Red Spider attack?

Liz_GardinerDecember 3, 2003

Hi all,

We have had a terrible spell of hot weather in Sydney and my Princess of Wales suddenly went yellow blotchy. Then it went brown and shrivelled. I assumed it was an attack of Red Spider so watered as much as water restrictions allowed for. The whole lot died off. I wasn't too worried until it began to appear on other violet patches. Could it be anything else?

Liz Gardiner

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rob_peace(VIC Aust)

hi, liz.
hope your violets are surviving the heat! we had more than 100mm of rain in 2 hours on tuesday night so i wont have to water for a few days. the storms were described as 'a 100 year weather event' 50 mm a month is average. there is millions of dollars of water damage but ironically almost none fell in the catchment zone, so our restictions continue. i see on the news you had 5 people struck by lightning in your area but not much rain....

to your red spider problem. if it is red spider, you will be able to see tiny webs and just visible reddish dots running about. this is on the underside of the mature leaves. princess of wales with the slightly hairy leaves seems to welcome these little devils, the smoother varieties, less so. kelthane is the specific treatment here. it stinks, but seems to work. i prefer to only spray the affected plants. i think it's unwise to 'broad acre' spray with anything, really. it leaves nowhere for the good guys to go!


    Bookmark   December 3, 2003 at 3:12PM
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Mike Hardman(Cyprus, 100m altitude)

Hi Liz,

Sorry to hear about that.

The suddenness make me think "not RSM"; maybe collapse due to heat stress and/or root pathogens. What are the roots of affected plants like? If they are mushy or otherwise insubstiantial, maybe with black patches, it is a root problem, not RSM. Also, as Rob says, you should, with the naked eye just about or with a hand lens certainly, be able to recognize the little buggers. Be aware though that, species dependent, they are not all red all of the year and at all stages of their lives - often they are straw-coloured or even a little greenish.

In general, if you have RSM, I'd recommend a spray with fatty acid. I find this works really well, does not harm the plants, and if you get a version which includes sulphur, it is very good at stopping powdery mildew as well. Also, unlike predators, it can be used effectively all year round. The only downside is it is not systemic, so you have to get the whole plant wet, and repeat now and then since it is not so effective on eggs as later stages.


    Bookmark   December 3, 2003 at 8:27PM
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Thanks guys, will check the roots and follow all other advice. Keep you posted.

    Bookmark   December 4, 2003 at 12:44AM
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Dear Liz

I had very good results this summer using little beasts against red spider, named phytoseiulus... ((I am not totally sure all the same that once they have finished to eat the red spider they don't make up their mind to eat the violets too!)

    Bookmark   December 7, 2003 at 5:24PM
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Mike Hardman(Cyprus, 100m altitude)

Liz - yes - I've used Phytoseiulus persimilis as well, and they worked very well for me, too. They are not as tolerant of cold as RSM, and at the start of the season they don't breed quickly enough to keep up with the RSM. But by the middle of the year, they should be working their magic. The only trouble is, if RSM seem to be getting the upper hand, it is easy to want to spray the RSM -- but that would kill the P.s. as well... If you decide to give these predators a go, ask us for more guidance.


    Bookmark   December 8, 2003 at 6:34PM
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hmm... We have now had three days of wonderful rain. I am tempted to leave the rain to work it's magic. However, some of the new leaves look a bit wrinkly. I know that when we have an attack of black spot here in Hazelbrook no-one sprays they just remove leaves and wait until next year' s regrowth. I assumed that the RSM would eventually be beaten off with rainy weather conditions. Is there really a chance I could lose the lot?

    Bookmark   December 9, 2003 at 1:15AM
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Mike Hardman(Cyprus, 100m altitude)

You know - I have always wondered about that - the business of RSM being 'treated' by syringing with water like folks used to do decades ago, or using nature's own 'syringing' (rain). It may wash the blighters off, but they're pretty tough... Unless they get physcially swept away in a Biblical-scale flood (into somebody else's garden), don't they just crawl back up from the soil when things dry out? I suspect they do, and the intention of the water is to keep a humid atmosphere which will reduce the RSM's rate of reproduction. So they will become an infestation more slowly - great!

Removing the leaves is a good idea if you have a bad infestation (of anything), especially towards the end of the season - when the leaves of deciduous species would be soon shed anyway. That's also a good time to spray the remaining parts of the plant - because you can get to it all (many of the currently-allowed RSM-cides are non systemic) and because what RSM's climb back will have nowhere else to try to feed.

Not exactly an answer to your question, but at least I'm listening :)

Oh all right then...
You could lose the lot, but it might take a couple more seasons. A bad RSM attack will weaken plants but not kill them just like that. Next year they will still put out leaves, but they will also get sucked dry...

    Bookmark   December 9, 2003 at 12:45PM
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Have been off line for ages, only just caught up with the e-mails. It looks like I will have to spray as the area is too big for predator bugs. I will let you know how it goes. Especially glad to know that all the talk about water spraying may be part fallacy. I took it as gospel. The value of these discussion rooms helps to dispel such myths!
Thanks Liz.

    Bookmark   December 15, 2003 at 9:21PM
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Prediters only realy work if you can catch the attack very early, best thing to do is to clip or strim off all the leaves and destroy, with the fresh rain the new leaves will be as clean as a policemans boot!

    Bookmark   January 8, 2004 at 10:42AM
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