We apologize, but Mr. Smarty Plants needs some time to catch up after receiving an overwhelming amount of mail. Soon, we hope to be taking new inquiries once more. I’m grateful.
Before, Mr. Smarty Plants responded to a query regarding cholla cactus cochineal bug management (similar to your prickly pears). What Larry and Brigid Larson wrote is as follows: Cochineal feeding can harm the cactus and occasionally result in the host plant’s death. The Cactus Doctor talks about getting rid of cochineal. Their advice is as follows: 1) A hose with a power nozzle attached to the end. 2) It was advised to clean the affected areas with insecticidal soap or unscented dish soap to treat them if the infestation gets out of hand. Neem oil was also mentioned as a possible natural remedy.
In response to another Mr. Smarty Plants query about cochineal bugs on prickly pear cactus, Nan Hampton provided the following response. (As you can see, this is a common query.) It sounds like cochineal bugs are infesting your cactus (Dactylopius sp.). They are cactus-eating small scale insects. They generate fluffy white wax that covers their body as they consume the cactus and shields them from predators as well as the weather (especially drying out). The fluffy wax also acts as a sail or balloon to carry the bugs to a fresh cactus patch in the breeze. The carminic acid that the bugs create aids in shielding them from predators, particularly ants. Indigenous peoples of southwestern North America, Central America, and subtropical South America have been using this bug’s carminic acid for centuries—possibly millennia—to synthesize a vivid red dye that they utilized to create exquisitely colored fabrics. Cochineal bugs were formerly only found in the New World. The cochineal bug spread around the world when European explorers came to a place and saw the stunning red cloth made by the locals. Although they have also been employed to help reduce cactus populations, the need for cochineal bugs decreased when a synthetic red color was created. But recently, there has been a resurgence of interest in cochineal bug cultivation for red dye because it was discovered that synthetic red dyes can have harmful side effects on health. Today, food coloring and cosmetics both employ the bug-derived dye. Because of this, managing cochineal bugs hasn’t really been a top concern, and as a result, I haven’t been able to discover a lot of information on managing them. If you only have a minor infestation, I advise scraping them off (slowly, to avoid the cactus spines) and throwing them away. They might also come off with a water under pressure wash. To ensure that you don’t harm your cactus, test a tiny area first. Then, collect and get rid of any insects that you wash off the cactus.
The University of Arizona Extension also suggests a similar set of remedies in a publication on cactus diseases.
The usage of insecticides was discussed on multiple websites, and Wikipedia included several natural predators: “The population of the bug on its cacti hosts can be lowered by a variety of natural enemies. Insects appear to be the most significant group of predators. Numerous parasitic wasps as well as predatory insects including ladybugs (Coleoptera), different Diptera (like Syrphidae and Chamaemyiidae), lacewings (Neuroptera), and ants (order Hymenoptera) as well as pyralid moths (order Lepidoptera), which kill cacti, have all been identified.”
Here is more information on the intriguing world of the Dactylopius coccus cochineal scale insect and the carmine dye that was highly sought for fabric dyeing in the 15th century.
How are cactus spots treated?
It might be challenging to stop a fungus after it has started to infect your cactus. A fungicide application can usually help if the damage isn’t too severe. Finding some healthy, disease-free material and starting a new plant from a cutting may be the best option if the plant is covered in lesions. Cutting should be done with a sterile knife, and any potential spore adhering should be killed by sulfur dusting.
Many fungal outbreaks can be stopped by managing the cultural conditions with lots of heat, under stem irrigation, sterile potting material, and ventilation. Cutting off the diseased tissue is another approach to rescue a plant. Even though not all fungi respond to it, it occasionally works. To guarantee that every infection is eliminated, sterilize your cutting equipment once again and remove more tissue than looks to be impacted. As the area calluses, keep it dry and keep an eye out for any indications of reinfection.
Why does my cactus have spots?
Brown spots are unsightly blemishes that can be caused by a number of factors. The spots can harm your plant’s looks and are a sign of poor plant health. Some of these spots might be challenging to get rid of, especially if the root problem is not identified. How can you get rid of brown spots on cacti and what causes them?
The main causes of brown patches on cacti include sunburn, root rot disease, corking, or overwatering. Move the plant to a location with 4–12 hours of direct sunlight and let the soil dry out between waterings to eliminate the discolouration. If root rot is the root of the black areas, treat it with a fungicide as well.
According to my experience, if a succulent is too old, brown patches on cacti may also develop. There might not be a solution for this, but if there are other causes, you might be able to save the plant and bring it back to life.
What do the white flecks on a cactus represent?
The substance that appears to be cotton fibers is actually a fine wax made by adult cochineal scale insects, and the little black specks may be their nymphs. On cholla (Cylindropuntia spp.) and prickly pear (Opuntia spp.) cactus, it is typical in this region. The white beards that resemble those on other cacti, such as the Peruvian old man (Espostoa lanata) and Peruvian old woman (Espostoa melanostele), are not an insect byproduct but rather typical, healthy changed tissues. Landscape chollas and prickly pears have a white waxy coating produced by cochineal scale that helps shield these actual bugs from predators and insecticides.
I’ve seen prickly pear pads covered in that white fluff almost entirely. Mild infestations, like the ones Doa Ana County Extension Master Gardener Dael Goodman and I saw at in Las Cruces earlier new week, are more typical. In New Mexico, there are multiple native cholla and prickly pear species. There are numerous of them in the Goodmans’ front yard, and we immediately noted that some species were more affected by the cochineal scale than others.
