Resurrecting an old post: My 3-Year Experience with Lychee Erinose Mite (LEM) Management
Having managed LEM for three-plus years now, what is your summary/experience of where things are, and what are your plans going forward? Are you still growing lychee, or have you given up on it?
I will get us started with my experience:Wind, birds, insects—whatever the source—I got LEM in my yard. Of my five trees, three in one zone got infected, and the other two initially did not. One of them did eventually get it, some time later. I removed the limbs with visible bumps on the leaves; I did not defoliate the entire tree as often recommended. It is possible that the fourth tree got it via a transfer because of the initial approach I took. Whatever the case, once it did, I treated the entire yard as if all the lychees were infected, and every tree received the same treatment. For the last two years, it appears my approach has stabilized things, and I am back to getting fruit. Unfortunately, I still occasionally see some bumps and remove parts of the trees, but much fewer of late. In the last year or so, I have treated the two lychee growing parts of my yard differently again, focusing on the zone with the larger older trees, but keeping an eye on the two other trees.
Here is my current regimen:Spray sulfur on new growth: I spray sulfur whenever there is new growth. I try to spray every two weeks, though I have not been religious about it and miss some time. I believe if I were more disciplined, my approach would work better. The objective is to prevent infestation of the new growth, as that is the time when the leaves are most susceptible to mite infection.
Prune infested branches immediately: I remove any branches or nearby branches that show leaf bumps. I don't wait to get the felt (erineum or erinea); the deformed leaves are sign enough for me. I work "downstream" from the infected leaves. In my opinion, branches below whichever branch has signs of LEM likely already have mites on them. I remove them if the branch has relatively new leaves. Then I spray everything else. The problem is the erineum is like a fortress—there is precious little you can do to get to the mite once they are inside.
Optimized application method: To address the fact that the mites hang out under the leaf, I use the finest spray nozzle I could get my hands on with my powered backpack pump. The adjustable nozzle has a flexible end which I turn upwards and allows me to spray from the bottom up. On the one hand, it gets some spray to the undersides of the leaves; on the other, it creates runoff to the lower branches, potentially spreading the mite. But I assume that if the mites flow in sulfur spray runoff and survive, perhaps they deserve to
. More seriously though, short of an electrostatic sprayer, this is the best I believe I can do.
A Quick Aside on Systemic Treatments
While UF/IFAS does not recommend this product (they recommend Disperss as mentioned earlier in the thread), I have come across some literature that suggests there is a systemic insecticide/miticide called abamectin (brand names include Agri-Mek and Avid) that has some penetrating (translaminar) properties. This allows spray applied to the top of the leaves to penetrate the leaf. Even that research does not suggest this treatment is effective if you already have erinea, but it does suggest it could help protect new leaf growth. I have not tried this yet, but may if the situation worsens. For now, the scheme I am using seems to have stabilized things—not a cure, but an equilibrium of sorts that leaves me with fruit and mostly happy trees, but occasional flares.
Back to my Regime
I spray when the trees flower (not sure if it is good for pollination) and I spray during fruit set, always two weeks or more apart, if I get around to it. The trees away from the main cluster have gone almost a year without any spraying because close inspection has shown no bumps of late. They fruited this past year, and I have tried to make sure I don't infect them by transfer on my person or my tools. I am sure, though, that wind and birds will eventually reinfect them. The main cluster of trees gets a look during my weekly trip through the yard, and a few times a year I will find leaves with bumps and restart the treatment cycle. When I don't, I get lazy with my spraying.
Going forward: It has been three years now, and I think I will continue to grow lychee in my yard. I have a regimen that seems to work for me. Unfortunately, I live in an area where there are many lychee trees, including some growing in unmanaged and undeveloped (but fenced, large lots of two acres plus) areas, so there will always be a source of disease pressure. I just hope I have found the balance and can keep a productive tree, with more work than I would like to, in the south Florida yardscape.
I would like to learn what you have done that has worked. I am also very happy to get suggestions or critiques of my approach.
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