Does Malathion cause mold like snail bait does?
 

This poor Phal deliciosa had 2 problems which I didn't notice for 3 months (2 months in quarantine) - snails and critters I think were Thrips. It came in with some pretty black roots at the top, but the rest of the roots were mostly green, which then turned black in some places as seen through the clear pot. I saw the critters, sprayed with Imidocloprid and then two weeks later trimmed the poor-looking roots, spraying roots and leaves with water thoroughly, and repotted into new moss. I drenched the new mix and plant with Malathion for good measure, in case I hadn't gotten all the eggs. I found 2 snails in the old mix (yuck!) so hopefully that's also the last of the snails. But now, 1 week later, I'm noticing fuzz and mold but only on the top of the pot, or on a few roots (small white dots in picture.) Does Malathion commonly cause this, and should I ignore it, just let it run it's course? Or should I trim more roots and repot the poor thing again?

Thanks again for your patience and advice.

Moss, bark, leca- people prefer different medium- depending on growing environment.

I have problem with moss- just did a test with moss that was supposed to be pretty sterile- in my environment it grows mould within 48 hours if the humidity is higher than 75/80%, or if its too wet. Yeah- I actually tested different media without plants, and different humidity. (Setting up for seedlings)

When I rescue plants with bad roots I like to have them in a vase without media. And mist them every now and then, and when they are looking healthy I put them in mix again.

Its not the mix that is the main issue- its just that you need to find what works for you.

Not sure what is going on with your plant, but I really dont like the look of the roots/stem.

I actually have left roots with some bad spots, but pay attention to it- to see if it gets worse- thats not easy if in a wet medium.

I guess people have their own methods, and if you get many responses, do what you feel will work for you.
I have never used chemicals or things when bad roots- only water and paying attention. I let them be more on the dry side. Roots that are really bad I have cut. But sometimes a root that not too bad will help in the recovery and then die of naturally.

If the plant is infected with some fungus/virus/rot it might need something to stop it.

Like this- it was in bad shape last year, recovering nicely now.
http://images.tapatalk-cdn.com/16/02...aa1bd519cb.jpg

I use Malathion as my preferred contact pesticide to kill bugs on my orchids instantly. I have never seen mould result from it. I don't like growing most things in straight moss. I find my Phals prefer chunky bark with some moss mixed in to hold moisture a bit. The bark allows air to move thru and the roots to not stay dank and damp for overly long. They need air too. I suspect it is the moss causing the mould. Does your pot have a good amount of holes for drainage and air movement? That would help, but a few chunky pieces added would also help.

Editing to add: In photo 2 I see several white dots on the leaves. They look a bit too white, but are those scale? If so, immature scale also looks like fuzzy white mould. However, I think its mould since the roots appear to be rotting and it is on the moss as well. Make sure you don't also have a case of scale.

I do not think Malathion causes black rot but as shown in the photo I'm not wasting time with her. In less time starts orchid show. It's cheaper buying a new one.

We use Malathion on our fruit trees and it does coat the tree with a light, white residue but I have never seen it cause mold or any other issues. It works best if it stays on the plant for a couple of days so if you are going to have rain, you probably should cover the orchids. If you have pets, you and your pets should stay away from the area where your plants are, as much as possible, until it dries completely...even better to avoid the area until you get a good rain.

I have never used Malathion on snails but I know Sevin kills them, including the bush snails. Good luck!

What great roots Helene! That's quite inspirational.

I was using the malathion to get the thrips.

The "white dots" on the leaves are tiny bits of sphagnum moss - I checked :)

Perhaps I need to not use sphagnum moss then and repot it into bark and a little moss or lava rock and moss. Maybe a clay aggregate like lecca? It came tightly packed in moss, and I loosely packed it back in new moss, but perhaps I'm still not giving enough air ventilation. The orchid pot has a lot of ventilation holes at the bottom but perhaps still not enough. Hmmm, maybe I can cut slits in the side with an exacto knife.

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