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 look like cochinealV

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.

Aphid covered with waxy protective wool. A problem on bark and buds it also flies 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 below

Oh what a mess!

If you carelessly brush past the trunk you cover yourself with a 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 away this debris whether the aphid would produce a winged generation to fly back and reinvade the tree. I did not take chances and removed them after Cathi's hens had had a feast

Fortunately most of the top canopy of the tree was not infected

The scale-like nymphs can crawl to fruits and leaves. On Cathi's tree most of this infection was near the tips of the branches and twigs and was easily pruned away. In some cases on densely leaved  lower branches I just gave them a squirt of Ecover and/or pruned them away

After scrubbing the abnormal galls stimulated by the aphid  can be clearly seen. I hesitated about cutting them away and compromised by just taking out the big ones

Now a nicer looking tree. The adjacent red weeping apple is completely uninfected and is evidently resistant.

Pruning cuts will NOT be painted. I blanch at the thought.

link to tree paint myth

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 1^st 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' at the base of the trunk with my fingers

The aphids have returned at 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

July 2018.This post has been rousing some interest - perhaps woolly aphid is bad this year? I rushed round to Cathi's tree to find it in lusty health.
Another bad pest seems to be enjoying this Summer, box caterpillar

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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 has been scrubbed away by Parks and Recreation

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 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!