Need a nuke for Boisduval scale.

[BrassavolaStars]

Hello all,

Boisduval scale is destroying my collection. After months of just trying to power wash and neem oil them off, they just keep getting worse and worse. I'll spray them off plants only to find them covered in the stuff just a few days later.

I have had rare and expensive plants end up turning almost completely yellow from being eaten. I assume this means they have been killed. They only seem to attack the cattleyas and a few select dendrobiums.
I need something I can drench on the whole collection that will eliminate them.

What is my best choice?

Thank you.

[Roberta]

This is off-label so don't sue me... I have found that if I put about 1/4 to 1/2 teaspoon of Safari granules in the pots (as a top dressing), normal watering slowly dissolves it, and it it is a powerful systemic. (As opposed to spraying... which you could do for to get the easy ones "right now") In most cases, it's one and done, the scale doesn't come back. For the occasional really bad one, maybe repeat in 6 months, which should clear it up.

The stuff is pricey, but what won't we do to save our orchids? Direct application is referenced nowhere... I learned the trick from an elderly grower. There may be a downside to the approach but I haven't found it. Since it is limited to the affected orchids, which aren't a "bee target", the fact that Safari is harmful to bees shouldn't be an issue. (I have occasionally seen bees commit suicide by getting stuck in a flower, but don't tend to see them around the Catts, if you're growing in a greenhouse even less of a potential issue.) At any rate, nuclear warfare.

[estación seca]

My approach is to dunk in soapy water, use a brush to remove everything I can see, wait a few days until dry, then soak with the pot completely submerged (usually inverted) for 6-12 hours in a very dilute soap solution. I have had to repeat it once on some plants.

[BrassavolaStars]

Originally Posted by estación seca

My approach is to dunk in soapy water, use a brush to remove everything I can see, wait a few days until dry, then soak with the pot completely submerged (usually inverted) for 6-12 hours in a very dilute soap solution. I have had to repeat it once on some plants.

While this seems like it would work, I do not think I can practically do this for the number of affected plants (>50)

[MateoinLosAngeles]

Integrated Pest Management is extremely important, so you will need to combine different things. I've been hearing from East Coast growers increasingly having more difficulty managing different types of scale and I suspect there might've been some resistance to 4A insecticides developing.

Most insecticides recommended for scale are systemic and belong to the "4A" class which target nicotine receptors in bugs affecting life functions. Among these are Acetamiprid, Bifenthrin, Dinotefuran (Safari), Marathon, Thiamethoxam. They all have different concentrations, etc. Safari is really good stuff, but also really toxic to pollinators, and it's relatively toxic to humans. Good PPE should be used.

I haven't dealt with Scale but in my experience fighting other bugs, I've found the combination of an insecticide and an IGR (Insect Growth Regulator) to be extremely important. Insecticides kill mostly adults, whereas IGR stunt the development of the larvae and nymph stages. In some insects IGRs cause eggs to become inviable and females to become sterile. IGRs are generally harmless to humans.

Most bugs will go through a young phase in which they either won't feed or their nervous systems aren't developed, making them somewhat immune to many good insecticides. That's what the IGR covers. I would follow the label and find the right insecticide that can be combined with another IGR. Try combining Safari with an Azadirachtin based IGR. Azadirachtin is extracted from Neem Oil but Neem Oil formulations only contain about 0.25% azadirachtin or less. Azamax which a lot of people use for spider mites contains 1.2%. Generally, insects can't develop resistance to IGRs so even if you've been treating with Neem, you can try Azamax.

If your situation is really really bad and you want to save your expensive orchids, do a full treatment following label. I think you can apply most systemics every 2 weeks up to 3 applications, but you can apply the IGR weekly (try every 5-6 days) to control the young bugs.

If that first treatment doesn't work, then it's time to change chemicals completely. Don't go from Safari to another 4A insecticide.

Something that you can try is Spinosad, which also affects nicotine receptors but in a different way. It's not labeled as systemic but some studies show it has systemic properties.

