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Collapsing building © Daniel FriedmanFungal / Mold Growth on Prickly Pear Cactus
Opuntia Mill. fungal infections, white fuzz, mealy bugs

  • POST a QUESTION or COMMENT about problems with mold growth on cactus plants: cactus mold identification, cactus mold causes, & cactus mold remedies

Investigation of mold growth on the Nopal cactus and treatments for cactus mold contamination or growth:

The Mexican Nopal, or in English "prickly pear cactus" or "Barbary Fig cactus" is a member of the group Opuntia Spp. within the Cactaceae family.

Mold growth appears to be more common on cacti such as the Nopal when growing in higher and less arid regions such as the village of la Yerbabuena, near the foot of the volcano above Colima, Mexico.

This article describes mold growth on the Mexican Nopal cactus plants in the wild and on those grown as a food crop.

With a fungal growth sample collected from Nopal growing in Yerbabuena, Colima Mexico. in 2011 we began seeking an accurate identification of the fungus, and an exploration of its properties both on the plant and as a possible seasonal contributor to the aerobiological milieu.

Our project will also investigate and document the causes and effects of mold infection of Mexican prickly pear cactus plants, and the identification of other mold genera/species commonly found growing on and affecting those important plants.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Mold Growth on Cactus: genera/species of mold that infect cactus plants

Mexican Nopal pricklypear cactus Tuna fruits © D Friedman at InspectApedia.com Daniel Friedman

Here we describe common growths or pests that injure or even kill cactus and some succulent plants, including

Photo above: a Nopal Cactus in Guanajuato, with a pair of ripe fruits. [Click to enlarge any image]

Watch out: no matter how much you may like cactus plants, don't just buy anything from anybody. In many areas of the world cactus rustlers are invading protected areas, stealing cactus plants, and re-selling them on an illegal cactus market. Be sure that any plant you buy is from a legal and legitimate source.

In Mexico, some people have "rescued" cactus plants that were found along the roadside where they were ploughed up during new road construction. Depending on where that roadway is located, even those cactus plants ought to have been re-planted nearby.

Watch out: while there are photos of various cactus and some succulent plant afflictions here along with discussions of their cure and prevention, I'm not a cactus expert nor even a botanist. For valuable plants you should be sure to consult a cactus expert or at least your local farm and home center expert. There are 127 cactus genera and at least 1750 individual cactus species in the order Caryophyllales - it's not likely that anybody knows all about all of them.

Most of our cactus photos are from the plants in the wild or cactus plants as observed in a botanical garden or preserve. Others are from legally obtained plants from cactus growers. We cannot claim to know the source of cactus plants in photos posted by our readers.

Black mold on a Nopal cactus in Yerba Buena, near Colima, Mexico (C) Daniel FriedmanThe Mexican Nopal, or in English "prickly pear cactus" or "Barbary Fig cactus" is a species or group of species of Opuntia Spp. within the Cactaceae family.

While some sources [22] claim over 200 species in that group, the USDA lists 59 species and 75 accepted taxa within the Genus Opuntia Mill.[20]

I am particularly interested in fungi found on species of Nopal found at altitude in more wet or humid highlands of Mexico.

These include fruit-bearing prickly pear species (Opuntia ficus indica) that are widely used as a food (both the cactus fruit or Tuna and the younger cactus pads or nopalito) and drink product (an intense purple juice in water) in Mexico as well as an export product in the form of Nopal fruits, Nopal juice, and in power and cosmetic forms. [22]

Some might think that because cactus plants generally grow in dry locations that they never suffer from fungal attack, but that's certainly not the case.

The page top photograph of a mold-infected Nopal (prickly pear) cactus plant was taken in Yerbabuena, Colima Mexico.

Yerbabuena is a tiny village located at a comparatively high altitude and close enough to Mexico's Pacific coast to receive more rainfall than some other areas of the country.

I have observed both superficial fungal growth on the intact skin of cactus plants and plants injured or destroyed by fungal attack.

Experts report fungal invasion of cactus plants by other vectors such as through wounds, cuts, and direct penetration of the cactus.

Watch out: while this article discusses cactus diseases that appear to be fungal or mold growths, some insect or parasitic cactus diseases maybe mistaken for mold.

At CACTUS COCHINEAL INFESTATION you will see examples of white fluffy or barnacle-like diseases on cactus that may not be funguses at all.

Above: small round black fungal colonies on a Nopal in Yerba Buena in Colima, Mexico.

Also see MOLD GROWTH on SURFACES, PHOTOS - What Does Mold Look Like on Various Materials & Surfaces? An extensive photographic guide to mold as it is found growing on various building materials & surfaces.

Appearance of Mold on Cactus: on the plant & under the microscope

Black & Other Dark Colored Molds on Cactus Plants

Cactus mold growth at 1200x © D Friedman at InspectApedia.com

Mold growth on cactus is more common in areas where cacti such as the Mexican Nopal (below left) grows in higher and less arid regions such as la Yerbabuena, near the foot of the volcano above Colima, Mexico.

(Photographs by DF, la Yerbabuena, Colima, Mexico, November 2011) Prickly pear cactus (Opuntia Mill.) are also found in the U.S. in Florida and Hawaii as Opuntia cochenillifera.

