Q: I don’t know what is on the beavertail cactus. It just appeared this summer. It’s about seven years old and I’ve never seen this white stuff before. The cactus doesn’t have a water source — no bubblers, no overspray — it’s completely on it’s own. I sent you a picture. What should I do?.
A: This problem is called cochineal scale. There is a tiny bug that covers its body in white to protect itself from the outside world.
To feed both the pads and fruits of the prickly pear cactus, also known as the beavertail, we grow it at the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas. The Mexicans call them nopales and tunas, respectively.
It is possible to see when an insect is hurt because some of its scales make a red dye. These bugs can crawl from one place to another, but once they find a good spot and make it their home by covering themselves in white, they usually stay put and start eating. They feed by sucking plant juices from the cactus. When hundreds of them find homes on a cactus they can cause enough damage to kill the cactus.
You have so many of these scale insects that they merely cover the entire plant and its pads.
There is a chance that a bird visited an infected cactus and brought the bugs back to yours. But it doesn’t have to be birds; it could be people, bugs, or anything else that could bring them to you.
They are difficult to control. We usually get rid of these bugs by running a strong stream of water through a hose with a sweep nozzle attached to it. The stream of water or simply blasts the scales off all of the plant. This needs to be done about twice a week in the summer to keep them off.
Straight water can also be used, but soapy water doesn’t seem to be much better.
The bug spray Sevin can also be used, but only after a hose is used to get rid of the scale insects that are on the pads. You might be able to get enough of the white covering to kill the protected insect, though, if you add something called a spreader to the spray. Once the plants are infested, I’m sure this insecticide will need to be used several times a year to get rid of the bugs.
Some people believe that only stressed beavertail cactus are infested. I have seen both stressed and nonstressed plants heavily damaged by this insect.
Q: Our beautiful, once-thriving Mimosa tree that is at least 15 years old is still dying even though we’ve watered it with shock stuff and cut off any dead branches.
Mimosa wilt is the most common problem with them, and there isn’t much you can do about it. The disease is fungal and plugs the water-carrying system inside the tree.
This happens a lot to Mimosas, also known as silk trees, which is likely why there aren’t many old ones around. It is recommended to remove the tree and replace it.
The disease spreads from the soil into plant roots, particularly when the tree is in a weakened state. Mimosa trees should never be planted in rock mulch or in a dry area of a desert landscape.
Mimosa should be planted in the drier parts of a desert landscape. It will do best with organic mulch, regular watering, and the right amount of fertilizer.
Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at morrisr@unce. unr. edu.
As a proud cactus parent, I know how distressing it can be to notice strange spots appearing on your prized succulents. Recently, I noticed some abnormal white dry spots surfacing on a few of my cacti. Naturally, I panicked! Were these innocuous spots or a more sinister sign of disease?
To get to the bottom of this cactus quandary, I did some digging into the potential causes of white spots. What I uncovered provided some fascinating insights into cactus care and reassured me that my spotty spiky friends would be A-okay
In this article, I’ll share what I learned about the main causes of white dry spots on cacti, along with tips to prevent and treat them. Let’s get to the root of this prickly problem!
What Triggers White Spots on Cacti?
After consulting cactus care experts and poring over forums, the consensus was that white spots generally stem from one of three issues:
Sun Exposure
Too much sun is the number one cause of white spots on cacti. We all know cacti thrive in sunny conditions, but excessive or sudden light exposure can scorch their skin, resulting in bleached white patches. This phenomenon is known as sunburn or sunscald.
Cacti sunburn easily for two reasons. First, their thick, waxy epidermis acts like a magnifying glass, intensifying the sun’s rays. Second, most houseplant cacti originate from deserts where they grow under nurse plants or rocks that filter sunlight.
To avoid sunburn, gradually acclimate new cacti to increased light levels. Rotate indoor plants frequently so all sides receive equal sun. Outdoor cacti may need shade cloths to shield them during intense afternoon light.
Overwatering
Another common culprit behind white spots is overwatering. Cacti have adapted to thrive in arid desert environments. Too much moisture can lead to fungal diseases like root rot, which manifest as dry white marks on the outer skin.
The way to avoid overwatering issues is to stick to a “less is more” watering routine. Wait until the soil is completely dry before watering again. Cut back on watering in winter when plants are dormant. Make sure cacti have free-draining soil and pots with holes for excess water to escape.
