White spots on cactus


What are these brown spots on my cactus?

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Brown Spots on Cactus?

What can I do when a small cactus gets burnt from being in direct sunlight too long?!

Hi reader! Thanks for your question.

Let’s say you bring home your new plant buddy and you are looking for the best place to put it. In Vancouver, we tend to stick our cacti in the sunniest spot in our house. After all, they are desert loving, right? Doesn’t your new baby needs all sun it can get?

Caroline, our author today, is a well known dessert-loving cactus.

No, not dessert loving.

The answer is no!

We start to run into issues if they have been growing in a shady nursery. Cacti have a number of different defenses against light damage, like white hairs, lots of spines, or even a tougher skin! However, if it never needed to defend itself against light, a cactus might not bother to grow these additional defenses. Much like how you might regret skipping gym class when it’s time to run away from an angry mama bear, your cactus suddenly realized it had been living life all wrong when you moved it into the sun.

As with any plant, big changes in environment can be extremely stressful; acclimation is key. Sunburn can actually happen to a lot of houseplants, especially ones that have been trapped in the store for a while. However, cacti can be especially at risk to damage due to poor acclimation. Other plants can adapt to high or low light by growing different leaves or developing more protective pigments. Cacti tend to be slow growing, so they adapt and recover from stress a lot slower.

So, how do we fix this? Is sunscreen really one weird trick for saving your houseplants?

Well prevention is the biggest step! Take note of where your cacti has been growing and place it in a similar spot in your home, which will probably be a little shady at first to start out with. If you know that one side of the cactus has been facing a sunny south-facing window, try keeping that side pointed at some sun.

However, what if the damage has been done? The fix is pretty simple: move it to a shadier area. Get your cactus out of that sun and give it some time to recover. Also, make sure you are watering the amount appropriate for your plant friend. A little bit of R & R goes a long way.

Once your cactus has recovered a little, you can try slowly introducing it to some more light. Rotate your cactus into a sunny position and then back into the shade from day to day or consider sunscreen. Or rather, a sun screen. You can drape a shade cloth (any cloth that allows some light, but not all light through) over your cactus to reduce the intensity of sunlight and leave it in the windowsill.

Sunburns are an ugly problem with a simple solution. Hopefully your plant can recover! Happy gardening!

If you liked this article today, why not get one of your own questions answered? Post a question on our Facebook page or ask here. All of our questions come from club members and all of our answers are written by hard-working execs.

Succulents live in varying habitats across the world and can also be grown as houseplants. They use their fleshy parts as a water reservoir during droughts. But these same parts are also susceptible to diseases and disorders that discolor them with brown spots.


Although succulent leaves are thick, fleshy and water-filled, this does not mean you need to water them more than other plants. The reverse is true. Succulents perform best when their soil dries between waterings. If they remain in wet or waterlogged soils, succulents suffer from edema, which causes brown, corky spots on the leaves. Sometimes the spots form on the undersides of leaves, making it more difficult to notice this disorder. The brown spots are particularly noticeable on the white areas of variegated succulents.

Dissolved Salts and Chemicals

Succulents are sensitive to too much fertilizer, and typically need infrequent or dilute fertilizer applications. If you give your succulent plants too much fertilizer, the salts that are contained in fertilizers accumulate in the soil and can burn the roots. As the salty soil solution moves upward in succulents, it may also burn the leaves and cause brown spots.

Photo via reddit.com

Fungal Diseases

Succulents are susceptible to a host of fungal leaf-spot diseases. These pathogenic fungi require water to reproduce sexually and to spread, so these diseases proliferate in moist areas and foggy climates. As a fungus takes hold of a plant, it may form brown spots on leaves that may eventually join to form large lesions. Once the disease is present, there’s no cure.


Preventing brown spots on succulent leaves is often as simple as choosing an appropriate planting or potting soil and watering the plants properly. A porous, well-draining soil is best. If you grow succulents in containers, use only pots that have drainage holes so water can drain away. Water plants thoroughly until the excess water runs out of the drainage holes, which helps flush excess salts.

Source: sfgate.com


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Sticky White Mold on My Cactus

From a distance, your prized cactus looks as if a group of passing school children had plastered it with freshly chewed white gum. Closer inspection reveals something different, and it’s not mold. Depending on the type of cactus you have, the waxy white splotching is a cochineal scale or mealybug colony. To restore your plant’s good looks and preserve its health, you’ll need to act.
Target Plants
Pinhead-sized cochineal scales feast on prickly pear (Opuntia spp.) and cholla cactuses (Cylindropuntia spp.) both of which grow in U.S. Department of Agriculture plant hardiness zones 3b through 11, depending on variety. Flat, segmented mealybugs target orchid cacti (Epiphyllum spp.), which grow as houseplants outside of USDA zones 10 through 11. Both insects hide beneath protective layers of soft, fibrous white wax. The bright-red female scales have pigmentation so strong that they’re farmed as commercial dye sources in several warm-climate countries. Mealybugs are typically yellowish or gray.
Damage and Sun Deprivation
Both cochineal scales and mealybugs deprive the cactus of moisture and nutrients by draining sap with their hollow, tissue-piercing mouthparts. The biggest threat they pose comes from blocking the sun the plants need to manufacture food. An uncontrolled scale population eventually covers enough of the pads to interfere with photosynthesis by preventing sun from reaching the plants. If your cholla or prickly pear is withered and yellow, it’s time for action. Mealybugs’ sticky waste, or honeydew, attracts layers of sun-blocking sooty mold to orchid cacti.
Small Cochineal Problems
Chollas and prickly pears handle light cochineal infestations without much difficulty. To deal with a small number of the insects, put on heavy gloves and prune the infested pads off at the joints, disposing of them away from your garden. Avoid accidentally spreading disease accidentally by wiping your pruning tools off between cuts with a rag dipped in rubbing alcohol.
Cochineal Infestations
To eradicate a large colony cochineal scale colony, blast your cactus with a garden hose. The water’s force removes the insect’s waxy coverings. Then spray them with a solution of 1/2 teaspoon of non-detergent, liquid dish soap mixed in 1 gallon of water. The soap suffocates the exposed scales without leaving residue toxic to honeybees or other beneficial bugs. Dress in yard clothes when spraying, in case you’re splattered with runoff tinted red from smashed scales. You won’t eliminate all the pests, so repeat the spraying as the colonies rebuild.

