White 'fuzz' on plants - Orchid Board

gshep · #1 06-20-2019, 04:12 PM

Hello from New Mexico. We seem to have a lot of "white fuzz" on our orchids. It is primarily on the underside of the leaves or on the back of blooms or in various places on the stalks. We spray weekly with Ferti Lome Triple Action Spray but within a week this is back. I suspect it's from some type of insect but what we're spraying with is not correcting the problem. Does someone have a suggestion of a better spray to use? Thank you very much.

rbarata · #2 06-20-2019, 04:26 PM

gshep, welcome!

Please post photos...there are many kinds (and causes) of white fuzzes.

Thank you

Roberta · #3 06-20-2019, 04:27 PM

Photos? Suggest that this move to the "Pests" forum. Sounds like mealybugs, though. (I think "Phalaenopsis" is Latin for "mealybug magnet) Rubbing alcohol 70% isopropyl) will kill them - dissolves that waxy white coating (you can put a sprayer right into the bottle) or on a cotton swab. HOWEVER this will kill only the ones that it hits. Won't touch eggs. So you need to repeat AT LEAST weekly for several weeks to kill successive generations. Also, the medium is probably infested, so repotting them is also likely to be necessary. Soapy water (or insecticidal soap) can also help once you knock down the visible ones, but again you need to keep repeating the treatment because it only kills on contact, has no residual effect. I have not found systemics to be particularly useful against mealybugs... you need to get rid of the nasties, and keep getting rid of them, and get rid of the source such as their medium. (This means ALL of the plants at the same time, or they'll just keep reinfesting each other. )

gshep · #4 06-23-2019, 06:33 PM

Thank you for the info. Here are photos. Does this change previous advice?

Roberta · #5 06-23-2019, 06:42 PM

Ick! Serious mealybug infestation. There might be some scale in there too, but mostly mealies. If you spray with that isopropyl alcohol you'll see that white stuff dissove, leaving soft naked little bug bodies. Clean them up - squishing them is satisfying. Then, unpot the plants, give another good spray with the alcohol (including roots), and follow up with a good spraying with soapy water (few drops of dish soap in water works, or insecticidal soap) Wash well under running water. (you want to remove as many "corpses" and eggs as possible) Pot in fresh media in clean pots. (You can use the ones you have if you run them through the dishwasher... and make sure nothing is stuck to the sides) And watch carefully, if you see even one, nail it sooner not later. Eventually you'll get ahead of them. But it will take persistence. When it's one or two you can get them with an alcohol-soaked cotton swab.

rbarata · #6 06-24-2019, 06:40 AM

I had really good results with imidacloprid.
Repot is always needed.

Ray · #7 06-24-2019, 08:10 AM

A topical spray of alcohol isn't going to remedy the problem, but will set you up for a long-term approach to getting carpal tunnel syndrome.

Mealies appear to only populate the green leaf tissue, but they are notorious about populating the root system, too.

Buy a decent commercial insecticide. I recommend a systemic formula. Mix it to the recommended concentration for roses (I am assuming orchids won't be on the mixing list) and wet every plant surface AND completely drench the potting medium.

Repeat that process two more times at one-week intervals.