Pests
Certain insects and bugs can leave white spots or trails on cacti. Mealybugs are fuzzy white parasites that extract nutrients, leaving dots where they feed. Scale insects affix themselves to cacti and secrete white waxy coverings. Spider mites form silky white webs and suck the juices from plants.
Insect infestations often start in hard-to-see nooks of the cactus. Check regularly for any small white critters or spots. Remove pests with tweezers, soap and water, or insecticidal spray. Isolate infected plants to prevent spreading.
Dry Spots Versus Wet Rot on Cacti
When examining white spots, it’s crucial to determine whether they are dry marks or evidence of wet bacterial rot, as the two require different care. Here’s how to tell the difference:
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Dry spots have a bleached, papery texture. They are flat and harden into scab-like marks over time. The inner flesh beneath is still firm.
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Wet rot spots feel mushy or slimy. They start off translucent then turn brown. The inner tissue is water-soaked and disintegrates easily. Foul odor may accompany rot.
Dry spots can simply be monitored over time. But wet rot requires immediate action to prevent decay spreading. Severely rotted sections should be cut off using sterile shears. Apply fungicide to the wound to prevent infection.
Natural Remedies to Treat White Spots
While white spots rarely seriously harm cacti, you can take steps to improve their appearance and prevent further damage:
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For sunburn – Gradually re-acclimate to proper light levels. Apply aloe vera gel to soothe scorched skin.
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For overwatering – Repot in fresh, dry soil. Sprinkle on cinnamon powder, a natural anti-fungal.
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For pests – Wipe leaves with cotton balls dipped in rubbing alcohol to kill bugs. Use neem oil spray as a natural deterrent.
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For scarring – Consider transplanting damaged sections below soil level to hide marks.
When to Worry About White Spots
In most cases, small white spots are purely superficial and not a major cause for concern. Here are some signs that may indicate a more serious underlying problem requiring prompt attention:
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Spots rapidly spread across multiple cacti.
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Marks are accompanied by soft, oozing rot.
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You notice tiny insects congregating on spots.
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Inner tissue under spots feels mushy and deflated.
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Plant seems weak, wilting or collapsing.
If your cactus displays any of these more troubling symptoms, isolate it from other plants and investigate solutions with a horticulturist. Catching issues early maximizes the chances of recovery.
Cactus Care Tips to Prevent Spots
Prevention is the best cure when it comes to problematic cactus spots. Here are some proactive care tips to keep your succulents happy and spot-free:
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Allow soil to dry between waterings and reduce water in winter.
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Provide strong light but avoid hot afternoon sun.
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Repot in porous cactus soil for drainage.
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Rotate plant to evenly distribute light exposure.
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Check for pests regularly under leaves and spines.
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Clean shears between clippings to prevent bacteria spread.
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Transition indoor cacti outside gradually to avoid sunshock.
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Water at the base, not on leaves, to discourage rot fungi.
Embrace Your Spotted Cactus!
If your beloved cactus does end up developing some cosmetic white spots, don’t despair! Dry spots don’t have to be the end of the world, or even an eyesore. Some people creatively transform sunburnt scars into decorative features by painting them with contrasting colors or inking them into designs. Personally, I’ve come to accept my spotty cacti as they are – quirks and all! Cactus maintenance inevitably involves some minor flaws. Just be sure to keep a close eye on spots to catch any problems before they spiral. With vigilance and care, your prickly pal will continue to thrive spots and all!
WHAT ARE THOSE WHITE SPOTS ON YOUR SUCCULENTS? | SUCCULENTS CARE TIPS
Why are there white spots on Cactus?
White spots on cactus become an alarming sign when they appear on attractive cacti and ruin the aesthetics of the plant. Cacti require less care, water, and precision than most non-succulent plants making them suitable for busy plant-lovers.
Can one drink cactus water?
Even the ideia of drinking cactus water sounds strange, it’s totally possible to drink it. Not only is recommended but also is a new trend among people who are trying to loose weight.
Are white spots on Cactus reversible?
The high UV intensity damages the cactus’ skin, leading to bleaching and the development of white patches. These white spots are irreversible and cannot be fixed. The affected areas may become hard and callused, and the Cactus may appear dehydrated and wrinkled.
Are white spots fatal to Cactus?
While white spots are not fatal to cacti, they can lead to stunted growth, yellowing, and deformed foliage. When temperatures drop suddenly or there is a frost, the water in the cactus cells freezes and expands, resulting in the rupture of cell walls. This damage leads to the plant tissue turning white or brown and eventually dying.