Scale Mite Infestation

[Anton]

Today, much to my horror I discovered my outdoor cymbidiums have scale mite infestation. Not having had a pest problem in my short "orchid career" I had to do some quick reading and looking up and found this forum as a result.

What is the best way to control these pests ?
I used Pyrethrum spray on the tops and under sides of all the leaves, but not sure how successful Pyrethrum actually is. Any comments or suggestions welcomed.

[Cynthia, Prescott, AZ]

You can use neem oil to eliminate the scale, but I would use it a couple of times, a week or two apart. Look for ants. They will bring scale to your plants and farm them. Outdoor growing is tough, as your plants will probably get reinfected from nearby non-orchids. You say a scale mite. Did you mean scale and mites? There is no such thing as a scale mite.

Neem can be used on mites too, but I have read recently that neem doesn't kill the adult mites, although I have had good luck with it when the entire greenhouse is treated. Maybe the adults starve to death not wanting to eat the oil covered plants. Some times you can find neem oil combined with pyrethrins. This will probably do the job. But still I would use the neem a couple of times, a week or two apart. Most insectacides will not kill mites, unless they say so on the label. Also, I have been very disapointed with systemics. The newest ones don't seem to transfer thru the plant, and the older ones no longer work on mites.

Neem oil comes in two forms. One is pure neem, and needs to be mixed with water and a little soap. Not having used this version yet, I can't give any instructions. The other version is called a hydrophylic extract of neem. I have used this according to container instructions, and the wetter/stcker is already in the version I use, as there is no instruction to add any soap. This mixture needs to be agitated often.

ALWAYS, keep the plants out of warm air and under low light conditions for a day or so after spraying the plant very thoroughly. If you are having very warm weather, another product should be used , or the plants brought into an airconditioned house. If weather is cool, you may just be able to cover the plants with extra shade cloth for a day, or spray in the evening. If you do not do the above, the plants can develope a mottled appearence on the leaves, phytotoxicity and phototoxicity. Cynthia

[Anton]

Thanks for the quick reply Cynthia, as a newby I thought that the scale was a mite. / What brought my attention to it was ANTS.......lots of them, hence my closer inspection to find out why.

My plants are outdoors under a gazebo, next to a small frog pond, and at present we are coming to the end of winter here in Australia, so conditions are still coolish (48F - 60F).

With so many leaves infected, do you still need to clean EVERY one individually to remove the scale ?

Also not sure if we have neem oil here, but will make further enquiries tomorrow (Monday our time).

Thanks again.

[Cynthia, Prescott, AZ]

You do not have to do any wiping or that sort of thing. The oil of the neem will smother the scale and kill the eggs and mobile nymphs, which I assume is what you have, since ants generally farm these.

Scale looks like little bumps on the plant and can be nuged gently off their feeding location with a finger.

Mites are extremely tiny, and even a hand lens will not likely show much, maybe little dots that move, but not usually legs and the like. Some mites are smaller than others, so some are hard to see in a microscope, it takes high power (30X) to see the legs on some. Mites are usually identified by the damage they do. A silvery look to the leaves results as they are chlorophyl eaters. Red mites can be determined by whiping the underside of the leaves with a white cloth ot tissue and a rust color shows up on the material. Spider mites can some times be identified by the very fine webs and the little dust particles that slowly move along the web are the mites. Scaring on the under side of the leaves is another indication. Cynthia

[Anton]

I have photographed the infestation macroscopically if anyone would like to see scale close up.

I ended up cutting the leaves on all my plants down to around 6 inches long as the infestation was too widespread to just wait for the Pyrethrum to do it's job. The leaves have now been quarantened and destroyed away from any where near my orchids.

So it's just wait and see and hopefully not see any more ants for a while.

[Cynthia, Prescott, AZ]

Anton, did you really cut ALL of the cymbidium leaves down to 6". That is pretty severe treatment of the plant, and may not get you where you want to be. If you can't find the neem oil, look for any product with Imidacloprid. Here it is found in products made by the Bayer company. This will kill scale if you spray the leaves thoroughly. Another name to look for is Merit, which contains Imidacloprid. Cynthia

[Anton]

Yes, I am afraid drastic action WAS required Cynthia. Luckily I only have 8 plants and not a full shadehouse full. )

On closer examination the infestation was more widespread than initially seen, so I decided this best way of getting rid of these little critters.

There was also infestation of the bulbs, and the only way to get to them was to cut the leaves back. Wasn't happy about doing it, but I feel the end will justify the means.

Now I know what signs to look for (ants and discoloration of leaves) I will be able to get on top of the problem before damage is done in the future.

I photographed the scale attack and will put the pictures up when I get the film back. THEN you will see what I was up against and why I took the action I did.

[Ellen]

Bayer Rose and Flower spray contains the ingredient that Cynthia mentioned, and is available in most stores that have a garden section. It comes in a blue bottle. Anytime you're growing outside it's a good idea to treat plants prophylactically with a systemic insecticide before the pests come and party on them. But you know that now...

[Anton]

Thanks for that tip Ellen, and yes, it was a HARD lesson to learn.