pear scab ?'s

windfall_rob(vt4)September 10, 2013

I have a Harrow sweet that fruited this year for the first time.

I lost all the fruit to what I believe is pear scab. The fruit looked normal early in the season...perhaps a bit russeted by early summer and definitely undersized. Now all the fruit are cracked and corky (in appearance)on the surface.

This is the same tree that I had concerns in spring about a possible fireblight infection. I had a number of lesions on the leader and some small branches that were corky, sunken, and showed cambium stained brownish red when scratched. All effected wood got cut out.

At the time I was surprised to see it. Fireblight is pretty uncommon here in northern VT and harrow sweet is reputed to be fairly resistant (none of my other pears or apples showed symptoms)

I now read that pear scab can infect twigs, and that has me wondering if that wasn't the problem all along.

Is the pear scab limited to new twigs only? I was seeing damage to twigs as well as growth several years old.

Are the lesions present for a single season or can they become a perennial problem like a canker? Could this wood have become infected when young and maintained the scab lesion as it grew?

Is harrow sweet particularly sensitive to pear scab? Again none of the other pear varieties I have (even those on the same tree) show symptoms.

I spray the apples in spring with sulfur to control scab, but always skipped the pears. Hopefully including them in the sulfur sprays will eliminate this issue.

Any advice appreciated. I am not 100% on this being scab, No leaf damage was readily apparent nor did the fruit show the early signs of infection that I have read about and seen in a quick google search.

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beeman_gardener(5)

I don't know Harrow Sweet, but it sounds like the same problem I have.
It seems to affect just the twigs, but look for early leaf drop, these turn brown and crispy.
I sprayed both my trees with Lime sulphur, but ran out on the second tree which now suffers with scab. This year it will get two treatments, fall and spring.

    Bookmark   September 10, 2013 at 8:14PM
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mamuang_gw

Rob,

Can't answer your questions but my 2nd year Harrow Sweet has fruited for the first time this year too.

This summer was hot and humid, it had something that looked like fire blight. I cut of several inches of infected branches. Then, there was pear blister mites on many leaves. I sprayed with wettable sulfur. As of now, the fruit look fine, a little russeted, nothing else (fingers crossed). Maybe, the sulfur helped with scab.

Then, I just went out to check HS again today. The tip of the main branch has wilted!!! Don't know it's a beginning sign of another round of fire blight or the weather. It's cool (50's -60's) for a week and today was up to 90.

What get me nervous is the fact that my nearby Blake's Price shoot is fine, nothing wilted. Both trees planted at the same time and have about the same amount of growth. In fact, BP got more fire blight and pear blister mites this summer. (it's supposed to be more disease resistant!!).

    Bookmark   September 11, 2013 at 5:11PM
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alan haigh

Fire blight should be no mystery, leaves suddenly brown with a slightly bleeding canker at base of dead wood.

Harrow Sweet tends not to get scab or psyla here- one of my healthy type pears. I have much more trouble with Seckel, Bosc and a couple of others. The book says psyla can lead to fab. leaf spot which I really don't know the difference from scab. Either can create the symptoms you describe. You can see psyla with a strong mag glass at the point leaves come out of growing tips. Find a picture on the internet.

    Bookmark   September 11, 2013 at 8:05PM
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