Pest advice from a Netherlands greenhouse grower

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I have extracted here a few things about dealing with pests, from a talk I watched on orchid cactus, since they have the same pests we do.

CSSA Live Video Presentation: Frank Süpplie, The Splendour of Orchid Cacti
Saturday March 6 2021
Via live videoconference

The Cactus and Succulent Society of America has been having biweekly Saturday morning (US) video talks. Cactus and Succulent Society of America - Home Page.

The videos are available on the CSSA Facebook page for a week, CactusAndSucculentSocietyOfAmerica. Frank's orchid cacti video is no longer visible. The current video available is a talk presented just this morning by Jon Rebman, Curator of Collections at the San Diego Natural History Museum, on the plants of Baja California. Jon is an amazing speaker; I highly recommend all of you watch his talk before it disappears.

I made a transcript of the orchid cactus recording. It was a presentation by the speaker, followed by a Q&A session with the panelists, all Epi growers. I have added some of my own comments because the talk was directed to cactus growers already familiar with these plants. I put my additions within [brackets.]

You can see the part of the talk dealing with growing orchid cactus here on Orchid Board:
Frank Suepplie: The Splendour of Orchid Cacti

Frank runs the Epiphytic Cacti Research and Information Centre in the Netherlands.
Stichting Epric
He also sells Epis online (EU only) at
www.epiphyllum.online – the Epric foundation – the Netherlands
where you can see many, many photos of things you will want.

Frank: If you grow Epiphyllum hybrids, you also have diseases and pests, of course. And nobody likes that, and nobody wants to see that, but you have to see also this side of our hobby.

Rust causes red spots on the flower. It is a result of being too wet and too cold, and sometimes the combination of too wet and too cold. It is better to keep your hybrids a little bit drier in the winter period. The only thing you can do for rust is to buy something from a garden center which is good for rust on roses; and then, you can treat them with anti-rust stuff for roses.

This is something we don't want to see actually in our collection. These are mealy bugs. And also these can be treated with methylated spirits [alcohol]. But don't forget that the eggs of mealy bugs do survive two years. So they can be two years in your collection without coming out. Here we have taken some tests about this in the laboratory, and still after two years the plants get infected by mealy bugs. We did this with Hoya species. We put them in a glass jar with the old eggs and still mealy bugs came out after two years. So you have to be clean in your greenhouse.

[Photo shows isolated large deep brown spots on Epi stems] Something quite different and quite new is this kind of mealy bug. It's a kind which came in from the US, from California. It was spotted first on Epiphyllums. It's very strange; it doesn't look like the mealy bug we actually know; but it's a family of them and we have to take care of them as well with methylated spirits [alcohol], or cutting away the branches.

This is something new for Europe, and not so new for America. And these are stinkbugs. They are actually causing this on Epiphyllum hybrids, these brown spots. And the only way to treat them is to, with chemicals, or to catch them and with a blue [ultra-violet] insects lamp, or catch them and drown them, whatever. Because they survive nearly everything. They are actually coming from China Indonesian region. And we did some tests with this. We have seen that they still survive eight to nine hours' frost at minus seven degrees Celsius [18.5 degrees F.] So they are not going to be dead as normal bugs do in the winter period and freezing. So you have to be careful for your collection. They are causing here in Europe millions and millions of damage to the food crops, and they are spreading out more and more to northern parts of Europe. They came in actually in through Italy and Spain, and now already are in the north part of the Netherlands. So they are actually everywhere.

This is also something, snails and slugs, it's quite simple with a beer trap. [Pour beer into a shallow pan like a pie pan; the snails and slugs crawl in and drown. These are the large garden snails.]

Something very difficult to catch is the virus, very streaked flowers are nice, but they actually have a virus, and you should actually remove the plants and clean the area where it was growing.

And this little fellow is only one millimeter, so it's very very small, it's spider mite. You see it's laying its eggs there. And the only treatment is chemical, or a quite simple treatment is to raise your humidity in your greenhouse, at least 80%. Or, spraying your plants with water, which actually shouldn't do too much [to harm your plants], but if you have red spider, spider mites in your collection, that's a way you can treat them.

Q&A

Panelist: How does the [cactus] variegation virus spread?

Frank: It's upon mealy bugs.

Panelist: If you take cuttings... and don't sterilize it between....

