Episode 143: mealybugs

Mealybug on a jade plant. Photograph: sk on Flickr.

Mealybug on a jade plant. Photograph: sk on Flickr.

Transcript

Episode 143

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Jane: Hello, I'm Jane Perrone and this is a podcast - it's called On The Ledge! In episode 143 we are tackling the furry and disturbing topic of mealybugs. Plus I answer a question about a floppy Calathea.

Before we get started, this show is usually a refuge from the events of the outside world but the goings-on in America and around the world in response to the death of George Floyd is something I can't ignore. I never thought I'd be quoting Meghan Markle, but as she said the other day, the only wrong thing to say was to say nothing. I just wanted to say that all of you who are in the US, or indeed anywhere around the world, who are feeling enraged, angry, sad at the fact racism is still a part of our lives in a fundamental way, then I join you in spirit because I feel that too because it needs to be said and needs to be shouted from the rooftops, "Black lives matter".

I've decided to give the ad revenue from this episode to a number of different causes that are tackling racism both in the UK and the US. So far I've given money to the Marshall Project, which is a non-profit journalism organisation which writes about criminal justice, to the Innocence Project, which works to inform the US criminal justice system by helping to get wrongly convicted people exonerated, I've also given a donation to the Loveland Foundation, which is a therapy fund for black women and girls in the US - thanks to listener, Paula, for flagging that one up and she's running a raffle for a painting she's done and I'll put details of that in the show notes. Seeing as I'm in the UK, where I'm sad to say racism is also a major issue, I've also given donations to the Stephen Lawrence Charitable Trust and the Black Curriculum, which works to get black history on to the curriculum in British schools. I have got some more money to give and I'd like to offer you guys the chance to tell me who you'd like me to donate to. So, do have a think and if there is a worthy cause anywhere in the world that tackles racism, then let me know and I will try to select as many as possible to give a donation to, so that all the ad revenue from this episode goes to anti-racist causes.

As a white person it's part of my responsibility to listen and to learn and I am going to continue and ratchet up my efforts to make sure that the guests that I get on this show are as diverse as possible. I've been tweeting about lots of people of colour in the worlds of horticulture and botany this week, but I'd also like to hear from you. I'll put a list of all the organisations I've donated to so far in the show notes. Also, there you will find a couple of Google documents that are really excellent if you want to find out more about what's going on and I hope you do and donate and offer your support in lots of different ways. There's one for the UK and one for the US. So do go and check those out as well. I've heard from listeners who are directly caught up in events in the US and my heart goes out to you. There is a post on the houseplant Fans of On The Ledge group, where you can share your experiences if you wish to do so.

The final thing to say is that I hope that On The Ledge will always be a community where everybody, whatever your sexuality, race, geographical location, religion, is welcome. I'm sure that all of you feel the same because we're all brought together by that wonderful thing, the plant. Okay, cue slightly awkward segue... and now it's time to get on with the show.

This week I'm talking to Professor Raymond Cloyd about mealybugs. Oh God, a shiver down the spine when we think of these furry little beasts that take up residence in our plants and are very hard to get rid of. In fact, in this interview Professor Cloyd calls the mealybug the pest of the 21st Century. That really does set my heart rate doubling! We're going to find out not only what these things are, how they attack our plants, but also, most importantly, how to tackle them! Just before we do that, I've got a crucial job to do. That job is going out to my greenhouse to check for mealybugs. Want to join me? Let's go!

Jane: Here we go. Wolfie is staying inside. Probably a good idea. It's not great weather today. You're familiar with the sound of this door by now, aren't you? Okay, so let's have a look. When you are looking for mealybugs, I'm down here with my cactus and succulent collection which spends the summer out here in the glasshouse. That's a fancy name for what it really is which is a potting shed / greenhouse combo with a half-glass roof. The things to look for are the nooks and crannies, really, because that's where these mealybugs will hang out and duplicate. Furry stuff, white blobs, that's what we're really looking for. When I'm examining each plant, knowing the ones that have had infestations in the past, that's what I'm looking for and it's easy to get a bit of perlite mistaken for mealybugs so don't panic if you do see something because it needs close examination before you know what you're dealing with. So far, so good. I'm working my way down - no, that's just a bit of dust - I'm working my way down the line, to see what we've got.