Our Mexican Nopal cactus mold photo (at left, 1200x) seeks expert help with confirming its identity, and is discussed below.

Below (right) and tentatively identified as a Lasiodiplodia theobromae -like fungus are microscopic images (approximately 600x) of the mold we found growing on the Mexican Nopal cactus.

The conidia (spores) are obovate to pyriform, with a thick cell wall, dark brown, smooth, with a single transverse septum near the base.

They appear to grow in opposed pairs on either side of the hypha. The upper larger segment of the spore is generally darker than its base.

We also found, no surprise, species of Cladosporium sp. on this cactus surface.

Some experts report that superficial molds such as powdery mildew may appear on some cactus houseplants.

Mildew on cactus will appear white or gray-white and is principally a cosmetic issue. [1]


Photo of mold on Nopal cactus, la Yerbabuena, Colima, Mexico  (C) Daniel Friedman ... Photo of mold on Nopal cactus, microscopic image ca 600x (C) Daniel Friedman

Lab microphotographs and work to identify the black cactus mold shown above are in process - Ed.

Photo of mold on Nopal cactus, microscopic image ca 600x (C) Daniel Friedman

Question: cause & treatment for black mold on cactus

(Feb 5, 2015) Darlene said:
I have a Suharo that looks healthy but it has several hard black circles close to the bottom of the cactus. Is the mold? and what should I do to stop it?
Thanks

Reply:

Darlene

Over-watering or too much shade are factors that can increase the risk of mold growth on a cactus but of course by e-text I can't see what's going on with your plant.

If you like use the email found at our CONTACTS link (page bottom) to send me some photos of your Saguaro (Carnegiea gigantea) cactus common in the Sonoran desert and in the Organ Pipe Cactus National Monument in the U.S. A 5-armed saguaro is likely to be as much as 200 years old.

Below is a photograph of round black fungal attack on a different cactus, the species discussed on this page, the Nopal.

Round black "circles" or fungal attack on a Nopal cactus (C) Daniel Friedman

List of fungal diseases of cactus plants

Mold colony on cactus © D Friedman at InspectApedia.com Here our photo shows a typical colony formation on the surface of a cactus plant, viewed by stereo microscope.

Here are some of the many fungal species associated with cactus plants and/or the soils around them.[16]

Keep in mind that many fungi may be helpful to certain cactus species both in soils and at cactus roots and at other plant locations or in controlling cactus pests[13][19].

But some fungal genera/species are indeed reported to invade or attack and damage or even kill cactus plants including:

Diseased organos cactus San Miguel de Allende (C) Daniel Friedman at InspectApedia.com

Comment: Apressoria or hyphopodia on cactus

(Sept 8, 2015) Ludovic said:
The mold you show here is none of the one suggested. The peg-like projection from the darkly colored hyphae are called 'appressoria' or 'hyphopodia', used to anchor on their substrate and also suck up nutrient from it.

The ones you show are characteristics of epiphyllous fungi in the Orders Meliolales (or black mildew) or Asterinales, depending the ascoma (=fruiting body, spore containing structure) associated with them. Did you find big spore with 3 to 5 cells (Meliolales) or small spore with only 2 cells (Asterinales)?

I love fungi but I have no idea how to treat plant that carry them. It seems to me that these fungi proliferate in particularly wet places (tropical?). I saw many of them on almost all sorts of plants in some very wet part of Costa Rica. I don't know if that will help.

Reply:

Thank you Ludovic, I've continued to collect fungal growth from succulents, particular cactus plants in central Mexico.

From the in-situ look these do not seem to be a mildew - the surface is very scaly and hard.

When I'm back I'll take a look through the microscope to see what spores we can isolate - if any. Possibly during wet weather they'll make a cameo appearance. But generally these are appearing at various altitudes up to 7000 ft but in a usually-dry climate.

I'd be grateful for any citations / references you can add for cactus-infecting cacti.


White & Light Colored Mildew & Other Molds on Cactus Plants

Mildew on a Jasmine plant, closeup (C) Daniel Friedman

White stuff found on both indoor and outdoor plants (photo at left) including cactus plants may be mildew,

If the cactus is being kept in a too-wet or too-humid environment.

Mildew infection of a cactus is more likely for plants grown out of their native (dry) environment, and when the cacti are kept close to other mildew-infected plants.

Mildew spores (C) Daniel Friedman

Our photo (above left) shows what mildew spores look like under the microscope.

Photographs of mildew on plants are at MILDEW in buildings ? and advice on curing & preventing mildew on plants is at MILDEW REMOVAL & PREVENTION

Because the skin on most succulents is so thick, mildew may do less damage to a cactus than to other plants.

However other white and light colored molds found in buildings and on some plants can be harmful to people and animals as well, such as some species of Aspergillus sp. and Penicillium sp.

See WHITE MOLD PHOTOS for photographs of white mold growth in buildings.

Other "white stuff" we see on cactus plants may be a left-over deposit from having sprayed or washed the cactus plant with vinegar or other solutions.

