Growing Venus Flytraps – Pests & Problems
As with any plant, there are a number of problems that can occur when growing Venus Flytraps. Some of them are addressed below.
There are several common insect pests that occasionally affect Venus Flytraps and other carnivorous plants. Perhaps the most common are aphids and spider mites (technically not insects, in the spider and tick family), but other insects such as mealybugs, thrips and scale insects sometimes destructively colonize the leaf surfaces of carnivorous plants, and grasshoppers occasionally munch on the leaves of a Venus Flytrap (and sometimes are caught!).
Most insect and mite pests can be controlled and killed with any of a large number of general-purpose insecticides, of which there are two primary categories—
The dried exoskeleton of a dead grasshopper caught and digested by a Venus Flytrap.
- Systemic insecticides
- Systemic insecticides are absorbed into the plant and often make the entire plant poisonous to insects that chew on or suck the juices from plants. How potent the insecticide is, how quickly it acts and how long it remains effective, vary among systemic insecticides.
- Superficial insecticides
- Superficial insecticides typically remain on the surface of plants sprayed with them, often a coating of insecticidal oils or soaps, or a powder, perhaps coated with a surfactant, that was dispersed into water and then sprayed on the plant. Superficial insecticides can be as effective as systemic insecticides, and can sometimes act more quickly.
Grower's note— This grower (Stephen Doonan, the author of VenusFlytrap.info) has used acephate for many years as a general purpose systemic insecticide. Acephate is the generic name of an insecticde that used to be called Orthene. It is effective, fast-acting and remains reasonably potent for six weeks or more. It is often sold for a particular purpose (such as "fire ant killer") but is very effective for almost all common pests including aphids, mealybugs, thrips and scale. Spider mites however can be unusually difficult to control and eliminate, so a dedicated miticide in the water mix with the acephate helps greatly to treat and eliminate outbreaks or infestations of spider mites.
Spider Mites (Tetranychus urticae), including the red spider mite and two-spotted spider mite, despite being so tiny they are hardly visible to the human eye, are among the most destructive pests of Venus Flytraps and many other plants.
Red spider mite (tetranychus urticae)
Two-spotted spider mite (tetranychus urticae)
Spider mites reproduce very rapidly and in great numbers. A few spider mites on a plant can grow to a colony of dozens in just days, and to an infestation of many hundreds or thousands in just two or three weeks. Spider mites punch a hole in individual leaf cells to suck the juice from the cell, creating a tiny sunken area that browns. When many spider mites do this at the same time, to cell after cell, the leaf can rapidly brown, wither and die.
Spider mites (tetranychus urticae) can be extremely destructive pests
Spider mites love warm and dry conditions, so it is recommended to anticipate them during prolonged periods of warm-to-hot and dry weather and either spray a preventive treament during those times, even if no mites are visible, or to be watchful for them and treat them as soon as possible, to avoid a problem turning from mild to alarming and extreme in a matter of days.
Dedicated miticides include Talstar (bifenthrin), Avid (avermectin), Mavrik (fluvalinate), and Pentac (dienochlor).
Aphids are small insects of many colors including clear green, yellow, red and black, that use their sharp mouth parts to pierce the outside of a plant leaf or stem in order to suck liquid from the plant.
Tiny green aphids on the stem of a plant
Aphids reproduce rapidly into a large, destructive colony
Aphids are probably more often seen than spider mites and can be very destructive, but even a serious infestation is fairly easy to control and eliminate with one of the many effective general-purpose insecticides. Some growers recommend neem oil based natural insecticide.
Fungus gnat is a generic term for many species of very small, short-lived flying insect. Fungus gnat larvae, tiny whitish translucent "worms," live in the soil and feed mostly on fungi. They then metamorphose into the winged adult and emerge from the soil.
There are many species of the tiny fungus gnat.
Fungus gnats are usually not a problem for Venus Flytraps. They typically grow in small numbers in the soil and harmlessly feed on fungi usually present in sufficient quantity in most soils. However, if the population of fungus gnat larvae becomes very large, and the fungi in the soil has been exhausted or is scarce, fungus gnat larvae can begin to feed on plant parts, including the roots and rhizome of a Venus Flytrap. The damage is usually minimal, but the superficial scratching and damage to the plant cells makes the Venus Flytrap susceptible to fungal or bacterial infection or rot at the site of the damage, and that infection can spread.
If one notices an unusually high number of adult fungus gnats on the surface of the soil of a particular planting container, and then notices that some Venus Flytraps in the container are looking obviously unhealthy (aside from normal older-leaf browning and die-back), a quick remedy is to empty the plants from the container, soak and rinse the soil from the roots of the Venus Flytraps, throw away the old soil and the rinse water, wash and clean the planting container and transplant the Venus Flytraps into fresh, new soil.