It's easy with cacti, sometimes, to mistake the fluffiness that you get of the areole with a mealybug. I've got a lovely Easter Lily Cactus Echinopsis subdenudata, which is just coming into bud. Those aren't mealybugs, they're buds, so that's good! Hang on here. I've got a Kalanchoe here, a Kalanchoe Dorothy and I'm seeing a little bit of fluffiness here. This plant is coming back slightly after being knocked back in the winter, but yes, darn you, look at that! I'm seeing, in the new growth, top growth, of a little bud at the bottom and on the leaf, the telltale cotton wool signs of mealybug. I'm immediately going to remove that shoot because that's the easiest way of dealing with it. I'm going to examine the plant closely all over to check if there's anything else. I'm going to put that to one side. That's going to go straight in the bin. Let's see if I can see anything else to worry about on this plant, hopefully I've caught it early. It doesn't look like there's any more on here. I will examine it over the next few days and keep a really close eye out for more.

That means that I need to look at all the plants that have been around that plant very carefully because if there's one mealybug there will no doubt be more. That's all I'm seeing for the moment. A further examination will occur and it really is a case of constant vigilance with mealybugs and doing these checks and that way you can catch it early.

Jane: Please do excuse me while I go and stick my head down the office toilet and scream. Yes, we have mealybugs, I repeat we have mealybugs. It's Professor Cloyd to the rescue.

Raymond: I'm Dr Raymond Cloyd. I'm a professor of entomology in the Department of Entomology in Kansas State University in Manhattan, Kansas - the state of Kansas instead of the country. I focus primarily on horticultural insect pests in a number of cropping systems including greenhouse, nursery, turf grass, landscape, interiorscape, conservatory, fruits and vegetables and Christmas trees. I handle pollinators and now I also handle hemp. I do not handle field crops. I only handle horticultural, special crops.

Jane: I believe that you are a mealybug specialist. This is great to have your expertise to deal with this pest that so many houseplant growers have problems with. I guess my first question is this - sounds like the most naive question and I'm sure you must laugh at my ignorance - but what exactly is a mealybug? Where does it fit on that spider diagram of different kinds of insects, invertebrates and so on?

Raymond: That's not a dumb question, Jane. Mealybugs are very much related to scale insects. Scale insects are also houseplant pests. Brown soft scale is a big one. Mealybugs are very culture-related, in terms of their feeding behaviour, to aphids, white flies, leaf hoppers and scales. They feed within the phloem sieve tubes. The phloem is the food conducting tissues. They emit honeydew, which is a sticky liquid, and the honeydew, of course, is a viable substrate for the black sooty mould which you'll see on your houseplants if you don't manage mealybugs, and that blocks photosynthesis. Mealybugs are in the order we call Hemiptera, which used to be called Homoptera and they're in amongst, again, related to aphids, white flies, leaf hoppers and scales. So that's where they fit in that whole category.

Jane: I guess the thing that distinguishes these from any other pests is their kind of white fluffiness. You could even think they look cute but if you've got in an infestation of these things, it's not cute really because they can be quite devastating. Are there particular types of plants that they are attracted to more than others?

Raymond: Yes, that's a good question. They are prolific, meaning they feed on a wide range of plants and not just houseplants. I think one of their favourite hosts is Coleus. In fact, that's the plant we use in our research and have for the last 20 years. You'll find them on houseplants, I'm thinking of the Cissus rhombifolia, African Violets, you'll see them on Dieffenbachia, Prayer plants, Fig or Ficus. They're a problem on many houseplants but also they can be a problem on some plants like Chrysanthemum, Marigold and Gerbera Daisy, Transvaal Daisy. Gerbera Daisy - you could grow them on there. If I was to pick the number one host, I think Coleus would be the main one.

Jane: That's so interesting. I grow Coleus and I don't think I've ever had a mealybug on them, so there you go! They're obviously not attracted to my Coleus. I have had mealybugs on other plants.

Raymond: You're lucky, Jane. I could send you some! The other group of plants that they really are a problem on, are succulents. In the United States, we have a lot of growers getting into succulents. Succulents are getting very popular. I don't know if that's the same in Europe? Mealybugs are extremely problematic on succulents, hens and chicks and stuff, because it's hard to control them. Once they get down into these very tight areas, it's very hard to get them with any type of spray.

Jane: How do the mealybugs make it onto our plants? Are they always coming in on new plants that we add to our collection, or is there any way that they're travelling to us other than on plants we've brought in?

