chestnut weevil control

The trees are hanging heavy with chestnuts this year. We have had some trouble with weevils in the past. I'm hoping this year will be better because last year was a terrible chestnut year and we had almost none at all. No chestnuts, no weevils?
We shall see.
Our only defense has always been to pick them up every day as soon as they fall, but I'm so busy this year that I'm worried I'll miss them and I'm not sure I want to be taking care of wwoofers to do it for me because they can be as much work as they are help...

Any experience to share?

It's time!

I'm wondering if guiding the chickens over under the chestnut trees in the morning when they're hungry and raking a bit would help them find weevils in the soil under the trees.

When designing a food forest with chestnuts or other spiky hulled nuts it's worth noting that children will be deterred from walking near them.

Is it that nobody has lots of mature chestnuts hitting the ground or is it that nobody's chestnuts have weevils?

I have three mature chestnut trees that produce lots and lots of nuts. The market is there to buy them but I need to beat this maggoty looking problem if I am going to sell them.

One obvious solution is to be out there getting every chestnut as it ripens but harvesting is tricky for me because wherever I go, I am taking a baby and toddlers with me. Harvesting blueberries like that is one thing and harvesting chestnuts is another. It getting chilly for wwoofers in the unheated quarters...

I wonder if the chestnut weevil is the same one that also attacks acorns? If so, the abundance of weevils may have more to do with neighboring oaks than anything else, especially since chestnuts are about extinct in the wild where you are. Chickens are too small to eat most acorns, much less chestnuts, so they would have to scratch up the grubs when they exit the nuts and go into the soil (which they will eventually do). So you'd have to pen the chickens under the trees and just leave them there for several months at least, even after you gather up the rest of the nuts, assuming you do so, so as to scratch the mulch and find the grubs that have already bored out. A pig, or perhaps a ratite or even a turkey, on the other hand, would swallow the whole acorn (and the chestnut too, in the case of the pig), and so bye-bye weevil too.
I've found working with acorns that if I open them as they fall, sometimes the weevils are very small or still just eggs, and if I dry the nutmeats hard in the sun right away, they can be ignored; the visible grubs have not eaten much of the nut and this portion can be clipped away with a pair of hand pruners (this is also how I shell both acorns and chestnuts) But that is for subsistence use, markets will want the chestnuts fresh, and in the shell.
Native peoples often would burn the ground under nut trees of many kinds, which would destroy insects in the ungathered nuts and the mulch layer if done at the right season.

I'm pretty sure they are chestnut weevils. The trees are mature and have been producing for years. Our local land trust has been doing work on chestnut breeding for years. I think there are enough nuts to sustain a population.

I too am very interested in this, we have a small stand of chestnut trees and could possibly have a harvest if we could find out how to control the worms in them. I'm fairly certain ours get them before they hit the ground... I have modified a leaf blower to be a backpack fogger and it works really well, storebought backpack foggers run around 800 bucks and while this one isn't quite as versatile as a dedicated unit, it works great. I put a misting nozzle at the end of the blower (you do need a decent backpack blower for this) and have it hooked up with an air compressor quick connect to one of our sprayer tanks that fits on a 4 wheeler. It will reach to the top of a very tall tree and apply a very good "fog" coat of whatever I'm spraying to the point that an entire tree can be dripping wet with a minimal usage from the tank, only real issue is you're tethered to the atv with whatever length of hose you have. Not much of an issue though. I guess you could do it with a pump sprayer, but it would require constant pumping. This little critter works like a champ and allows you to get whatever you are choosing to spray applied all over the plant since it's incorporated in a real gale force wind...

Anyhow, this setup would be great for applying some sort of liquid to deter them, just unsure of what I should be using. Something "organic" of course. Any suggestions?

I'm going to try to get a good photo of the weevil. They lay eggs in the chestnuts which hatch out of the nut and look like maggots. If the chestnut is on the ground in the orchard the larva crawls into the ground for the next part of its life cycle. If it's in a bucket on the floor the larva writes on the bottom of the bucket (if someone leaves a basket on the floor with chestnuts in it I am left with maggots crawling across the floor- great for company!) The larvae leave the chestnuts with holes in them.

Good orchard hygiene helps, getting all the nuts right when they ripen. The chickens do like the larvae. We really don't mind much. It does increase the labor because the holey chestnuts need to be sorted. The maggot look is a real turnoff in the marketplace though.

I don't spray anything in my orchard with anything, organic or otherwise. I could be convinced to spray something organic and non toxic but haven't been convinced yet.

I have read about treating them in hot water of a specific temperature for a specific amount of time. It seems like a sort of big operation. Buying the equipment and getting the science right.

Apparently the weevils live mainly on the ground and attack the nuts just as they begin to harden. See the link below. The alternative to spraying is shaking the weevils onto a sheet on the ground.

http://www2.ca.uky.edu/entomology/entfacts/ef206.asp

I bet the chickens would like a sheet covered in weevils!

They are big trees, that would take a lot of sheets. I guess we could whack the branches with long poles?

I watched a larva chew through a thick clear plastic bag last night.

