White 'cotton' fungus on a columnea?

domeman(NSW Aust)July 23, 2005

One of my Columnea has just dropped nearly all of its leaves while flowering and looks in real trouble. I decided to cut it back and noticed that there is a white cotton like fungus(?) at the base of each flower.

I need to identify this in order to look for a treatment. The only possible thing I could come up with in my reference book on plant diseases was sclerotium stem rot, however I am not fully convinced. Does this sound reasonable?

Can anyone suggest an alternative identification of a treatment?


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domeman(NSW Aust)

Oops! Mealybug.

I have sprayed with a recommended insecticide. Any other special precautions I need to make to prevent spread?

    Bookmark   July 24, 2005 at 9:46AM
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domeman(NSW Aust)

Perhaps not mealybug on my sick plants!

I looked through a microscope. Inside white cotton like material there are bugs which are a couple of mm long. The body is pink and the flat 'wing' is flat and grey. It broadens towards the back. The insect has longish legs and a substantial antenae.

What the heck is it??

    Bookmark   July 25, 2005 at 5:24AM
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komi(z7/8 DC)

it still sounds like it could be a mealy (assuming those aren't real wings). I'm sure you've looked at pics on line already.

make sure you repeat the treatment 2-3 times, to match their egg cycle. I find that 3 days after a treatment, a very careful inspection will usually find 1 or 2 missed/newly hatched bugs per plant.

    Bookmark   July 25, 2005 at 11:49AM
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jon_d(Northern Calif.)

Welcome to the unwonderful world of mealie bugs. They are all over the world, I guess. They reproduce pretty rapidly and will kill plants if not eradicated. The cottony mass is the egg laying stuff. The bugs will crawl around on the stems and leaves, where they are pinkish whitish, oval and can be easily seen. There are many insecticides that will kill them but here in the US most of these have been banned over the years. New ones come along but then they are usually not licensed for hobbyist purchase, only for commercial growers. So, we have to scramble to get our hands on them. Right now, the best insecticide is found in variously named products, but the active ingredient is imatacloprid, owned by Bayer. They now have a drench on the retail market but the granule form that I like is restricted to commercial sales and is expensive. I have it and use it often. It is absorbed by the plant such that when the buggies ingest the plant juices they ingest the imatacloprid, and then they die. This insecticide is supposedly fairly safe on us mammals but deadly to insects like mealie bugs, white fly, aphids, scale, and as I just learned yesterday, ants. Being a life long plant grower/collector I am resigned to the fact that I will always have infestations so I will always have the appropriate solutions, to the bugs that I get--mealie bugs, aphids, scale, white fly, thrips, mites, ants (who farm the other pests), mildew, slugs, and whomever or whatever I am forgetting now. So I am prepared, I just need to use these in a timely manner--like before the infestation becomes out of control.

    Bookmark   July 25, 2005 at 3:08PM
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domeman(NSW Aust)


I have treated with Imadacloprid. It comes in a 5 pack of 5g satchels (as granules) from Bayer in Australia under the name 'Confidor' Makes 25 litres and costs approx $16.

I sprayed fairly heavily since I have been warned that incomplete spaying is a waste of time.
I will repeat after 2 weeks and then again 2 weeks later according to the instructions.

Here's hoping!!!!!!!!

Thanks for all of the advice.

    Bookmark   July 25, 2005 at 5:36PM
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komi(z7/8 DC)

Your treatment regimen is rather interesting. It may be that formulations are different etc, but FYI here is what I do.

I usually use imidacolprid in the potting mix or I water with it, so that it is taken up through the plant. This means that actively growing parts of the plant take it up faster than older non-growing areas. It also means there is a time delay for it to take effect, and it is not very effective in hardwood areas of the plant.

So, when I find an infestation of mealies, I also use a contact killer to immediately get rid of as many of the adults as possible. If the number of plants infected is small, I usually use alcohol - either as spot dabs or as a spray (followed shortly afterwards by a water rinse).

And I repeat the contact killer every 3-7 days.

    Bookmark   July 25, 2005 at 6:35PM
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domeman(NSW Aust)

Another learning experience for me -

SInce I had tree ferns below the columnea, which caught some of the possibly infected leaves, I also treated them It appears that tree ferns do NOT like Imadacloprid and I hope they recover.

    Bookmark   July 26, 2005 at 4:19PM
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korina(9b, Sunset 17)

Easy way to check if it's mealies. Squish one; if it's red inside, ya got a mealy.


