spot them. They were quite widespread last year but thankfully no sign this time round.

    ReplyDelete
    Replies
    1. yuk, horrible beech aphid!
      Glad it's gone Rick!

      Delete
  7. I'm not sure who's post made my skin crawl most, yours or Helene's Roger :)
    I've read on a few garden forums that they tend to recommend those 'eco' soaps for such things as they are far more organic that the run of the mill liquid soaps.
    I do hope your efforts are successful and Cathi has a very healthy tree next year.

    ReplyDelete
    Replies
    1. I think the wooly aphids are more messy but Helene's aphids fascinating and in their way quite beautiful! My skin perhaps crawls at squashing one and picking up all that toxin. I rub my face far too often! So much more toxic than any pesticide.

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  8. Try this to see if you have the same success as I have had.

    Go buy a bottle of Tesco anti+bac original multi surface cleaning spray.

    Don't worry about the anti bac part, the real trick is that it contains 5% nonionic surfactants and has a nice squirty jet and it wets right through the waxy wool the aphid protects itself with and drowns the aphid. Oh, and it is cheap...

    Just give a nice sharp squirt to each bit of 'wool'.

    Using this I have got about a 90% kill, going over the trunk a week later to just to polish off those that were missed by the first 'squirt'.

    Be careful though not to get it in your eyes - it stings like buggery...

    ReplyDelete
    Replies
    1. Very useful tip - and no scrubbing. If it returns again on Cathi's I will try it.
      It's common for manufacturers of chemicals to give a list of warnings. I like your style. Oh and does it smell nice?

      Delete

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