It sounds like the grubs will spend most of the year in the ground around the trees. If I could teach the chickens how to find the grubs I bet they would scratch them all out by next fall. They might scratch the ground to shreds looking but it would be worth it.

chestnut weevil is a huge problem that I have thought about for the past few years. there are two species of weevil that attack chestnuts, they are not the same as the ones that go after acorns. sanitation is the main organic method in this country, as the only effective spray is seven (a nasty synthetic insecticide). the problem with sanitation (picking up all the nuts or running pigs and poultry through) is that the when weevils emerge from the ground in the spring, they can fly up to a mile in search of chestnut trees. so if there are other trees in the area, sanitation will not be a complete solution.
i have tried the hot water treatment, and it does kill the weevils, but often the nut can taste bad depending on how mature the weevil was at time of treatment.
i have often wondered what did/ or do people do in europe and asia where wild trees abound and weevils are sure to find any orchard. i have heard of hot water and cold water treatments as well as smoking the nuts.
the best idea i can come up with for my orchard is to clean up as many nuts as possible every year. then put the nuts in bags for a few weeks in the fridge. by then the weevils will emerge and i can pick out the bad nuts one by one by noticing the exit holes left by weevils. using a hot water treatment actually hides the bad nuts.
i'm glad people are talking about this, chestnuts are such an amazing food to grow for so many reasons.

Thanks for your response, I'm happy to hear from folks who deal with this. There is a great market for chestnuts here but I am beginning to despair of selling them. I have sold then to the local food co-op in the past but I don't want to have anyone have a bad experience with surprise maggot-looking grubs. Word of mouth can be great and it can do a lot of damage.

We do the same thing, wait for the holes and eat the others.

What did they do back in the days of the great American chestnuts?! There must have been weevils but you never hear about them roasting on an open fire....

Actually, the weevil larva are excellent scrambled in eggs. They are not really maggots but beetle larva and I saw a show where the guy was eating them. Hmmmm. I know with acorns, the ones that float are the ones with larva. We put them in a metal bucket with some sawdust on the bottom. After a very brief period of time in a warm house they burrow out and drop into the bottom of the bucket where they can be gathered to either feed the chickens or feed us. Pretty much flavorless but lots of good fat and protein. The key seems to be consistently harvest everything you can clean up and do it enough that over the years the population of weevils declines. Not much you can do when all the neighbors are not doing the same.

It's good people have been getting this conversation going... It's a bit late to provide input for this past falls season, but I'll put in my 2c of experience...
I've been gleaning chestnuts from a research orchard at Cornell outside of Ithaca, NY. THe whole area is completely deer proofed, and super mowed/clean/etc, so very little wildlife... As you can imagine, the chestnut weevil population is massive.. Very good reminder that allowing wildlife access to some of the food you grow can help your food grow! I was collecting nuts with nearly 100% weevil load for a bit, then got things at least a bit better...

I would collect a big pile of nuts (ideally as soon as they drop), and immediately do a hot water soaking bath... THat would be 120F water around the nuts for 10-15 minutes. I used a thermometer and kept adjusting so it would hold like the instructions told, it's like a hot water canning bath but for killing!
The nuts that had a lot of damage already would cook up later on with an off flavor and color, but ones that had only baby baby worms in them were pretty good to excellent in flavor... And unlike the first rounds I was picking up that literally every nut had a hole in it a week later and the 5 gallon bucket was writhing with worms, these had NO worms come out after a time. I'm hoping the hot water will not kill the germ (as it was documented to not do), so that I can grow these trees out from seed this spring. That is my main interest.
Hoping this discussion gets bumped up and explored EARLY next season so we can be eating more of these great nuts next fall!

"Chestnut weevils" do in fact attack acorns, and hickory nuts such as pecans as well. The species you're dealing with is most likely Curculio Nucum although it could be any of the Curculio species. The adult weevils lay their eggs on the developing nuts while they're on the tree, and the larvae eat the nuts before boring out and dropping to the ground, where they remain until maturing into adults.

There are two main biocontrol methods against the weevils. The first is Heterorhabditis Indica which is a nematode you can buy from various suppliers and which attacks larvae in the soil. The other is Beauveria bassiana, a fungus which is used to control various different insects and has been found very effective against Curculio larvae if applied to soil, and adults if it's sprayed on developing nuts. The main problem is that, while you could easily kill off the larvae around your own trees, if they have natural habitat nearby they'll quickly return. If you spray beauveria on the developing nuts, you could infect adults and get them to carry the disease around, but it'll probably be an uphill battle either way.

I am interested in the nematodes, Marc, have you tried them? Has anyone else?

'fraid not. I don't have any trees myself, I just happened to look it up since I'd never heard of those weevils before and figured it'd be good to know since I do eventually plan on growing chestnuts.

Some of the American indians would do controlled burns underneath the nut trees right before they emerged from the ground. The adults almost move like moths but are more slender.

Uphill battle indeed! I have found out that the neighbors across the way have chestnut trees that they ignore. Hosts for weevils no matter how meticulous we are. Argh. The nuts seemed to be much improved when we began harvesting but it was a false impression. So. Many. Larvae.

I have six nut bearing trees that produce tons of nuts. A large number of them contain weevils. How do I stop the invasion?  I have never seen the adult that lays the eggs an don't know how to prevent the infestation.
Any suggestion on how to stop the continuation organically? I live in Upstate NY
Bob

Bob and others, I've heard there are preventative measures worth exploring but once the infestation hits different strategies need to be taken. Primarily, gathering chestnuts daily (or once every 3 days at the least) and promptly treating them in a precisely 20 minute 120dF water bath then drying them off. This kills the weevil and sterilizes the nut before the weevil gets too big for consumer comfort.

Would it be possible to just bag the burrs? I'm not sure with what since they're sharp but that would prevent the grub from entering. Similar to what we do with apples.

on a big productive chestnut tree, you harvest by picking up fallen nuts. there should be way too many nuts that you couldn’t reach to bag.

the hot water bath that r. spencer notes is definitely the industry standard for the orchards i know in ohio.