Best Organic Fungicides in Australia (2026 Guide) | Dr Greenthumbs

Best Organic Fungicides in Australia: 2026 Guide for Every Climate

Fungal diseases smashed Aussie gardens right through 2025—powdery mildew on zucchinis up north, rust on roses down south and black spot wherever the summer storms rolled in. Chemical nasties are out, but “organic” isn’t one-size-fits-all. This no-B.S. guide sorts the proven, APVMA-compliant options from the backyard myths, so you can knock out spores without nuking the ecosystem (or your harvest).

Quick take: If you only buy one product, make it Kendon Lime Sulphur – it’s the broad-spectrum workhorse most gardens need.

Fungus-Fast Chart

Disease / Situation	Humid Sub-Tropics	Temperate Coastal	Cool Inland	Go-To Product
Powdery Mildew	PureCrop1 preventative every 10 days	Baking-soda back-up	Kendon Lime Sulphur curative	PureCrop1
Black Spot (roses)	Kendon Lime Sulphur fortnightly	Same	Same	Kendon Lime Sulphur
Rust on Turf / Citrus	PureCrop1 + soil aeration	Kendon Lime Sulphur	Micro-Kill	Nefarious Micro-Kill
Botrytis (grey mould)	Increase airflow + PureCrop1	Same	Same	PureCrop1
Scale insects with sooty mould	Kendon Lime Sulphur direct spray	Same	Same	Kendon Lime Sulphur

Need something else? Browse the full Organic Pest Control range.

DIY vs Ready-Made

Option	Pros	Cons	Best Use-Case
Milk Spray (1 part milk : 9 parts water)	Cheap, adds a calcium boost	Short-lived; stinks in heat	Light mildew on cucumbers before fruit set
Bicarb soda + Horticultural Oil	Kitchen-cupboard simple	Needs oil or soap to stick; can scorch leaves	Roses in low humidity
Ready-Made Organics (like Kendon, PureCrop1)	APVMA-compliant, predictable results, longer residual	Costs a few dollars more	Outbreaks you actually care about controlling fast

Verdict: DIY is fine for a hobby fix. When crop yield or prized ornamentals are on the line, reach for a proven concentrate.

Spotlight: Kendon Lime Sulphur

Broad-spectrum fungicide, miticide and insecticide in one bottle.

What it kills: Powdery mildew, rust, black spot, scale, spider mites — even overwintering spores hiding in bark.
Dilution guide: 15 mL per litre (dormant); 10 mL per litre (growing season).
Pro move: Spray trunks and canes mid-winter to reset disease pressure before spring flush.
Why we rate it: Sulphur changes the pH on the leaf surface, making it impossible for spores to germinate — without leaving persistent chemical residues.

Grab it here → Kendon Lime Sulphur (250 mL / 500 mL)

PureCrop1: Nano Tech, Zero Residue

If you need a harvest-day safe spray for edibles, PureCrop1 is your ticket. Plant-based surfactants form 1–4 nm micelles that burst fungal cells and dehydrate sap-sucking pests — then biodegrade. No sticky film, no flavour taint on herbs, and it doubles as a biostimulant thanks to natural oils that improve nutrient uptake. Ideal for greenhouse or hydro setups where every spray shows up on test results.

Nefarious Micro-Kill: Heavy-Duty Drench

Soil-borne nasties like pythium, fusarium or lingering mould spores? Mix 100 mL Nefarious Micro-Kill into 900 mL water and drench the root zone. Plant-derived antimicrobials create a residual bio-film that blocks pathogens for up to two weeks, yet remains safe for edible crops. Handy after a wet La Niña season when beds stay saturated.

Seven Rules for Safe Spraying

Read the label, then read it again. Dilution rates matter.
Spray in the cool. Early morning or late arvo minimizes leaf burn.
Good coverage beats extra strength. Mist the underside of leaves.
Rotate modes of action. Alternate sulphur with oil-based or biological products.
Keep bees out of the spray zone. Cover flowers or spray after sunset.
Wear gloves & goggles. Organic ≠ harmless to eyes.
Wash gear straight after. Residue corrodes metal nozzles fast.

Prevent-Don’t-Cure Checklist

Prune for airflow; humidity breeds spores.
Sterilise secateurs between plants.
Mulch—but keep it off stems to avoid collar rot.
Water at soil level; wet foliage invites mildew.
Feed balanced nutrition—stressed plants get sick first.

Stick this list on the shed door and 80 % of fungal drama disappears before it starts.

