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Author Topic: How to deal with Leaf Miner  (Read 480 times)

SoCal2warm

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How to deal with Leaf Miner
« on: October 31, 2020, 11:27:09 AM »
This question has repeatedly risen again and again and again.
Rather than attempt to repeatedly answer it in multiple different threads, I am just going to answer it here, and then whenever someone asks this question, someone can just simply link back to this page.

Leaf Miner is a very common problem, and is caused by the larvae of a very small insect burrowing inside the leaves. Typical signs are many of the leaves looking twisted and deformed. But upon closer inspection, one can often see maze-like patterns on the undersides of some of the leaves.

Since the insect larvae is actually burrowed inside the leaves, typical treatment focuses on interrupting this pest's life cycle rather than trying to kill the larvae itself.
The life cycle of the pest, from larvae to little adult moth, is about 2 weeks. If you continuously kill all the adult moths, eventually it will eliminate the larvae.

Getting rid of leaf miner is not easy and takes some work and dedication.

One of the best combinations is a mix of insecticidal soap combined with spinosad.

Thoroughly spray the leaves of the entire tree, making sure especially to thoroughly spray all the undersides of the leaves. Newer younger leaves are the ones most vulnerable to leaf miner, they do prefer younger leaves, so make sure those are sprayed well.

The best time to spray is early in the morning, or in the evening when temperatures have cooled off. This will help prevent the spray from evaporating away too fast.

After spraying, you will need to re-spray the tree again, 7 to 10 days later. This is important, because after the first spray, the larvae will emerge from the leaves and become moths, which will then lay eggs again.
After this, you might even need to spray a third time, just to be sure.

Adequately spraying all the leaves is not easy and can be very labor-intensive for a large tree. Every leaf needs to be sprayed.

If you see any leaves that look very infested, you can just pluck (or cut) them off. You only need to do this if almost the entire underside of the leaf is covered in a maze pattern.

This strategy can be successful in getting rid of leaf miner, which can be difficult to get rid off.
It is possible the leaf miner could come back to the same tree, in which case you will need to spray again.

Make sure to check any nearby citrus trees for any signs of leaf miner. Carefully look at each leaf. (Or if very large trees, carefully look at several different leaf areas throughout different parts of the tree) If there are any other citrus trees very close by, you should probably give them a very light casual spray. If any of the surrounding trees are harboring leaf miner, the leaf miner will just hop back to the original tree you just treated.

For large trees, or repeated use, it is most economical to mix from concentrate. This will take some basic calculations and rough measurement. There should be instructions on the packaging.

The common advise given by most citrus experts is that (if you can believe this) Leaf Miner does not really need to be treated. I believe this is only somewhat true. If not treated, it can spread. To either other parts of the tree, or to other surrounding trees. Leaf Miner will disfigure many of the leaves, making things not look nice. It can also reduce the health of the tree, resulting in slower growth. For newly planted very small trees, it can even ultimately sometimes lead to the death of the trees, if the tree has very few leaves that are functional. In my opinion, leaf miner should be treated as early as possible.

The only situation where this may not be true is in a large commercial orchard where Leaf Miner has already completely spread and it's a hopeless case.

It's best to wear gloves while mixing and spraying so the liquid does not get on your hands.

Some people might use neem oil as a way to treat leaf miner. It's more "organic", though probably not quite as effective. Neem oil can also sometimes lead to leaf burn, especially with heavy spray applications.

For very small trees, you might even be able to use your fingers to crush the little larvae inside the leaves. If you look very closely, at the end of the trail on the underside of the leaf, you might be able to spot where it is. A good rinse spray with the hose could blow off any little moths that happen to be on the tree. The little white moths are very small, only about 2 millimeters long. You might have to look very closely, with the right lighting, to even notice them.

A leaf being deformed may look very unsightly, but it will not pose any damage to the tree. It might even still be functional. So there is not necessarily reason to remove it. The twisted deformation is caused by liquid being sucked out of the leaf by the insects while the leaf was still small and growing.
You just want to make sure the insects are gone so new leaves will not become that way too.
« Last Edit: October 31, 2020, 11:28:44 AM by SoCal2warm »

roblack

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Re: How to deal with Leaf Miner
« Reply #1 on: November 01, 2020, 12:27:21 PM »
Great info!

Hoping Tree Defender bags are a good alternative to insecticide use.


Laaz

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Re: How to deal with Leaf Miner
« Reply #2 on: November 01, 2020, 04:08:26 PM »
Lol.Anyone who believes they can eradicate CLM from a tree grown outside in the ground is delusional. Once they are there you will learn to live with them, period. Some years they are very mild & other years they are heavy.

lebmung

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Re: How to deal with Leaf Miner
« Reply #3 on: November 01, 2020, 05:44:37 PM »
If you have a severe infestation a biological control seems to be more logical especially in a greenhouse.
Yellow traps are good for identification and after use of the predatory parasitic wasp
'Diglyphus isaea', they will eat everything.