 

How to Remove a Mealybug Infestation on Cactus

Watch out: some "white stuff" on cacti and certainly on other plants may be mealy bugs not a fungal infection, but deserving action. Our mealybug photo below was provided by Iranian reader P.C. 2018/10/12.

Mealybug found on white infested cactus in Iran (C) InspectApedia.com  Pedram

Treatments for Cactus Mold Growth - may also be helpful with mealybug infestation

Some, perhaps most molds, observed on cactus plants may not actually harm the plants but may remain a cosmetic issue for hobbyists. Popular cactus mold cures include:

Question: treatments for white fungus on cactus

(May 20, 2014) mark said:
White mold or fungus treatment on Nepal cactus

(Oct 11, 2015) steven said:
have a 12 foot cactus and i see white mold on it. How do I save it or is it doomed?

Reply:

Mark, I guess you meant to type Nopal. Indeed there can be more than one genera/species of fungi on a plant, or the same fungus may appear differently at different growth stages.

I'm doubtful that a spray fungicide is the best approach for the plant - at least not before diagnosing the cause of the fungus growth. For example an over-wet plant may continue to have trouble.

Australia's Garden Web (www.au.gardenweb.com) has listed these fungicides used successfully on cactus plants

Depending on where you live, different products may be available.

Watch out: if you are harvesting nopal for food use be sure to read the MSDS and toxicity data for the fungicide that you are considering.

White "Mold" on Cactus may be an insect scale: Cochineal, Not Mold

Collecting Cochinieal with a deer tail brush, Ramirez 1777 at Wikipedia, cited & discusse at InspectApedia.comShown here: Using a deer's tail as a brush, the worker is collecting Cochineal. The painting is by José Antonio de Alzate y Ramírez (1777), and the caption reads: Fig. 1, Indio que recoge la Cochinilla con una colita de venado, Fig 2. Dicha [colita de venado], Fig 3. Xicalpeftie en que aparan la cochinilla.

- source: Wikipedia, retrieved 2021/06/09, original source: https://en.wikipedia.org/wiki/Cochineal

[Click to enlarge any image]

Cochineal (Dactylopius coccus) is a white cactus scale insect that is both a cactus plague and a fascinating organism with a long history in Mexico.

Remarkably, if you smash a bit of this white scale on a cactus you may find an intense carmine red liquid (alizaron crimson) under your thumb.

While Cochineal (Dactylopius coccus) is a cactus parasite, it was also very valuable as a source of red dye that was so valuable as an export product that until the close of the Mexican War of Independence, Spain kept this source of red dye a state secret and held a monopoly of its production in Mexico. The Wikipedia article we cite above notes that

Pigments produced from the cochineal insect gave the Catholic cardinals their vibrant robes and the English "Redcoats" their distinctive uniforms. - Wikipedia Op. Cit.

Continuing today in the Mexican state of Oxaca, the intense red Cochineal dye is still used to give a stunning carmine color to hand-woven textiles.

In Mexico we find this parasite and dye source particularly on the prickly pear or nopal plant, though I have found it on organos and other cactus plants too, though on those plants it usually appears at a much lower volume and area.

Reader Question: tons of white mold on cactus trees

2016/08/22 Jane C. Ti said:

Dear Cactus Specialist, Our Cactus trees which are about more than 12 ft. tall, & they did have pink fruits, guess = Prickly Pears; are all sick with tons of white mold, please see the attached picture.

Cochinilla en Nopal, Artes de Mexico, El Nopoal, No. 59 at InspectApedia.comWould you please advise me, regarding: how to rescue these poor sick ones.

Thanks in advance! Sincerely looking forward to hearing from you at your convenience! Desperately, Jane

Shown here, la Cochinilla (Cochineal) on a Nopal cactus, illustrated in "el Nopal", Artes de Mexico, No. 59.

Reply:

Jane:

With regret, I'm a cactus-interested investigator but not a cactus expert by any means.

Your description sounds like one of the species of Nopal or prickly-pear cactus (Opuntia is the "prickly pear cactus" genus in the cactus family, Cactaceae). There are about 90 species of Opuntia.

You can use our page bottom CONTACT link to send us photos for posting or comment.

From what I've read as an amateur, fungal diseases on cactus plants are difficult to treat, in my opinion largely because the fungus is environmentally caused - all molds are everywhere all the time: it's the local conditions that make a mold flourish and become a problem.

In the left of this photo you see a light gray-white fungus on the nopal and a common parasite climbing on the organos cactus in the right of the same image.

These cacti were photographed in Pozos, in Guanajuato, Mexico.

Fungal and parasitic attack on Nopla and Organos cactus, Pozos, Guanajuato, Mexico (C) Daniel Friedman at least one cactus "expert" (cactiguide.com) gives the depressing advice that you give up, take a clean healthy cutting and start a new plant.

In my view that's not gong to cut it if problem source in the local environment - too much water, shade, or something else isn't also found and corrected.

I'm doubtful that a fungicidal spray will be effective for dark scaly mold damage: the cacti I've examined with such black or dark molds were almost impossible to clean of mold growth.

But here's the good news. Well good of a sort.

Often a white "mold" or "fungus" people think they see on cactus is not a fungal disease but rather an insect. In fact often a white fuzzy "deposit" seen on Opuntia is cochineal (Dactylopius coccus) a scale insect in the suborder Sternorrhyncha, from which the natural dye carmine is derived.