Mealybug Management
Treating mealybugs on a spine-free orchid cactus is relatively simple. Use the hosing technique on an outdoor plant. After wrapping an indoor cactus’s container in a plastic bag to prevent overwatering, set it in a sink or shower for spraying. Dabbing a small number of mealybugs with cotton swabs dipped in a solution of 1 part rubbing alcohol to 3 parts water also works.
Preventing Problems
Always quarantine a new cactus before introducing it into your yard or home. Check it daily for a month and treat scale or mealybug infestations immediately. Check and treat an orchid cactus that spends the summer outside before bringing it in for the winter. If many people grow cactuses in your area, it may be almost impossible to prevent all infestations of cochineal scale.

Cactus rot is a super common problem, and one of the main causes of cactus death. But just because your cactus is rotting doesn’t mean you can’t save it. In this post, I talk about the causes and symptoms, answer all of your questions, and give you step-by-step instructions for how to save a cactus from rot.

Rot can start anywhere on a cactus plant. It could start from the bottom and spread up the plant. It could start at the top and spread down. Or it could start anywhere in between.

No matter which parts of a cactus plant are rotting, there are steps you can take to save your plant. The steps are a bit different depending on where it’s rotting.

But don’t worry, I’ll give all the details for saving a rotting cactus in this post! Here’s and overview of what you’ll find…

  • Why Is My Cactus Turning Brown At The Top?
  • Why Is My Cactus Rotting Top Down?
  • How To Save A Rotting Cactus
    • How To Save A Cactus Rotting Top Down
    • How To Save A Cactus Rotting Bottom Up
  • Cactus Rot FAQS
    • Why is my cactus turning black on top?
    • Why is my cactus turning yellow?
    • How do you save a dying cactus?
    • Why did my cactus rot?
    • How do you bring a cactus back to life?
    • What causes a cactus to die?

Why Is My Cactus Turning Brown At The Top?

When a cactus starts to turn brown and mushy at the top, it likely has something called tip rot (aka cactus stem rot).

Basically that means that your cactus is rotting. Cactus stem rot will spread quickly if nothing is done about it.

Once a cactus starts rotting top down, it won’t stop. It will continue to spread all way down the entire stem, and will eventually kill the plant.

So, once you discover cactus tip rot, it’s important to act fast in order to save the plant.

Why Is My Cactus Rotting Top Down?

There are a few things that can cause a cactus to rot from the top down. Cactus rot is caused by either fungus, disease or water getting into an open wound on the plant.

If a cactus is damaged in any way, it is vulnerable to being infected with disease or fungus spores. It’s also very common for water to settle into the wound, causing the plant to rot from the inside out.

The damage could have been caused by anything, including bugs or animals feeding on the plant. Someone could have brushed up against it, the plant could have tipped over, or maybe something fell on it.

You may never know the exact cause, so don’t beat yourself up about it.

The good news is that the steps for saving a rotting cactus are the same no matter how the it started in the first place. Below I will show you how to stop cactus rot from spreading so you can save your cactus.

My cactus turning brown on top from cactus tip rot

How To Save A Rotting Cactus

Once a cactus starts rotting, all the rot must be pruned off in order to save the plant. If it’s not completely removed, it will continue to spread, eventually killing your cactus. And cactus rot spreads very quickly.

You don’t want to end up with a dead cactus plant, so you’ll definitely want to act fast.

The steps for saving your cactus depend on where it’s rotting. So first I will show you the steps for how to save a cactus that is rotting top down.

Then, in the section below that, I’ll talk about how to save a cactus that’s rotting from the bottom up.

Cactus rotting bottom up

How To Save A Cactus Rotting Top Down

Cactus tip rot can be very deceiving. You may notice small brown spots on a cactus and think that it’s just a tiny bit of rot.

Then once you start removing the bad spots, you realize that it’s much, much worse on the inside than it looked on the outside.

So first, take a moment to prepare yourself for what you may find once you start cutting. Ready? Ok, follow these steps to remove cactus stem rot…

Step 1: Choose your pruning tool – You can use a sharp knife or pruning shears to remove the rot. If your cactus is really thick, then I recommend using a sharp knife.

Otherwise, for small plants with thin stems, precision pruners or bonsai shears would work great. Just make sure they’re super sharp so the cactus stem won’t be crushed.

Step 2: Clean your cutting tool (do NOT skip this step!) – Whatever tool you choose to use, it’s extremely important that it’s clean and sterile before you make any cuts. Using a clean pruning tool will help prevent the spread of disease and fungus spores.