Raymond: It's important to understand that they do not fly. The only flying stage is the male but they don't feed. There are a number of ways they can travel on to plants. One is on people's clothing or hands; plants that are touching, where the leaves are touching, they can move from one adjacent plant to the next; wind currents, wind or from doors opening or horizontal airflow fans, can be there. Because they're so small you don't notice them until you start seeing the blobs of white and then it becomes problematic because at that point the females, which can lay about 600 eggs, start producing lots of different generations.

Jane: 600 eggs? A day? A week? Don't tell me it's a day!

Raymond: Let me give you the life cycle - that might help. A female mealybug, especially a citrus mealybug, which is the predominant species we see in houseplants, but there's also the long-tail and others, she can lay up to 600 eggs. Those hatch and we call them nymphs or crawlers and they're very small, they're very hard to see on a plant. They start moving around and they go through a series of moults or instars, and after about four or five, the male becomes a winged individual. He has no functional mouth parts, he mates with a female and then dies, but they do feed on the plant and so then, as they're feeding, they're sucking up the phloem, they're producing honeydew and then you get black sooty mould. You'll see ants in the area. Ants will feed on the honeydew, sometimes they'll tend to protect the mealybugs. Then the female will lay her eggs under a cottony mass -- the citrus mealybug - and under her is between 400 and 600 eggs and then she dies, but not before she lays her complement of eggs and those eggs will then hatch and then nymphs will emerge from the eggs and you'll start another generation. So the number of eggs produced by the female is within one generation.

Jane: Wow, I see. So if you start with one mealybug that lays 600 eggs, that's going to go nuclear fairly fast, isn't it? That's why we can end up with these really bad infestations really quickly. How long do they live for? The males obviously for a short and limited existence. How long does a female mealybug live for? Is it a matter of days?

Raymond: The entire lifecycle can occur between 25 and 60 days, depending on temperature. Females can live several weeks, overall, before they die, but not after laying her egg complement. Each life stage will have a certain number of days and like all insects, it might depend on temperature, but the lifecycle from egg to egg-laying female ranges between 30 days to 60 days.

Jane: Is the issue of mealybugs something that's stayed level in terms of the industry? Have mealybugs become more of a problem in recent years, or is it something that's always been around and has always been tackled by growers?

Raymond: That's a good question, Jane. They have actually increased. I actually am calling them the pest of the 21st Century and I'll explain why. In our research we have found that systemic insecticide, your audience might know those, as you apply them as a drencher granular to the soil, the plants take up the material which then gets into areas where insects like aphids, white flies and mealybugs feed. In our research, we found that systemic insecticides are not effective against mealybugs. What that means is you have to use what we call contact insecticides as well. You have to get good coverage and you have to make frequent applications because of the lifecycles of the mealybugs. Mealybugs are extremely sneaky, they hide in cracks and crevices of plants, especially larger plants and that makes it difficult to get good coverage. They are increasing and the other problem is we don't have very many good biological controls that are predators or parasitoids commercially available for mealybugs. That's why mealybugs to me is much more problematic than some of the other common pests that greenhouse producers and home-owners deal with on a regular basis.

Jane: Those of us who are still in the wonderful honeymoon state of never having experienced a mealybug infestation, what are the first things to look out for so that you can catch them early before they start to multiply too quickly?

Raymond: That's difficult for home-owners because they don't always do this. If you know your plant is susceptible, it's regularly monitoring, checking the plant. Yellow sticky cards will not work for mealybugs because they don't fly. You have to look at your plants closely. The first instar nymphs are hard to see, so sometimes I tell people, shake your plants gently over a black piece of paper and you'll see the nymphs there. Once they get to the plant, the egg-laying females, and you have 50 females on a plant and you've got crawlers, it's too late. At that point, you might as well just throw the plant away because it's not going to be effective in managing populations.

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Jane: Don't despair, Professor Cloyd will be back after the break with a solution to the mealybug issue. Now, it's time to hear from our other sponsor for this week's show. When it comes to looking after our pets, we all like to make sure that they get the absolute best and that's where Be:Loved Pets comes in. Thanks to Be:Loved Pets for supporting On The Ledge this week. Their range of wellness products includes shampoo bars, nose and paw balms and an odour eliminating candle. I've been trying them out on Wolfie and they all smell so good. Be:Loved products are free from parabens and extensively tested on humans because if it's not good enough for us, it's not good enough for our pets, which is totally true. I've ended up washing my hands with the shampoo bar because it feels so good, plus all the packaging is plastic free. So for 15% off your first purchase from Be:Loved Pets, visit wearebeloved.co and enter voucher code JaneP. Be:Loved Pets ship to the US and Canada, UK, Europe and Australia. Visit wearebeloved.co now and enter voucher code JaneP for 15% off your first order. Be:Loved - proper pampering from palm to paw. Now it's time to get back to the mealybugs!

