On Dendrobium Leaf? Disease or Pest?

[Roberta]

Pest control doesn't lend itself to shortcuts. Insects were on the planet long before we were, and are likely to be there long after we're extinct. Zapping that one with soapy water spray is harmless. You could put ant spray on surfaces, it sticks around... and also doesn't smell very good, the odor sticks around too. If you're sharing living space with the plants you are somewhat limited in how aggressive you can be, especially on the airborne ones. You really don't want to be breathing a constant dose of pesticide. But a drench of medium with a systemic product (which will kill adults that might be lurking, and make the plant unappetizing and likely fatal for any that manage to grow up) should help a lot. If you want to go after larvae, a drench with a BT product could also help. There are bigger guns, such as insect growth regulators (like Enstar AQ), which tend to be extremely expensive, not cost-effective for small collections. From a practical point of view, just continued vigilance and treatment when you spot a problem, will be your best bet. Not something that you can put on "automatic".

[c123anderson]

That's sage advice, Roberta.

Sharing the space and enjoying my orchids are two things that go together, but sometimes sharing the space isn't very appealing when there's creepies around. However, this has been a learning process, and me and many orchids will come out the other side of it intact.

[KatieM]

They'll land eventually and try to eat and then.....r.i.p. I like to use a systemic to help try to prevent some as well..keep doing your weekly treatment until they're gone. Remember they'll get your roots too so rinse well. Of all orchid pests mealys just make you cringe don't they?

[c123anderson]

Oh yeah. They’re just ….. <shudder>

But I’ve sprayed and doused. I think the one thing for orchid enthusiasts — that I’m dealing with at the moment, too — is to keep from over treating a problem. Too much “love” can be just as bad if not worse.

I’m going to give them some time. Keep an eye on things but wait.

[c123anderson]

Update: after stressing about this, and perusing various advice and sources, I talked with a local ag person whose advice was very helpful and worth sharing to all.

He suggested, first, that the organic or non-chemical treatments may be ineffective with an infestation. One or two, fine, but on several plants and seemingly spread out, the organic stuff will do little. In fact, the nitrogen byproduct runoff is more harmful. He highly recommended imidacloprid as a systemic treatment to repel mealybugs and other unwanted bugs. I have seen other posts that recommend this treatment. I leaned heavily towards this solution since I found some mealybugs on my vanilla vine, which has plenty of leaves and new growths and lots of places for mealybugs and others to establish themselves. If that will deter them, then that can help other plants remain pest free.

The local hardware store versions of pesticides will be highly diluted for a consumer (non-professional) user. Keep that in mind when applying, depending on the severity of the infestation. In other words, watered down pesticides can’t be as effective as a professional strength. BUT repeated applications at those lower doses may do less damage to plants.

What I am seeing for most imidacloprid treatments from my local Lowes is that the treatments can be effective for up to 6 months. That doesn’t mean I will wait to treat again in 6 months; once the problem is “under control”, a periodic maintenance application is recommended.

I have tossed 5 plants as a result of this: 4 were dead or so far gone the treatment would’ve likely killed them if they weren’t already dead. I was nursing them back but let them go. One “rescue” phal was tossed yesterday. Its root system was very poor and damaged and the undersides of its few leaves were communities of mealybugs. It was just being eaten and acting as a host for the rotten creatures.

On the plus side, I feel I’m coming out of this learning a LOT and very grateful for all those who’ve posted directly or otherwise added to the ongoing discussion here. Now, I’ll be following Roberta’s advice and be supplementing with Kellpmax and fertilizing to help strengthen everyone though treatment. And, on the plus side, I do seem to have some plants that are continuing to have new growth carefully watched), with one even developing some new buds!

Question: I was using some gardening velcro to secure stems. Any risk of this being a hiding place for pests that anyone has seen or knows about?

[Roberta]

I use that gardening velcro a lot, and have had no problems with bugs hiding under, It's really convenient. It is loose enough (with somewhat sharp edges) that it is likely not a particularly welcoming environment for the nasties.