You can simply wash your pruning shears or knife with soap and water, and then dry it before starting. I also recommend washing and drying it again between each cut. You could also dip it in rubbing alcohol to sterilize it.

Step 3: Remove cactus stem rot in layers – It’s best to prune off the rot in layers so you’re sure that all of it has been removed.

Here you can see that the center of the healthy looking portion of my cactus plant still has rot on the inside. So we have to keep going…

Rot inside of the cactus stem

Step 4: Continue removing layers until all signs of rot are gone – As you work your way down pruning off layers of the plant, the rot will get thinner and thinner.

But remember, even a tiny bit of rot can continue to spread. So be sure you remove all signs of brown, soft and mushy cactus material until there are no more signs of rot left on the plant.

If your cactus is an outdoor plant, try to make the last cut at an angle so that water won’t settle on top of the wound (which will likely just cause it to rot again).

I would also move the plant to a dry area where it’s protected from rain until the wound has callused over, if possible.

Removing cactus stem rot in layers

Unfortunately, the rot on my plant was really severe before I noticed that the top was turning brown. I had to cut off over half of the cactus to remove all of it.

As difficult as it was for me to remove a large section of this cactus, I know my plant would be dead in a matter of weeks if I left behind any rot.

My cactus after all of the tip rot has been removed

Cactus Care Tips After Pruning

If you have to perform this type of surgery on one of your beloved plants, keep an eye on it afterward to make sure it doesn’t continue to rot. If it starts rotting again, follow the same steps above to remove the new rot.

After a couple of days, the wound should callus over, and your cactus will eventually send out new growth near the cut.

I was super sad to have to cut my cactus in half to remove all the rot. But heck, in the end I think it added more character to the plant.

New growth on my cactus after saving it from tip rot

How To Save A Cactus Rotting Bottom Up

Unfortunately, if your cactus is rotting bottom up, or the cactus roots are rotted, then there’s not much you can do to save it.

The best thing to do in this case is to cut off the healthy stem pieces, and propagate the cuttings.

Prune your cactus back in layers as shown in the steps above so you’re sure to get all of the rot off the cuttings. Allow the cutting to dry for several days until the cut end has callused over.

Then dip the stem in rooting hormone and stick it into a sandy cactus soil mix.

Don’t water the soil until you see new growth on the cutting. Depending on the variety you have, it can take several weeks for cactus cuttings to root.

Taking cuttings from a rotting cactus

Cactus Rot FAQS

Here are answers to some of the most frequently asked questions about troubleshooting common cactus problems. If you can’t find your answer here, go ahead and ask in the comments section below.

Why is my cactus turning black on top?

Because of cactus tip rot. Cactus rot can look black or brown in color.

Why is my cactus turning yellow?

When a cactus starts turning yellow, it’s a sign that it’s probably starting to rot. If only parts of your cactus plant are yellowing, then you can follow the steps above to save it.

However, if the entire thing is yellow, and your cactus is soft and mushy, then you may not be able to save it.

How do you save a dying cactus?

It’s really hard to say how to save a dying cactus without more information. It depends on how it’s dying. Most of the time a cactus will start dying either from tip rot or from bottom rot.

So check the plant carefully to see if you can find any parts that are changing color, or if the cactus feels soft. A soft cactus or a squishy cactus are both signs of rot.

Why did my cactus rot?

As I mentioned above, the main causes of cactus tip rot are either that a fungus or a disease has infected a wound on the plant, or water settled into it.

For a cactus bottom rot, it’s usually caused by overwatering. An overwatered cactus doesn’t always start rotting right away, so it might not be obvious that was the cause.

How do you bring a cactus back to life?

Well… that depends on how dead it is. But if the cactus is completely mush and there’s no green left on it at all, then I’m afraid you’re probably not going to be able to bring it back to life.

If, however, there is still a decent amount of healthy growth on the plant, then you might be able to save it by following the steps above.

What causes a cactus to die?

Overwatering is the number one cause of cactus death, especially for potted plants. A consistently overwatered cactus plant will starting rotting at the roots, and eventually work its way from the bottom of the cactus up.

Signs of overwatering cactus plants are difficult to spot though. Many times once the obvious signs show up (cactus turning yellow, black or brown, or a soft and mushy cactus plant), it’s too late to save the plant.

If you’re unsure of how much to water your cactus plant, I recommend getting an inexpensive soil water moisture gauge to help you get it right every time.

Cactus rot can be super frustrating, but it’s not always a death sentence for your plant. Unfortunately, it’s a pretty common problem with cactus plants.

So it’s a good idea to check your plants regularly for signs of rot. And remember, if you ever notice your cactus rotting make sure you act fast in order to save it!

If you struggle to keep your houseplants alive during the long winter months, then my Winter Houseplant Care eBook is for you! It has everything to need to in order grow healthy houseplants that will thrive all year round! !

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Share your tips for saving a rotting cactus in the comments section below.

