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Minimising garden pests & diseases in Autumn

Posted by Kelly Jean Reyland
12th Apr 2023

Minimising garden pests & diseases in Autumn

Just like hygiene and cleanliness is used to help prevent pests and diseases in our bodies and our homes, the same is true in our gardens and fruit trees. While we associate a ‘spring clean’ with a fresh start and clean slate, the work in our gardens needs to start right now in autumn. How well we clean up in autumn helps prevent the pests and diseases from the previous spring and summer reappearing or re- infecting our plants next spring. In areas of NZ that have had a milder than usual winter and a very wet spring and summer, it has been a bad year for pests and diseases in our gardens. Why? Fungal diseases thrive in warm and damp conditions and pests weren’t killed off like usual by the cold in a mild winter.

So, it is vital to do a thorough clean up this autumn! Fruit trees in particular benefit from an autumn clean up. Did your peach or nectarine have a case of leaf curl this spring? It’s really important that you clean up the fallen affected leaves and discard them in the rubbish bin. Don’t leave them around the tree or put them in the compost bin for the spores to reinfect or spread infection later in the year. Did your apple trees have codling moth damage to the fruit? Ensure that all the hanging ‘mummified’ fruit or dropped fruit around the tree is collected and again, discarded. With any fruit tree affected by pests or diseases, discard those affected leaves or fruit. The physical act of cleaning up is a very important first step.

The second step is to carry out an early winter clean up spray to help knock out those lingering spores or pests on the tree itself. If you have carried out any pruning recently, these cuts are an easy way particularly for diseases to infect the tree. We don’t think of it due to its part in a trees yearly cycle but scars from where the leaves were attached before falling provide many small entry points.

For this reason, we recommend you start your winter clean up spray of Mineral oil such as Grosafe Enspray 99 oil and Freeflo Copper in Autumn. Specifically at about 30% leaf fall and again at 95% leaf fall. This protects the leaf scar sites and helps minimise overwintering infection. Follow up with a late winter spray and an early spring spray, at bud swell.

Just like us, if we ensure the fruit trees are as healthy as they can be, this will help them withstand or avoid pest and disease attacks. Pests and diseases are more likely to attack any plant that is stressed. Too much or too little water or not enough food are common causes. Keep a regular eye on your plants, water and feed them regularly and appropriately and deal with any problems as soon as you see them.

Some ways we can minimise pest and disease issues are by ensuring the soil the tree is planted in is healthy and free draining. Adding compost to the soil before we plant and regularly spreading it around the tree as a mulch helps improve the soil structure (drainage and aeration), encourage healthy soil bacteria, fungi and earthworms and helps to maintain consistent soil moisture levels.

If you are choosing a new fruit tree to plant, look for a variety with higher natural resistance to pests and diseases. This will make your tree less likely to suffer from infections and pests as it grows and matures (and minimises the work for you!)

Remove host plants, as much as possible. Some pests or diseases are attracted to particular plants and will affect them first. From there they spread to other plants. Remove the host plant from your garden and there is less risk of the pests or diseases appearing in your garden.

Home grown fruit is such a pleasure to eat, share and preserve for enjoying in the colder months. The flavour of fruit from the supermarket pales in comparison to homegrown sun ripened fruit. With a little care and attention, a healthy fruit tree will give you a generous harvest for years to come. As the saying goes ‘ A pinch of prevention is worth a pound of cure’. Make sure you carry out your autumn /winter clean up and reap the delicious rewards!

By Kelly Jean Reyland of Garden Advice NZ.


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