Plum Curculio (PC) Questions and tips

I titled this post so it will come up in searches and be a good reference for PC.
There are a lot of growers with experience in PC control and also a lot people who need help. My intent is to both post your advice and ask questions. This could help a lot of people me included.

My first question:
According to published literature and my observations PC come out when the nighttime temperatures reach 65. We had a warm night a week ago and I got hit by them. Now the nighttime temperatures are in the 50s to low 60s. Will they continue to come out or will it have to get above 65?

Maybe another way to salt it: Does 65 degree temperatures wake them up and they are active thereafter as long the temperature is above some minimum threshold?


If by “come out” you mean emerge from pupal stage to adult stage, this can be affected by the weather but is usually a general seasonal event that can vary slightly from year to year.

Otherwise, adult weevil activity would be similar to honeybee activity that for the bees starts around 60 degrees. Butterflies are also temperature-activated. The insect activities then vary day-by-day and even hour-by-hour depending on the current temperature, so your last sentence is accurate.


i was wondering when these guys are active in the soil temperature or season wise and what forms they are in while in the soil?

The honeybee thing was very helpful as always @LarryGene

I would like to timely apply some beneficial nematodes on them

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My impression is a certain number of growing degree days causes them to hatch, and once they are out the activity is scaled by the time of day and temperature. They are most active at night and at warmer temps. But they are still active at lower temps, just moving more slowly. I have personally found them cutting crescents at night in a long stretch of cool weather. But when it is warm at night they are moving what seems like 5-10 times faster with 5-10 times as much damage.


Thanks for the contributions. I would like to see members post their experiences on control, both organic and non-organic. Please don’t make it a debate. Each method is valid and each person is entitled to their methods and opinions. Speaking of opinions please don’t state opinion as fact. I know it can be hard to do, suntimes unknowingly.

Are these evidence of Plum Curculio damage???

I just sprayed yesterday. How often does one need to spray to limit the damage?
Guess it’s time to whip out the Surround. ?

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Yes. You got PC


That damage looks maybe three days old so it was from before your yesterday spray. The wider the “C” crack gets the older it is.

If you are using Surround make sure the coverage is good. I wrote a long list of Surround tips in the Low-Spray Guide.


How many days does it take for the eggs to hatch? Are the eggs exposed in the cut where spray will kill the eggs? If the spray won’t kill the eggs will the hatched PC die if spray is on the fruit.

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It depends on what agent you are using to kill the PC and if it has kickback

It is chilly again, in VA, after a couple of warm nights . . . so all of the above makes a lot of sense. I check out the development of my fruit (as some of us joked about in other threads) at least once . . . sometimes 3 or 4 times each day. Little ‘dents’ appeared just a few days ago . . . and I was waiting for all the stone fruit petals to fall - and then I sprayed ASAP. On Monday morning.
Last evening I gathered the little plums as samples - to use to ask if this was PC. There was not a lot of evidence, yet . . . but enough to be able to find a few damaged plums to photograph.

Thanks for the speedy answers . . .
@scottfsmith I will have my first Surround experience today! I have your very thorough Spray Schedule and am combining it with a couple synthetic ‘players’ as well. I am determined to end up with some fruit this summer!!! :rage: So far I have some great fruit set happening. I never recall seeing this many little fruitlets in prior years! And what we did get . . . always dropped. Here’s hopin’ . . . .

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I’m preparing to spray for PC in the upcoming days based on petal fall. Most of my plums were frozen out but I’ll have a fair amount of peaches and nects that will need coverage. I’m going to spray surround and also add imidan. It’s probably overkill but this is the best shot I’ve had in the last few years of getting a harvest so I’m going to be a little overzealous.


It’s probably overkill but this is the best shot I’ve had in the last few years of getting a harvest so I’m going to be a little overzealous.

Yes, @speedster1 . . . at the risk of being non-PC about PC :grimacing: . . . I sprayed with Imidan, too. I’ve avoided using anything like Imidan - but after years of dropped, rotting and bug-eaten fruit - I’m up for trying most anything these days! It’s a really cruel world here in southeastern VA . . . Every disease, insect and weed known to man!

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Do PC cause fruit drop only if the larvae successfully reaches the center of the fruit vs superficial cuts?

It would be impossible to pull all PC’d fruitlets off . . . but should they be removed, if you see them? And destroyed?

On some thread Scott described the different appearance of a harmless “feeding” scar vs a damaging “egg laying” scar (classic crescent). The feeding scar is cosmetic damage only and perfectly acceptable IMO. Edit: Scott reports feeding scar is a round divot.

That applies more to apples and pears as the fruit cells expand very quickly. I do have PC scars on apples and pears that were only “skin-deep.”

Karen’s fruit are plums so PC can reach the fruit’s centers with ease.

My experience with PC is that the first wave (generation) of PC is more damaging than the second wave.

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Good point on plums (I edited my post).

I admit I cut up so many damaged fruit. My memory may be fuzzy but I think PC larvae make a straight line to the center of the fruit. Then, there are coddling moths and OFM aiming at the same fruit.

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The feeding scar is just a round divot. The egg laying have the crescent which is designed to keep the growing fruit from crushing the egg. They only make crescents after laying the egg so if you see a crescent there is an egg.