Brown Spots On Cactus – Knowledgebase Question

There are a few common cactus pests that fit the description you’ve given, so you’ll need to put on your detective cap, take a magnifying glass, and get up close to your cactus. If the affected areas are bronzed and mottled, the likely problem is spider mite damage. If the patches are corky, it could be due to physical injury, insect damage or sudden chilling. Brown soft patches indicate a rot disease, and hard brown spots can be scale insects.
Based upon your observance that the color is draining out, I’d suspect scale insects. These common pests attach themselves to stems (or in this case pads) and suck the juices out of the tissues. The result is a pale-looking area where the scales are feeding. Try dislodging the spots. If they pop off, they’re probably scales. If the spots won’t peel off, and affect the tissues below the skin of the cactus, they may indicate disease.
After you’ve done a little detective work, let us know the results (via this Q & A platform) and we’ll provide some treatment options.

Cacti are amazing plants and are quite hardy. But even though cacti are hardy, some small mistakes can lead to getting diseases and pests. This happens to most cacti hobbyists, and today we will discuss all cacti diseases, how to recognize and treat them. Caring for cacti’s health is very important for them to live longer and look appealing.

Most cacti diseases are caused by bacteria, viruses, fungi and other microorganisms. It is quite hard to treat a cactus for pests and especially diseases, so it is the best practice to monitor growing conditions regularly. Prevention is always easier than treatment. Now, let’s look at the common cacti diseases and pests.

General tips on preventing and treating cacti for pests and diseases:

  • Check your cacti’s roots every 2-3 months. Many changes take few months to show, and your cactus might be already suffering from pests/diseases. You can find out about many problems by looking at your cacti’s roots.
  • If you use alcohol to treat any pests/diseases on a cactus, make sure to shield it from direct sun for 3-5 days after application. Alcohol and sun can burn cacti’s skin, so shielding it from the sun can help avoid phototoxicity.
  • When treating your cactus for any diseases/pests, make sure to disinfect the pot and the soil (fresh one) before planting your cactus. Otherwise, there is a big chance of reinfection.
  • Quarantine (isolate) your newly purchased or affected cacti. Newly bought cacti might be carrying pests and will cause infection of other plants. Same goes with infected plants – quarantining is a must.
  • Don’t overwater your cacti, as this might cause many problems. Read about watering cacti correctly here.

Cacti diseases

Cactus rotting – dry and wet rot caused by bacteria and fungi

Your cactus might rot due to different causes – mainly bacteria and fungi, but can be also viruses. There might be few reasons that lead to cactus rotting. Rotting is a very common problem that new cacti hobbyists might face.

  • First of all, if you live somewhere with cold winter, you will need to provide your cactus with rest period in a cold spot.
  • What is more, you will need to water you cactus much less in winter. If you overwater your cactus in winter, it won’t use the water, and the plant is likely to start rotting.
  • Another problem that can lead to rotting is underwatering your cacti in spring and summer. Yes, this can lead to dry roots and your cactus won’t grow throughout the active season. This will lead to poor root system in your cactus and it is unlikely to survive winter and will rot.
  • Your cacti need rocky and well draining soil + a pot with drainage holes. Don’t fertilize the soil with manure or other fertilizer with high organic content. If cacti’s soil remains wet for prolonged periods of time, it will cause rot. Stagnant air, high humidity and low temperatures can cause slow water absorption. Read about making the cacti soil here.
  • When repotting your cactus, be careful not to damage any roots and the stem. Any small cuts on the roots or the stem might cause rotting. Read on repotting cacti here. A very important rule is not to water your cactus before and after repotting for up to a week!
  • If you accidentally cut your cactus, its roots or cause any mechanical damage resulting in open wounds, use activated charcoal to disinfect the wounds. Otherwise, it can cause bacterial and other infections.
  • Drying your cactus after washing roots is a must. Hang your cactus vertically or place it in an empty pot.

How to spot if your cactus is rotting?

Rotting can be a slow process if it’s a dry rot, and will be much faster with soft rot. If you notice that your cactus has not grown through the active growing season and doesn’t respond quickly to waterings – there might be a problem with roots. You should also be alarmed if you notice drying out of the stem. Most rotting processes start from roots and work their way up. Regular checks of cacti roots can help you spot rotting early. Wet or soft rotting (black or white spot on the roots and stem) progresses faster than a dry rotting.

Soft rotting will feature wet roots and even stem, with shriveled stem and black/brown spots. A dry rot looks more like a brown spot that spreads through the stem. With a dry rot, the stem becomes dry from the inside, and it is usually hard to notice early.

There are few types of fungi and bacteria that cause cactus rotting. For example, Phytophtora cactorum fungus causes a rot to the roots and the plant stem. Rot progress quickly, so you need to act fast. This type of rot has a ‘classic’ look – wet and black roots and dying of the plant. Your cactus is likely to get this infection if you leave any untreated cuts on the plant.

Dry cactus rot caused by fungi

Diplodia, Phyllosticta concava and other fungi cause black spots on the cacti, leading to dry rot. You can also notice prominent brown/rust-colored spots (causing dryness on the cactus) often surrounded by brown rims, all of which also mean rotting of the cactus. Act fast and remove affected parts of the plant.

Otherwise, you will notice the black/brown spots get larger. If you can’t cut affected parts, then quarantine and the best thing is to get rid of the cactus completely. You can also try fungicides, but they usually fail to treat the plant fully.

Soft cactus rot caused by bacteria

Wet, or soft rotting is usually caused by bacteria in the genus Erwinia. Wet rot usually follows any damage or cuts to the cactus, and that is how bacteria enter the plant. The main symptom is softening of the stem, which can also become dark in color, coupled with black spots. You will need to cut off affected areas to treat your cactus.

