I have added some pictures here to help show this observation. Thank you very much for the advice on imidacloprid and spinosad. I'm seriously considering a systemic; all this time I've been thinking to keep this as a sacrificial citrus tree to help keep others from being infested.

This is the Genoa/Genova lemon with no leafminer damage or very very little damage.

Here are the grafts on different rootstocks with and infestation of leafminers;

The rootstock is not the issue; it is the phenology of the shoots. CLM, like many other pests prefer the newest, tenderest leaves.

I would agree except that the Genoa/Genova tree that is in the ground also puts out new growth, and the new growth hasn't been attacked by the leaf miner. It seems like the trifoliate rootstock is putting out "chemicals" or properties into the limbs that citrus leaf miners enjoy more so. Could you comment or give more insight? I am just trying to learn.

Thanks for posting.

It seems they do have a preference with "smell". Here's a source I looked at:

http://stoppinginvasives.com/dotAsset/587ddfa1-b644-4b54-9cdf-43cf5ccebddf.pdf

It says they prefer grapefruit and pummelos, but are found on other plants in the family Rutaceae. Interestingly, they also infect incompatible hosts like jasmine, but are unable to complete their life cycle in them. I know that citrus blossoms smell awfully like jasmine---so it looks like you're on to something, McLovin'!

-Tom

I repeat, it is not the rootstock that is making the difference; unless it is because of different timing of the flushes. Sometimes the CLM is present and sometimes it is not, or is in between life cycles.

mc lovin, what John said :-) The CLM simply hasn't discovered your other tree's very tender leaves, yet. YOur rootstocks cannot impart insect-repellant qualities to the scion. I have never head of this quality imparted to the cultivar scion. The treatments of choice for CLM are either Spinosad (which you can mix with a hot oil such as Volck or Neem for a "sticking" quality, as long as your daytime temps are below 85 degrees F), or systemic imidacloprid. You will need to spray the Spinosad every 3 weeks through about October (in my area), or, apply Imidacloprid about 2 weeks prior to CLM showing damage in your area. For me, that is usually mid-June application. There is no "preference" with citrus cultivars, I think this article, being rather old, is simply missing data. Re-read the article, and you'll see there isn't a "preference" listed or stated, just that the article mentions that is "most commonly found on pummelos and grapefruits". When in fact, ALL citrus are affected if they have new and tender flush, as John has mentioned. What you will find, is during their infestation time, those cultivars that tend to flush heavily at that same time will also suffer the most damage. For me, that tends to be grapefruit/pummelos and lemons. Which may be why this early article cited these two citrus cultivars. But, I can tell you with complete certainty, that any of my citrus with new flush will be attacked without preference.

Patty S.

Thanks for the post Patty S. I keep going out in the mornings and the evening and use my finger nail to split the little CLM larva within the leaf, but I've reached my limit. You wrote that I should use Imidacloprid 2 weeks before showing damage. Would it help to use it now? All of my trees are very young. Where do I get Imidacloprid?