Jane: The treatment that I often see bandied around on the internet - that den of bad houseplant advice - the treatment I've used on my own plants, what we would call here in the UK a cotton bud, but what you would call a q-tip, soaked in, what you would call rubbing alcohol and what we might call surgical spirit or similar, applied to the mealybug body which is all very well when you've got a smallish plant but if you've got a huge citrus with an infestation, that's not quite as practical. If you have a small plant, a) is that a good treatment and b) what's the alternative? Is there a better treatment for larger plants where you just can't have enough cotton buds/q-tips around?

Raymond: I would say the rubbing alcohol or ethanol alcohol 70% is going to be for people with a lot of time on their hands and small number of plants and very small infestations. It's not very practical when you've got many plants, orchids or other houseplants and you've got an infestation. What we typically recommend is, if you can take your plants outside, is to use a force of water spray to dislodge the mealybugs by getting thorough coverage of all plant parts. That saves you from using an insecticide. In some cases the insecticides we typically recommend are the insecticidal soaps, the potassium salts, the fatty acids or some of the horticultural oils based on petroleum, mineral or Neem. These are only contacts, they don't have very long residual and you're going to get thorough coverage of all plant parts and you have to make applications at least once a week and people just don't remember that, so that's why the mealybugs take off. When the plants are over 50% infested with mealybugs, it's time to throw the plant away, RIP, because you're not going to be able to get adequate suppression or sufficient suppression at that point. Again, mealybugs, it's really high preventative maintenance to avoid your plants from being infested with mealybugs mainly because of the biology, reproductive nature of the females, and most of your insecticides are contact-only and they don't last very long in the environment. There are other insecticides available, but I don't always like to recommend them in homes because they can cause, probably, allergies, or something like that. If you take them outside you might be able to use some of the more non-selective materials that you would use, although soaps and oils are not selective but they're less toxic to humans than some of the other materials that are commercially available.

Jane: One of the things I wanted to ask you about was, are there different species of mealybugs? Are there ones that specialise in roots as opposed to top growth? I've lost a few African Violets to what seemed to be more of a root mealybug infestation, which really was something that I wasn't prepared to battle.

Raymond: Yes, we have mealybugs that feed on above-ground portions, that includes citrus and long-tail are probably the most common ones, and then we do root mealybugs, and they are a big problem in the United States on cannabis crops. Because they're in the soil it's harder to get at them with some insecticides and even some of the biological, so that has been a big problem in some commercial operations with cannabis and even non-cannabis crops. So there's root mealybugs, yes.

Jane: Even if you've got an infestation on top growth, is it worth taking the plant out of its pot and dislodging or washing off all the soil just because there might be mealybugs lodged in the stem and nooks and crannies around the point where the soil meets the top growth?

Raymond: There are mealybugs that feed on the above-ground portions, leaves and stems, and those that feed on the below ground parts. So if you have mealybugs feeding above ground, you don't need to worry about the soil, but if you notice your plants getting stunted and wilting even after full water applications, then it might behoove you to take them out of the pot and see if there is an insect like a root mealybug that's feeding on the root system.

Jane: I think, for me, the root ones are worse than the top ones because they just are really, really tricky to get hold of. In a way though, what I do like about finding a root mealybug infestation is that it then makes the decision to get rid of them easy because I know I can't fight them, so I don't try and battle, I just give in, which I guess saves me a lot of work. It did occur to me that maybe the old q-tip and rubbing alcohol method during lockdown, if people don't have a lot to do, this could take up quite a few long stretches of hours of treating your plants individually, mealybug by mealybug!

Raymond: Just put on some nice music and sit there and do it while you've got nothing else to do, Jane.

Jane: It sure is a mindfulness activity. Okay, let me look at my list, we've talked a bit about those chemical treatments but you did say there weren't many biological controls. Is there anything on the market in terms of biological controls that you can opt for?

