Is This Pear Leaf Blister Mite?

Bradybb(wa8)April 14, 2014

I have a young Chojuro Asian Pear and as far I can tell,it is Blister Mite that is affecting quite a few leaves,but wanted to make sure.
I was told by a nursery that Carbaryl (Sevin) will help during the growing season,if it's PLBM and Lime/Sulfur during dormancy.If more pictures are needed,I can provide them.Thanks,Brady

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Scott F Smith(6B/7A MD)

Yup. I use sulphur (wettable powder) and it controls it. All the recs say lime sulphur but sulphur works for me during growing season. Dormant I spray lime sulphur. Lime sulphur may also work in growing season at lower doses as per label; never tried that.

Scott

    Bookmark   April 14, 2014 at 10:55PM
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Bradybb(wa8)

Thanks Scott.Can Sulfur be sprayed during bloom? Brady

    Bookmark   April 15, 2014 at 12:23AM
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alan haigh

Scott, for years I thought the mites couldn't be treated once they enter the leaves and must be eliminated while trees are dormant. I'm almost sure I was told that by a consultant that worked for the company I bought pesticides from. I almost contradicted you, but thought better of it knowing how information based your management is and found confirmation on your treatment from UC Davis.

Apparently oil only works when applied when trees are dormant and the mites are in the leaf scales. I am glad to know of this alternate treatment because I'm usually putting down oil too late to treat pear blister mites. Thanks.

    Bookmark   April 15, 2014 at 6:09AM
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ltilton

I sprayed oil a week ago, just before the pears were starting to get some green on the tips. Hope that will do the job.

They were looking pretty bad by last fall.

    Bookmark   April 15, 2014 at 1:22PM
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alan haigh

Oil has worked for me when I get it down before growth.

    Bookmark   April 15, 2014 at 1:42PM
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olpea(zone 6 KS)

Agree it's blister mite.

Apparently there are pear blister mites with two different types of life cycles, those which affect CA, and those which affect the rest of the country. (See link below).

Hman,
I've had good luck controlling them with 1% oil even during the growing season if I missed dormant sprays. They have 2-3 generations per growing season, so intellectually this would also make sense to me as well. I think oil has some penetrative abilities. Even if it's not enough, oil is bound to get some of the mites crawling around on the leaves.

BTW, as an FYI for anyone who wants to try this. When I talk about oil during the growing season, I'm not referring to one spray, but several oil sprays.

Here is a link that might be useful: Pear Leaf Blister Mite

    Bookmark   April 15, 2014 at 4:01PM
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alan haigh

Olpea, that is interesting what is stated in your guidelines- they only recommend applications of sulfur post harvest and oil no later then delayed dormant (I believe I sometimes get mites on pears that received a delayed dormant spray).

Are you basing your judgement on the efficacy of later oil on your monitoring of the mite numbers or on reduced damage that seems the result of subsequent sprays?

For me, pear blister mites don't generally affect the crop and damage doesn't continue very deep into spring.

    Bookmark   April 15, 2014 at 5:28PM
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Scott F Smith(6B/7A MD)

Brady, you can spray sulphur during bloom. I don't do this unless its critical however.

I used to use oil for PLBM but while it would kill a lot of mites they would build back up the population. Every time I have put down sulphur they were pretty much gone for the season. Last spring a delayed dormant l-s spray gave me completely clear trees except a few spots I missed. Before that I used wettable sulphur for control during the season.

hman, my guess on the post harvest l-s spray is to significantly reduce the population heading into dormancy. Its similar to bacterial spot spray recommendations of spring and fall. Also any potential for setting back the tree is mitigated since its going to be going dormant in not too long.

I have been getting more and more positive on sulphur (including lime sulphur) in the last few years, its a fantastic low-toxicity spray material.

Scott

    Bookmark   April 15, 2014 at 8:35PM
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olpea(zone 6 KS)

"Are you basing your judgement on the efficacy of later oil on your monitoring of the mite numbers or on reduced damage that seems the result of subsequent sprays?"

Hman,

I'm basing it on reduced damage. I should explain the damage I am referring to is partially exacerbated by pyrethroid sprays.

As a background, I use pyrethroids early in the season on stone fruits because they are good against PC and stink bug. Additionally they have a longer PHI, so are most conducive to early season use. Since I already have a pyrethroid mixed in the tank, I use the same spray on apples and pears for stink bug and 1st gen. codling moth.

I've found spraying pear trees infected with blister mite with a pyrethroid will turn a mild infection into a raging infection to the point of severely stunting the leaves and even new growth. By including 1% oil in the tank, the blister mite infection slowly goes away.

I know it's not listed in the literature anywhere (that I've found) but it seems to work based on my anecdotal observation.

That said, Scott's method of sulfur sounds like it would work better.

    Bookmark   April 15, 2014 at 9:59PM
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Bradybb(wa8)

I appreciate your replies very much.Thanks,Brady

    Bookmark   April 16, 2014 at 2:09AM
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NadiaP(8)

I have just been told that my Colette Pear has PLBM. It has fruitlets about 1" in size and I would like to try to mitigate fruit damage by using sulfur as Scott recommends. Can anyone recommend a good organic sulfur product to use? Also, would it help at all to cut off some of the leaves showing the most severe infestation?
Thanks!

    Bookmark   June 15, 2014 at 11:51PM
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Scott F Smith(6B/7A MD)

All pure sulphur products are similar. I use a powder but there are also liquid products, Bonide for example sells one. Lime sulphur is different; you could also use that at a reduced dose.

Please followup here with how it worked. I have never heard anyone else using sulphur besides me.

It does help to pick it off. Now that I spray I only get a few isolated spots missed by the spray, and I cut those all out so they don't spread.

Scott

    Bookmark   June 16, 2014 at 8:13AM
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