FAQ

Is Lime Sulphur safe for food crops?
Yes—just observe the 3-day withholding period before harvest.

Can I mix PureCrop1 and Lime Sulphur?
No. Sulphur alters pH and can denature the nano micelles. Alternate sprays 72 hours apart.

Will any of these harm worms or soil microbes?
Used at label rates, all three products are worm-safe and will not sterilise living soil.

What temperature is too hot to spray sulphur?
Avoid spraying above 30 °C; leaf scorch risk climbs fast.

Ready to act?

Reset fungal pressure today with Kendon Lime Sulphur.
Need zero-residue protection? Pick up PureCrop1.
Soil trouble? Drench with Nefarious Micro-Kill.

Free shipping on orders $250 + — stock up and stay ahead of the next spore storm.

Happy growing!

About the Author

Scott Cheney is the Director and Founder of Dr Greenthumbs, with over a decade of hands-on experience in organic gardening. Growing up in rural NSW, Scott’s passion for unusual plants – from cacti to entheogens – evolved into a full-blown commitment to chemical-free gardening when he bought his first property in Wollongong. For the past 8 years running Dr Greenthumbs, Scott has developed unique, first-to-market products like TurboDirt Water Only soil and 100% dry amendment fertiliser blends. When he’s not testing new mixes, you’ll find him swapping gardening tips like your local mate, not giving the hard sell.

Awesome product...Trust the Doctor.

Thanks legend! Love the trust—glad Fruit Roids is doing the job for you. Here’s to more awesome results in the garden!

Great product, great staff!

My best mate handed me a sample of root roids around the time my passion for growing big beautiful flowers began, and I/we have never looked back. We top dressed it like dumb asses and watered it in before realising it was soluble, but the plants still loved it haha! Now days I have my favorite plants in Turbo Dirt and they look forward to their weekly drinks of Fruit/Root Roids! Inoculating the girls with Boost and or Granular at the right moment can only be compared to the first time you karate chop a squid and it changes colour, riveting sh*t. The roots explode with funky dank growth! I'm also a big fan of the Alfalfa Meal, Go & Grow, Bud & Bloom top dresses all throughout my garden wherever a plant is in need. Same goes for the Ocean Grown range! If all this wasn't enough the team are super helpful and knowledgeable. Colin the legend helped me over the phone with all my teething questions as I'm interstate and have never been able to visit the shop in person. It's clear the team are passionate and know their stuff. Highly recomend Dr Greenthumbs and the team!

Thanks Alex! What a ripper review—love your passion and the honesty about those early experiments! Sounds like you’ve got the full Dr Greenthumbs lineup working overtime in your garden, and that’s exactly what we love to see. Big cheers for the shoutout to Colin and the team too—always here to help, even from across the country. Appreciate you sticking with us and sharing the good word!

Root roids

So far.... amazing products. plants are thriving, Very easy for beginners like myself.

Thanks Meg! Awesome to hear your plants are thriving and you’re finding it all beginner-friendly. Appreciate you giving Root Roids a go—happy growing!

Trellis net

Great product, easy to erect and is forgiving when a bit of wind is around

Thanks Matt! Good to hear the trellis netting’s holding up and easy to use—even with a bit of wind. Appreciate the feedback!

The wizard vault

If you’ve found your self here reading to see what people have to say id love to add mine,
I started buying Scott’s products back in early 2017 and made my first super soil with his help and a friend that put me onto him, it was my first time trying the organic no bottle salt free way and I’ll never go back the quality of the plants growth to it’s looks to it’s smell and tastes are just unrivalled in my opinion and plenty of people I know iv shared my garden with always say what brand nutrients you use and I couldn’t recommend him enough I started telling as many hydro stores in Western Australia I could about this man’s Scott’s (drgreenthumbs) products and they needed to get them in and try that’s how good it is , if your after real food/flowers/medicine,plants the way they are supposed to look and taste you’ve made it , not one thing he has put together him self is nothing but incredible well done this is huge for Australia and needs to be everywhere, thanks for helping me put the best in aus out mate

Thanks Jordan! That’s a massive wrap—appreciate you sharing your journey and spreading the word since day one. Nothing better than seeing growers switch to organic and never look back. Me and the crew put everything into making top-notch gear for Aussie gardens, and legends like you keep us pushing. Here’s to many more epic harvests and sharing the good stuff!

Best Organic Fungicides in Australia: 2026 Guide for Every Climate