Cochineal produces an intense red dye whose cultivation in pre-hispanic Mexico and whose later production was kept secret by the Spanish in Mexico.

Without over-pricking yourself, scrape off a bit of the white stuff and rub it between thumb and forefinger.

If your fingers become stained with an intense red dye, that's Dactylopius coccus (some texts refer to it as a "mealybug" ).

If that's what's on your cactus you might be able to clean it off with a soft long-bristle brush and dish soap or an insecticidal soap.

I'd avoid very strong power washing as it's likely to damage the cactus itself. Locally here in San Miguel de Allende our jardinero expert uses neem oil on several plant species to resist insect attack.

How to remove Cochineal from your cactus

We have successfully cleaned off small infections by the Cochineal scale insect using a soft brush and an insecticidal soap; those products are discussed in this article. You don't have to use a deer's tail.

Frankly I don't like to disturb the scale unless it's become a serious infection on a valuable plant.

White Growth on Melon Cactus in Iran

White fluffy and barnaclie like gowths on cactus including Melocactus diamantinus (C) InspctApedia.com Pedram Clash

Reader Question: white growth on Melocactus diamantinus and other cactus

2018/10/07

im from iran
I have a few cactus and i have a problem (disease)

My Melocactus diamantinus and a few other cactus have a disease but I can't find a treatment.

I need to help find diseases and treatment ? I send few picture this email .
Thanks for help. - Anonymous by private email

Reply: diagnosis & treatment of white fluffy or barnacle-like infestation on cactus: mealybug / cochineal insects

As we illustrate starting at CACTUS COCHINEAL INFESTATION you will see examples of white fluffy or barnacle-like diseases on cactus that are insect-based rather than fungal.

Try scraping off some of the larger white growths on your cactus and mashing those between a thumb and forefinger. If you see a red dye in the result your cactus are infested with mealy bugs or cochineal insects.

For other readers, English names for Melocactus diamantinus include Turk’s Cap, Melon Cactus

White fluffy and barnaclie like gowths on cactus including Melocactus diamantinus (C) InspctApedia.com Pedram Clash

Treatments for Dactylopius sp. - cochineal mealybug infestations on cactus

What are Dactylopius sp. - mealy bugs, or cochineal bugs ?

[Mealy bugs] are small scale insects that feed on the cactus.

They produce fluffy white wax that hides their bodies as they feed on the cactus and protects them from the elements (drying out, in particular) and from predation.

The fluffy wax also serves as a sail or balloon to float on the wind and take the bugs to a new patch of cactus.

The bugs produce carminic acid that also helps protect them from predation, especially from ants.

This carminic acid in the bugs has been used by indigenous peoples of southwestern North America, Central America and sub-tropical South America to make a brilliant red dye for centuries, perhaps millennia, to produce beautifully colored textiles.

Originally, the cochineal bugs were limited to the New World. When the European explorers visited and saw the beautiful red cloth of the natives, they took the cochineal bugs back with them and now they occur all over the world. - source: Ladybird Johnson Wildflower Center, 4801 La Crosse Ave., Austin, TX 78739 USA, Tel: 01 512.232.0100, https://www.wildflower.org/expert/show.php?id=9592 retrieved 2018/10/07

Other Prickly pear Cactus Nopal or Tuna Photographs

Photo of mold on Nopal cactus, la Yerbabuena, Colima, Mexico  (C) Daniel Friedman

Nopalitos are sold in local markets as well as larger supermarkets and are exported as well. The young nopalito pads are harvested and cleaned of thorns for sale. (Left and below left).

Nopal is sliced into strips or diced, then cooked alone (boiled or grilled) or with a mixture of onions and other herbs, and consumed as a vegetable.

The Nopal fruit or Tunas (see photo near page top and below right) are harvested using a long pole on the end of which may be a forked nail-pair used to hook the fruits.

Tunas may be peeled and eaten as a fruit but quite often are immersed in water, on occasion with added sugar, to make a fruit beverage.


Photo of mold on Nopal cactus, la Yerbabuena, Colima, Mexico  (C) Daniel Friedman ... Photo of mold on Nopal cactus, microscopic image ca 600x (C) Daniel Friedman

Below, two more common afflictions of nopal cacti in San Miguel de Allende, Guanajuato, Mexico.

Cactus disease Mexico (C) Daniel Friedman at InspectApedia.com Cactus disease Mexico (C) Daniel Friedman at InspectApedia.com

Below: parasitic attack on Organos cactus

Parasite attack on organos cactus, Pozos, Mexico (C) Daniel Friedman at InspectApedia.com

 

Cactus Rot Damage

Watch out: the number one killer of cactus plants kept by many enthusiasts is over-watering. Cactus rot kills of the roots of the plant first so by the time you see rot there may be more damage than is obvious.

But it may be possible to save your rot-damaged cactus by judicial cutting, drying, sun exposure, and avoiding over-watering.

Below: Organos cactus that are telling you they've had enough water. Stop watering these plants.