Topical pesticides, especially natural ones like petroleum oils and insecticidal soaps, are unlikely to be effective no matter what time of year it is if the insects are shielded by a white covering. Also, keep in mind that the ultimate goal isn’t to completely eradicate cochineal scale from your garden—partially that’s impossible—but rather to control the populations of insect pests until beneficial insects come to the rescue.
You will be shocked to see a bright red liquid that seems to appear out of nowhere if you squeeze a glob of the white goo that has healthy females hidden inside. Carmine, a natural dye used for millennia to color textiles and create artwork, is produced inside the bodies of cochineal scale insects. Because this carmine component is also utilized in red foods and cosmetics like sausages, lipstick, pie fillings, and vividly colored alcoholic beverages, check product labels for it. Before the firm converted to an artificial dye in 2006, it was used to create the vibrant color of Campari liquor, but a new generation of craft distillers and other producers are increasingly adopting it as a substitute for synthetic red components.
Goodman and I attempted to film the flowing red fluids squeezing the white tufts on her prickly pear pads with a small stick, but we hardly noticed any redness. The female cochineal population may be declining at this time of year, or those specific tufts may be so old that the residents have long since disappeared and have only left that waxy material behind. We’ll give it another go with a fresher sample in the summer.
Six cholla species and seven prickly pear species are covered in Robert DeWitt Ivey’s stunning reference work Flowering Plants of New Mexico. There are five yellow-flowered prickly pears in that group. Identification might be aided by paying close attention to the pad sizes and spine specifics. If you intend to approach closely, make preparations and carry tongs.
At the Agricultural Science Center in Los Lunas, Marisa Thompson, PhD, is the Extension Horticulture Specialist for New Mexico State University.
How frequently do cacti need to be watered?
The most frequent reason for cacti failure is improper watering, whether it is done too much or too little. Cacti have evolved to store water for extended periods of time and can maintain moisture through droughts because they are endemic to arid regions and dry temperatures. They have a limited capacity, which is why over-watering can result in a variety of issues.
When it comes to regularity, watering your cacti will largely depend on the season but also on the variety. Checking the soil is the easiest technique to determine whether your cactus needs water: It’s time for a drink if the top inch is dry. That entails applying the “soak and dry procedure” on cactus.
What is the soak and dry method?
The soak and dry technique is thoroughly wetting the soil until part of it begins to flow out the drainage hole, then waiting until the mixture is nearly dry before wetting it once more. If done properly, this strategy will help them endure a period of under-watering should you need to travel or leave the house because it takes use of their natural tendency to store water (or if you just get busy and watering falls to the wayside, as happens to all of us now and again).
Watering during the growing season versus the inactive season
Like with many houseplants, the season affects how frequently you need water. It becomes more crucial that you get in the habit of examining the soil to determine whether your cacti are thirsty. A healthy cactus needs watering every one to two weeks during the growing season, according to general wisdom. The frequency changes to once every three to four weeks during the off-season.
Even then, it’s crucial to examine the soil. The same way that not all interior spaces and not all cacti are alike. The only way to be certain that your cactus require watering is to carefully examine the soil to determine how dry it is because there are so many different factors.
How is a sick cactus treated?
While skin-deep disorders in the upper body of the cactus can be easily handled, those that have spread to the roots typically result in a plant that is slowly dying. Excision of the diseased tissue works successfully for the majority of cacti. Dig out the damaged flesh with a clean, sharp knife, then let the hole dry out. When the wound is healing, avoid overhead watering.
There is not much you can do if the roots have been affected by the harm. You could attempt to repot the plant by removing the unhealthy soil and adding sterile soil in its place. Before replotting the roots in a new potting medium, thoroughly wash the roots out.
Taking cuttings and allowing them to grow roots for a brand-new plant is another way to salvage a mushy, soft cactus. Before inserting the cutting into the sand, let it a few days to callus over. The cutting may need to be rooted for several weeks. A healthy cactus that looks exactly like the parent plant will be created using this method of propagation.
How can you determine if a cactus has been overwatered or not?
The cactus won’t typically seem radically different from day to day because underwatering typically happens gradually over time.
There are a few indicators, nevertheless, that will let you know if your cactus is submerged.
Signs of an Underwatered Cactus
Knowing the warning signals of an underwatered cactus is crucial for prompt response. Your cactus will have a better chance of recovering if you do this.
The most typical warning indicators of a submerged cactus include:
The Cactus Is Light Green or Yellowish
Since this normally happens gradually over time, the color change might not be apparent right away.
If your cactus begin to become light green or yellowish, keep an eye out for more symptoms of an underwatered plant.
The Spines Are Falling off Easily
A well-watered cactus has roots that go far into the ground and take in water there.
Their root systems do not, however, work correctly while they are underwater because the dearth of nutrients in the soil leads them to wither away.
As a result, the spines become fragile and easily detach.
another typical indicator of a submerged cactus
The Cactus Is Wilting
Due to nutrient deficiency, their spines cannot support the plant adequately, which causes them to lose their shape.
As a result, plants that were formerly upright and in good shape gradually start to sag or droop.
Decay at the Base of the Plant
Roots will cease developing and begin to deteriorate over time if they are unable to absorb enough nutrients from the soil as a result of a lack of water, which will eventually result in decay at the base of the plant.
It’s possible that you won’t immediately notice whether or not your cacti are underwater because this normally happens gradually.
The New Growth on Your Cacti Is Weak and off Center With Older Growth
Lack of nutrients will have an impact on how a cactus develops new limbs.
In this instance, you’ll see that the younger growth is somewhat deformed and less symmetrical than the older ones-another indication that the cactus has been submerged.