Woolly aphid aftermath on apple tree

[bazzaboy]

Last year one of my apple trees got infested with “woolly aphid” (sucks sap from under bark, protects itself by producing a covering that looks like cotton wool). I removed/reduced them with a fierce jet from a hosepipe (not 100% effective when tree in full leaf) followed by a soapy spray…. Winter has revealed the extent of the damage caused by the sap sucking, disfiguring woody corpuscles (see pic). Although currently dormant, woolly aphids evidently overwinter on the host tree and then re-establish the colony once temperatures warm up. I’m certain they’ll reappear. So 2 questions…
a) what do I spray with and when? (would like to do it before leaves start to appear if useful)
b) How do I stop it spreading to other apple trees, is there a preventative spray?

Thanks for any help. Don’t want to lose the tree as it’s still quite productive but would rather lose it than have them spread….
bb.

[mrbadexample]

My mate tried all sorts to get shot of them from his tree - painting with meths, blasting them off with a water jet - you name it. In the end we found that they really don't much like a blowtorch. Repeat as often as is necessary.

[FB.]

Once a tree becomes infested, it is almost impossible to completely eradicate them, especially if it is on a rootstock which allows them to hide underground where no treatments can get them.
The MM106, MM111 and M116 rootstocks were bred to help resist this terrible pest by preventing the woolly aphids from hiding on the (resistant) roots. However, some varieties are so hopelessly susceptible to woolly aphids that very little helps to keep them away.

Woolly aphids do the same damage to roots as is visible on the shoots, which impairs nutrient uptake, allows fungi/disease to invade the split roots (in the same way that canker may invade the damaged branches) and the tree often gradually declines.
Damaged branches and roots also become brittle and break off more easily - branch losses or fallen over trees can occur.
Death by woolly aphid can also occur as a result of debilitation - woollies have in the past made a fine mess of some of my trees; I now grow a number of varieties with resistance or which aren't noticeably susceptible.

As for dealing with them: the woolly coating protects them from sprays.
The best way is to use a hosepipe to blast them off (I successfully cleared a Scrumptious tree with a hosepipe alone - but I acted swiftly as soon as I was aware of the colonisation).
Also pruning-out badly infested parts or badly damaged parts (since the galled twigs and branches will probably always remain distorted and weak).

Painting with meths will help get rid of them (but a hosepipe is quicker and cheaper). I have also heard of people "torching" the aphids but take care not to scorch and damage the tree.

I suspect that if one tree is infested, it is "incubating" on the others too. Woolly aphids spread like the plague and can jump across several previously-uninfested trees in one season. I would wait to see whether the others show signs this year before rushing to remove any trees. It's possible that your others are varieties with partial resistance, so may never be significantly affected.

[bazzaboy]

Many thanks for advice MrBE and FB…. Hmmm, this seems to be a bigger problem than I’d anticipated, e.g. I hadn’t anticipated they’d attack the roots… I don’t know the rootstock of this particular tree as it was here when I moved in (18 years ago), it’s a Bramley-type cooking apple on a fairly small tree c.10 feet. It’s always been quite productive but not so clever last year… I will adopt strenuous treatment this year and be prepared to lose it if it declines further. Will also keep a sharp eye on other apples, thanks for the warnings.
Also am about to try my hand at some grafting (I’m a novice at that…), have some MM106 rootstock which sounds as if it should be OK, also trying M27 (very dwarf, patio pots) – is that woolly resistant? Also have some M26 1, 2 year olds heeled in the garden at the moment for the allotment when weather and energy levels coincide…. They’re not near the infected tree but perhaps I’d better do it sooner than later…
(but snow forecast tomorrow… “I don’t beleeeeve it!”)

Many thanks for tips. bb.

[FB.]

M116 and M25 have varying degrees of partial resistance.
MM106 and MM111 have strong resistance.
Other rootstocks can't be relied upon to resist woolly aphid, although sometimes they don't get attacked while at other times they do.

The more vigorous the rootstock, the greater its ability to outgrow the damage. M27 and M9 will not cope well with infestation.

Even resistant rootstocks can be attacked to a small extent. This is especially true if there is a heavy burden of woolly aphids on the above-ground part of the tree. I also find Bramley's young shoots to be very susceptible to woolly aphid.

If your "Bramley" (it does look like one from the pics) is only about 10ft after many years, it is probably on M26 or maybe M9. If the soil is unusually good (or bad) it might be on a more dwarfing (or more vigorous) rootstock.

I would not let the woolly aphid attack change your plans for grafting - but make sure that you keep blasting them off with a hosepipe and hand-squashing any which remain. If you fight the woolly aphids with determination like you really mean business you may be able to get rid of them. Half-hearted attempts at clearing woolly aphid are a waste of time. All or nothing.

[bazzaboy]

The more vigorous the rootstock, the greater its ability to outgrow the damage.

Half-hearted attempts at clearing woolly aphid are a waste of time. All or nothing.

The "vigour equation" makes good sense, FB, many thanks. Sounds like you have to admire the determination of the woolly aphids but I can be fair bladdy-minded too so we'll see who wins... Hand me the Winter Wash, the HosePipe, the Meths (to drink?), the Flaming Torch, the Gladiator's Sword in the tasty form of DeltaMethrin, Lambda Cyhalothrin and ThiaClopid (anyone fancy an apple after that lot?). Yup, it's them or me!