Scottish Rock Garden Club Forum
Cultivation => Cultivation Problems => Topic started by: ArnoldT on April 29, 2013, 04:03:05 AM
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Can anyone help to identify what this is attacking a Beurre Giffard pear.
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Arnold,
looks similar like a fungus infection on peaches caused by Taphrina deformans.
I've no knowledge if it can infect pears, too.
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Armin:
Thanks It does look similar.
I found some similar images on the web. I may have to contact our local University to get a beet idea.
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Just got the answer from our University Diagnostic lab.
Pearleaf blister mites.
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Is the culprit Phytoptes pyri?
Minute, only 0,16 to 0,2 mm...
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Eriophyes (=Phytoptus) pyri , is an eriophyid mite found on pear, Pyrus, species.
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Which treatment is general recommended against pearleaf blister mites ?
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This RHS page says there is nothing chemical available to the amateur gardener :
http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=661 (http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=661)
Control
Non-chemical
In light infestations it may be worthwhile removing infested leaves or shoots to stop the pest spreading all over the tree. However, taking infested leaves off a heavily affected tree will do more harm than good.
Chemical
There are currently no pesticides available to amateur gardeners that are effective against this mite, so its presence has to be tolerated.
Fortunately, although heavily infested trees may look unhealthy, the mite has little impact on the tree’s ability to produce fruit.
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Maggi:
That's interesting. I sent a sample to our State University system and got back the diagnosis along with a list of what to use to control it..
Here's the list:
abamectin
acephate
carbaryl
deltamethrin
fluvalinate
methiocarb
oxydemeton-methyl
spinosad
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Well, Arnold, I am not at all familiar with most of those chemicals - but I have a strong suspicion that one could wipe out half the population, never mind the plant problem, by using them! :-X :-\
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Earwigs I have read are predator of these tiny pests. To attract earwigs to your pear tree place a pot filled with straw upside down at the base of the stem. During the day the earwigs will hide & rest in the straw and by night they will climb in the tree to feed. Earwigs are also wonderfull to keep greenfly under controll.
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Maggi:
I was surprised at the list a well.
The only one I would consider is spinosad which is listed as an organic pesticide.
I believe it's derived from a bacterial source.
The earwig idea sounds like it maybe possible to do.
Thanks,
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Earwigs I have read are predator of these tiny pests. To attract earwigs to your pear tree place a pot filled with straw upside down at the base of the stem. During the day the earwigs will hide & rest in the straw and by night they will climb in the tree to feed. Earwigs are also wonderfull to keep greenfly under controll.
Hello Francosi, I did not know that earwigs would predate on such tiny pests , so this sounds like sensible advice, thank you.
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Here's a reference from a journal:
Augmentation of European Earwigs (Dermaptera: Forficulidae) for Biological Control of Apple Aphid (Homoptera: Aphididae) in an Apple Orchard
Authors: Carroll, Devin P.; Hoyt, Stanley C.
Source: Journal of Economic Entomology, Volume 77, Number 3, June 1984 , pp. 738-740(3)
Publisher: Entomological Society of America
Abstract:
European earwigs, Forficula auricularia L., reared on dogfood in an insectary, were released five to six per tree in an experimental block of prebearing apple trees and provided with artificial retreats on the trees and straw spread on the ground. The number of apple aphids, Aphis pomi DeGeer, on these trees declined in 3 weeks from near 500 per tree to less than 50, compared with over 3,000 per tree in an adjacent block kept free of earwigs and nearly 2,000 in a control block.
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Thanks for the inspiring conversation.
Reminds me to mount a pot filled with wood wool as new home for earwigs in my Viburnum opulus shrub to control black aphid population.
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Hi Arnold,
I try using a formulation containing Neem oil, which works well against most mites and does not harm any other animals (except insects feeding on the leaves). Needs to be used repeatedly to kill the offspring, but as it does no harm to other animals I'd try this, if available in your country.
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Michael:
Thanks I've Neem oil on the shelf.
This pear mite can be completely controlled with a dormant oil application. I missed the oil spray this year, so I'm seeing the results of not spraying.
One of the quotes I saw was that the pear leaf blister mite is found in abandoned orchards.
Ooops!
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Hello Francosi, I did not know that earwigs would predate on such tiny pests , so this sounds like sensible advice, thank you.
Nature often surprises us ... I have now earwigs living in my greenhouse, and I assume this is why I don't have any problems with aphids on the vegetables growing in the greenhouse, where last year (the first year for my greenhouse ) I have had plants literally killed by the greenfly. Whenever I find a pest I look after who is the natural predator and then make sure I can attract this predator by providing the suitable habitat. To fight slugs I have attracted hedgehogs, to fight snails I am working on making the environment even more attractive to mavis birds. I must admit that this is relatively easy for me living on the countryside but I can imagine attracting birds or mamels to an urban environment may simply be unrealistic.