Top 7 tips for aphid control

Have you seen any leaves like this on your tree? If you have—you’re not alone. It’s a classic sign that you might have aphids, and many of our Grow Great Fruit members are reporting high aphid numbers this year.

Leaves on a plum tree showing classic signs of aphid infestation
Leaves on a plum tree showing classic signs of aphid infestation

The curly leaves on these plum trees are the typical response to the sap-sucking aphids taking up residence on the inside of the leaves. It’s different to the Leaf curl disease that you sometimes see on peach and nectarine trees.

If you tease open one of the leaves you’ll usually find aphids of some sort on the inside.

If you get a really bad infestation, there’s no mistaking it because you’ll be able to see hundreds (or thousands) of aphids crawling around, as you can see on this peach tree.

Black aphid infestation on a peach tree
Black aphid infestation on a peach tree

These are black aphids, which are one of the more common types that infest fruit trees, and will usually be seen on cherry, plum, peach and nectarine trees.

Another common type on apple trees is called woolly aphid, for a very good reason:

Woolly aphid on an apple tree
Woolly aphid on an apple tree

There’s a third type of aphid that commonly affects fruit trees, and that’s green peach aphid, which — you guessed it — you’ll find on peach and nectarine trees.

Green peach aphid infestation on a nectarine tree
Green peach aphid infestation on a nectarine tree

Sometimes when you look inside a curly leaf to see if aphids are responsible, you might see something like this instead:

There’s only a couple of live aphids here, but those small black smudges are a really good sign, as they are the dried and shrivelled remains of aphids that have been killed by other insects – “beneficial” insects that do a wonderful job of keeping pest insects under control in healthy, biodiverse gardens.

Inside this leaf is a little community of insects that is a great sign of a healthy ecosystem. A spider, and an aphid-eating wasp are co-habiting and both eating their fill of aphids (or the spider might be eating the wasp – you can never be sure who’s eating who in the insect world!)

We’re often asked how to get rid of aphids, and unfortunately people aren’t usually very happy with the answer!

Biodiversity and patience really are the keys to getting the populations of these pesky pests back under control.

Whatever you do, DON’T SPRAY INSECTICIDE! It can feel like an easy solution, but you’ll inevitably kill predator insects and just make the problem worse. In most commercial orchards, aphid populations are high – and stay high, year after year, due to the use of insecticides that routinely kill the “good” insects that would naturally keep the aphids under control.

It’s expensive, it’s ineffective, and it’s bad for the health of the tree, the user, the eater of the fruit, and the whole ecosystem.

There are a number of home-made remedies that can help in the short term with aphid control, but our experience has shown over many years that similar to bought insecticides, if you rely solely on a solution in a bottle you quickly become dependent on needing to use the same solution every year, and in fact you can be making the problem build up over time.

So, here’s our top 7 tips for getting rid of aphids:

  1. Monitor your trees regularly, particularly checking inside any leaves that have curled up, so you actually know whether or not you have aphids.
  2. If you identify that you do have aphids, watch very carefully to see whether you also have any predator insects around that are eating them – spiders, ladybirds and wasps are all particularly voracious aphid-eaters.
  3. Check whether you have ants in the tree associated with the aphids. Ants like to ‘farm’ aphids by moving them from tree to tree and guarding them from predators.
  4. If you find ants in your trees, exclude them by any means necessary. Don’t bother trying to kill the ants as they bring excellent eco-services to your garden and are very hard to get rid of, but stop them getting to the aphids by putting sticky tape around the tree between the aphids and the ant nest.
  5. Focus on building the biodiversity of plant life under your fruit trees. Flowering plants, particularly white and yellow flowers are really good at attracting predator insects and providing them with habitat.
  6. Unhealthy trees will attract more aphids, so concentrate on improving the health of your tree by improving the soil it’s growing in.
  7. Use short term solutions (like organic sprays) only in extreme circumstances, and with extreme caution!

We recommend taking a more long term view by creating such a healthy garden that aphid populations are kept under control naturally.

Having said that, short-term solutions can have their place and are part of the “toolbox” of solutions in the Aphid Management Plan you’ll find in our Protect Fruit Trees from Pesky Pests short course.

How can you tell if your trees are healthy?

If all is going well with your trees this spring, you should be seeing growth like this on your trees:

New spring growth on an apple tree
New spring growth on an apple tree

This time of year we like (and expect) to see a flush of strong, healthy new growth in our trees, particularly on young trees.

Successful fruit growing is all about helping the tree to balance its energy between growing new wood (i.e., new shoots, as you can see in this photo of a young apple tree) and growing fruit. If it grows too much of one, it tends not to grow much of the other.

We need the new wood so the tree continually has new buds being formed to produce next year’s fruit (though the buds can also form on older wood in some trees).

But we don’t want the tree to put too much energy into growing wood at the expense of putting its energy into growing fruit – it’s a balancing act.

Shoot length is one of the best indicators of the overall health of your tree, and spring is the time to monitor it – so visit your trees and have a look.

If you see plenty of young vigorous shoots (anything from a few cm to 1 metre long, depending on the type and age of the tree), you know the tree’s pretty happy.

And if you’ve done a great job with your pruning, you’ll also notice that the new shoots are growing in the right place in the tree to make future fruit picking easy and manageable.

Here’s what healthy spring growth looks like in cherries:

On a young plum tree…

Healthy spring growth on two year old plum tree
Healthy spring growth on two year old plum tree

On a mature plum tree…

An Angelina plum tree showing vigorous spring growth
An Angelina plum tree showing vigorous spring growth

and finally, a mature apricot tree that’s growing beautifully (note the beautiful red colour of the fresh new growth, which will gradually fade through orange to green).

Beautiful new growth on a mature apricot tree
Beautiful new growth on a mature apricot tree

Thinning to protect your tree

As part of our continuing series about fruit thinning (a very relevant topic in spring) this week we’ll talk about the second main reason we do thinning, which is to protect the structure of our trees.

A broken lateral in an apricot tree caused by to much fruit (or not enough thinning)
A broken lateral in an apricot tree caused by to much fruit (or not enough thinning)

Most fruit is carried on the small side shoots, or laterals, that grow from the main branches — they are a very precious part of the tree, and need to be protected. Left to its own devices, the tree will frequently set so much fruit on a branch or lateral that the weight of the fruit breaks the branch, as you can see in the photos above and below.

Too much weight has broken branches in this apple tree
Too much weight has broken branches in this apple tree

Our job when thinning is to remove some of the fruit that the tree has set, leaving only as much as any structural part of the tree can easily carry.

Bebeco apricots after thinining - not too much weight for the lateral to carry
Bebeco apricots after thinining – not too much weight for the lateral to carry

It’s important to imagine how large and heavy the fruit will be when it’s fully mature – as a very rough rule of thumb, a short lateral can only bear the weight of one piece of fruit, and a longer or stronger lateral can carry two or more pieces.

Tatura 211 peach after thinning - just one peach on the lateral
Tatura 211 peach after thinning – just one peach on the lateral

Of course the actual amount of fruit you can leave on the tree depends on many variables:

  • the type of fruit,
  • the variety (cultivar),
  • the ultimate size of the fruit at harvest,
  • whether the tree is heavy, medium or light crop,
  • when it’s due to be harvested,
  • age of the tree, etc.

It’s fine to just follow the rule-of-thumb guidelines we provide, or if you’re keen to protect your tree and in a hurry to get good results you can use the charts we’ve developed in the Grow Great Fruit program and the Fruit Tree Thinning short course to save yourself a few years of trial and error!