Tuesday, February 16, 2010

Wilting in the humidity, beating root rot

In many senses February is the worst month for garden plants here in Sydney. I've had more plants die on me in February than any other month, and it's always that killer combination of heat, humidity and a lot of rain that sees some plants saying: "This is nothing like my natural homeland's dry summers, buddy, I'm out of here!".

I can't count how many lavender plants have failed to see out a Sydney summer over the years, but some Australian natives struggle at this time of year, too, because they come from places with hot but dry summers and Sydney doesn't really suit them at all.

Yesterday I was surprised to see our tough old Correa alba wilting with symptoms that had all the suspicious signs of root rot. And if you're on Australia's East Coast in particular and reading this blog, here's a big tip. Spray your wilters and those plants showing signs of fungus disease right now. Not tomorrow. Right now. Here's what I did, and I hope it works as well as it did last time.

First, let me set the scene. Correa alba is one of the mainstays of our front garden. Pam chose it, so it's one of 'her' plants. It's the greyish-green dome-shaped thing behind the blue-green Cootamundra groundcover wattle. Never had a day's illness in its life, until today. It flowers unspectacularly in autumn with little white star flowers, and so it's main job is foliage colour contrast, and it does that very well.

We've been having record rainfall lately, and lots of heat and humidity too. Classic fungal disease weather, and not all fungal diseases are visible. A lot of it goes on underground, around the roots. The disease is generically known as root rot, and a classic symptom is wilting foliage. When native plants die, they do it in days, not weeks, so you have to act fast. The first signs of wilting appeared on Sunday, and so yesterday I sprayed it. I'll spray it again in a few weeks' time.

Now here's the good news. The spray I used, called Yates Anti-Rot, is a remarkably safe spray to use. It doesn't have a withholding period when used on fruit trees, and so you can even spray it on citrus and other fruiting trees. The substance it's based on is phosphorous acid, also called Phosacid, and it's a relatively new-generation fungicide that is replacing many of the nasty, toxic older-style fungicides that I would never dare or want to use.

I'm hoping the Anti-Rot will work as well for my Correa as it did for my extremely sick grevillea last year. Check out this previous posting from last year, which shows the dramatic turnaround in the grevillea's fortunes, following the spray treatment. But I certainly hope the correa doesn't get as sick looking as my grevillea did last year!

Finally, I also played it safe and sprayed both my lovely backyard grevilleas as a preventative treatment. The product, Anti-Rot, is readily available at most Australian garden centres, but just in case you're not sure what to look for, here's a link to the product listing at the Yates website. I use the concentrate, which comes with a little measuring cup. I mix 5ml of concentrate in a 1-litre spray bottle of water. I used 1 litre of spray per plant, so the concentrate is easily the most economical option.

And no, this ain't a commercial! I just like the way the product saved my grevillea last year, and hope that some of my blog readers might find it a life-saver in this horrible, humid weather, too.


Robyn said...

Thanks for the good advice. Its ricky having pots on my balcony. With the alternate rain and heat, Im constantly placing or removing saucers under my pots. They are alternatively really dry or sitting in suacers of water.
Also, thanks, have been meaning to identify this plant for a while. It grows on the cliffs of the coast around Coogee. (I think its been planted by regenerators!)

Chandramouli S said...

Urrggh! Root rot! I've lost quite a few to it, Jamie, mainly because of my ignorance. I thought it was because of my irregular watering but later realized that it was root rot, but it was too late. Good luck with yours.

Dirty Girl Gardening said...

that ground cover is gorgeous... great blue color.

Michael said...

Make sure it's just root rot and not also something like grubs. I thought I had root rot in my organic garden two years ago, but it turned out to also be grubs. I used the organic insect spray, End All, and it took care of the problem.

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Robert said...

Some of my Correa Albas are wilting. based on this post I wondered if it was root rot. However, it's only affecting a few plants and the other plants are healthier than they've ever been. Could I have the grubs Michael mentioned? If so, what do they look like - are we talking witchetty grubs or some other sort of grub? I live in Melbourne, if that makes a difference.

Jamie said...

My Correa alba has stabilised after the Yates Anti-Rot treatment, but the plant ended up with about one eighth of it pretty much dead or dying. I've cut out those sad looking bits and the rest of the plant is OK now. Hopefully it will bounce back next spring.

Not exactly sure what the grubs might be that Michael mentioned. One possibility is the very common curl grubs, which are about 2-3cm long, white and usually are curled up when you find them down in the soil (not on the plant). They eat the roots of plants and are a common cause of plants wilting. I did a thing on them a while back. Here's the link to that posting:

Robert said...

Thanks Jamie. Loved your link about the grub massacre :-)

Nebula Haze said...

I have had great success combating root rot with a product called "Aquashield" by Botanicare. I believe it's made out of some sort of compost solution. With potted plants, adding some Aquashield to my watering solution has pretty much cured the root rot within days.

Robert said...

I've learnt my lesson - in clay soil it's always best to grow plants from seedlings. There's much less chance of root rot. Putting an established potted plant into clay soil is a recipe for disaster: the potting mix lets the water drain to the bottom where it gets trapped by the clay.

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