Wet or soft cactus rot

Yellowing of a cactus

You might also notice yellowing of your cactus, and there might be few causes of this. First of all, yellowing of a cactus might be a symptom of nutrient deficiency. If you notice yellowing of the cactus, which often affects top parts of the plant, use some fertilizer to feed the plant.

But what is more, yellowing might be the symptom of viral/bacterial disease, and is usually called ‘cactus jaundice’. There is no treatments for cactus jaundice, which leads to rot and dying of the plant. If fertilizers don’t help, it is probably the jaundice. Affected cactus can die in few months or few years.

How to prevent and treat cactus rotting

To prevent cactus rot, make sure to follow the tips mentioned above (mainly watering and winter care). What is more, make sure to spray/mist your cactus once a day in the evening (during its growth period). Cactus is mainly opening its stomata at night – to reduce water loss. Misting the plant will remove any dust, prevent any mold and help your cactus breathe and evaporate water.

Check your plant’s roots once a month to make sure there is no rotting. If you see your cactus rotting, you can still save the plant if the infection hasn’t spread heavily.

If the roots have become black and thin or with any type of rotting, you will need to clean the cactus, remove dead roots and cut off affected parts. For this, you will need to sterilize shears or scissors (use fire or rubbing alcohol), and cut all the dead roots and all rotten parts, even up to a stem if needed.

When cutting, make sure there are no black or brown spots on the stem, and keep cutting until you are left with clean, green stem. Then, wash your cactus and its roots in a warm water and make it a warm bath.

Corking of a cactus vs. sunburn (phototoxicity)

Corking of a cactus can look similar to a burn. While corking is a natural process of an aging cactus, sun burn is negative for your cactus.

Corking will look like brown cork around the plant’s base, and there is nothing to worry about. If it’s corking from the top, there is another problem, such as mites. Corking can also be a result of improper conditions and care.

Sun burn is caused when you let your cactus face direct sun light straight after rest period, without shading it beforehand. Same happens when you use any pesticides or alcohol on the cactus and let it sit under the sun. Too much sun will burn plant’s epidermis, preventing it from breathing and growing. Any burnt areas become brown and can’t be treated.

Please note that if your cactus becomes purple or red, this can be normal if you have prepared your cactus for direct sunlight. This can happen in prepared cacti or if your cactus has been experiencing cold winds (which means that your cactus is too cold).

Burnt cactus

Underwatering/overwatering cacti

Overwatered cactus that started to rot

Both underwatering and overwatering cacti is a big problem and can kill plants. Many new hobbyists make these mistakes, and end up kill the cacti.

Overwatering: all cacti are succulents and they store water in their cells. If you overwater your cactus many times (especially need to be careful in cold weather and winter), it will start rotting. You can also cause rot or rupture of cacti cells.

To treat overwatering, you need to take out the cactus out of the pot and let it and the soil dry out before potting it again. Give your cactus roots a warm bath and hang it vertically to dry for 3-4 days before repotting. If it started rotting, cut the affected areas and use the fresh soil for repotting. Some cacti can burst if overwatered, so you will need to wait for the scar to heal.

Underwatering: There is a big myth that cacti don’t need water, but that is not true. If you don’t water your cacti, especially during the growth period, it will shrivel and go dormant to survive. In this case, don’t expect any growth or flowering. Make sure to water your cacti right throughout the year. Read about watering cacti here. Many underwatered cacti lose their roots, so you will need to water them with little water and increase amounts gradually. Make sure that your cactus dries between waterings.

How to treat sun burnt cactus

Burnt cactus

While corking is natural, you will need to treat sun burnt cactus. If you notice that your cactus becomes weak and brown, take it to the shade immediately, spray it with water and cover with a small bag. Leave it there for few days and take it out. Shield your cactus from direct sun and prepare it for summer. Read more about sunlight requirements and preparing your cactus for summer here.

With mild burns, your cactus will continue growing and will have to grow out of the burn. The brown spot will remain and heal. But with severe burns, your cactus might stop growing at all and die. Make sure to increase time in the sun gradually, especially after the rest period.

Frost damaged cactus or damage caused due to cool temperatures and wind

There are different reasons why your cactus might get sick due to cold weather or water. For example:

  • You have left your cactus on a cold windowsill
  • There is conditioning in the room and your cactus has been cold
  • You have watered your cactus with cold water. Please remember that you need to water your cactus with warm water (read about how to water cacti here).

Your cactus might also become ‘sick’ if it experiences cool weather and watering, which can cause rotting. Anyways, you will notice if your cactus has become frost damaged – it will shrivel and turn dark brown to black after few days of frost. Rotting in case of cold weather or water will have classic symptoms. Not all cacti can survive cold temperatures, and some can only survive them for short periods of time.

There is nothing you can do to treat affected areas of damaged cactus – you will need to change the conditions immediately and wait for your cactus to ‘grow out of it’.

  • Pests affecting cacti

Red spider mites and cacti

Your cacti might also become infected with mites. Red spider mites are ones that can attack your cactus and kill it by sucking its juices. Spider mites are very small and red in color. They can live and multiply in the soil all year round. You might not see spider mites, but they will also create small webs around the plant. Your cactus will start becoming dry and brown, because mites will drink the cactus juice from the stem.

Affected spots will have a rusty brown color. Spider mites like attacking fresh parts of the plant, which is usually from the top. This can look like corking of the cactus, so you can use a magnifying glass to examine the cactus for mites. Cactus will need to grow out of the infestation, and after you have treated it for red spider mites, it will have fresh growth from the top and will remain brown part on the bottom. Mature red spider mites can be yellow-greenish in color, but also red (especially those that are brumating).

