MEET
THE
THRIPS
THRIPS
Thrips are very destructive at all life stages. They can cause a wide range of damage and can be tricky to treat due to their life cycle.
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SPIDER MITES
SPIDER MITES
Spider mites are very small mites that have the ability to spin fine webbing. The most common spider mite on houseplants is the two-spotted spider mite.
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MEALYBUGS
MEALYBUGS
Mealybugs are part of the soft-bodied scale family. The adult females are white, round, and hairy while the adult males are can fly and closely resemble fungus gnats.
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SCALE
SCALE
Scale are hard-bodied insects. Once reaching maturity, the adult female scale will attach itself to the plant and become immobile.
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FUNGUS GNATS
FUNGUS GNATS
Fungus gnats are small, black flying insects. They generally do not cause harm to your houseplants unless they are in very large numbers.
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Thrips
About Thrips
Thrips, an insect in the family Thysanoptera, are tiny, slender insects with fringed wings that feed on the plant by piercing the outer layer of the leaf and sucking the contents out. They can be particularly destructive and move between plants with ease, as, though they cannot “fly”, they can leap about two feet.
Understanding the thrips life cycle is essential to treating them successfully. Thrips adults are the long slender black insects we are accustomed to seeing in images. The adults will lay eggs within the leaf tissue of your plant. As the larvae hatches out of this egg, it will eat its way out of the leaf (causing distinctive damage marks). This larvae will then feed on the plant for about five days, depending on environmental conditions. These larvae are typically orange/clear in color and are very, very small. They resemble dust specks. However, if you look long enough, or poke them with a chopstick, they will wriggle away, like little worms. They are often hidden in the crevices of the plant, or along the leaf veins.
Once the larvae matures through two more life stages, depending on the specific thrips species, it will typically drop down into your growing medium to pupate. The pupal stage takes about three days depending on environmental conditions, and then the thrips adult will emerge from the growing medium as the long, black, and thin adult where the cycle starts again. The adults move quickly and jump when approached, almost like fleas.
When inspecting your plant for thrips, be sure to pull back where the leaves meet the stem or any leaf-like material that is attached to the base of the plant. They like to hide in there.
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Thrips Damage
Thrips are excellent at hiding. By the time you are seeing the adults, you have a lot of thrips. It is essential to monitor your plants for thrips damage—and treat at the first sign of damage.
Classic thrips damage presents like coppery streaks or circles on the backs of the leaves, indentations on the leaves, yellowing and browning around the leaf edges, and what has been described as a sort of fish scale pattern of damage. You may also see new growth coming in distorted or with lines/holes. Another early sign of thrips may be small dark brown spots on the leaves. This is thrip poop!
Spider Mites
About Spider Mites
Spider mites are a type of arachnid that belong to the family Tetranychidae. There are over 1,200 species in this family but the most common is Tetranychus urticae, more commonly known as the two spotted spider mite. True to their name, they have two dark spots on either side of their abdomen when viewed under a microscope.
Spider mites create a webbing on plants where they lay their eggs and are protected from predators and move around. The webbing helps lift them off the surface of the plant where the humidity is higher. If you have caught a spider mite issue early, however, it is likely you won’t see any webbing at all. You may see what looks like a fine dust on the backs of the leaves (these are the spider mite eggs and shed skin) or a dulling/speckling of the plants foliage.
Of all the common plant pests, spider mites may be the most resistant to pesticides and many commercially available sprays often cause their population to increase. This is especially true of imidacloprid, the active ingredient in systemic granules. Use of systemic granules has been scientifically proven to increase spider mite populations, as have the use of pyrethrin based sprays.
Your best first line of defense is to literally remove the spider mites with just water and a wet washcloth or paper towel. Make sure to get all the eggs and webbing, and do so as often as possible. Every two days is best, as the eggs hatch every three days. If showering the plant off, do so on an angle so the pests go down the drain and don’t just fall off into the pot, where they can climb back up onto your plants. Then you can follow up with the recommended predators (check out our treatment plans page for more information).
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Spider Mites Damage
Spider mite damage presents primarily as a speckling on the leaves. The leaves may not initially appear “damaged” as with thrips, but the color will start to appear muted and small white specks will appear across the surface as well as at points where the stems meet the leaves. Eventually, if not treated, you will see yellowing and leaf death, and the entire plant will die.
Mealybugs
About mealybugs
Mealybugs are a slow moving, white, oval shaped insect easily visible to the naked eye that create a cottony, wax debris. They belong to the family of scale insects, all of which suck plant sap and secrete a substance called honeydew. The presence of this honeydew will cause the surface of your leaves to be sticky (as if juice has been spilled on them) and is one of the earliest signs of a mealybug infestation. This honeydew can cause secondary bacterial and fungal infections, and their feeding can also spread plant viruses.
The females are small, white, and hairy, while the adult males have wings (and you can catch them on sticky traps to help knock down a population). They tend to congregate in hidden crevices and just below the soil at the root line, so make sure to check and clean these areas thoroughly if you suspect an infestation. Different species of mealybugs tend to prefer different types of plants, but they are all similar in appearance.
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mealybug Damage
Unlike other pests such as thrips or spider mites, mealybugs don’t tend to have a typical damage pattern. Instead you’ll likely see overall plant decline: yellowing leaves, stunted and distorted new growth, or no new growth at all.
Scale
About Scale
There are many different types of species of scale insects, but generally when we refer to “Scale” in the houseplant community we are referring to a hard bodied, immobile insect that sucks plant sap (either armored scales or soft scales). In their juvenile stage, the scale insects are nearly microscopic and mobile, and they travel the plant looking for a spot to settle. Once they find it, they build a hard-covered waxy coating around themselves (which protects them from predators) and affix themselves to feed. The eggs are laid underneath this dome and, once they mature, they stream out to roam and feed on the plant and start the cycle over again. Similar to mealybugs, the adult males of the scale insects are winged.
This hard covering is a very effective protection against both synthetic pesticide and natural enemies, and all of the hard-bodied adults you can find should be removed manually.
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Scale Damage
Unlike other pests such as thrips or spider mites, scale doesn’t tend to have a typical damage pattern. Instead you’ll likely see overall plant decline; yellowing leaves, stunted and distorted new growth, or no new growth at all.
Fungus Gnats
About Fungus Gnats
Fungus gnats are often mistaken for fruit flies, as their adult form looks very similar to a fruit fly. Small and winged, you’ll notice them when you shake or move your plant, as they will fly up from the soil. These adults are not harmful to your plant (but they are annoying). Their larvae, however, live in the soil where it feeds mainly on dead or decaying organic matter, although some species can feed on root hairs and living tender roots.
In small numbers, the larvae also shouldn’t damage your plant, but as their numbers increase they can cause root damage and plant decline. They can also be more damaging to cuttings and seedlings than to established plants. They prefer moist soil, so their presence can also be an indicator that your plants may be staying too moist and you should check the roots for any root rot they may be feeding on.
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Fungus Gnats Damage
Fungus gnats don’t usually cause visual damage, and indications of their presence will be the adults flying around the plant when you move or shake it.