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.
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.
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.
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.
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.
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.