Thrips are a particularly destructive houseplant pest that can move between plants with ease as they can “fly” a distance up two feet. Understanding the thrips life cycle is essential to treating them successfully. Thrips adults will lay eggs literally within the leaf of your plant. As the larvae hatches out of the 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.
Then, this larvae will drop down into your growing medium to pupate. The pupal stage takes about three days, and then the thrip adult will emerge from the growing medium as the long, black, and thin adult. 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.
Thrips in particular, more than other houseplant pests, 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 sight of damage.
Classic thrip 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!
About Spider Mites
There are several different kinds of spider mites. The most common on our houseplants is the two-spotted spider mite. Spider mites most often appear white or red in color, and some may be brown. True to their name, spider mites create webbing that you’ll often see where the leaves meet the stems. If the infestation is at this stage, the webbing will be full with moving spider mites and their eggs. However, if you have caught a spider mite infestation early, it is likely you won’t always see webbing! You may see what looks like a fine white dust on the backs of the leaves (these are the spider mite eggs), or a dulling of the vividness of the foliage.
Of all the pests, spider mites are the most resistant to pesticides, and many 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. Similarly pyrethrin based sprays also cause spider mite populations to increase. Captain Jacks will not kill spider mites. 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 – the webbing actually serves to protect the spider mites somewhat from predators. 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 on your plants.
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 are a type of scale insect, a family of insects that 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.
They also produce a type of waxy substance that is white in color and looks like dirt or debris on the leaves. The females are small, white, and hairy while the 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.
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 is a similar pest to mealybugs.They are a sap sucking insect that produces honeydew, a sticky substance on the plant leaves and stems. Honeydew is one of the earlier signs of a scale infestation, but the most common indicator is seeing the scale insects themselves. While the juveniles move around the plant, the adult insects are hard bodied and immobile. They fix themselves to the plant and live out their lives underneath a hard outer shell, which makes them extremely resistant to pesticide sprays.
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.
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 on dead or decaying organic matter. 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 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.
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.