Organos cactus with scale and a bit too much watering (C) Daniel Friedman at InspectApedia.com

In the case of Organos that appear in several photos on this page including just above, the cactus will show you that it has had plenty of water by its swollen appearance.

On 2021-06-03 by mak.church (mod) - black rot on cactus tip

Cactus rot at tip (C) InspectApedia.com@Heidi Sebastian,

You're on the right page and I would direct you to the section: on this page:

Treatments for Cactus Mold Growth or mealybug infection. Or rot.

Your spray might be helpful but as we both will read in cactus mold treatment advice from experts, one needs to match the spray or other treatment to the specific pest: molds, insects or,

if the problem is over-watering that causes root rot. But rot can appear at the cactus at any location, near its base, along its stem, or as in your case, at its tip.

I think your cactus has stem rot showing up at the tip, better called "cactus tip rot".

Cactus pros say you have to act quickly to remove the rotting tip of the cactus.

Use a sharp and clean knife or other cutting tool (disinfect it with soap and water or in 95% alcohol before using it) to cut off the damaged tip.

When you cut off that tip, look at the cross-section of the cactus top that remains: if there is any rot in its center, you need to cut a bit lower down on the plant until you see only healthy tissue.

Now keep the cactus out of the rain and give it sunlight until the exposed cut area has dried and become callused over - it will turn a thick gray colour.

Don't over-water your cactus.

On some of our organos in pots in Mexico we have had to stop watering them entirely as even when rains are intermittent more watering was killing the cacti.

On 2021-06-02 by Heidi Sebastian

My cactus has recently got black spots and more so at the tip. Can you please advice how to treat? I’ve cut some of it out and sprayed with an organic garden spray.

[Photo above]

On 2020-06-08 - by (mod) - saving a cactus paddle or pad by re-planting

Cactus rot - still may be salvagable by judicious cutting and sun treatment (C) InspectApedia.com readerEmili

That looks to me less like mold than like cactus rot. Over-watering or too much rain can indeed cause rot. The cactus roots will be totally gone.

If I were trying to save that pad I'd pull the over-wet, partly-rotted end out of the planting soil and instead flip it over, put the stem side down (assuming its dry), and keep watering to a minimum for a time;

the rot-damaged area won't get pretty but you may get some new growth off of the sides of the paddle.

On 2020-06-08 by Emili

What should I do with this Santa Rita pad?

It got rained on one day and I believe this caused it to mold

 

Other Black Damage on Cactus

Anon from Feb 2: re: black cactus fungus - Sun Scorch

That looks to me like Henersonia opuntiae a fungal infection aka "sun scorch" (which isn't really due to sun).

You should remove those infected Nopal cactus or "paddle cactus" pads by cutting or twisting them off (we use cooking tongs to hold the paddle).

Then dispose of the paddles as bagged garbage or burn them so as to avoid spreading this fungus to the rest of your cactus plants.

Sun scorched cactus at InspectApedia.com

On 2020-02-16 by Anonymous

I have white substance on my cactus and when I scrape it off it looks like a cross between soft rice and very small styrofoam. How do I get rid of it?

 

Cactus Scale Damage & Scale Removal

These Organos cacti, gift of my sister-in-law Lili, live in pots, get pretty-good sun, and were sometimes over-watered. ( I didn't do it!)

Definition: Cactus scale is a small light colored or white flattened "armored" (hard-surfaced) scale that is circular and has a dark center spot. It's found growing only on cactus, though of course there are other armored scales found on other plants.

Organos cactus with too much scale (C) Daniel Friedman at InspectApedia.com

Above: you can see that this cactus has got a lot of water; its pleats are quite expanded. It's also got a lot of scale that developed over several years. At first we just watched it and hoped (in futility) that the scale would magically go away.

Left alone, the scale simply has a fantastic time growing all over the cactus. More sun helps fight it but that's not enough. Below: feeling aggressive and frantic we decided to use, household food-grade white vinegar, straight out of the bottle, as a cleaner. That's a bit strong.

Using vinegar to clean off cactus scale (C) Daniel Friedman at InspectApedia.com

I decided not to use the white brush shown in the photo above as its bristles seemed a bit too stiff and scratchy. Instead I used the softer natural bristle brush shown below.

Cleaning scale off of organos cactus (C) Daniel Friedman at InspectApedia.com

I scrubbed, but not too hard. It's better to scrub gently, with more liquid cleaner, and take more time. You want to leave the cactus' skin un-harmed. The result is below.

Cactus after scale removal (C) Daniel Friedman at Inspectapedia.com

The photos show a successful effort to remove cactus scale growth from these fellows. I used household food-grade vinegar, but will describe some other remedies below.

Treatments for Cactus Scale

A common treatment for cactus scale is gentle cleaning of the surface using either a commercial insecticide or treatment sold for cactus scale such as those listed here.

Insecticidal soap may be helpful for several cactus diseases - this is from GardenSafe - cited & discussed at InspectApedia.com

Neem oil spray broad spectrum pesticide and fungicide for plants cited at InspectApedia.com

Cactus mold medicine

If you clean off the scale before it coats most of the cactus you can probably save it.

I also avoid over-watering and too much shade.