Frank: Yes, that's also a way, but actually in collections it's mealy bugs, because the virus can survive two hours in the jaws of a mealy bug. And that's the first thing you have to control, the insects. And then you have to clean your knife every time you take cuttings. We have gloves on when we take cuttings. And every time we are using new gloves, and a new... disinfect the knife, of course, with alcohol. So you have to take some prevention measures.

Host: Others? Anything you want to add to that question?

Panelist: No. I just also make sure that I, when I'm washing pots I wash it with a solution of soap, and bleach, and Physan, to make sure that the pots are clean, too, because I reuse my pots.

Frank: Ja. Physan is the best thing to use, because it does affects everything. But you have to take care for your own health with this product. But in EPRIC and also in my collection I never use containers twice. For the reason, to prevent infestations of mealy bugs, or whatever. Because here in Europe the containers are very cheap. I'm paying for a nineteen centimeter, which is eight inch, only twelve cents [Euro], which is only ten dollar cents.

Panelist: Can you prevent mealies by baking your dirt and pots if you're using clay pots?

Frank: No. No, you can't. As I said in the talk, mealy bug eggs survive two years without any plant. So, if there's somewhere in your greenhouse, or your house, or whatever, infested plants, and these eggs are on your bench, or under your chair, or under a pot, or in your greenhouse, even if you have that greenhouse two years empty, you still got mealy bugs in. If you have Epiphyllums, you get used to mealy bugs. Quite honest to say, I can say, ja, use this chemical, or use that chemical, but if you have Epiphyllums, you have mealy bugs.

Host: Jerry, what is your experience with mealy bugs?

Jerry Williams, Rainbow Gardens, Vista, California: One thing here in Southern California we need to do is to control the ant population, because the ant population likes to farm these little critters from plant to plant. So if you're using chemicals at all you're using ant baits, things like that to control the ant population, because I live on an acre and a third ant hill, and I'm constantly fighting ants. I try not to use other chemicals other than the ant bait. I'm using 70% alcohol and liquid detergent and Pam spray [cooking oil in an aerosol can] and cleaning with it. But it's an ongoing job. It's something you just have to do all year long.

Frank: You can actually make some light oil, which is two third of sunflower oil, plus one third detergent, and that's very helpful to prevent mealy bugs spreading. Which is not poisoning yourself, because that's also a problem. Because you have to work in that greenhouse, you have to live with these plants. Or actually I do. And you don't want to poison yourself with all the chemicals. So I'm actually not using any chemicals now in my greenhouse.

Frank: [To a participant asking a question via written chat] OK, there are several viruses identified, of course. There's a cactus X virus. And Opuntia virus already identified. I know you are in Germany. Send me an E-mail and I will send you a list of all viruses there in cacti.

Panelist: Uhlrich Haage of Haage Nursery actually had done a study where they did a Western blot. They did gel electrophoresis where they identified different viruses. And he has information on that, too. Eventually I think he's going to throw out a paper on that. I know that cactus virus C was one of those, too. But there are three or four cactus viruses that caused the streaking, and eventually caused root problems, and probably the demise of the plant.

Frank: A very interesting question I see. "We have a lot of snails." I want to answer that. Because that's a very interesting question. Because if the beer doesn't work, you should use some copper strips, which are available in the better garden centers. Snails and slugs don't like copper. So, if you have anything with copper, they will not go on your plants. I have some copper rings. Ja, I don't want to use too much chemicals.

Frank: The spider mite control. Repeat question. Easily, keep your humidity in your greenhouse, on your plants high, at least 80%, and spray water on your plants if you have a spider mite infection. Because the eggs are exploding with water. They can't survive water.

Frank: Someone ask about the percentage of alcohol [for killing pests.] It's at least seventy to eighty percent. Not lower. You can buy that at a grocery shop everywhere. You can buy that very cheap.

Panelist: If I can only get the 91% alcohol I use that, and I just dilute it [to 70%.]

Frank: And also in this Covid period, you have these gels, sanitary gels. You can also use that. I've used that also because I didn't have any alcohol. You can use that also because it's seventy percent alcohol in it. And it's also a very good product against mealy bugs, because it's not drying too fast as alcohol, these gels. So that's a thing we learned from the Covid period. It stays on the plant about one hour to one and a half hour on the plant before it dries up.