Anzac peaches need thinning
Anzac peaches need thinning

The Anzac peaches (one of the first to flower at our place) have set a good crop as usual, and it’s time to start thinning.

This is a good time of year to start assessing the impact of a couple of common diseases that can play havoc with our fruit trees, often without our realising it. 

You’ll also be thinning your apricots soon (if you haven’t already started), so while you’re doing so, it’s a good time to be looking our for signs of blossom blight in your tree.

Castlebrite apricot tree with blossom blight
Castlebrite apricot tree with blossom blight

Even though this disease does most damage when the tree is flowering, it can also affect the fruit that has set – because the disease that causes blossom blight also causes brown rot.

It’s not unusual to see remnants of it alongside healthy apricots, if you’ve had a mild case.

Flowers infected with blossom blight
Flowers infected with blossom blight

If you notice any of these diseased flowers on your apricot tree and you also have healthy fruit, it’s a good idea to knock or prune any diseased flowers and shoots off, for two reasons.

The first is that they can contribute to disease outbreaks next year, but the more urgent reason is that the pathogen that causes blossom blight also causes brown rot later in the season, and developing fruit is very vulnerable, as you can see in the following photo:

Photo showing Brown rot infection of a young apricot (blue arrow) that started from a flower that died due to Blossom blight infection (red arrow)
Photo showing Brown rot infection of a young apricot (blue arrow) that started from a flower that died due to Blossom blight infection (red arrow)

The other disease to check for is leaf curl, which is usually fairly obvious, the red leaves are a dead giveaway.

Leaf curl on a peach tree
Leaf curl on a peach tree

Only peaches and nectarines are affected by this tree, and if you’ve had a really bad case, it can also affect the fruit, so this is another thing to be looking out for while you’re thinning because you may as well pull the infected fruit off.

Affected fruit looks like this:

Leaf curl infection on a Goldmine nectarine
Leaf curl infection on a Goldmine nectarine

It’s not uncommon to end up with one of these infections despite having sprayed, which is super annoying.

There’s a couple of potential reasons for this. The first is that you may not have the right spray equipment for the size of the job you need to do – you can review the various options in this short course (because if you’ve gone to the trouble and effort of spraying, it would be really good to make sure it’s going to work!)

The second reason is that you may not have got the timing quite right, and the right conditions were in place for the fungal disease to take hold in the tree unimpeded.

Of course the long term aim is to get our orchard and trees healthy enough so they don’t need spraying, but while we’re building this biodiverse paradise, a bit of crop protection can go a long way!