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2022-06-14 by InspectApedia-911 (mod)

@steven,

Super. Do keep us posted, perhaps taking photos of your work, as that will help others.

Daniel

On 2022-06-14 by steven

@InspectApedia-911, thanks again, so I will try option 1 on 4 cactus, and option 2 on the remaining 3, after a month I will tell u the results. by the way, your website is great and has so much good stuff on it. well done creating it.

On 2022-06-14 by InspectApedia-911 (mod) - trimming and repotting may save overwatered cacti

@steven,

I'm not sure, but some cactus experts - more expert than I - have described two vastly-different approaches;

1. leave the cactus unwatered and watch it for signs of recovery - stabilizing and eventually new growth - I'd skip watering for no less than a month.

2. remove the cactus from the pot, cut off any rotted damage at its base, let it dry out - days or more - then re-plant it in sandy soil.

If when you remove the cactus you see that its base and roots are not totally rotted away, then you'd wash off the roots, cut away rotted cactus body, let that dry, re-pot in new sterile soil. Some cactus experts also use sulphur powder as a disinfectant on the wounded area.

Others, concerned with aesthetics, excise all of the rot and dry the cactus and re-pot it so that the injured area is no longer visible.

If the cactus base is badly rotted, people cut away salvageable parts from the upper cactus and re-root those as new plants.

Bottom line: based on our experience with cactus in Mexico, we cut off the intact top of the plant, let it dry for a week or longer until the base is a dry scarred surface, then re-pot the cactus in new clean "sterile" sandy soil. That plus patience is what have worked for us.

On 2022-06-14 by steven

@InspectApedia-911, thanks a lot for answering. so, I will reduce the amount of watering. Do you think these symptoms indicate a disease that will progress and kill the plants? what can I do besides reducing watering to make sure they won't die?

On 2022-06-13 by InspectApedia-911 (mod)

@steven,

I suspect those cactuses are being over-watered. We have quite a few of them on a hot dry sun exposed rooftop in central Mexico and it is still the case that we would never water them every week. Sometimes a clue of over watering besides stem rot is that the folds of the cactus begin to open up or the cactus looks a bit bloated.

On 2022-06-12 by steven

Due to the symptoms, I thought my cacti's disease was a kind of fungus, so I sprayed it once a week, for 2 weeks with carbendazim+iprodione "these are fungicides", however, the disease is progressing. In addition, the disease has only affected the epidermis of the plant.

Could these symptoms also be due to bacterial disease? Can someone help me diagnose and treat my cactus disease?

The size of these cacti is small, so larger pots are usually watered once a week, and small pots are watered twice a week.

Overwatered cacti (C) InspectApedia.com Steven

On 2022-06-01 by InspectApedia-911 (mod) - cactus scarring

@Jen,

To me that looks more like scarring than a fungus. It's possible that the cactus was rotted from watering and is healing itself.

On 2022-06-01 by Jen

What is this whiteish stuff on my cactus. It can be scraped off with my fingernail but it looks weird

Cactus scarring (C) InspectApedia.com Jen

On 2022-04-03 by Inspectapedia Com Moderator - cut away dead part and repot green portion

@Kb,

There's a good chance you can save the green upper portion of that cactus (Organos ?) - cut away all of the damaged base, then let the cut-end of the salvaged cactus plant dry thoroughly for a week or so - until its cut-base is no longer fresh or damp.

Then you can re-plant it in a fresh pot of sandy soil - well drained.

On 2022-04-03 by Kb

I've had this cactus for 19 years and am heartbroken something is wrong with it . After noticing I repotted and added neem oil

dying cactus needs to be trimmed and replanted (C) InspectApedia.com Kb

On 2021-10-22 by inspectapedia.com.moderator - cochineal scale treatment needed

@Nicolas,

In the above article, you will want to take a look at our description of cochineal scale and its treatment in the article above.

On 2021-10-22 by Nicolas

I have had this cactus for a little more than a year, and this white stuff has grown all over one of the cacti. Additionally, it also appears to be releasing many tiny tiny flying bugs (they are almost microscopic). Please help!

Cochineal scale on cactus (C) InspecTapedia.com Nicolas

On 2021-07-12 by inspectapedia.com.moderator

@Clare,

You will want to take a look at our description of cactus scale and its treatment in the article above

On 2021-07-12 by Clare

What is happening to my only cactus? This white stuff has increased rapidly over the last 3 to 4 weeks.

Cactus scale (C) InspectApedia.com Clare

On 2021-06-08 by (mod) - remedies for light colored scale on cactus

@Maria

On the page above you will want to read the problem description and recommended remedies at

On 2021-06-08 by Maria

I don’t see it I just took some off and this is what it looks like [Photo above]

On 2021-06-08 by (mod)

@Maria, in the article above take a look at the discussion of scale on cacti.

On 2021-06-08 by Maria

hi! I need help I don’t know what this is growing on my cactus. PLEASE HELP!!

Question: identify & treat white growth on succulent plants

I am growing these seeds and am not sure if this is mold and if so the best way to get it off these babies. - Anonymous by private email 2021/06/08

White fungal growth on succulent plants grown from seed (C) InspectApedia.com Whiteside ... White fungal growth on succulent plants grown from seed (C) InspectApedia.com Whiteside

Moderator reply:

Above and below on this page we illustrate several white growths on cactus and succulent plants, including

mold and mealybugs or other pests along with recommended treatments.

