Pesky Powdery Mildew

Happy winter to everyone here in the southern hemisphere, and what a wonderful winter it is here in South West Australia!

Winter comes with many benefits, plenty of water for those summer parched plants, a time for us to plant and get some new things in and settled before the heat, and cooler weather for us to catch up on all those jobs we've been itching to do. But it comes with some down-side, one of which being, the dreaded POWDERY MILDEW!

Powdery mildew isn't just one fungus as such, there are various culprits responsible, these include:
. Erysiphe
. Golovinomyces
. Levellula
. Oidium
. Podosphaera
Each species 'attacking' different groups of plants, but unfortunately all causing a very similar appearance and result.

Powdery mildew forms chains of conidia that develop from the mildew hyphae, this presents itself as a ash grey to white powdery growth on the surface of the leaves, and, occasionally if really bad it may spread to other parts of the infected plant. They can emit a musty odour too. They will start is small patches initially and eventually spread across the entire leaf and plant.
Whilst they generally don't kill their 'host' it does weaken the plant, as it interferes with photosynthesis, you may notice an increase in leaves dropping (always pick these up, and either bag and bin them, or burn them to reduce further spread), leaves may also distort or discolour. Due to the plant being weaker, it then opens up your plants to other pests and diseases as the immune system is compromised.

Depending on the fungal pathogen they can either prefer warm and wet conditions, making the end of winter merging into spring where there's still plenty of moisture but a warming in the sun the perfect time to pounce, or warm and dry conditions, honestly I tend to notice these a lot less.

So, what plants can be affected by these scoundrels? It's a decent list:
. Zucchini
. Pumpkin
. Squash
. Cucumbers
. Mangoes
. Strawberries
. Peas
. Roses
. Dahlias
. Grapes
. Hydrangeas
. Tomatoes
. Apples
. Pears 
This is not a definitive list but it is a few common plants that you should keep an eye on.

What do we do when we find it then? Well as mentioned, any leaves that have dropped and the worst affected leaves on the plants should be removed or collected and destroyed, do not put them in the compost, it's just going to spread the spores further.

Try avoid watering at night, instead watering plants in the morning as this allows water to disperse and not sit around perpetuating the problem. Try increase airflow through and around the plants too, as this reduces humidity.

There are a couple of more natural or less harmful alternatives that can help slow or reduce the spread such as a bi-carb soda or baking soda solution, or a milk spray.
There are also some store bought solutions that can assist in ridding us of pesky mildew, most can be found at your local Bunnings or garden centre:
. Lime Sulphur
. Yates Fungus Gun
. Mancozeb Plus
. Yates Rose Shield
. Yates Rose Gun
. Eco-Fungicide
. Eco-Carb

The key thing is looking for a fungicide that shows the below on the packet or specifies powdery mildew!

Please ensure you read the packaging and follow instructions carefully to ensure you are not causing further damage, and ensure there are no with-holding periods for fruiting plants. Also some are systemic; meaning the plant absorbs them and spreads the substance through-out the plants entire system, whereas some are contact; meaning the substances has to physically come in contact with the mildew in order to get rid of it. Systemics can be useful as if you miss part of the problem, because the plant has absorbed it, it still acts, this can have cons too, as some chemicals are extremely harmful to our beneficially insects. So proceed with caution, and try use the more gentle approach first.

The key is, making sure you're out and about, keeping an eye open for those first signs. So what are you waiting for? Off you go!