Raymond: There is an insect called the mealybug destroyer, that's its common name. It's a ladybird beetle. The problem is it needs a lot of mealybugs so we don't recommend it unless it's an interiorscape because it's not going to clean up your plants very well because it needs so many of them. For a houseplant situation, we have isolated plants, biologicals just don't work, but for an interiorscape where you have lots of plants, that might be something to use when you're not looking for 100% elimination. That's really the only one commercially available. There are Green Lacewing larva, but their efficacy is not very consistent. The parasitoids, there is one out there, but I don't know how readily commercially available - it is in Europe and it has limited availability in the United States right now. It's called Anagyrus pseudococci. It's a parasitoid that attacks the early instars of the citrus mealybug. We've been trying to get some to do research but we get them and we can't get them to establish. It's out there but I really don't know how effective it is in regulating, especially in houseplants mealybug populations.

Jane: We've talked a little bit about some of the symptoms. Are there any other symptoms of mealybug? We don't always spot these things. Are these things moving fast enough that we might, at the adult stage, see them actually moving about our plants, or are they slower than that?

Raymond: They're pretty slow. The mealybugs will move around after they've found a place to sit and feed. They will move around. They're very slow-moving, lethargic. The problem is the nymphs and the crawlers, which are more active, are difficult to see, but the later instars, especially when they get the waxy coating, are very easy to see. However by that point, it's almost too late. If you have a very minor infestation you can use your rubbing alcohol, q-tip or a water spray, or one of the insecticidal soaps or oils and direct your application to these localised infestations. When you start seeing a lot of mealybugs on plants, on stems, the under sides, it's probably time to dispose of the plant because you're going to have a difficult time dealing or managing the population.

Jane: After 20 years of studying mealybugs, do you have any - I don't want to say fuzzy feelings for these creatures - have they wormed their way into your heart at all, or do you just want to destroy them all?

Raymond: I enjoy mealybugs. I reared them for 20 years. We rear them, they have a special place in my heart, I call them fuzzy insects, it would be a great children's toy to have - a nice fuzzy, white mealybug, because they are kinda cute, a little bit. Like all insects I'm enamoured by their evolution and how they can adapt to certain situations. Systemic insecticides just don't work and they have developed resistance to insecticides. Not at the same level of other insects. Insects are the most abundant organism on the planet and they are for a reason and mealybugs are just part of that system. Right now, it's a concern because it's very difficult to manage populations. There's a lot of inputs from insecticides and losses of throwing plants away because of this insect.

Jane: One of the things that's often recommended when it comes to controlling any pest or protecting your plants from any pests is this idea of quarantining new plants that arrive. Is it enough to have my newly-arrived succulent on one side of the room and six foot away to have my other plants? How far apart would a plant have to be and how long should be a plant be in quarantine before you're convinced that there isn't an infestation of some kind, particularly mealybugs?

Raymond: Your idea of quarantine is quite relevant under our coronavirus situation, but I think if your plants are wearing a mask and six feet away you're in good shape. When you do get a new plant like an African Violet, and you have a collection, I'd isolate or quarantine it for at least a week and then check it daily for any insects because by that point under the temperatures in a home, you should see some insect or mite activity. That's about a week and keep it in another room, or if you have an extra greenhouse space. If you bring a plant, like an African Violet, that you buy and it has mealybugs and you put it with your collection, then they're going to spread them on the rest of the plants and that's why isolation or quarantine is recommended. It isn't always feasible but we do recommend it as much as possible.

Jane: Many of my listeners are fairly new, in terms of the last few years, of getting into houseplants and they're just not ready for that moment when the first infestation happens. Having grown plants for a long time myself, I'm possibly more cynical now about that. I do hear stories of people buying plants from reputable growers and them arriving with mealybugs and that's presumably because it is such a successful pest that is so hard to control in a nursery situation.

Raymond: Yes, and the growers do the best they can do to alleviate the problem but you can't kill every mealybug on a plant. It's just not possible, no. Dealing with mealybugs is a lot of prevention. Once they're on the plant and infested, it's too late and you might as well throw it away. It involves scouting your plants regularly, especially the ones you know that are susceptible and then you can apply the rubbing alcohol under low level on low infestations, or apply insecticidal soap or a commercially registered soap or oil on a regular basis, but you also have to get thorough coverage of all plant parts including leaf, undersides and stems if you really want to mitigate any issues of mealybugs.

