Cultivating Carnivorous Plants (2015)
COMMON PESTS AND DISEASES
Unfortunately, every carnivorous plant grower will, at some point, encounter a plant pest or disease.
These are unavoidable, unless the impossible is achieved and every plant is started from seed in a sterile
environment and kept in a similar environment for the duration of its life. Most pests will, unfortunately, be
brought into a collection through trades or purchases of unknowingly infected plants. As with all gardening,
some growers and nurseries are better about watching for and treating pests than others. Still, some exposure
to pests is inevitable.
The best possible way to combat pests spreading to a collection is to isolate newly acquired plants for 1-
2 months. This isolation period will allow plants - which may have arrived looking healthy - to exhibit signs
of any pests or diseases they may be carrying. While such quarantining may seem burdensome, it is much
easier to place a potted plant in a plastic bag for a month than to treat an entire highland Nepenthes collection
for a Thrips infection in the dead of winter.
The second best way to combat pests and diseases is to give plants their proper light, temperature,
humidity, and water requirements. A healthy plant is less likely to get infected, and better able to survive
treatment. Ensuring that Sarracenia are getting full sun, that highland Nepenthes are getting cool nights, and that
Heliamphora is placed in a high humidity environment can prevent those plants from encountering many
dangerous pests and diseases.
Aphids, also known as plant lice, are tiny, sap-sucking insects that usually attack
Dionaea, Drosera, and Sarracenia plants. Numbering some 4,400 species, it would be
impossible to give a detailed account of how to get rid of aphids. Generally, non-
soap, non-aerosol-based insecticides work well and do not do too much damage to
Aphids can come in
Natural pest control remedies, such as Lady Bugs, are often recommended to
many colors, but
new growers. In my experience, Lady Bugs are prone to becoming trapped by Drosera
green and orange are
leaves and Sarracenia pitchers, so I would not recommend attempting to use Lady
the most common.
Bugs with those two genera.
Exyra moths are a Sarracenia-specific pest. These nasty moths lay eggs in Sarracenia pitchers. The eggs hatch
CULTIVATING CARNIVOROUS PLANTS
and the larvae eats the pitcher. Signs of infection are typically obvious before the larvae reaches the rhizome.
Any infected pitchers should be cut from the plant and burned or sealed in a plastic bag before being thrown
away. Leaving infected pitchers on the ground or composting them risks future generations of Exyra moths
being born, or larvae surviving to infect other plants.
Fungus: Dampening Off & Others
Fungus can take a serious toll on
seedlings, dormant plants, and, rarely,
growing plants. Often, fungus will appear
on the surface of the soil and appears to
spread towards seedlings. The first line of
defense should be scraping off the surface
of the soil and allowing it to dry out more.
Additionally, consider removing dead
vegetative matter and exposing the soil
surface to brighter light, particularly
A good second line of defense is to
add a small portion of hydrogen peroxide
(H2O2) to water and spray that mixture on
the fungus. A 3% hydrogen peroxide
solution - the strength commonly found in
drug stores - diluted with one-to-four parts
water will kill the fungus without harming
Botrytis cinerea fungus on a grape.
For more serious fungal infections, or before placing plant rhizomes and hibernaculum in the
refrigerator for dormancy, consider treating these with a non-copper-based fungicide. Note, however, that
these will often cause deformations in plant growth, and great care should be taken to avoid contact with
these chemicals as they often have harsh, negative effects upon humans.
Japanese Beatles, Caterpillars, and Other Chompers
The greatest threats for outdoor collections are
large, chomping insects. These will often be able to do
significant damage to a collection before pesticides take
effect and often have a large territory, preventing
effective treatment with pesticides. Encouraging the
development of a diverse garden ecosystem should result
in predators eating many of the large, chomping insects
doing damage to an outdoor collection.
While it may be tempting to feed some of these
chompers to the very plants that they have been eating,
avoid doing so. Often, they will be able to eat their way
out of otherwise deadly traps. In doing so, they will
further injure the collection.
Mealybugs are related to scale,
but, instead of small, hard shells,
mealybugs have soft bodies and
often appear to look like little bits
of white cotton. Treatment is the
same as with scale - insecticides
mealybugs. Small scale infections
can be treated with cotton balls or
cotton swabs dipped in rubbing
treatment is necessary.
Do not attempt to use ants as
a natural treatment as many species
of ants will actually protect
mealybugs and encourage their
growth and development. This is
because mealybugs secrete a liquid
that ants harvest for food.
One of the most common pests for growers to
encounter is scale. There are around 8,000 species of
this pervasive pest, and it is one of the few that can
appear on plants a month-or-two after initial
infection without other signs. Scale - like Thrips - is
one of the primary reasons plants should be isolated
for a month or two after being added to a collection.
Some places, such as Hawai’i, have endemic species,
such as Pinnaspis strachani, which have a thirty day
lifecycle, meaning signs of infection may not be seen
until up to a month after plants leave that
Small infections can be treated with cotton-
balls or cotton-swabs dipped in rubbing alcohol, but
this treatment will only kill the adults. Harsh
pesticides, such as Orthene, or diverse pesticides,
such as Talstar, are good choices for treatment.
Several treatments will be necessary over the course
of several months for complete eradication. Some
pesticides, such as Orthene, are prone to weakening
plants and can easily kill growth tips on genera such
as Nepenthes. ( Nepenthes hamata, dubia, jamban, and
Scale on a Nepenthes leaf.
their offspring appear to be particularly vulnerable).
CULTIVATING CARNIVOROUS PLANTS
Whenever a scale infection is found, the affected plants should be isolated immediately. Scale is
particularly prone to spreading to nearby plants. One infected plant can infect an entire collection within a
week. Therefore, proactive isolation and treatment is necessary. Fortunately, signs of infection are usually
fairly obvious - small, hard bodied “scales” appearing on new growth or near growth points.
Thrips damaged Nepenthes leaves.
Thrips are, next to scale, the most problematic pest that can attack carnivorous plants. Unlike scale,
Thrips are much harder to spot. If plants appear to be suffering and conditions appear fine, it is likely that
they are infected by Thrips.
The best way to determine
whether Thrips are present is to
disturb the plant by blowing on it or
tapping it during warm temperatures.
Within a second or two, the small
(less than 1 mm) insects will be seen
to run or fly off the leaves of the
plant. Given their small size, it is
often best to examine a plant for
Thrips by using a magnifying glass.
Infected leaves can be cut off,
but, often, the infection will have
spread across the entire plant and
throughout the collection by the time
it is noticed. Due to the tiny size of
Thrips and the difficulty in spotting
them, treatment should occur on all
plants within the vicinity of the plants
known to be infected.
Thrips must be treated with a
Thrips-specific insecticide, such as
Avid. General-use insecticides, such
as Orthene, are not nearly as effective
against Thrips, and, often, actually
have no impact. As with general-use
insecticides are often harmful to
humans, so precautions such as
A young Nepenthes leaf heavily damaged by Thrips.
rubber gloves, protective eyewear,
and masks are necessary.
Sarracenia Root-Borer is an awful, grub-like pest. Thankfully, it only infects Sarracenia and is not a
common pest. A common sign of infection is a small hole atop a Sarracenia rhizome with wood-pulp colored
powder around the outside of the hole. Over time, the infected plant will wilt as the borer infects the plant
Infected plants should be destroyed immediately. The chance of the root-borer surviving and destroying
other plants is too great to allow infected plants to stay within a collection. Infect plants should be dug up,
along with some of the surrounding soil, and sealed in a plastic bag prior to disposal at a landfill.