BajaNomad

Fruit trees with black leaves

Marie-Rose - 7-25-2006 at 01:26 PM

Arrived to Casa Loma to find that our favorite limon tree seems to be afflicted with something on the leaves that does
not look good. You can rb it off with your fingers and it is
like a sticky black dust. Has anyone any ideas on how to treat????

[Edited on 2006-7-25 by Marie-Rose]

Diver - 7-25-2006 at 01:40 PM

Have the leaves started to "curl" as well ?

Taco de Baja - 7-25-2006 at 01:41 PM

Probably aphids, ants and mold.
the ants are farming the aphids for honeydew. the aphids suck plant juices and produce honeydew that the ants like. the honeydew is also liked by mold, which is the black stuff.

You can organically get rid of the problem by first spraying the tree with a hose to wash as much black goo off as you can.
Then mix 1 TBS of dish soap in a gallon of water and spray the tree with a pump sprayer.

Or you can spay off the black goo with a hose and then use a commercial aphid killer like Diazinon.

You need to get as much ot the black mold off because it hinders the trees ability to photosynthesize

You should also trim the tree so no leaves/branches are touching the ground or an adjacent plant. And spray the trunk with an anti-ant chemical, Diazinon works well too. Keep the ants away and you will reduce the aphid problem and the mold problem


Here's what an expert has to say:
Quote:
Sooty mold is controlled indirectly by controlling insects (white flies and scale), which excrete the honeydew on which the sooty mold fungus grows. When these insects are killed, the sooty mold disappears after a few weeks. You can speed up this process by mixing one tablespoon of a mild liquid detergent with one gallon of water and spraying this mixture on the affected areas. Wait 30 minutes and wash off with a pressure hose and repeat until the sooty mold breaks up and washes off. The use of ultra fine oil as per label directions will also break up sooty mold. Do not apply oils to your trees after mid August as this can impact the natural maturing of your fruit. Always read, understand, and follow all label directions.

Article

[Edited on 7-25-2006 by Taco de Baja]

bajajudy - 7-25-2006 at 02:08 PM

Once you get rid of the black sooty stuff, be sure to keep the trees trimmed so that air can pass freely through them.

Cincodemayo - 7-25-2006 at 02:16 PM

Could also have armored scale as black sooty mold is another byproduct of the scales secretions...they REALLY produce the sticky stuff...

Taco de Baja - 7-25-2006 at 03:09 PM

Cinco is correct could be scale or even white-fly producing the honeydew.
Still, get rid of the insect pest producing the honeydew and you should get rid of the mold.

Scale is a tough pest to get rid of. Sometimes if the tree is small the best way is to individually smoosh them with your finger nail. They will be on the undersides of the leaves, black and about the size of a tomato to chilie seed, but raised off the leaf surface.

cathart - 7-25-2006 at 10:10 PM

I have this problem too, but I kind of think that the ants are eating the aphids--isn't that true? So if I kill the ants, what will eat the aphids?

Taco de Baja - 7-26-2006 at 07:18 AM

More than likely they are protecting the aphids. Not eating them. This is a complex world in which we live.
Several other insects eat aphids such as ladybugs and lacewings.
But if you have a heavy infestation there is no way for the natural predators to catch up, which is why you should at a minimum spray the tree with soapy water to get them under control until the natural predators can take over.
Quote:
Herder Ants and Aphids
"The extreme myremecophilous [ant-loving] aphids have evolved to the status of little more than domestic cattle."
?E.O. Wilson, in Sociobiology (1975).

In addition to ant farmers, there are ant herders and nomadic pastoralists as well, with aphids playing the role that cattle and sheep do in human systems.

A variety of ant species rely for some or all of their sustenance on the excretions of aphids. Aphids feed on the sap of plants, and their sugary excretions are known as honeydew. Other insects in the same group, called Homoptera, excrete similar substances. The Biblical "manna from Heaven" was most likely the excretion of a scale insect, which is still sometimes collected in the Middle East.

Aphids that are not associated with ants either kick away the honeydew droplets with their hind legs or squirt the drops away as they emerge from the anus. Aphids attended by ants, however, defecate in such a way as to make it easy for the ants to lap up the honeydew. In some cases, the aphids have setae that form a basket around the anus to hold the honeydew until the ants eat. In other species, an aphid does not release the honeydew until stimulated by an ant fondling it with its antennae and forelegs. Other aphids appear to solicit ants by lifting their hind legs and exposing the anus when an ant is nearby.

