Scottish Rock Garden Club Forum
Cultivation => Cultivation Problems => Topic started by: Giles on August 20, 2009, 06:08:59 PM
-
Dear All,
I'm having particular problems with the 2 Spotted Red Spider Mite this year, experiencing severe infestations of outdoor trees and shrubs: leaves bronzing, then turning to a brown crisp and falling off over the course of two to three weeks,leaving totally defoliated lilacs, roses and philadelphus. Some shrubs being obviously killed. I have tried all of the available products licensed, and a few that have now been withdrawn, several times, without any effect. I am left with using soft soap sprays, with limited response on their numbers, and often causing leaf scorch. (Remarkably, the daphnes in the greenhouses remain pest free). It seems I'm left with rampant, resistant spider mites, killing my plants and no effective treatment.
I gather the use of predators is a waste of time outdoors, and I do my best to raise humidity by frequent misting (inbetween the frequent rain ;D )
I have never experienced anything this bad before, and wondered if any of you had similar experiences this year? (or any top tips?)
-
Giles - Avoid spraying anything containing carbaryl (sevin), that will only dramatically increase the mite population.
A daily stiff jet of water against the leaf undersides and frequent misting can help. A good mite spray - may be unavailable there - was a combination of resmethrin and tetramethrin.
johnw
-
Crikey John !
Resmethrin is not licensed for use (for any reason) in the EU, and Tetramethrin is licensed for 'Professional Use' only, in pest control in cleaning barns !
The only pyrethroid we are allowed to use 'in the garden' is bifenthrin - to which mine have complete resistance.
The EU have withdrawn so many products, that we no longer have any effective treatment options left open to us.(which makes me 'most unhappy').
-
Giles
I am a bit hesitatant to recommend Safer's End All. It can be fairly effective but can also burn leaves in bright sunlight. It is a combo of insecticidal soap, pyrethrum and canola oil. The oil smothers the eggs. I defoliated a batch of cyclamen one year with just the soap. They all recovered but magnolias might not be so forgiving at this time of year, especially the exotic evergreen ones you have.
The resm/tetra is long gone here as well. And we are left with no fungicides either - bordeaux and sulphur, that's it.
johnw
-
Giles,
I got an infestation on my roses in front of a south sided wall too likely caused by high day temperatures with low humidity.
I successfully sprayed Dimethoat (Supplier in Germany: Spiess-Urania, Brand Name "Rogor 40L").
But you need to repeat the treatment min. 3 times on a weekly base to kill all mites.
As John mentioned a daily stiff jet of water against the leaf undersides and frequent misting can help too but for instance roses you risk fungus infections if leaves are left wet overnight :-\
After 1st treatment all brown dry leaves have been removed (no chance to rescue any) I gave an extra fertilizer portion of kalium phosphate, nitrogen and ferrumsulphate to initiate new grows. After 3wks I got again healthy looking new slips and leaves.
Since then I regularly checking the lower sides of leaves for mites gossamers / new infestation.
-
We can't buy dimethoate here anymore :-[ (although it's available for commercial growers).
I think it's time to visit a friendly nurseryman.....
-
Why are you having such problems with spider mite this year and not in previous years?
Any idea? Have you inadvertently killed of their predators?
-
dimethoate here anymore :-[ (although it's available for commercial growers).
I think it's time to visit a friendly nurseryman.....
That stuff is scary and very dangerous. Someone here 30 years ago was using it on spinach for leaf miner, he thought it was an organic insecticide! Worse he was selling the spinach.
johnw
-
Hi Giles !
I have found Polysect (with Bifenthrin) to be quite effective against red spider mites !
(also on Pleione - with problems of Brevipalpus which is also a spider mite)
Have a look on Paul Cumbleton's Pleione site.
Good luck !
-
dimethoate here anymore :-[ (although it's available for commercial growers).
I think it's time to visit a friendly nurseryman.....
That stuff is scary and very dangerous. Someone here 30 years ago was using it on spinach for leaf miner, he thought it was an organic insecticide! Worse he was selling the spinach.
johnw
Good grief!
Mind you, have you noticed it is a common thing for folk to regard "organic" as equalling "safe".......whatta mistake-a to make-a!
-
Hi Giles,
I understand you have an enormous problem with spider mites. I garden on 2 balconies and many years ago I've experienced attacks on my plants by all kinds of pests, including spider mites. I've used spraying of insecticides but it only resulted in destabilizing the eco system on my small area of gardening. Then I've used predators like ladybugs. Then I had a cat and decided to ban every chemical treatment. I also got rid of plants prone to be attacked by spider mites and white flies. I only use water sprays( as you did ) and it's not so bad this year despite the very hot weather we have this summer in France ( 30° at least since early july... ). I think watering the plants very regularly could help, and may be try not to gather too many species sensitive to spider mites. Destroying all the leaves infected as you probably managed to do.
