What’s eating my plant & how do I get rid of them - Ask Extension
Hello! I have a white bird of paradise plant (I call her Eva) I purchased from Home Depot about four months ago. I didn’t know what she was at the t...
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What’s eating my plant & how do I get rid of them #673725
Asked August 06, 2020, 4:30 PM EDT
Hello! I have a white bird of paradise plant (I call her Eva) I purchased from Home Depot about four months ago. I didn’t know what she was at the time but fell in love with her leaves. I have other plants as well, and have had to fight off fungus gnats three times from other plants (they are now outdoors or in quarantine). I noticed two-three months ago two types of bugs crawling in Eva’s soil, and nothing I’ve done has gotten rid of them. I starved her of water and used diatomaceous earth. I used a neem oil spray. And now I have a Bayer BioAdvanced insect killer, and it’s doing nothing. I read that these could either be soil mites or root aphids...maybe both. One bug type is whitish and oval shaped. The others are brown and a rounder shape. I had spider mites in my ivy plant (outdoors now) so I don’t think that’s what these are. I never see them on the plant...only in the soil when I disturb it. Now that Eva is sprouting new leaves (on the second round of new leaves) I’m seeing the bottoms of the older leaves turn brown at the edges. I don’t want her to die and I don’t want this infestation. I have also watered her with 1part hydrogen peroxide/4parts water...it killed the fungus gnat larvae, but not these two pests. Should I wash and repot her again?
Baltimore County Maryland
Expert Response
We do not see any pest insects in the photos, so if you see the soil insects in question, we will need a close-up photo to identify them. There are a couple of small insects (or insect relatives) that can inhabit houseplant soil that do not damage plants - booklice (Psocids; not really lice) and more commonly springtails (Collembola). Both feed on decaying organic matter in the soil, including fungal spores and algae, and do no harm. Soil mites are less common but also detritivores, breaking down organic matter and not feeding on the plant. Root aphids are far less likely and would not be crawling around on the surface, if visible at all unless the plant were un-potted. Houseplants can contract root mealybugs, but they tend to be quite noticeable when the root ball is removed from the pot and they generally cause overall decline in vigor of the plant rather than pinpoint symptoms.
Fungus gnat larvae are best controlled by letting the soil dry out more in-between waterings (where the plants can tolerate it), repotting into fresh soil, or treating the soil with mosquito bits dissolved in water (according to product label directions). The bits are made with B.t., an organic pesticide which affects only fly larvae like fungus gnats.
The oval white bugs you mention could be mealybugs - that is their basic shape and color. Rounder, brown pests on houseplants tend to be scale, but they would be sedentary and present on leaves or stems.
Home remedies are not recommended due to their ineffectiveness or potential to cause plant tissue damage, since the ingredients are not intended for use on plants and are not proven to be plant-safe. Peroxide too diluted will have no effect on anything (pest/disease or otherwise) and when concentrated enough to damage a pest or fungus, will also be strong enough to damage the leaves or roots in the process. Similarly, baking soda is a salt (not table salt, but the principle is similar) and causes water loss and results in plant cellular damage. (If it didn't do damage, then it also wasn't strong enough to be an effective treatment either.)
Diatomaceous earth should be used very carefully, as (especially indoors) the fine powder is easy to disperse; wear goggles and a dust mask to prevent inhaling it or getting it in your eyes. It may discourage insects from running around on the soil surface, but would not impact the lower layers.
The Bayer product you mention appears to contain imidacloprid, a systemic insecticide which may prove helpful for plant-feeding insects but needs time to be absorbed and moved into all plant tissues. We do not have timetables on this, as it depends on many factors, but it would not be unreasonable for this process to take two or more weeks before it actually starts working. If any of the soil insects present are not actually feeding on the roots however, like the springtails mentioned above, then they will probably not be affected.