So what's in it for the aphids? The ants provide them with a variety of services. They keep the aphids' neighborhood clean of sugary dung, which would likely attract other sugar-eaters. When the aphids are enclosed in an ant nest, they are protected from weather. And ants directly defend the aphids from predators, the aphids having lost their own defenses as domesticated animals often do. The ants' success in protecting their flocks is attested in the lengths that green lacewing larvae (Chrysopa glossonae) go to sneak past ant defenders to catch woolly alder aphids (Prociphilus tesselatus). H?lldobler and Wilson wrote, "The aphids derive their common name from filaments of waxy "wool" that cover their bodies. The [lacewing] larvae disguise themselves by "plucking" some of this material from the bodies of the aphids and applying it to their own backs. In other words, they employ the "wolf-in-sheep's?clothing" strategy to fool the ant shepherds that guard the aphids."

An extreme example cited in The Ants is that of the American corn-root aphid (Aphis maidiradicis) and an ant (Lasius neoniger). Colonies of this ant keep the aphids' eggs in their nests over the winter, and, when the eggs hatch into nymphs in the spring, carry them to the roots of the aphids' food plants. If the plants are uprooted, the ants retrieve the aphids and tote them to another food plant. The ants also repel potential predators and parasites from their aphid flocks and, similarly, the ants treat the aphid eggs as their own, by, for instance, carrying them to safety when the nest is disturbed. When the aphid nymphs turn into winged forms that disperse without the help of ants, they may be adopted by the ants that live in the aphids' new home.


Article

Marie-Rose - 7-27-2006 at 03:01 PM

Thanks for all the replies! With the huge rainfall in Todos, it may be my imagination, but it looks a bit better already! When my friend sprayed hers with soapy water there were little white "bugs" that flew from the leaves?? I will take
your recommendations and hopefully save the little guy!!

thebajarunner - 7-27-2006 at 03:42 PM

Scale is the real culprit almost every time with citrus.
All the advice is good, including a good strong wash with soapy water.
However, you need to get to a Home Depot or similar and get some scale spray mix in the nursery dept.
They also will have cans of "sticker" (not sure what tradename it is under, but it makest he application 'stick' to the tree and leaves.)
If no 'sticker' is available then mix some detergent in with the scale spray and it will help to make it stick.
Get it well sprayed,
do it again as needed,
and do not neglect the trunk because it too will be infested.
Good luck, that stuff is nasty, and it is always hanging around citrus trees waiting for a chance to move in.

El Jefe - 7-28-2006 at 08:17 AM

We have had real good luck with a sticky goo that comes in a tube. With disposable gloves or a stick you apply it in a ring around the trunk of the tree or bush, and the ants cannot cross it. Of course you apply it after cleaning the tree per above. Then you gotta make sure that there are no other ways for the ants to climb the tree, like branches hanging down or and adjacent wall etc.
We havent been able to find it down here, but you can get it a lowes or home depot in the garden section.
It is really sticky, so you have to be careful working around the plant.

Cypress - 7-28-2006 at 08:49 AM

Fire Blight? Do the tips of the limbs curl up? If so, it could be fire blight. Think that's the name? Bad stuff!

i didnt know

pacificobob - 7-28-2006 at 10:04 AM

that there was such a wealth of horticulture knowledge among the forum members. im impressed. i have no doubt this will be a great resource when i get my trees planted.

Cincodemayo - 7-28-2006 at 10:05 AM

Marie...If you noticed little white bugs it's definitely whitefly....
The spreader sticker they talk about just breaks the viscosity of the water and makes it "wetter"....Dish soap does the same thing.

[Edited on 7-28-2006 by Cincodemayo]

Diver - 7-28-2006 at 11:15 AM

We get the similar symptoms on our organic peach and pear trees in Washington.
We spray with a dish soap mixture every few weeks and dust the tree's base and trunk with diamotacious earth.

oladulce - 7-28-2006 at 06:29 PM

Quote:
Originally posted by El Jefe
We have had real good luck with a sticky goo that comes in a tube. With disposable gloves or a stick you apply it in a ring around the trunk of the tree or bush, and the ants cannot cross it.


Is that "Tangle Foot" ?

It kept the ants away and got rid of the black stuff on my papaya trees but tends to melt in the Baja sun so it helps to reapply every few weeks in the summer.

But right next to the papayas was a lim?n tree that suffered the same fate as Marie's with the black soot. I never saw ants, whiteflies, or scale but tried Tangle Foot anyway. I sprayed with h20, then soapy h20, and progressed to chemicals. I eventually got rid of the black stuff, but then the leaves began to curl and had yellow veining which didn't respond to iron and minerals. Had this happen to Lim?n trees on 3 different occasions and I lost all the trees.

We can be gone from the property 4-5 months at a time and maybe I could have salvaged them if able to treat the problem sooner.

[Edited on 7-29-2006 by oladulce]