Please take a look and don't hesitate to ask follow-up questions if you need.

On 2021-05-06 - by (mod) -

@Michael Harrigan, worth the try, just bring them in if it rains. Let me know if that helps.

On 2021-05-05 by Michael Harrigan

Thank you for your comments and advice. I think I'll try rotating them outside the greenhouse for direct sun and fresh air!

On 2021-05-05 by (mod) - cactus fungal attack, Gulf of Thailand

@Michael Harrigan, thank you for all of the cactus-mold photos; you're not over-doing it.

I agree that it's probably humidity that invites mold growth on your cacti, particularly as you already know not to over-water them.

Short of installing a dehumidifier, about all you can do is increase sun exposure and be sure that your indoor RH is as low as you can get.

On 2021-05-05 by Michael Harrigan

I just noticed that we have what looks like mold/fungus on a few types of opuntia. I'm attaching photos as I'm not sure

We live in Thailand, on the Gulf of Thailand and are coming out of our hot season (hot and dry) and the humidity is on the rise.

The rainy season starts in a couple of weeks. I have been keeping the plants in a small greenhouse with an open flap, with the idea that I would keep them from the heavy rains. Any suggestions?

Cactus fungus infection (C) Inspectapedia.com Harrigan ... Cactus fungus infection (C) Inspectapedia.com Harrigan ... Cactus fungus infection (C) Inspectapedia.com Harrigan

On 2021-02-25 b danjoefriedman (mod)

I'm not the most-expert but that looks like a form of scale or rot; You could try gently rubbing the spots with alcohol on cotton and then make sure the plant is getting sun.

On 2021-02-25 by Melinda

I know nothing about this cactus as it was given to me. It is planted on the same pot as a big aloe plant and was doing great. Had 3 babies grow off it and now suddenly these spots and drooping started happening.

Black cactus scale or rot (C) InspectApdia.com Melinda

On 2020-12-16 - by (mod) - white cactus mold Rx

White cactus mold or parasite (C) InspectApedia.com AlexAlex

I'm not sufficiently expert to be sure that I have exactly the right opinion for you here but it sounds to me that if you have gone through all of the white cactus mold examples described on the page above, reviewing their appearance, cause, and treatment, and you're left with an unidentified fungus and rotted cactus, then you need to cut out or excise the infected part of your cactus.

I know that's traumatic but that may be the only solution if in fact the cactus is rotted.

I can't tell from your photo but if this surface material is fuzzy and white it's not rot; see if you can wipe it off, and then read our suggestions above for dealing with mealybugs, mites, and for cleaning cactus surfaces using a plant soap or mixture.

On 2020-12-15 by Alex

There is a white growth on my cactus. The whiteness does not rub red so I don't believe it is mealybugs.

The tissue under the white mold is soft when pressed although the rest of the cactus is firm. Unfortunately the infected area is at the base. Is there any advice on how I can save him?

On 2020-10-05 by (mod) - cactus probably finished off by scale

Looks like scale;

I'm afraid that cactus is a goner. I'd keep it away from the others if not send it to the trash. Light scale can sometimes be gently scrubbed off but in my OPINION (I'm not expert) that one is about as scale-covered as I've seen. \

On 2020-10-05 by Rachel

My aunt bought this cactus like 6 months ago and now it looks like this. What could be growing all over this cactus?

Severe scale infection of a paddle cactus nopal (C) InspectApedia.com Rachel

On 2020-09-28 - by (mod) - Ferocactus has started showing yellow dry spots

Nate:

Cactus experts usually tell us to cut out the infected moldy parts of the cactus and let the wound dry and heal; perhaps your cactus needs more sun. A plant light may give the required UV but not the warmth.

On 2020-09-28 by nate

Ferocactus Pilosus rot or mold forming. In the last week my Ferocactus has started showing yellow dry spots on it, it has gotten worse over the last few days and now one spot has white stuff on the yellow dry spot. Any idea what is causing this?

I have had the cactus for over a year, it doesn't get a lot of sun, but I have a plant light shinning on it daily. I watered it about once or twice a month. Not sure what to do about this.

Ferocactus Pilosus rot or mold forming (C) InspectApedia.com Nate

On 2020-09-10 - by (mod) -

Becky

I have not seen that exact growth on a San Pedro or similar cactus, but it looks to me as if we may be seeing a combination of scale on your cactus and an oozing sap that has built-up near the plant base.

I've seen similar damage ascribed to bacterial growth in the cactus. You might try cutting away the damaged "growths" and making sure your cactus gets adequate sunlight.

On 2020-09-10 by Becky

I've had this cactus growing for about 5 years. the last year or so it has Developed this growths . no flowers or fruit or new growth.here are some pictures of it
.

On 2020-07-26 - by (mod) -

Without knowing exactly what the white dust is I can only suggest the most mild remedy such as I dilute dish soap solution at a toothbrush to do a little gentle scrubbing.

Make sure your cacti are getting enough sunlight. And of course rinse thoroughly but don't over water the cactus itself.