Some fungal growth in potting soil is normal and not harmful to the plant - the fungi are merely breaking down the organic matter in the soil, just as they do outside to the benefit of plant roots. If a concern, or if soil is staying too wet because it is older and compressed, repotting is always beneficial. Frequent repotting stresses plant roots, so only do so about once a year or less, or as needed based on issues affecting the plant.
Make sure the plant pots (this one and the others) have drain holes, as pots without drainage are highly likely to damage roots through over- or under-watering. Mineral salts from fertilizer build-up would also not have the chance to leach out, also causing root damage over time. If there are drain holes, empty the saucers underneath as soon as they collect water so the roots do not stay saturated.
This Bird-of-Paradise looks good from what we can see. Browning/drying of leaf margins, particularly on older leaves, is normal for many houseplants. Our lower indoor humidity is primarily responsible, though soil salt buildup can also be a cause. (Misting will have no measurable affect on humidity but using a room humidifier can help.) Plants whose roots are sensitive to chlorine, chloramine, and fluoride in tap water can also develop dried leaf tips from repeated exposure. (For these plants, switching to another water source or diluting the tap water with distilled will help.)
Over time, old leaves will die off as new leaves are grown. How quickly or slowly this happens depends on various conditions, one of which is light. If a plant needing bright light is kept in lower-light conditions, it will cycle-through shedding older leaves more quickly than normal because it does not have enough photosynthetic resources to maintain a full complement of leaves; it has to ration its resources for the newest leaves and removes nutrients and jettisons the oldest as a result. In brighter light, the plant can sustain more leaves at once and tends to shed more gradually. Browning leaf tips (more often, leaf yellowing) can sometimes be the first signs of leaf senescence, which is the process of being shed.
Miri
Fungus gnat larvae are best controlled by letting the soil dry out more in-between waterings (where the plants can tolerate it), repotting into fresh soil, or treating the soil with mosquito bits dissolved in water (according to product label directions). The bits are made with B.t., an organic pesticide which affects only fly larvae like fungus gnats.
The oval white bugs you mention could be mealybugs - that is their basic shape and color. Rounder, brown pests on houseplants tend to be scale, but they would be sedentary and present on leaves or stems.
Home remedies are not recommended due to their ineffectiveness or potential to cause plant tissue damage, since the ingredients are not intended for use on plants and are not proven to be plant-safe. Peroxide too diluted will have no effect on anything (pest/disease or otherwise) and when concentrated enough to damage a pest or fungus, will also be strong enough to damage the leaves or roots in the process. Similarly, baking soda is a salt (not table salt, but the principle is similar) and causes water loss and results in plant cellular damage. (If it didn't do damage, then it also wasn't strong enough to be an effective treatment either.)
Diatomaceous earth should be used very carefully, as (especially indoors) the fine powder is easy to disperse; wear goggles and a dust mask to prevent inhaling it or getting it in your eyes. It may discourage insects from running around on the soil surface, but would not impact the lower layers.
The Bayer product you mention appears to contain imidacloprid, a systemic insecticide which may prove helpful for plant-feeding insects but needs time to be absorbed and moved into all plant tissues. We do not have timetables on this, as it depends on many factors, but it would not be unreasonable for this process to take two or more weeks before it actually starts working. If any of the soil insects present are not actually feeding on the roots however, like the springtails mentioned above, then they will probably not be affected.
Some fungal growth in potting soil is normal and not harmful to the plant - the fungi are merely breaking down the organic matter in the soil, just as they do outside to the benefit of plant roots. If a concern, or if soil is staying too wet because it is older and compressed, repotting is always beneficial. Frequent repotting stresses plant roots, so only do so about once a year or less, or as needed based on issues affecting the plant.
Make sure the plant pots (this one and the others) have drain holes, as pots without drainage are highly likely to damage roots through over- or under-watering. Mineral salts from fertilizer build-up would also not have the chance to leach out, also causing root damage over time. If there are drain holes, empty the saucers underneath as soon as they collect water so the roots do not stay saturated.