I have serious doubts that insecticidal soap will kill the larvae and eradicate everything.

EricSC

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Re: How to deal with Leaf Miner
« Reply #4 on: November 02, 2020, 12:56:56 AM »
Very appreciate the summary.  I will definitely give it a trial.   

spaugh

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Re: How to deal with Leaf Miner
« Reply #5 on: November 02, 2020, 03:27:47 PM »
Lol.Anyone who believes they can eradicate CLM from a tree grown outside in the ground is delusional. Once they are there you will learn to live with them, period. Some years they are very mild & other years they are heavy.

Also every house in southern CA has citrus.  Millions of trees.  You can try and spray for them but the other 5 million people arent. 

Just dont use so much fertilizer. Use mulch and mild fertilizers during the hot months.  Its usually during summer when the are out. 
Brad Spaugh

EricSC

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Re: How to deal with Leaf Miner
« Reply #6 on: November 02, 2020, 06:38:36 PM »
spaugh,

Yes.  A lot of them.  It is the homeland of CLM. 

SoCal2warm

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Re: How to deal with Leaf Miner
« Reply #7 on: November 02, 2020, 09:35:43 PM »
I have serious doubts that insecticidal soap will kill the larvae and eradicate everything.
The larvae is not killed. The point of the treatment is to kill the moths before they can lay more eggs. All the larvae will eventually develop into moths and leave the leaves. As long as the larvae are inside the leaves, it is near impossible to kill them.

If a moth lands on a leaf that is still wet and has been sprayed with spinosad, that moth will suck up some of the moisture and then die.

SoCal2warm

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Re: How to deal with Leaf Miner
« Reply #8 on: November 02, 2020, 09:37:44 PM »
Also every house in southern CA has citrus.  Millions of trees.  You can try and spray for them but the other 5 million people arent. 
You might have to check your surrounding neighbors yards for citrus trees, and offer to inspect and/or spray them.

Millet

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Re: How to deal with Leaf Miner
« Reply #9 on: November 02, 2020, 09:49:33 PM »
Citrus leaf miners are a big problem, but doing nothing is not the answer.  As far as I can see the best  "answer' is Spinosad.   Or you can move to Colorado (PLEASE do not do that) where leaf miners do not exist.

spaugh

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Re: How to deal with Leaf Miner
« Reply #10 on: November 03, 2020, 12:28:01 AM »
You can and should ignore it.  It wont affect your trees crop.  Im telling you this from experience.

Another one of our members here and friend of mine greg has a blog on gardening.  He is a master gardener with the UC and very knowledgable guy.  He has also come to the conclusion not necessary to do anything for CLM.

Heres his article on the CLM
https://gregalder.com/yardposts/dont-spray-for-citrus-leafminers/

Brad Spaugh

roblack

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Re: How to deal with Leaf Miner
« Reply #11 on: November 03, 2020, 09:28:51 AM »
Awesome Brad! That's great info, and fits with my usual style of doing as little as possible.

I read that using Tree Defender bags when trees are young greatly reduces infection and damage, and they remain cleaner after removal of the bags. Getting them established is the idea perhaps, in addition to natural predator population increase.

Going to bag Sugar Belle and a few kumquats, and leave everything else exposed and unsprayed.



Laaz

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Re: How to deal with Leaf Miner
« Reply #12 on: November 03, 2020, 12:16:45 PM »
Use Bayer Advance on new grafted trees to protect the new flush. Once established leave them be.

spaugh

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Re: How to deal with Leaf Miner
« Reply #13 on: November 03, 2020, 01:51:28 PM »
I dont even bother with that.  They will grow out of it.  I would just reccomend using some patience.  It seems many new gardeners have zero patience.
Brad Spaugh

Citradia

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Re: How to deal with Leaf Miner
« Reply #14 on: November 03, 2020, 07:59:05 PM »
I donít have leaf miner either. I donít think. The only insect problems I ever see are spider mites when potted citrus are indoors in winter. Like Millet said, living where thereís no other citrus trees or their pests/ diseases has a few perks.

Millet

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Re: How to deal with Leaf Miner
« Reply #15 on: November 03, 2020, 08:21:14 PM »
I agree with Laaz concerning leaf minors on small grafted trees.   On small citrus trees I would definitely control miners.   On large mature trees, I would not bother.

laidbackdood

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Re: How to deal with Leaf Miner
« Reply #16 on: November 07, 2020, 12:23:43 PM »
I mix neem oil/eco oil with a small amount of fish emulsion/seaweed and spray with that.......works for me and they get a foliar feed as well.

 

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