If you think that it's parasite you could try a dilute vinegar spray

On 2020-07-25 by Brenda

What can I put on my cactus to get white dust off of them

On 2020-05-30 by Teddy

How to naturally get this off my cactus

On 2020-05-06 - by (mod) -

Maiya

My guess is that the in-focus cactus suffered from rot from over-watering. Both of them have some bulges that may indicate trouble moving water up through the plan or episodic over-watering.

On 2020-05-06 by Maiya

I am wondering what is going on with two separate cactus. They were growing side by side in a fairly well lit window sill. I may have over watered one and the other one may have got sun burn from my research so far.

The over watered one is showing signs of rot or fungus , or it could be an infestation.

The sun burned one is also having brown lesions spreading and both of them have very white fuzzy prickles.

On 2020-03-25 - by (mod) -

Thanks for the follow-up, Joe.

Over-watering can cause paddle rot and whitening too - though usually we see obvious soft, soggy rotted areas during that event.

Watch out: the bad news is that over-watering can kill the cactus root system. I'd put the cactus on a water-diet. I don't water our cactus until the soil is thoroughly dry - for at least as far into the sandy soil as I can get my finger or a probe.

I find that many people over-water their cacti or perhaps like yours the cactus location gets more water than wanted.

I would consider installing gutters and a downspout to get water away from both the cactus and the house.

On 2020-03-25 by Joe

Thanks for your comments. The affected Pear located in Oro Valley AZ (Tucson area) is in a front yard facing NE with rock/gravel drainage. I tested for the parasite infestation and don't believe that is the cause. This white substance is quite hard and dry.

While I believe that the drainage is quite good, I noticed that part of the roof where there are no gutters drains straight the area in which the PP is located and there has been quite a lot of rain this winter/spring.

I'm suspect that it may be the result of over-watering for the reasons mentioned and that it seems to start at the tips of the pads though it's fairly widespread, some areas more than others. Thoughts and comments appreciated.

On 2020-03-22 - by (mod) - large patches of dry scaly white areas on several cactus pads

Joe:

I think your cactus may be sunburned.

Is this a hothouse or greenhouse-raised cactus that was later moved outdoors?

What are the country and state and nearby city of its location?

Try:

- watering the cactus at a consistent time (of course not over-watering)

- erecting a fabric sunshade (these don't block all sun, just much of it) over the most-injured paddles of the cactus between 11AM AND 2PM daily for a few months and let me know if the shaded paddles are in better shape than other un-shaded areas - this will help both you and other readers diagnose these white patches.

Unfortunately nothing will bring back the white areas of damage. But as we've seen marching around the deserts of central Mexico, even very ugly damaged paddles can support new growth. (Some people cut the damaged area of paddle away but I'd not do that unless it's increasing in area).

See Amy Grant's article on sunburned cactus at

https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/saving-sunburned-cactus-plants.htm

On 2020-03-21 22 by Joe

I have a mature prickly pear with large patches of dry scaly white areas on several pads (see photo). Can anyone tell me what this is and if it needs to be treated to preserve the health of the plant? Thanks.
IMAGE LOST Please re-post the image if you can. Sorry. Mod.

On 2020-02-16 - by (mod) - White fuzzy cactus growth:

Anon:

RE: White fuzzy cactus growth:

If smushing a bit of the white material shows a clear or red liquid I suspect you're seeing either a scale or a parasite or fungus - see CACTUS COCHINEAL INFESTATION inspectapedia.com/mold/Cactus-Mold-Identification.php#Cochineal

It's easy to remove using a soft brush and a mild dish soap solution or better, an insecticidal soap or horticultural oil, but

Watch out: test your treatment on your cactus in just a small area for 48 hours and watch to assure there is no yellowing or other damage - before treating the whole plant.

See the CACTUS SCALE treatments given above.

On 2017-09-15 - by (mod) -

You'll see some remedies for cleaning off soft modes on Cactus in the article above. You might want to look at where your Cactus is located in to be sure it's getting plenty of soon and not being soaked by sprinkler system.

On 2017-09-15 by araceli moralez

My nopal has white spore-like growth all over them. They almost look like foam

On 2017-06-06 - by (mod) -

Anon

I'm not a cactus expert but it sounds to me as if there may be an over watering or rot problem. YOu are welcome to use our page top or bottom CONTACT link to send me some photos of Colin and we may be able to comment further.

On 2017-06-06 by Anonymous

We have a beloved cactus, (Colin), who is around 25 years old and 6 feet tall...he has outlived all of my partners previous relationships, though he has been nurtured since he came to live with me. He has pride of place in a bright spot in the kitchen french windows, and was re-potted last year into a larger pot, with fancy specialist compost and given a good feed.

All of a sudden,this year, he has developed small black spots, and has begun looking 'withery'. He also feels rather spongey, towards the top rather than the bottom; which still looks strong.Your thoughts would be much appreciated, as my partner has stated that if he does die, I will be booking a coffin which can fit both of them in (not that he is being dramatic of course!)

We have attached a selection of pictures which may help to diagnose the problem..

Many thanks and best wishes
Sally and a deeply distressed Alan (Nottingham)


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