plum curc scars - cull now?

cousinfloydMay 14, 2013

I'm seeing lots of plum curculio scars on the 1/2"-1" diameter Asian pears and also on the few plums I have. I think I saw some on the apples, too. I'm not going to spray (although maybe it's too late anyway), and I'm okay with cutting a bad section out of a fruit, but how bad are they going to be? Should I just cull the scarred fruitlets now? If the fruits are going to be ruined I figure I'll be better off culling them now. I've been doing some thinning, and I figure it makes sense to thin the scarred ones first. The curcs won't be able to complete their life cycle in the thinned fruitlets now on the ground, will they? I haven't really noticed the scars on the peaches, but are they there, too, just not as noticeable?

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You cannot let any infected fruit lay on the ground, no matter what size it is. If you do, you're only helping the curcs complete it's life cycle. You should pick up and destroy all fallen fruit on a daily basis. If you're finding infected fruit on the tree, I'd remove it also. You're only going to have to stoop down and pick it up sooner or later.

    Bookmark   May 14, 2013 at 8:54AM
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olpea(zone 6 KS)

As Rayrose mentioned, on the plums, you need to cull all the fruit with curc scars. Infected plums will not grow to maturity. The curc produces a chemical inside the fruit which mimics ethylene and causes the fruit to drop prematurely. The exception is that, when using some insecticides which have "kick-back", the insecticide will kill the plum curc inside the fruit, so that the fruit can be harvested, but will have scarring.

Peaches aren't as susc. to plum curc because the fuzz is an irritant to the insect - as it is to me, which is why I peel them. Plum curc can affect peaches without producing the tell-tale crescent scars.

Apples are different. They are hard enough that many times curcs are crushed inside the rapidly expanding fruit. The apple will be severely scarred but you can cut the bad part out. The problem is that if you have plum curc in apples, you will probably end up with codling moth in the apples as well.

I'm not certain if most curcs can complete their life cycle in Asian pears. I don't grow them.

    Bookmark   May 14, 2013 at 8:58AM
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franktank232(z5 WI)

Apples are OK..most of the for the ones that drop in the "june drop" or whatever it is...if the apple drops, and the egg is inside, a lot better chance it survives and grows and haunts you next year.

Your plums are toast...they'll grow inside and then drop. I'd pick any with scars now and garbage them.

Pears? Pears will grow just fine with scars...I've had a lot on mine that have always turned out fine. The pear is too hard and crushes the egg..only time it ever happens ...which is very rare from research, is if the pear drops for some reason. I think Asian pears are a little softer then Euro pears, so maybe play it more like an apple?

    Bookmark   May 14, 2013 at 9:13AM
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I have Asian pears. The bugs have caused damage only on the skin. No damage inside. i personally think that russetted Asian pears like Korean Giant and Shinko, have tougher skin than that of Euro pears'.

The yellow skin Asian pears like 20th Century has thinner skin.

So far, no damage inside any of my 3 Asian pear varieties. I hope my luck does not run out this year!!

    Bookmark   May 14, 2013 at 12:05PM
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Thanks, everyone, for the replies. Of course, it's very helpful to know to cull the plums and hold out some hope for the Asian pears. I didn't know there would even be any difference.

How would you dispose of the plums if you don't just thin them onto the ground early? I was hoping if I thinned them early that the fruits would rot before the curcs had a chance to complete their life cycle, but it sounds like that tactic won't work.

    Bookmark   May 16, 2013 at 8:05AM
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Scott F Smith(6B/7A MD)

When I pull off the plums I crush them in my fingers if I can, small plums are easily crushed. I carry a waistbelt and any other ones I put in there for later trashing. Well, if the bite is recent I figure I can just drop the fruit since its going to shrivel. You can tell how recent the bite is with experience, it goes from looking like a slice in the fruit to looking like this healed scar which keeps expanding and flattening over time.

One thing I found is the curc often reaches maturity in my crabapples. Maybe they grow slow enough that they don't get crushed, or the flesh is softer.


    Bookmark   May 16, 2013 at 11:03AM
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