Q. I planted a “cows tongue” or
sometimes called “angel wing” cactus last spring and over
the summer it began to develop some white cottony looking growth
around each of the spines on the lower pads. The white growth has
continued and now covers much of the pads and some of the lower pads
have actually fallen off. What is this white growth? Is this a common problem with the cows tongue or
is it common to all padded cacti and if so what can
be done to rid the plant of the growth. Someone had mentioned
that it could be because of my watering schedule. What do you think?
sometimes called “angel wing” cactus last spring and over
the summer it began to develop some white cottony looking growth
around each of the spines on the lower pads. The white growth has
continued and now covers much of the pads and some of the lower pads
have actually fallen off. What is this white growth? Is this a common problem with the cows tongue or
is it common to all padded cacti and if so what can
be done to rid the plant of the growth. Someone had mentioned
that it could be because of my watering schedule. What do you think?
A. I don’t have a picture of this problem on your cactus so I am following the KISS (Keep It Simple Stupid) diagnosis technique. The stupid part is to remind me that nine times out of 10 it is a common problem, not a rare event.
This is most likely problem is Cochineal scale, a common problems on cacti.
.JPG) |
| Heavy infestation of cochineal scale on Opuntia cactus. |
If you touch it and it leaves a blood
red liquid on your finger it is Cochineal scale. Both are scale insects hiding
under that cottony growth and feeding on plant juices. When they reproduce and
their populations increase, the feeding damage is so great it causes the plant
or parts of the plant to collapse and ultimately die.
 |
| The red dye produced by cochineal scale when it is damaged. Notice how cochineal scale is commonly found close to the spines. |
For either of these insects the
control measures are the same. You can take a cotton swab and dab each of the
cottony growths with alcohol or apply a systemic insecticide to the soil such as those containing imidicloprid so the
poison will be taken up by the roots and moved to where this scale insect is
feeding thus killing the insect.
The cochineal scale has an
interesting history in Central America where this red extract was valued by
Spanish colonizers as a dye until it was replaced by synthetic dyes. The actual
insect was a very close relative of the Cochineal scale we see in our
landscapes now.
interesting history in Central America where this red extract was valued by
Spanish colonizers as a dye until it was replaced by synthetic dyes. The actual
insect was a very close relative of the Cochineal scale we see in our
landscapes now.
I have 2 Huge prickly pear cactus totally loaded with this, they are both falling apart. I am concerned that with the hot temperatures (100 F +) if it is safe to do treatment.
Temperatures wont have an effect on treatment. POwer wash the pads with a sweep nozzle then follow up with an insecticide spray. If you only use a sweep nozzle it will be a weekly job.
Confused by your answer. You say it’s likely cochineal scale but then refer to “treatment is same for EITHER insects” and “BOTH are scale insects” but I only see you mention one insect (cochineal scale). What’s the second?
Thanks for pointing it out. It was awhile back when I wrote that and I don't remember exactly what was going through my mind except that my colleagues from the University of Sonora in Hermosillo told me that this scale insect (technically) is not the exact same insect the Spaniards were using for the dye. This cochineal scale insect is a close cousin to the actual cochineal scale that was used at the time. Both produce the scarlet dye but technically not the same insect. Same genus, different species. Treatment for control is the same. Just me being a bit anal about the explanation and wanting to be technically correct respecting the information they provided to me.
Confused by your answer. You say it’s likely cochineal scale but then refer to “treatment is same for EITHER insects” and “BOTH are scale insects” but I only see you mention one insect (cochineal scale). What’s the second?
I had the same thing on my prickly pear cactus and got tired of treating it with many different healthy solutions that would not damage the cactus but it wouldn't disappear and instead it was infecting other cactuses that were near by so, what I did was that I spray this solution that I use to mop my floors and it contains bleach, lots of bleach! As soon as I sprayed on it, a red color started to run through and it clean up pretty good and never came bk again
Thanks for the tip. The insect causing this red dye color is probably cochineal scale. It is a problem on many cacti and succulents during the summer. For organic control, I would hose the cochineal scale with a strong burst of water from a hose. This would last about one week during the summer and the cochineal scale would be back. I would have to hose it again in a week!
Perhaps the chlorine in the bleach got rid of this problem.