How to treat your cactus for red spider mites?

Red spider mites reproduce quickly in dry areas with stagnant air and high temperatures. They hate higher humidity and fresh air, so make sure to have fresh air in the room. As they reproduce quickly, you need to quarantine your plant. Check all the plants with a magnifying glass and transfer affected ones to a different room.

Then, start treating your cactus or cacti. Length of the treatment will depend on the season and how affected the plant is. You will need to get a pesticide or arachnicide to kill the spider mites. Most insecticides won’t work as mites are not insects, so make sure to pick one that targets spider mites, such as this natural non-toxic pesticide. When treating your cactus, make sure to shield it from the direct sun to avoid burns. In summer, when it is hot, you will need to continue the treatment for a bit longer.

Mealybugs on a cactus

Mealybugs are very common pests that attack different parts of the cacti – roots, stem, spines etc. They reproduce quickly and will suck its juices. If untreated, they will kill your cactus. Mealybugs on a cactus will have a white residue or spot look that can also look ‘fluffy’. As soon as you notice this fluff, start the treatment immediately. Otherwise, your cactus will become weak and die.

How to treat cactus for mealybugs?

Mealybugs will reproduce quickly, so act as soon as you notice them. You will need to quarantine your cactus and spray it with pesticide until the plant is free of them. The ‘fluff’ on mealybugs protects them from pesticides, so you will need to start the treatment by water spraying the cactus with high pressure spray, to physically remove them.

What is more, you can use cotton buds dipped in alcohol to physically remove them. Alcohol will dissolve their outer layer and will kill them quickly. After spraying the plant and removing mealybugs physically, use pesticide spray.

If your plant is weak and has stopped growing, you might check its roots – some mealybugs hide in the soil and affect roots. You will see the same white ‘fluff’ on the roots. In this case, you will need to wash the roots in warm water (gradually move to hot water), then dip the roots in the pesticide solution and repot your plant.

Make sure the roots are dry before potting the plant. If roots are affected, try giving a few hour warm-hot bath and drying your cactus by hanging it vertically before repotting. Make sure to disinfect a pot and use fresh soil.

As mealybugs are very common pests, you can use a systemic insecticide to prevent any mealybug infestation at the start of the growing period.

Aphids on a cactus

Aphids are small green bugs, but sometimes they can be grey or yellowish. These small bugs are often found in groups and suck the juices out of cacti’s stem and kill the flowers. Aphids are usually seen with ants.

How to treat a cactus for aphids?

It is possible to kill aphids without using any chemicals. Start the treatment by quarantining your new or affected plants. Use a high pressure water spray and try to remove all the bugs from the cactus. If spraying the cactus with water doesn’t help, you can make a DIY solution at home at clean your cactus with it.

To make it, mix some soap with water and spray your cactus with it. If nothing helps, you can use an insecticide. You can also rub your cactus with rubbing/methylated alcohol.

Cactus scale

Scale can attack many types of cacti. Scale insects infect cacti and start sucking out the juices. They move in colonies and also have a whitish coating, similarly to mealybugs. Scale bugs multiply very rapidly and usually cover specific spots on the cactus, sucking the juices. These bugs move around very slowly, and it can seem like they are still.

Scale bugs are brown in color (females have white coating). They can also be yellow, and there are many other types of scale bugs. Affected areas of cacti will become dry and have white or yellow spots. The whole plant will have a white fuzzy look, but if you look closely – bugs will be most probably brown, covered in white fluff.

Sometimes you can mistaken the rotting for scale bugs. To check that, use tweezers to dig under the brown spot. If you can see a wet residue but the skin remains untouched- these are scale bugs. If the infection is under the skin and you can’t remove it – these are fungi or bacteria.

How to treat a cactus for scale bugs

Scale bugs multiply very quickly, as well as suck plant’s juices and leave scars. That is why it is important to act quickly. Make sure to quarantine an affected cactus. First of all, start the treatment by spraying your cactus with high pressure water from a sprayer or a hose. Your can also try to remove scale bugs physically by using tweezers or cotton buds soaked in rubbing alcohol. If you rub alcohol on the cactus, make sure to shield it from the sun for around 2-3 days after application. Otherwise, it will cause burns, also known as phototoxicity.

Scale bugs tend to come back easily, to repeat the treatment until they are all gone. Also, at the beginning of the growing season, you can use a systemic insecticide to prevent scale bugs, especially if your cactus had them before.

Nematodes on a cactus

Nematode bugs are very parasitic and affect the plant’s health drastically. They hide in the soil, so owners usually find out about the problem quite late. This is why it is important to check your cacti’s roots from time to time, to make sure they are healthy. Nematodes are very small bugs and are not visible to an unaided eye.

The symptoms of nematode infection is the slow growing cactus and changes in the stem color. Cactus becomes weak and loses its vivid green coloration. And when you look at the roots – they will look swollen (also called galls), thick and often brown because rotting has started to progress. Nematodes hide in the roots and block the movement of water and nutrients to the cactus, making it weak. Another way to check for nematodes is to soak the roots in the jar with water – and if you notice small black dots left on the walls of the jar, this indicated nematodes.

How to treat a cactus for nematodes

Reinfection is very common with nematodes. This is why you will need to get rid of the soil and disinfect the pot with boiling water and soap.

