Most fruit trees grown in Australia, especially deciduous ones, will have a period of dormancy over winter.
This is the best time to spray them to eliminate any fungal problems that may occur once the trees start budding up again.
It’s also an excellent time to get rid of certain pests that may be hiding under the bark, ready to emerge once the weather warms up.
With fruit trees, prevention is much better than trying to control pests and diseases once they have infected your trees. This is because many fungal diseases can be difficult to treat once they appear on your trees.
Stone fruit trees such as peaches, nectarines, apricots, and almonds are particularly susceptible to fungal diseases such as peach leaf curl.
For these, winter spraying is crucial because it will kill any fungal spores before they have time to infect the tree.
Winter washing to get rid of fungal spores
Winter washing is the term given to spraying your fruit trees during winter to remove fungal spores.
You can use either copper oxychloride or lime sulphur for this. In fact, it’s a good idea to alternate these two products each year so that the fungal diseases don’t build up resistance to either spray.
Spraying with copper oxychloride
In the first year, spray your stone fruit trees with copper oxychloride to help control any fungal spores.
You should apply the first dose in late autumn, just after your trees have dropped all of their leaves.
Then, it’s important to give your trees another spray just before bud swell. Usually, this will occur in late winter or very early spring.
Once the tree starts producing leaves, it will be too late to control fungal diseases such as peach leaf curl effectively.
Spraying with lime sulphur
The following year, instead of using copper oxychloride, use lime sulphur instead.
Once again, you want to spray your stone fruit trees in autumn after the leaves have dropped. Then, spray again in late winter or very early spring.
When you spray your trees, make sure that you cover all the branches well to the point of run-off. This is when the spray starts to drip off the branches and falls onto the ground below the tree.
Also, ensure that you remove the fallen leaves as they may easily harbour fungal spores over the winter. Do this before you spray your trees.
Use lime sulphur on other fruit trees like apples and pears
It’s not only stone fruit trees that can be infected with fungal diseases.
Apple trees are also susceptible to various fungal diseases such as apple scab. This creates black spots on the skin of the fruit.
The best time to spray your apple trees for fungal diseases is also winter. This will kill the spores before they have time to infect the tree.
Use lime sulphur to help control any fungal diseases on apple and pear trees.
Spraying for fruit fly
Fruit fly is a common pest that infects fruit trees in northern areas of the country such as Queensland, but it can also be a problem further south in places like Perth.
Most commonly, fruit fly is controlled by using traps rather than by spraying the trees. However, there are bait sprays that can be used to attract and kill these insects.
These sprays are best applied to the trunk and foliage of the tree and should not be sprayed on the fruit.
The reason for this is that the sprays are designed to attract the insects and the insecticide contained within the spray will then kill them.
The insecticide used in these bait sprays is spinosad which is a naturally derived toxin from soil bacterium. This is the only organic spray that is effective against fruit fly.
If you want to use a bait spray rather than just fruit fly traps, it should be applied while the insects are active during the summer months. Make sure that you follow the directions as per the product label.
However, do take care that you spray this only onto the tree and not the fruit or other beneficial insects such as bees.
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How to make dormant oil spray
Dormant oil spray can be used on your fruit trees to control many different insect pests such as aphids, scale, and mites. This spray simply suffocates the insect pests and they die.
Products such as white oil and neem oil are commonly used but you can also make your own by using the following instructions:
- Mix one cup of dishwashing liquid with two cups of sunflower oil.
- Place this into a glass jar and put the lid on tightly.
- Shake the jar until the liquid turns white. This is now concentrated white oil. Store in a cool, dark spot until ready to use.
- When you want to spray your fruit trees, mix one tablespoon of the concentrated white oil with one litre of water. Use this mixture to spray your trees.
Once again, spraying your fruit trees with white oil is best done in early spring just as the new buds are starting to swell.
However, white oil spray can be used at other times of the year if you have a pest problem.
Just avoid spraying in temperatures over 30 degrees Celsius because it may cause damage to the tree.