Tuesday, January 12, 2010
Do you have Cochineal Scale?
If you have prickly pear cactus (Opuntia spp.) in your landscape, you might have cochineal scale. If you have Santa Rita prickly pear cacti, you probably do have this obnoxious invisible insect weaving its snowy-looking, cottony masses of wax on the surfaces of your plants’ stems (pads). If you’ve investigated closely, or tried to scrape off these tiny webs, you’ve uncovered the blood red liquid ooze, (see close-up--upper left-hand side of pad..tiny drips of red) and can be sure you’ve discovered cochineal scale (Dactylopious spp.)
Schalau’s article further states that this insect “uses the cottony wax to shelter female insects (that produce the red dye) and egg masses. The eggs hatch into nymphs (called crawlers) that feed for about three weeks before settling and becoming immobile. The crawler stage is when they spread on and among cactus plants. Once settled, they spin the waxy fiber that shelters them from predators and the weather. Multiple generations are produced each year in warmer areas.”
Don’t panic immediately if you notice these white spots all over your prickly pears, but you might eventually choose to address the tiny nesters to rest your plants from their sucking appetites. I panicked as I watched “multiple generations” make their tiny white castles on my beautiful Santa Rita. I wasn’t thrilled about the polka-dotted look, and our plant began sicken and lose its color. We had sprinkler drips on this cactus and watched it grow a number of plump pads until these microscopic (you can’t see the actual insect) fellows moved in.
On our walks, we’ve noticed several Santa Rita prickly pear plants in our neighborhood covered with the scale. I began to ask around. We found that we could wash them off with our high-pressure hose, but also discovered that the scale are drawn more readily to the well-watered cactus (possibly over-watered), so we removed the drips from our cactus and voila, they’ve been free since.
I realize, we’re all different. You may like seeing your Santa Ritas looking like they’ve been through a snow storm, (one man I talked to did), but I prefer to see their clean faces. It is a natural symbiosis between the prickly pear and the cochineal scale. If you like to dye your own fabrics, make paint and your own lipsticks, I say let them camp out on your cacti, but I think I’ll hose ‘em off of mine if they show up again.
I like the way this one looks. This one isn't in our yard--ours isn't this mature yet, so it didn't make the blog. I notice the drip next to it, and surmise this neighbor isn't overwatering this Santa Rita prickly pear.