Four reasons for yellow leaves on fruit trees

Welcome to autumn! Though we’re having quite a warm summery week here in central Vic, we’ve had the first few cool, crisp mornings, and there’s a definite shift in the air.

Leaves on Angelina plum trees (on the LHS) starting to turn yellow in autumn
Leaves on Angelina plum trees (on the LHS) starting to turn yellow in autumn

Even if it still feels quite summery at your place, you can expect to start seeing some typical autumn features in your fruit trees soon.

For example you might start to see the leaves on your fruit trees start to turn yellow (if they haven’t already), especially if you’ve already picked the crop. The typical pattern is that the leaves will stay green and continue doing their job as long as the tree is bearing fruit, but once the fruit is off, it will quickly start go into senescence, or winter dormancy.

Close-up of yellowing leaves on plum tree
Close-up of yellowing leaves on plum tree

At that time, the tree starts to withdraw all the useful nutrients from the leaves back into the buds and bark — the first sign of this happening is the leaves changing colour. This type of yellowing is completely normal, and you see it every year.

Another reason for yellowing leaves that is of more concern is caused by lack of water, as you can see on this cherry tree.

A cherry tree that has turned yellow from lack of water
A cherry tree that has turned yellow from lack of water

It’s all too easy for this to happen when you have an automatic irrigation system, because drippers can easily block up, and unless you’re checking them regularly (which is a really good idea), you might not realise you have a problem until the tree starts telling you loud and clear by the leaves turning unseasonally yellow (you can see all the other trees nearby are still green).

Another common reason for leaves to turn yellow is from nutritional deficiencies.

Iron deficiency (chlorosis) on peach leaves
Iron deficiency (chlorosis) on peach leaves

A number of nutritional deficiencies can cause yellow leaves as one of their symptoms, including iron (as you can see above), manganese and zinc.

The fourth reason for yellow leaves is because of a virus disease, such as apple mosaic virus as you can see in this leaf.

Apple mosaic virus on leaf
Apple mosaic virus on leaf

Viral diseases are not good news, but unfortunately are not really treatable, so the best bet is to look after the tree as well as you can, and try to avoid the virus spreading by not planting other trees of the same type nearby.

So if the leaves on your fruit tree are turning yellow it’s probably a perfectly normal seasonal response, but your tree might also be trying to tell you something! If you feel like you need more detailed help diagnosing what your fruit tree is trying to tell you, please download a copy of Keep Your Fruit Trees Free From Disease short course.

Apricot leaves showing beautiful autumn yellow and orange colours
Apricot leaves showing beautiful autumn yellow and orange colours

What are those brown marks on my apples?

We had a great question from one of our Grow Great Fruit members recently about what causes russet on apples, which describes both the yellow marks (as you can see on the side of this Cox’s Orange Pippin apple), and the rough brown marks around the stem end of the apple.

Russet is one of those curious conditions that occurs naturally – in fact several heritage apple varieties include it in their name, like Brownlees Russet, Egremont Russet and Old Somerset Russet. It’s also commonly seen on pear varieties such as Beurre Bosc.

These days, russet is not considered an attractive trait on apples (have you even seen a russeted apple in the supermarket?), and it’s just one of the reasons many of these beautiful old varieties have gone out of favour (which is one of the reasons we’ve planted a new heritage apple orchard to preserve many of these old varieties).

Russet can also be an injury caused by environmental conditions like frost, sunburn, or hail, or by spraying your apples at the wrong time – even using sulphur (which is an organic fungicide we use occasionally) at the wrong time can cause russeting on some apples (as can a lot of the chemicals used by chemical farmers).

This damage-type russet – think of it like scar tissue – usually happens in the three weeks after petal fall, when the trees are flowering, or when the environmental challenge happens. It is often not a problem in itself, but it can make the apples much more vulnerable to other diseases, like various fungal rots, cracking, or even sunburn.

Heritage varieties that were bred in the UK, such as the divine Cox’s Orange Pippin apples (above) or the much-loved Bramley (below), are really not suited to the harsh and hot conditions in Australia, and so it’s very common to see this type of damage on your apples.

Of course once you realise that, you can set about creating micro-climates that these trees will prefer, and you may find that much of the damage is preventable.

You can find out more about creating micro-climates in your garden in Permaculture in Action.

Netting options for backyard fruit trees

Fruit damage from birds, bats and possums is high on the list of complaints from home fruit growers. This week we look at various netting options,and how they can protect your crop from most of these problems.

The birds left us the stems!

Our new cherry trees are now producing fruit (hooray), and even though we drape netted some of them, it wasn’t completely successful – partly because we were a bit late getting some of the nets on, and partly because the type of birds that were giving us a hard time (parrots) are also particularly clever at getting under drape nets!

So, successful netting is not just about doing it in a timely fashion, it’s also about having the right system for your situation.

Another big advantage of netting your trees is providing some protection against hail, and if you’ve experienced hail before, you’ll know what we’re talking about! Hail storms are a pretty common occurrence on the farm and we lose at least some fruit to hail most seasons.

This is what hail damage looked like on our apricots last year:

Hail damage on apricots

Birds not only damage the fruit, but can help spread brown rot as well. There are lots of different ways to try to scare birds away, such as CDs hanging in the tree, fake predators and the like, but the only real solution is to net your trees – the sooner we all resign ourselves to this necessity, the happier we’ll all be!

This simple net below is made with a frame of star pickets and pipe, and is the easiest and most effective solution we’ve seen (and used).

It’s easy to put up (and take down again if you choose), and easy to peg down around the perimeter to stop persistent smaller birds getting in under the net, which can happen with drape netting (as we saw this year!). This particular set up also has wire netting around the base, which can be useful for stopping larger animals from getting into the enclosure.

Drape netting is easier if you are doing a lot more trees, and is very effective against big birds, and can also deter fruit bats, both of which descend on the tree from above and don’t like to get in under net.

Unless you are really diligent about tying off the net around the trunk, it won’t stop smaller birds like parrots, which are happy to nip under the edges of the net and help themselves. Having said that, it does keep the damage to minimum and is definitely worthwhile.

Learn practical strategies that actually work to protect your fruit from birds and other critters in Protect Fruit from Pesky Pests.