You can also switch up (or even combine!) IGRs. Fenoxycarb might work. I've heard a lot about Buprofezin (brand: Talus) but that's prohibitively expensive.

More suggestions on an IPM approach are here: https://irac-online.org/documents/su...rsion/?ext=pdf

Finally, if you find success but want to do some sort of maintenance, you should look into Beauveria bassiana, which is a fungi that is parasitic to many insects but seemingly harmless to humans (or maybe I'm saying this because I, like in The Last of Us, have been controlled by this fungus...)

Beauveria bassiana hasn't been studied well for scale but it is effective in mealybugs and whiteflies which are actually fairly closely related to scale and it might help keep new infections from settling in.

[Ambrose]

Scale is my number one pest. I had been using insecticidal soap for a number of years with variable success. I noticed that the soap was damaging the roots so I stopped using it.
I also needed the 'nuclear option' so I did some research. I used Orthene WP at 1/3 teaspoon per gallon plus a teaspoon of spreader/sticker. I applied this once a week for 3 weeks and it worked great. When using this material, you must wear protective clothing and a respirator. I know it sounds like overkill but why take chances. Also, Orthene smells really bad so you will want to apply it outdoors on a wind-free day.
I have also used EnstarAQ biologic on scale indoors and it also works very well for scale infestation. I applied at 2 teaspoons per gallon of water plus 1 teaspoon of spreader/sticker for the first week. Thereafter, 1 teaspoon of EnstarAQ plus 1 teaspoon of spreader/sticker once a week for 2 weeks. I do wear rubber gloves and a particle mask just to be safe.
With both of these materials make certain that you drench the entire plant including the potting material.
Good luck!

[Ray]

Boisduval scale is particularly difficult to eradicate.

1. Select a systemic and/or translaminar insecticide listed for the specific bug.
2. Mix it to the recommended strength.
3. Spray the entire collection thoroughly, wetting all exposed plant surfaces AND drenching the pots.
4. Repeat two additional times at one-week intervals.

If, in a month, you see a reinfestation, repeat that process with an insecticide having a different MOA.

[kwubb]

I am just finishing (hopefully) a 6-8 week treatment for boisduval scale. Persistence, strict attention to schedule, and a combination of different agents is key. I wish I had know Roberta’s way of applying Safari prior to starting my regimen. Most of the chemicles have been described in previous posts, so I won't repeat that, but will list what I used each week. Every week (7-10 days) the orchids were sprayed with a mixture following label instructions. This is what I used:
Week 1&2 Safari
Week 3&4 TriStar-main ingredient is Acrtamiprid, a broad spectrum insecticide that acts on nervous system. Same family as Imidicloprid, but with a wider spectrum.
Week 5&6 Distance- an insect growth regulator. This is not a systemic, but rather it has strong translaminar activity. It just doesn't travel far, but will concentrate within the leaf, so if tops of leaves are sprayed, insects on the underside will also be affected. Any IGR would work. This was already part of my arsenal.

I have a question myself about B. scale. In most articles I've read they talk about the ability to wipe this scale off of plants, or at most to use a fingernail. It's mentioned, almost as a diagnostic, in identifying. I've even been told that if it can't be scraped off, it's not scale. Most of the scale on my plants is going nowhere. It's as if it's imbedded in the structure. I'm afraid of doing more damage, leaving spots open for bacterial/fungal invasion. I'm sure I'm dealing with B scale, but this is very confusing for those trying to identify what is happening to their orchid. Thoughts??
Hope this is helpful.

[Leafmite]

I hate these things. The ones I have are resistant to the pesticides I have tried. They do not bother the orchids much but they love my coffee/jasmine/and citrus trees.

This spring, I used isopropyl alcohol in a spray bottle and sprayed the jasmine when I saw it was infested. The plant has been free since. I might go this route for now.

[thefish1337]

I had good luck getting rid of scale treating the whole collection with Azamax. 3 applications via irrigation over a month did the trick.