Pear disease

[ArnoldT]

Can anyone help to identify what this is attacking a Beurre Giffard pear.

[Armin]

Arnold,
looks similar like a fungus infection on peaches caused by Taphrina deformans.
I've no knowledge if it can infect pears, too.

[ArnoldT]

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.

[ArnoldT]

Just got the answer from our University Diagnostic lab.

Pearleaf blister mites.

[Armin]

Is the culprit Phytoptes pyri?
Minute, only 0,16 to 0,2 mm...

[ArnoldT]

Eriophyes (=Phytoptus) pyri , is an eriophyid mite found on pear, Pyrus, species.

[Armin]

Which treatment is general recommended against pearleaf blister mites ?

[Maggi Young]

This RHS page says there is nothing  chemical available to the amateur gardener :
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.   

[ArnoldT]

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

[Maggi Young]

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! 

[François Lambert]

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.

[ArnoldT]

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,

[Maggi Young]

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.

[ArnoldT]

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.

[Armin]

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.