As nematodes are not insects, no insecticides or pesticides will help to get rid of nematodes. You will need to cut all the affected roots on the cactus to help it get better. Make sure to cut the roots with disinfected shears or scissors. After cutting the roots, put some ground charcoal on the plant and pot it in a fresh soil. Before potting your cactus in the fresh soil, you can give it a bath with water temperature of around 131 Fahrenheit (55 Celsius) for 20 minutes, and drying it by hanging vertically for 4-5 days.

To prevent nematodes, make sure to quarantine new plants and check them before adding to the collection. What is more, you must disinfect the soil before using it for a cactus. Read about making and disinfecting the soil for cacti here.

Thrips on a cactus

There are thousands of thrips types, but not many affect cacti. Thrips are usually either green or grey-black in color. One of the thrips that can affect your cacti is called Heliothrips haemorrhoidalis, also called greenhouse thrips or black tea thrips. Thrips are very small in size, around 1.5 mm in length and can live all year round in the soil of indoor plants.

How to treat a cactus for thrips

Thrips are very small and will be problematic to kill. The best solution for treating a cactus for thrips is to use cotton buds soaked in alcohol, removing them manually. This is not likely to remove all of them completely, so you will need to use pesticides and systemic insecticides during the growth season to get rid of the thrips. Make sure to dilute pesticides greatly to avoid burning the plant.

Fungus gnats on cacti

These fungus gnats are small black flies. They look similar to common flies, but are much thinner and smaller in size. Adult fungus gnats are harmless and don’t cause any damage to your cactus. But you should be careful, because gnats’ larvae in the soil are ones that cause damage to your cacti.

Fungus gnat larvae look like white worms with black heads, and are around 4 mm in length. Larvae feed on organic matter in the soil as well as roots of the cacti. Because of fungus gnats, cactus stop flowering, becomes weak and stops growing.

How to treat a cactus for fungus gnats?

As fungus gnats enjoy living in the moist soil, you will need to dry the soil a little. Don’t use any manure or other fertilizer with high organic matter. To kill adult fungus gnats, use sticky traps that you can hang around the cactus. To get rid of larvae, you will need to either dry the soil + use an insecticide, or repot your cactus into fresh soil. Avoid overwatering your cacti.

Woodlice/slugs/snails/caterpillars/worms on a cactus

Damaged cactus

Snails as well as slugs are small molluscs that are mainly active at night. There is a small chance that you will get snails or slugs indoors, because they prefer staying outside to survive and to avoid drying out. You will know that your cactus was damaged by snails or slugs if you notice a slime lines across the plant. Snails and slugs mostly enjoy eating flowers, seedlings as well as fresh grown parts of the cactus.

Woodlice also become active at night and enjoy eating fresh parts of the cactus. Caterpillars and worms often affect prickly pear cacti, hiding in the plants and laying their eggs on a cactus – which later hatch and damage the plant.

How to treat your cactus for woodlice/slugs/snails/caterpillars/worms

Make sure to check around and under the plant to find any snails and slugs. To kill them, you will need to physically catch and remove them by hand. If plants are outdoors, you can come out at night and look for them – they are very likely to come out when the sun goes down. Another good way to get rid of snails and slugs is to put some bait around the cactus or directly in the soil. Make sure to use a non-toxic bait, such as this Garden Safe Slug and Snail bait. Same goes with worms, caterpillars and woodlice – you will need to catch and kill them or use a bait.

Mice and birds attacking cacti

Some mice and birds might attack and eat your cactus. This is very common, and many rodents and birds are not afraid of cacti spines. Mostly, only outdoor cacti suffer from bird or rodent attacks, and this might happen when you are not looking. If a big piece of your cactus is gone, or you can see multiple small holes overnight, this is most probably an animal attack.

How to prevent rodents and birds from attacking your cacti

The most disappointing thing with rodent or bird attacks is that you won’t be able to bring your cactus back to its normal condition. The only thing that you can do is to fight them by covering the cacti or setting up traps & poison. With poison, be cautious if you have any pets or children.

Bud drop: The premature dropping of flower buds. The cause of this problem is primarily environmental. Temperature fluctuation due to drafts is commonly seen as a cause. Bud drop can also be caused by the lack of or excess water and changing light levels. In Christmas cacti, a lack of potassium or an excess of nitrogen can also cause this problem. Sometimes buds fall off a cactus simply because the plant has too many blossoms. Rough handling or turning a plant also will cause buds to abort.
It is important to maintain the care that a flowering cactus is used to when it is in bud. Resist moving your cactus to another site if it has buds or open flowers.
Corky scab: Brown, irregular spots developing in older parts of a stem. Most of the spots affect the epidermis of the plant only, so, damage is superficial and only affects the appearance of the plant. More severe or widespread attacks can destroy entire shoots or decrease flower production. Corky scab is normally the result of poor cultivation (i.e. overwatering, poor ventilation).
To control, increase light exposure and decrease humidity. The prickly pear (Opuntia sp.) are particularly prone to corky scab.
Etiolation: The abnormal elongation of cactus stems due to insufficient light. Stems may be pale or yellow with unusual spine characteristics. Commonly seen in plants taken from a commercial nursery into a dimly-lit retail environment. This may also occur if a cactus is fertilized while in its normal Winter dormancy period.
To correct etiolation, move the cactus into stronger light. While this will prevent further etiolation, the spindly elongated section of stem will remain as proof of improper care. You may also choose to prune the etiolated stem back to the healthy part; this acts to promote the growth of ‘perfectly-shaped’ offshoots or stems that may be removed and re-planted.
Rot: Rot is caused by microorganisms: fungi and bacteria. It may affect the roots, stem, and/or the crown of the plant. Typically, the diseased tissue takes on a watery, slimy, soft, and blackened appearance. Damage often starts at the base of the plant and progresses to the top. Plants start to lean, then often collapse and die.
Overwatering, particularly in cold weather when cacti are dormant, is the chief cause of the problem. The disease-causing organisms thrive in moist conditions. Cold temperature and plant wounds aggravate the problem.