    Bookmark   July 27, 2005 at 12:14PM
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q tips and alcohol and get them off!!!!!

also, there is a pest called root mealy bug but to find out if that's what you have it is recommended that you remove plant from pot , see if there is an infestation and get them out!
another recommendation i found for your plant is "If you find soil mealy bugs, lift the plant out of the pot, sprinkle 1/4 teaspoon of Marathon granules on the bottom of the pot. Replace the plant. Do NOT water in, or do any extra watering. That should take care of the problem!"

re ferns, i have learned the hard way too that not all plants react kindly to certain pest solutions so always check out the plant before spraying it even if it is a "next door neighbour" and infested in order to take care of the problem without harming your plants.

good luck!

    Bookmark   July 30, 2005 at 3:15PM
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domeman(NSW Aust)

Perhaps I have overdone things but........

I sprayed plants with imidacolprid and a week later sprayed the obviously infected (columnea) with white oil.

Hopefully this will get them all!

Dabbing one at a time didn't appeal at all - I have more than 100 plants and had no confidence that I would locate all of the infestations.

I cut back the imidacolprid affected tree ferns and hopefully spring will bring regeneration ;-)

Thanks for all the suggestions.

    Bookmark   July 31, 2005 at 4:22AM
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jon_d(Northern Calif.)

Some plants really hate oil sprays. If the ferns got the oil spray that may have damaged them. Also, many liquid sprays are in an oil solution which damages the plants even though the active ingredient does not. So, I suspect something along those lines hurt your ferns. They should recover though. Soil mealie bugs are a big problem. The easiest way to see them is by unpotting so as not to disturb the root ball, which on a root bound plant is not a problem; and, then, look at the inside of the plastic pot. If you see white patches on the plastic then there is probably soil mealies (SMB). You will also then see the white cottony patches on the outside of the rootball. Marathon is a great way to get rid of them. I just sprinkle on the surface and water in with a very slight amount of water, and hopefully use a saucer so that any run-off is reabsorbed. Of the thousands of different types of plants I grow, the two that are most apt to get SMB are succulents in the crassulacea, especially sempervivum and aeonium.


    Bookmark   July 31, 2005 at 4:43PM
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domeman(NSW Aust)


Thanks for your wisdom.

Can you advise the active ingredient in Marathon? Names change between countries and Marathon does not seen to be available in Australia. I was intersted recently to see that imidacolprid is not easily available in the USA in solid form. In Australia it is readily available as 'Confidor' in a 50g (5 x 5g satchels).


    Bookmark   August 1, 2005 at 4:54AM
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komi(z7/8 DC)

The active ingredient in Marathon is imidacolprid.

    Bookmark   August 1, 2005 at 8:03AM
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jon_d(Northern Calif.)

Sorry, I know not to confuse by using brand names for insecticides, which are rarely used out of the US. I still can't spell imidacloprid. Or is it imadicloprid? At least I now know it isn't imaticloprid. Oh well, now none of you will be able to spell it either .( .

Supposedly this stuff works but is highly water soluble. So, it must be watered in carefully. The granules aren't water soluble though. But, the insecticide washes off the granules. So, one must not be confused by seeing the granules still on the surface of the soil. I would guess that the best way to use Marathon would be to water the plant while in a flat bottomed saucer, so that all the run-off is reabsorbed. Just make sure the run-off is not accessible to pets or wildlife, if outdoors. Hopefully one doesn't have wildlife indoors.

I have to admit that I have some plants that seem to be poorly treated by Marathon. I have some old nematanthus in my greenhouse that have mealies on their new growth. I keep putting in Marathon over and over. I know it is working because the pests are not taking over the plant, as they would if they could. But, at the same time they keep persisting. I wonder if it is that the plant isn't happy in its location, or the insecticide washes through and isn't absorbed enough. Or, that the plant is too large for the insecticide to fully innoculate all the growth out to the tips. Old foliage seems to be clean, its just the new tips that get bugged.

I know what I have to do though. I have another insecticide that unfortunately isn't sold anymore, called Knox-out. It is encapsulated diazanon--supposedly the incapsulation makes it very safe for us mammals. When sprayed on the plant it sticks to the surface and kills the bugs when the come into contact with it. So, it sort of works like a systemic, in that it kills long after spraying. But, it wouldn't be on new growth that occurs after spraying. I will clean up a plant with Knox-out and then use Marathon to keep it clean--HOPEFULLY!

Back in the good old days, people didn't have our problems. If they saw bugs they went in and sprayed with one of those super-powerful insecticides and killed everything including eventually themselves.


    Bookmark   August 1, 2005 at 3:50PM
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