A tiny Venus Flytrap seedling captures an even tinier adult fungus gnat.
Fungal and Bacterial Infections
Most fungal and bacterial infections can be avoided by allowing the surface of the growing medium to dry somewhat and not stay continuously moist, and by ensuring that the growing medium has plenty of air in it and is not compact and soggy.
If significant fungal or bacterial growth does occur, it can lead to infection of the plants or even rot and death, so it's good to try to prevent conditions that promote fungal or bacterial growth.
Some bacteria are extremely destructive, especially the anaerobic bacteria. These bacteria grow in a moist or wet environment that lacks air. If one uses pure sphagnum peat moss as a growing medium, it can become compacted and remain soggy for a long time, both of which encourage anaerobic bacteria growth which can lead to rot of the roots or rhizome and can lead to death. It is helpful to use a growing medium that forcefully incorporates plenty of air, such as sphagnum peat moss that is supplemented by about half its volume with silica sand or perlite. Coir (coconut husk pith), when the coir is desalinated, because of its stiff and springy nature, also helps to keep a grow medium aerated and resists compaction. (About Venus Flytrap potting soil.)
It is important to give Venus Flytraps plenty of light but not too much water, or fungal infections including a destructive or deadly crown rot can happen. Venus Flytraps are usually healthier in conditions that are moist, but not wet all the time. When grown indoors in diminished light, and kept too wet most of the time, the leaves of a Venus Flytrap will often grow spindly and thin, weak and prone to fungal infection or rot. In constantly wet conditions, a Venus Flytrap will often grow quickly at first, as though it's trying to use up the water and grow in healthier, less water-saturated conditions. But if left in those conditions for weeks or months, the Venus Flytrap will probably suffer and become subject to fungal or bacterial infections.
If a fungal outbreak or flush exists on the surface of the growing medium, or if the plant is already infected, a fungicide is helpful, but avoid any fungicide that contains a copper compound (like copper sulfate). Sulfur based fungicides can be helpful (so long as they don't contain copper). Chlorothalonil is an effective general purpose fungicide. Look for it as an active ingredient on the label of various brands of fungicide.
Venus Flytraps, like many plants, can occasionally be affected by problems other than insect pests or microbial (fungal and bacterial) infactions. Among those problems are infection with a virus, which generally makes the plant less vigorous and grow more slowly or weakly, and competition from surrounding plants, notably the very short but aggressively spreading carpet mosses (there are many species of carpet moss).
Over the course of two or three decades, many variegated Venus Flytraps began to appear. These plants had traps or leaves that were mottled or irregularly striped, with red or reddish patches or spots interspersed with green leaf tissue. The effect is attractive and very interesting. But it's also likely to be caused by infection with a plant virus.
There are many viruses that affect only certain types of plants, and some plants that are infected with a virus that are purposely grown for the ornamental value of the variegation caused by the virus. However, the characteristics valued in virus infected plants are not genetically intrinsic to the plant itself, and a virus can be spread, especially in cultivation where a lot of pulling and cutting of plant tissue occurs, exposing the liquid inside the plant and potentially exposing another plant that has been cut or torn to the liquid of a virus infected plant.
New growers of Venus Flytraps and other carnivorous plants often see a growth of short, bright green plants on the surface of a growing medium and regard it as attractive. More experienced growers usually regard these mosses (appropriately named "carpet moss") as a nuisance and try to discourage their growth. The reason is that carpet moss, once it colonizes a small area of the surface of a growing medium, begins to rapidly spread. When one waters the plant from above (rather that allowing it to absorb water from a tray or bowl through the drain hole below) one can often see tiny green specks that look like green dust floating on the water. These green specks of moss tissue rapidly take root and form other colonies of carpet moss.
If left to grow, carpet moss can form an almost solid mat several centimeters thick across the surface of the growing medium, rapidly sucking up water for its own use and growth. The mat of moss can become so dense that it begins to place a substantial amount of pressure onto the rhizome and leaves of a Venus Flytrap and deprives them of the necessary room to expand, grow and develop.
Carpet moss is especially threatening to very young Venus Flytraps. The tiny Venus Flytrap seedlings can easily be overcome by the moss and die. Laboriously and carefully weeding the carpet moss from around the plants, or uprooting and transplanting them into fresh, moss-free growing medium, are often the only ways to prevent the moss from thickly colonizing the entire surface of a growing container and crowding the young Venus Flytraps or crushing them even to the point of death.
Carpet moss and tiny Venus Flytrap seedlings. The carpet moss, if no action is taken, will spread rapidly, engulf and strangle the seedlings.