This Bird-of-Paradise looks good from what we can see. Browning/drying of leaf margins, particularly on older leaves, is normal for many houseplants. Our lower indoor humidity is primarily responsible, though soil salt buildup can also be a cause. (Misting will have no measurable affect on humidity but using a room humidifier can help.) Plants whose roots are sensitive to chlorine, chloramine, and fluoride in tap water can also develop dried leaf tips from repeated exposure. (For these plants, switching to another water source or diluting the tap water with distilled will help.)
Over time, old leaves will die off as new leaves are grown. How quickly or slowly this happens depends on various conditions, one of which is light. If a plant needing bright light is kept in lower-light conditions, it will cycle-through shedding older leaves more quickly than normal because it does not have enough photosynthetic resources to maintain a full complement of leaves; it has to ration its resources for the newest leaves and removes nutrients and jettisons the oldest as a result. In brighter light, the plant can sustain more leaves at once and tends to shed more gradually. Browning leaf tips (more often, leaf yellowing) can sometimes be the first signs of leaf senescence, which is the process of being shed.
Miri
Thank you. This is good information, and I’m glad to know my plant looks healthy. The small bugs are too hard to capture in photo...I only have video. I read that the aphids grow into adults and fly, which is why I was worried. I’ve attached pictures of what looked like two different types of flying insects caught in my fan trap. Are they definitely fungus gnats?
I will attempt to capture the crawling insects before repotting.
These do appear to be fungus gnats, yes.
https://extension.umd.edu/hgic/topics/fungus-gnats-houseplants
Aphids can fly as adults some of the time (not all adults grow wings, usually only when the population is high and they need to find more food sources), but a root aphid population would probably be fairly obvious upon visual inspection of the roots if they were present and ready to disperse.
Here's a bit more info. on springtails:
https://local.extension.umn.edu/local/rice/county-agriculture-educator/article/what-are-springtails-and-what-are-they-doing-your-soil#:~:text=Springtails%20that%20infest%20houseplants%20are,out%20and%20water%20less%20frequently.
https://extension.colostate.edu/topic-areas/insects/springtails-5-602/
https://extension.umn.edu/nuisance-insects/springtails
And Psocids: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/ENTO/ENTO-143/ENTO-143-PDF.pdf
(Most of this article refers to outdoor psocids, the "barklice," which can be ignored here. "Booklice" are what you might find in potting soil, though less commonly than springtails. They can be treated the same in that they don't do harm and use the same food sources.)
Good images of soil mites are harder to come by, being so tiny, but they will be much smaller than springtails or psocids and be fairly rounded in shape. They only crawl; they cannot jump as springtails do.
Miri
https://extension.umd.edu/hgic/topics/fungus-gnats-houseplants
Aphids can fly as adults some of the time (not all adults grow wings, usually only when the population is high and they need to find more food sources), but a root aphid population would probably be fairly obvious upon visual inspection of the roots if they were present and ready to disperse.
Here's a bit more info. on springtails:
https://local.extension.umn.edu/local/rice/county-agriculture-educator/article/what-are-springtails-and-what-are-they-doing-your-soil#:~:text=Springtails%20that%20infest%20houseplants%20are,out%20and%20water%20less%20frequently.
https://extension.colostate.edu/topic-areas/insects/springtails-5-602/
https://extension.umn.edu/nuisance-insects/springtails
And Psocids: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/ENTO/ENTO-143/ENTO-143-PDF.pdf
(Most of this article refers to outdoor psocids, the "barklice," which can be ignored here. "Booklice" are what you might find in potting soil, though less commonly than springtails. They can be treated the same in that they don't do harm and use the same food sources.)
Good images of soil mites are harder to come by, being so tiny, but they will be much smaller than springtails or psocids and be fairly rounded in shape. They only crawl; they cannot jump as springtails do.
Miri
