Mealybug treatment questions for effectiveness and to prevent re-infestation

[The Peloric Orchid]

I just discovered a few adult mealybugs on some orchids I was quarantining. What I have done so far is spray them one of those organic sprays full of essential oils and neem oil as a first step, but I know I need to do more. To that end, I have many questions about treatment plans.

1) If I go for a low tech approach and dunk my plants in a soapy water for a few hours, should I try to dunk all my plans at once (such as in a plastic tote)? If I do so in batches, do make a fresh soap solution each time? How often should I follow up with another soapy bath?

2) If I decide to spray and drench the medium as my treatment option, should I repot the plants before starting, after the last treatment, or both?

3) For whatever treatment I decide, I'm assuming I treat all the plants in the quarantine room, not just affected plants and their closest neighbors?

4) I've seen estación seca and others write that treating plants doesn't do anything about the eggs in or around the quarantine area. What should I do about that? Vacuum?

[Ray]

I cannot vouch for the efficacy of the soapy-solution dunk method, as when I last had to treat for mealies, I had a greenhouse full of plants, making that an impractical treatment method.

I am not a fan of putting multiple plants into the same bath of liquid.

As far as I’m concerned, the way to eliminate mealy bugs is as follows:

1) Use a commercial, systemic/translaminar insecticide listed for the bugs and the plants, mixed to the recommended proportion. I use Acephate, but imidacloprid, Azamax, and even the BioAdvanced 3-in-1 Insect, Disease, and Mite control will work.

2) Treat every plant thoroughly by wetting all exposed surfaces and drenching the potting media (mealies can live on roots, too).

3) Do 3 of those treatments at one-week intervals. Most pesticides only kill adults, so repeated treatments are needed to kill maturing eggs and juveniles before they can reproduce.

If you do that, repotting is unnecessary.

[Dimples]

I’m an organic farmer and even I bought a bottle of imidacloprid when I found mealybugs on one of my houseplants last fall. There’s nothing sustainable about the houseplant industry so it’s better to carefully and quickly knock down pests like MBs than have to toss and replace an entire collection. A few plants can be given the soapy water soaking treatment, but with 50+ plants, including some large trees, that wasn’t an option for me. I treated all of them twice one month apart. The label said it was a once and done treatment with “up to” 12-months of protection, but a second drench isn’t a bad idea. I haven’t seen MBs on anything (except a new plant) since I used it.

Water carefully for awhile if you use an imidacloprid root drench on plants in tradition potting mix. It will stick around in the soil for awhile and you don’t want any runoff going down your drains. You need to dispose of extra solution on your own property, far away from any water sources or plants that will attract pollinators, so only make up as much as you need. Bark probably doesn’t hold onto too much residue, but still best to avoid letting the drainage water go down the drain for a few waterings after.

[The Peloric Orchid]

I have imidacloprid powder. Is sprinkling it on the medium and watering it in per the manufacturer's instructions the same as a root drench?

[estación seca]

You can't get all the eggs everywhere. You must be vigilant and be prepared to treat.

[Dimples]

The granular form of imidacloprid is intended to be used with fine textured, traditional potting media, or with soil. It’ll wash out the bottom of a pot of bark before the plant has a chance to absorb it. Your best bet is to pick up a bottle of a liquid product. Others may suggest ways to use the granular product by going off-label but you won’t be able to deliver a known dose, and that’s never a good plan with pesticides.

[Ray]

Originally Posted by The Peloric Orchid

I have imidacloprid powder. Is sprinkling it on the medium and watering it in per the manufacturer's instructions the same as a root drench?

What does the label call it? If it’s something along the lines of imidacloprid 50WP or DP, it is a Wettable or Dispersable Powder, and is meant for mixing with water before application.

[c123anderson]

Originally Posted by Ray

I cannot vouch for the efficacy of the soapy-solution dunk method, as when I last had to treat for mealies, I had a greenhouse full of plants, making that an impractical treatment method.

I am not a fan of putting multiple plants into the same bath of liquid.

As far as I’m concerned, the way to eliminate mealy bugs is as follows:

1) Use a commercial, systemic/translaminar insecticide listed for the bugs and the plants, mixed to the recommended proportion. I use Acephate, but imidacloprid, Azamax, and even the BioAdvanced 3-in-1 Insect, Disease, and Mite control will work.

2) Treat every plant thoroughly by wetting all exposed surfaces and drenching the potting media (mealies can live on roots, too).

3) Do 3 of those treatments at one-week intervals. Most pesticides only kill adults, so repeated treatments are needed to kill maturing eggs and juveniles before they can reproduce.

If you do that, repotting is unnecessary.

So helpful! Gives me some hope!