Jane: Yes, that's where they're always hiding out, isn't it? In those nooks and crannies which is why they're so hard to control. That's really great to have your input. We will continue our fight against the mealybugs. This is your job, so of course you have to do it, but I'm slightly horrified about the idea of you raising generations of mealybugs. Presumably that's how you can test out different strategies and let them loose and then see if you can control them?

Raymond: Yes, we continue to do research, testing various materials and biologicals, but it's always a battle. They have evolved and they have these behaviours and mechanisms that really make it difficult to deal with them with insecticides. It takes persistence and diligence to get mealybugs, under our current situation such as lockdown, this is a prime opportunity to exercise diligence and patience and deal with mealybugs if you have them.

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Jane: Well that's your weekend sorted, isn't it? You're all going on a mealybug hunt. Thanks to Professor Cloyd for his help and if you want to find out more about him and his research and his top advice on dealing with mealybugs, check out the show notes where I link to a pamphlet full of information about this particular pest.

Now it's time for Question of the Week which comes from Laura and it is about a Calathea leopardina or Geoppertia leopardina as taxonomy freaks will know Calathea has been transferred to the genus Geoppertia. It doesn't sound quite so poetic but we'll go with it. This Calathea/ Geoppertia, it's been around for about three years in Laura's house and it's been doing okay but as it's got older and it's started to - sorry, I'm distracted by the fact it's so windy here that my quince tree is flinging its young fruits against the glass and making a noise. I've got a good harvest coming, so I hope they don't get damaged, but anyway. . . High winds here today, what can you say! - Anyway, where did I get to? The plant is getting droopy and hanging over because of its own weight. Laura can't seem to find the answer online. Apparently, the plant flowers regularly, she's got no idea if this is a sign of good health or procreation as a last resort. Good point. It's been both under- and over-watered over the years, so some of the leaves show signs of this, but generally it's put up with my poor treatment.

So Laura wants to know how she deals with it and can she keep her plant upright for the future? Looking at this picture, I think this plant is undergoing some drought stress. The leaves are currently rolled up at the sides which, with theMaranta group plants, is definitely an indication that there's a bit too much dryness going on. I think, generally, I find with drought stress that if you water the plants and moisture gets to those roots they will unroll fairly quickly. So if they're still rolled, I would say this plant is still probably a little bit unhappy with the water levels. I note it's in a terracotta pot and I would generally say that I prefer Marantas in a plastic pot. That's just because of my watering regime, but it might be worth giving it a good soak, especially at this time of year, that should be okay, providing it then gets the chance to drain and because it's in a terracotta pot it will dry out more quickly anyway and the water will evaporate. Give it a good soak and that should sort out the rolled leaves. In terms of the droopy growth, I think this plant, despite being a low light plant, needs a bit more light. I think it's becoming leggy and drooping over because it's just not getting enough light to make it happy.

So, I recommend, Laura, moving it somewhere that's a little bit lighter. So that might just mean moving it from its current location to a location another metre or two metres towards the nearest window, without dramatically changing the circumstances of the plant, that could be enough to make a difference because, you know what, when you get a light meter out and you stand in one spot and then go a metre or two metres near a window you'd be amazed by how much extra light there is. Just make sure it's not somewhere where the plant is getting direct sun. That though is not going to magically take away the leggy issue that you've already got. It will prevent the plant getting any leggier, the new growth will be more stocky, but it won't take away this issue of the current droopiness because that's already set in stone.

So what do you about that? Well, I know that you've tried some yarn and a large knitting needle, I'm liking your style there, Laura, you've got a couple of different options. Either you find some way of staking it, as you have done perhaps with some yarn, or you can go a bit more drastic. It seems to be this legginess is particularly on one side and you could go really drastic and repot the plant, literally cut it in half, repot into a smaller pot and keep the pot that's not so droopy. It sounds drastic, but it's one way of dealing with it and you might actually find it solves the problem. If you don't like the idea of that, then you could just cut away that droopier stem. The plant will respond by reshooting, as long as it's happy in every other respect and you'll end up getting a fuller plant in the longer term, which still looks comfortably stocky rather than this droopy look. It's worth bearing in mind Calatheas can get quite tall. If you look at the descriptions of them, oftentimes you're talking 50cm to 60cm in height, so they can get quite tall and the flowering, yes, plants can flower as a result of being a bit stressed therefore they're thinking I've got to get some reproduction going on here, so that could be an explanation. It may be that your plant is quite mature and has been happy enough to flower and I wouldn't say that's a bad thing whatsoever. I think if you can just get the light right then your plant will go from strength to strength and you can also address this issue with the slight humidity issues.