In Lyon ( France ) where I live they've planted in the streets dozens of plane trees and maples which are attacked every year ( for a few years only ) by spider mites and nothing seems to be done. The concentration of trees of the same species leads to problems difficult to solve. That's always the same song...
I'm sorry not to be able to give you any drastic solution but may be there's none...
Good luck
Regards
-
Maggi : Derris is a good example. Perfectly 'natural' but in the process of being withdrawn due to toxicity concerns.
Many of our food plants are carcinogenic (parsnips, celery, parsley) but it doesn't seem to put anyone off!
Jean-Patrick: I like your philosophy, but I'm afraid I'm a great believer in perfect plants, by whatever means. Abamectin proved the answer. Unfortunately only available in ready to use/ diluted (expensive !!) form. Unfortunately it has led to further, very bad leaf scorch, but thankfully it's killed the *uggers
and doesn't need a follow-up application.
-
Hi all ,
I have also sometimes problems with red spider mites .....and so I have a bit expierience with fithing against they ....
The problem is that normal insecticides not works against this animals -we have to use Akarzide ( like Kiron ( Fenproximat ) or Vertimec ( Abamectin ).
A new Akarzid is now Bayer Spinnmilbenfrei ( Acequinocil ) ....I'm testing it in this time ....
Shure - we can also use things like Promanal ( Oil ) -I would use it inside of house .
Importent is always to spray a second time ( after 10 -14 day ) when the next generation will come !
-
Hello Giles,
How is the Mite situation? just noticed your post. I had a similiar situation a couple of years ago, the whole garden was being attacked from soft perennials, shrubs, hedges etc. The cause is from favourable dry conditions from which the mite will flourish.
There is a predatory mite that will kill and eat your 2 spotted mite. They are available and they work in the open garden as long as the tempretures are still warm and I suspect it is if the 2 spotted mite is around. Spraying will only upset the balance and kill other preditors if your spraying the whole garden.
Also overhead irrigation at night helps, you want to keep the foliage wet as long as possible.
Hope your mites are gone
cheers
-
Sorry, Stephen, I've only just seen your post.
I ended up killing them in the end, but only at the expense of alot of leaf scorch from the sprays.
I'm going for predators next year. Introduce them as soon as the weather is warm enough, regardless of whether
there is a 'plague' of mites or not.
Atleast they will not damage the plants. :)
-
http://www.avoncrop.co.uk/product.aspx?productId=4349
You can use Spraying oil available from Avoncrop but they only sell in 5ltrs. This is what I use on Pleione.
-
After trying every concoction on the market to kill red spiders on my Daphne Jezoensis, I finally succeeded with a simple solution.
Doff organic pest spray, containing fatty acids. Killed the spiders and the eggs DEAD
-
Sorry, Stephen, I've only just seen your post.
I ended up killing them in the end, but only at the expense of alot of leaf scorch from the sprays.
I'm going for predators next year. Introduce them as soon as the weather is warm enough, regardless of whether
there is a 'plague' of mites or not.
Atleast they will not damage the plants. :)
Giles,
If there are no mites you'll waste your money. The predators basically only eat the mites, so if there are no mites they all starve and die. You need a certain population of the prey before there is any point in introducing the predators. If there aren't any mites there to eat then you might as well just send me the money instead, cause if you're going to just throw it away. ;D ;)
Seriously though, you do need an established colony of the mites before the predatory mites are of any use.
-
The most effective spray I've found for mites has been Methiocarb, found in Provado aerosol. Unfortunately I can't find it except mised with the Imidacloprid. Soaps, oils, alcohols, and plain water all have some effect but unless I get 100% kill on my greenhouse succulents they just come back twice as strong. They are also a pain because they mark some plants or mess up wool. My mites appear to be resistant to some other sprays. Westland Bug Attack with Abamectin is also a good one, also combined with a systemic insecticide.
P.S. I've also used Resmethrin. It stinks and the the slightest amount too much really burns the plants.
-
General Information from the side of Spraying oil.
'Spraying Oil is a thick white emulsion of petroleum distillates and surfactants which readily mixes with water. It is recommended for the control of red spider mites, mealy bugs and scale insects, pests which are difficult to control. Spraying oil works on red spider mites by both blocking their breathing pores and by making the leaf surface inhospitable to migrating mites. Scale insects and mealy bugs cannot tolerate the penetrating solvent and surfactant properties of Spraying Oil and they will not attach themselves to, or invade treated leaf surfaces.'