All Things Gardening forum: Black film on citrus

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Name: Jonna
Mérida, Yucatán, México (Zone 13a)
Garden Procrastinator The WITWIT Badge Region: Mexico I was one of the first 300 contributors to the plant database! Ponds Tropicals
Enjoys or suffers hot summers Plumerias Plays in the sandbox Dog Lover Cat Lover
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extranjera
Jan 20, 2013 7:18 PM CST
The lower leaves on my key lime tree have this black film on them, it will smear and come off if I rub it. I have a vague memory of this happening before but I'm not sure, is it a residue from aphids? Or something else?

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The tree is still young and won't bear fruit this year so would a systemic get rid of it? I don't mind using it now since it will be at least a year before it fruits.

A day without sunshine is like, you know, night.
Name: Jay
Nederland, Texas (Zone 9a)
Region: Texas Region: Gulf Coast Charter ATP Member I helped beta test the first seed swap I helped plan and beta test the plant database. I was one of the first 300 contributors to the plant database!
Celebrating Gardening: 2015 Plant Identifier Tip Photographer Garden Sages Garden Ideas: Master Level Hibiscus
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Horntoad
Jan 20, 2013 9:34 PM CST
Possibly sooty mold. http://aggie-horticulture.tamu.edu/galveston/Gardening-Handb...
wildflowersoftexas.com
texasnatureonline.com


Name: Kristi
east Texas pineywoods (Zone 8a)
Garden Ideas: Level 2
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pod
Jan 20, 2013 10:45 PM CST
I have a Mexican thornless lime and have this same issue. Mine is caused by aphids which are mined by the Argentine ants. The aphids secretion causes the sooty mould.

As it is only about five feet tall, I spray with Safer insectical soap on a regular basis. I do not have the same problem with my lemon or satsuma. I have often wondered why the lime is more susceptible to aphid infestation.

What systemic would you use?
Name: Jonna
Mérida, Yucatán, México (Zone 13a)
Garden Procrastinator The WITWIT Badge Region: Mexico I was one of the first 300 contributors to the plant database! Ponds Tropicals
Enjoys or suffers hot summers Plumerias Plays in the sandbox Dog Lover Cat Lover
Image
extranjera
Jan 21, 2013 2:45 PM CST
Remember I'm in another country and products are different. This is what I use:
Thumb of 2013-01-21/extranjera/5cd358

The active ingredient is Imidacloprid, I found this on Wiki:

Imidacloprid is a systemic insecticide which acts as an insect neurotoxin and belongs to a class of chemicals called the neonicotinoids which act on the central nervous system of insects with much lower toxicity to mammals.

Imidacloprid is currently the most widely used insecticide in the world.[3] Although it is now off patent, the primary manufacturer of this chemical is Bayer CropScience, (part of Bayer AG). It is sold under many names for many uses; it can be applied by soil injection, tree injection, application to the skin of the plant, broadcast foliar, ground application as a granular or liquid formulation, or as a pesticide-coated seed treatment.


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I'm concerned that it is toxic to bees, honey is one of the major agricultural products from the Yucatan peninsula. This is something that is readily available here so it is no doubt being used a lot, I use it sparingly when I have a huge infestation of aphids. I don't know if it kills ants as well, that would be nice. The only good ant is a dead ant in my book.

I bought it behind the main mercado here in the city. The mercado is a huge market, many blocks square and 2 stories tall, that is full of small stalls selling anything and everything. There are sections for produce, meat, fish, hardware, clothing, flowers, animals (chickens, turkeys, turtles, fish, dogs and ducks) food stalls, artisan products, and more I can't think of. Behind the mercado is what I call the 'street of poisons' - sort of jokingly. It has many stores selling all types of agricultural products. I buy fish food there, Frontline for the dogs, vet medications, fertilizers and all types of poisons. I also get advice about garden problems from the people who work there. I asked about aphids a few years ago and told them I wanted a systemic poison and that usually these things were sold for roses. The guy immediately brought me this container and I bought it, it's worked great when I need it the last few years.

I've seen people here refer to a Bayer product for pest control and now I'm wondering if this is the same stuff.

I think both of you are right, I have sooty mold as a result of aphids. I threw some of the above in the pot just now and will wash off the leaves this afternoon and see if it returns. No doubt I have a nest of ants in the pot, they love to move into large pots of soil.
A day without sunshine is like, you know, night.
[Last edited by extranjera - Jan 21, 2013 2:50 PM (+)]
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