What I always say whenever anyone's got a plant in the Maranta group, is do check for spider mites because general malaise in a plant can be an indication of the dreaded spider mite which is a very common problem for this group of plants. Do check out the spider mite episode if you haven't heard that already because there's lots of top tips on dealing with that in that episode. So, Laura, I hope that has in some way or other assisted you with your lovely Leopardina. It's a beautiful plant and I think you should be able to get it looking great without too much more work.

By the way, you need to go and look at the picture of this plant on the show notes because the knitting needle that Laura has put in the pot is flipping enormous. Wow! I'm not a great knitter so I don't know what you use that for, but it's a chunky old needle. Thank you very much for sending that question in, Laura. If you've got a question for On The Ledge then drop me a line ontheledgepodcast@gmail.com

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Jane: That's all for episode 143. I will be back next Friday. Just remember the words of Maya Angelou, as you go through your days this week: "If you're always trying to be normal, you'll never know how amazing you can be!" Bye!

[music]

Jane: The music you heard in this episode was Roll Jordan Roll by The Joy Drops, An Instrument the Boy Called Happy Day, Gokarna by Samuel Corwin, and I Snost, I Lost by Doctor Turtle. The ad music was by the Heftone Banjo Orchestra with the tracks Dill Pickles and Whistling Rufus. All tracks are licensed under Creative Commons. Visit janeperrone.com for details.

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The larvae of the mealybug ladybird, Cryptolaemus montrouzieri, a mealy bug bug biological control: Photograph: Jean and Fred on Flickr.

Mealybugs are one of the most common and hard-to-treat pests you’ll encounter as a houseplant grower, so it’s high time we devoted a whole episode to these furry terrors! So I recruited the help of an entomologist who has been studying mealybugs for the last 20 years to bring you some expert advice on the subject.

Also in this show: I answer a question about a droopy Calathea, and I take time out of my usual content to speak up about racism and how On The Ledge is supporting antiracist organisations. For more on that, click here …

Want to know root mealybugs? Listen to episode 243 for an interview on these pests.

Check out the notes below as you listen to find out more …

  • This week’s expert guest is Raymond Cloyd, professor of entomology at the Department of Entomology at Kansas State University. Check out his in-depth info sheet on mealy bug here for in-depth information on identifying and dealing with this pest.

  • Mealybugs are related to scale insects, aphids, whiteflies and leaf hoppers and are part of the order Hemiptera. They feed from the food conducting tissues in plants known as phloem, and emit honeydew, which can lead to black sooty mould.

  • Mealybugs feed on a wide range of houseplants and other pants - one of their favourites is coleus aka Solenostemon, as well as African violets, Dieffenbachia, prayer plants and figs. They also LOVE cacti and succulents!

  • Dr Cloyd calls mealybugs ‘the pest of the 21st century’ because he found in 20 years of research that systemic insecticides are not effective on these pests, while it is difficult to get good coverage with contact insecticides such as fatty acid sprays.

  • The mealybug’s lifecycle lasts 25-60 days: you can watch a video of it here.

  • By the time you spot a mealybug, the infestation may already be severe as females can lay as many as 600 eggs. Dr Cloyd recommends shaking plants over black paper to spot the nymphs, or mealybug babies, before they grow into adults.

  • Read Dr Cloyd’s info-packed pamphlet on mealybug control in interiorscapes and greenhouses here. There’s also advice on mealybugs from the RHS website.

  • If you have the time and dedication, you can treat mealybigs by applying a q-tip/cotton bud soaked in rubbing alcohol/surgical spirit to the bodies of the pest. You can also spray them off with water.

  • Another species of mealybug feeds on the roots of plants, and these can be even more tricky as you may not spot them, and they are hard to remove.

  • There is one widely available biological control for this pest: the mealybug destroyer, Cryptolaemus montrouzieri, although this may not be effective indoors unless you have a big infestation on a large number of plants.

Laura’s Calathea leopardina.

Laura’s Calathea leopardina.