In theory, rot in its early stages may be checked by moving plant to a dry, temperate environment. It has been our experience that once you spot rot it is already progressed past its early stages. If rot is above ground, cut out the diseased portion of the plant with a sharp knife and dust the wound with a fungicide. In many cases, the top of the plant appears healthy above a rotten base. This healthy top may be cut off, allowed to dry, and then re-rooted in a sandy medium. Remove and destroy infected plants and/or plant parts.
Proper cultural practices help to prevent rot. Sterilizing the potting media and placing a layer of gravel on top of the soil will kill or reduce bacterial damage. Water plants early in the day and avoid spreading disease by splashing water from one infected plant to a healthy plant. In Winter, the normal dormancy period for most cacti, water sparingly.
A partial list of rot-inducing microorganisms include: Fusarium oxysporum, Phytophthora parasitica, Pythium aphanidermatum, Bipolaris cactivora, Erwinia carotovora.
Sunburn: A change in the appearance in the plant due to too much exposure to the sun. The entire plant epidermis will turn a whitish, yellowish or reddish-brown color. In extreme cases, a sunburned plant may become sensitive to other diseases.
As mentioned, this disease is caused by too much light exposure. Typically, this occurs when rapidly bringing plants used to artificial light into intense natural light. Epiphytic cacti and seedlings are especially sensitive to sunburn. To prevent, a cactus should be gradually introduced to more light over a period of time. Plants should be placed into the shade, then into partial sun, and finally into full sun; this process may take one month. If you notice signs of sunburn, move the plant temporarily back into the shade. Also, sunburn is aggravated by hot weather and lack of water, so, make sure the plant is properly watered.

Cactus Fungus Treatment – Learn About Fungal Lesions On Cactus

Fungal issues plague almost every form of plant. The sheer number of fungal organisms is staggering and most survive dormant for long periods of time. Fungal lesions on cactus may be caused by any number of fungal types, but the important things to note are what causes them to colonize and how to prevent their damage. In this way, the gardener is armed with knowledge on how to treat fungus on cactus should any disease symptoms develop. Some fungal diseases simply cause cosmetic damage while others can develop into rots that completely eat the cactus from the inside out.

Types of Fungal Damage in Cactus

The vast amount of cacti species can only be outcompeted by the huge quantity of fungal varieties. Fungus spots on cactus pads are common, as in the case of Phyllosticta pad spot. It is often quite impossible to diagnose which fungal organism is causing the spots, but often that is unimportant since treatments are generally the same.

A few fungi types damage the roots and eventually the whole plant, so once their visual damage is seen, it is too late for the plant. Simple topical fungal spots are much easier to combat and are usually not life threatening to the cactus provided steps are taken to control the offending fungus.

Lesions on cacti may present in many different ways. They may be round, irregular, raised, flat and any other shape. Many are discolored but, again, the tones can range from yellow to brown and all the way to black. Some are corky, while others are weepy. These may ooze brown, rusty or black fluid, evidence of severe infection.

The cacti most frequently plagued by fungal lesions are Opuntia and Agave. Fungal lesions on cactus usually start as water spots or slight discolorations on the plant’s epidermis. Over time, as the fungi mature and spread, the symptoms can broaden and even eat into the cambium as the surface skin cracks and allows the pathogen to enter.

Causes of Fungal Lesions on Cactus

Outdoor cactus can come in contact with fungal spores in various ways. Spores may be blown in from wind, in soil or contracted from splashing water. Plants with consistently wet pads or stems are the worst affected. Conditions where rain or high humidity combine with warm temperatures promote the formation of fungal lesions.

Fungus spots on cactus pads are more prevalent in the springtime. They are also enhanced by overhead watering and in areas where humidity is high. Greenhouse specimens may be particularly susceptible unless there is adequate ventilation. Condensation adds to the ambient humidity and promotes spore growth.

Soil is another contributing factor. Many soils harbor fungal spores, which can persist for years until the right set of conditions occur. Even purchased potting soil may be contaminated with fungal spores.

How to Treat Fungus on Cactus

Once there is a fungus affecting your cactus, it can be difficult to stop. If damage isn’t severe, a fungicide spray can usually help. If the plant is rife with lesions, it may be best to find some uninfected healthy material and start a new plant with a cutting. Use a sterile knife to take the cutting and dust it with sulfur to kill any possible adhering spores.

Controlling cultural conditions with plenty of heat, under stem watering, sterile potting medium and ventilation will halt many fungal outbreaks. Another way to save a plant is to cut out the infected tissue. This doesn’t work with all fungi, but it may be effective at times. Again, sterilize your cutting implement and remove more tissue than appears to be affected to ensure all the pathogen is removed. Keep the area dry as it calluses and watch carefully for signs of reinfection.

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