[c123anderson]

Thanks for your thoughts, Roberta. I definitely went “scorched earth” in trying to remove these mealybugs, removing anything non-plant material that looked like it could be a hiding place. It's getting time to repot/secure stakes in several plants anyway, so it's an opportunity to tidy up.

I really, really appreciate the help and advice. I can't stress that enough. Thank you!

[c123anderson]

Hi everyone. I'm on day 17 of the mealybug fight. Thank you for all your thoughts. If I can share, my appreciation for your help is tremendous; I feel somewhat ashamed and embarrassed that I am having this issue. I should have been more wary and cautious and not so cocky and ignorant that this wouldn't happen to my plants. Plus, too, I am seeing what feels like a rapid decline from plants that seemed to be thriving, and there's definitely a feeling of frustration and powerlessness.

All that being said, I have some more questions on this topic, if I could post it out to the collective experience/wisdom of the group. I've looked through the board to see if there were already posts on these topics. If I missed something, please redirect me.

1) Mealybugs and roots: what is the value of dousing the media/plant with a diluted isopropyl alcohol solution? Or a hydrogen peroxide (H2O2) solution?

I see some recommendations for this. I am extremely hesitant to do this, since it seems like it may be drying or damaging to the roots. I did see a post about H2O2 use on orchids which I will revisit, but I am leery to soak my plants' roots in it for fear of damaging an already fragile plant.

2) I have seen some recommended treatment schedules posted. Would anyone be willing to share their treatment schedule for an infestation and what's worked/not worked for them?

Partly when I do an internet search, there are LOADS of suggestions, the majority of which are organic. After the first day's treatment, I realized organic was not going to be enough. I have insecticides which I have been using in a schedule of every week (2x) then moving to 10-14 days (2x), then as needed, watching for phytotoxicity.

My concern for a treatment schedule is watching the life cycle of the mealybugs and catching all them.

3) Any recommendations on a long-term, preventive treatment and intervals for using? Thoughts on needing a routine preventative on house plants?

I have seen estación seca post about dunking in soapy water. I don't feel that's a method I can use to deal with the infestation, but I would like to use that as a preventative.

I believe I may need a preventative, even with houseplants. I have dogs who will get into our garden. They have brought visible critters in on their coats. Although I don't know/believe this is how I got my current infestation, I suspect that this may be a possible means of transportation.

I live in an agricultural area. We have loads of pests and plenty of farmers, vintners, orchardists, et al. who are concerned about crops and spreading pests. There are likely many ways that bugs are introduced into a household plant collection, but I have every expectation that new infestations may occur.

Sorry for the very long post, but thank you for your thoughts and for your time.

[Roberta]

First, Isopropyl alcohol will be quite useless as a drench, don't know if it will harmful but certainly not going to solve your problem. Did you check out the YouTube video from isurus79, here's the link to his post:How to use hydrogen peroxide on orchids - Orchid Board - Most Complete Orchid Forum on the web !

This is an approach that may be safe for roots, involves only short contact time. But whether it kills the bugs? It is probably time to stop messing around with "organic" half measures and break out some bigger guns. Bayer's BioAdvanced has some systemic properties. You likely can still get imidacloprid by getting Merit lawn treatment though you can't get that in sprays any more in most places. Some Merit granules in the pots might be useful. The really big guns (such as Enstar which is a growth regulator, low toxicity for non-insects) are really expensive

The schedule... whatever you use, you need to do it weekly for 3 or 4 weeks at least. Ideally, you have more than one pesticide, with different mechanisms, to avoid resistance, rotating the different products. Other Board contributors have more experience with the various products.

[KatieM]

I am following this. I have had horrible infestations as well so don't feel bad! Mealys are just ugh. Definitely makes you cringe. I have used bonide granules but as everyone states they wash right through the medium (they do still work but not as well as liquids. This was just my quick fix until I could find a better solution, also worth noting when I water I soak so I imagine that helps the granules be absorbed a bit more). I have done organic but like you a systemic preventative is necessary for my environment so I'll be lurking to see what others recommend and sending good vibes to you for the death of all things mealy!