Question of the week

Laura got in touch because her Calathea is looking droopy and sad. She has had the plant for three years, but it’s getting droopy, although it does flower regularly. It has been over and underwatered. Laura wanted to know how to support the plant and fix the problem in the longer term.

First off, this is a Calathea leopardina, aka the leopard calathea - or as it should be known now, Geoppertia leopardina. Looking at the plant’s leaves (see left) it looks as if it is still undergoing drought stress - as indicated by the curled leaves. I suggest it needs a good soak - this should return the leaves to their regular shape. I suspect the issue with droopiness is due to the plant not receiving enough light: move it a metre or two closer to the window and it should respond with stockier growth.

The leggy growth that’s already there won’t change, but one option is to give the plant a haircut, taking out the leggiest stems. Otherwise, it can be held back with some supports and string (or yarn as in the case of Laura’s plant!).

Want to ask me a question? Email ontheledgepodcast@gmail.com. The more information you can include, the better - pictures of your plant, details of your location and how long you have had the plant are always useful to help solve your issue!

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this week’s sponsor -
Be:Loved Pets

Thanks to Be:Loved Pets for supporting this episode of On the Ledge. From shampoo bars to nose and paw balm, pamper your pets with Be:Loved’s range of pet wellness products: they are free from parabens, the packaging is plastic free and everything is extensively tested on humans, because if it’s not good enough for us, it’s not good enough for our pets!

I’ve been trying these products out on Wolfie, and they smell AMAZING (confession: I borrowed one of the shampoo bars to wash my hands!). Be:Loved Pets ship to the US and Canada, the UK, Europe and Australia. 

Get 15% off your first order from Be:Loved Pets by visiting wearebeloved.co and entering the voucher code janep.

Black Lives Matter

The events of the last couple of weeks have highlighted that racism is ingrained in our society, and that’s simply not acceptable. Everyone needs to start speaking out! If you are keen to educate yourself about the issues surround racism and police brutality that have been going on for years, but erupted to the surface of the public consciousness in the past few weeks, there are two useful documents to read - one for the US and one for the UK.

I am donating 100% of the ad revenue for this episode to causes in the UK and the US that fight racism. Listed below are the organisations I have donated to so far… if you have other suggestions, please let me know - you can comment below, or email ontheledgepodcast@gmail.com.

As a result of your suggestions, so far I have also donated to…

I am keen to make sure On The Ledge’s interviewees are from as diverse a range of backgrounds as possible, so please let me know if you have someone to suggest. you can read my twitter thread highlighting POC in horticulture and botany here.

HOW TO SUPPORT ON THE LEDGE

Contributions from On The Ledge listeners help to pay for all the things that have made the show possible over the last few years: equipment, travel expenses, editing, admin support and transcription.

Want to make a one-off donation? You can do that through my ko-fi.com page, or via Paypal.

Want to make a regular donation? Join the On The Ledge community on Patreon! Whether you can only spare a dollar or a pound, or want to make a bigger commitment, there’s something for you: see all the tiers and sign up for Patreon here.

  • The Crazy Plant Person tier just gives you a warm fuzzy feeling of supporting the show you love.

  • The Ledge End tier gives you access to two extra episodes a month, known as An Extra Leaf, as well as ad-free versions of the main podcast on weeks where there’s a paid advertising spot, and access to occasional patron-only Zoom sessions.

  • My Superfan tier earns you a personal greeting from me in the mail including a limited edition postcard, as well as ad-free episodes.

If you like the idea of supporting On The Ledge on a regular basis but don't know what Patreon's all about, check out the FAQ here: if you still have questions, leave a comment or email me - ontheledgepodcast@gmail.com. If you're already supporting others via Patreon, just click here to set up your rewards!

If you prefer to support the show in other ways, please do go and rate and review On The Ledge on Apple Podcasts, Stitcher or wherever you listen. It's lovely to read your kind comments, and it really helps new listeners to find the show. You can also tweet or post about the show on social media - use #OnTheLedgePodcast so I’ll pick up on it!

CREDITS

This week's show featured the tracks Roll Jordan Roll by the Joy Drops, An Instrument the Boy Called Happy Day, Gokarna by Samuel Corwin and I Snost, I Lost by Doctor Turtle.  Ad music is  Dill Pickles and Whistling Rufus, both by the Heftone Banjo Orchestra. 

Logo design by Jacqueline Colley.

Pests & diseasesJane Perronemealy bugs, Calathea/Goeppertia2 Comments