How to Get Rid of Cactus Fungus
Just like any other plant, your cactus can develop a fungal infection. Although some fungal infections do little damage to cacti, others that are left untreated can lead to the death of the cactus. For the best chances of success, treat your cacti at the first signs infection.
Types of Fungal Damage
The vast amount of cacti can only be outcompeted by the huge quantity of fungal varieties. Fungus spots on cactus pads are common. 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 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 Opuntias. 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
Outdoor cactus can come in contact with fungal spores in various ways. Spores may be blown in from the 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
Once there is a fungus affecting your cactus, it can be difficult to stop. If the 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.
- Succulentopedia: Browse succulents by Scientific Name, Common Name, Genus, Family, USDA Hardiness Zone, Origin, or cacti by Genus
Subscribe now and be up to date with our latest news and updates.
You Will Need:
- A shovel
- An ax or chainsaw (for large cacti)
- Pruning shears (for small cacti)
- A garden hoe (optional)
- Thick gloves
- A long-sleeved shirt
- Long pants
- Gardening boots
- Protective goggles
- One or more thick cardboard boxes
- A magnifying glass
- Salad tongs
Follow These Steps:
Before you do anything else, put on protective clothing. Wear a long-sleeved shirt, long pants, gardening boots, and thick gloves like the ones in this article about the best gardening tools. It’s wise to also wear protective goggles, especially if you’ll be cutting a large cactus.
Cut The Cactus With An Axe, Chainsaw, Or Pruning Shears
Image credit: flickr.com
An ax or chainsaw will work better for a large cactus, whereas pruning shears, like these, will suffice for a small cactus. Starting from the top of the cactus, cut off a little at a time until you reach the soil line. Don’t cut it from the base or it might fall on you!
A garden hoe is useful for gathering the severed pieces together. Using salad tongs, put them in a thick cardboard box. If you leave any on the ground, they may grow into new cacti.
Cut The Main Root
With a shovel, dig about 2-4 inches (5-10 centimeters) into the soil. When you see the main root, chop through it with the shovel or ax.
Dig Up The Roots
Image credit: flickr.com
Dig up as much of the root system as you can, being careful not to step on any spines that could go through your shoes. Put the root pieces in a cardboard box, as these, too can grow into new plants.
Remove Needles From Your Clothes And Shoes
Image credit: flickr.com
Check your clothes, gloves, and shoes for cactus needles. If you find any, pull them out with tweezers and put them in one of the boxes containing cactus pieces. You may need a magnifying glass to see some of the needles.
Dispose Of The Boxes Carefully
Dispose of the piece-containing boxes immediately. If the cardboard boxes become soft and decompose, the cactus pieces inside might root themselves in the ground.
Be considerate towards garbage crews who might poke themselves on the pieces. This could happen if the boxes get wet or if you don’t seal them thoroughly.
If you expect a garbage crew to load them into a truck by hand, seal the boxes with tape and put them in a garbage can. However, the best place for the boxes is in a dumpster or trash can that will be emptied by a machine.
1. What causes black spots on cactus?
There are a lot of factors that may trigger the appearance of black spots in your cactus. In general, we can categorize them as abiotic and biotic factors. The abiotic are the non-living organisms while biotic are the opposite.
It would be difficult to assess the problem at first glance but it helps to be familiar with the signs and symptoms of each cause. This will help you decide on which solutions are appropriate.
2. What do white spots on a cactus mean?
White spots in cactus are possibly caused by pests/insects that have found shelter on the plant. Specifically, the Cochineal scale (Dactylopius coccus) appears as white cottony tufts on the surface of the cactus pads.
Powdery mildew is another reason for the white spots you see on your cactus. It’s a disease caused by a fungus.
3. How do you get rid of white fungus on cactus?
To remove white fungus from your cactus, you’ll need to apply fungicide on the infected portions to eliminate the fungus. You can also use baking soda and soap water as natural alternatives.
If infection persists, you’ll have to cut the damaged portions. Provide a better air circulation around your cactus. To slow down reproduction of spores, avoid putting your cacti in a wet environment.
Cacti plants may have established the reputation of a hardy plant but it doesn’t mean it can’t be vulnerable. Every plant has a weak point and your cactus surely has its own. But it doesn’t mean you can’t be successful in keeping it indoors.
Black spots may appear as normal in the beginning. However, it does speak a lot about the general health of your cactus. It’s best to investigate and find solutions early than make regrets in the end.
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.
Common Succulent and Cactus Pest Problems
While other bugs might occasionally snack on these cactus plants and succulents, they’re usually not found in high enough numbers to cause any real damage – like that of cactus beetles. But the three most common offenders you may come across include the following:
Fungus gnats, similar to those pesky little fliers (fruit flies) that surround bananas and other fruit when it is a tad too ripe, may linger on or near your plants. Too much water in the soil attracts them. Avoid overwatering succulents to help keep fungus gnats away.
If you’ve soaked your plants and then notice succulent and cactus pest problems like this, let them dry out. For houseplants, put them outside to speed up drying when temperatures permit. If soil is soggy, unpot and remove soil from roots to avoid rot. Rot develops quickly on wet roots and stems. Then repot in dry soil.
A swarm of small bugs around new foliage are usually the dreaded aphid. You may notice cottony threads among the young leaves. These bugs are about 1/8 inch and may be black, red, green, yellow, or brown their color depends on their diet. Aphids suck the sap from new growth, leaving foliage crinkled or stunted. These pests spread rapidly to other plants.
Treatment varies if plants are indoors or outside. A blast of water usually dislodges them and they do not return. Houseplants often can’t be blasted with a spray of water. If foliage is too delicate, use an alcohol or horticultural spray. One application will usually take care of aphids, but keep check to make sure they’re gone and check nearby plants.
Root aphids are a different variety of these pests that feed on the roots of your succulents. If your plants are yellowing, stunted or just not looking well, check for root aphids. Loss of vigor and no other visible pest or disease symptoms is a good reason to unpot and look.
These sneaky ones try to hide beneath the rootball, although they are sometimes found on top of the soil. Make sure you unpot outside, or at least away from other plants. A systemic insecticide or products containing Spinosad, new soil, and careful monitoring can help keep root aphids away. Dispose of infected soil far away from anything you are growing.
A white, cottony mass on your plants often indicates the presence of mealybugs. Eggs overwinter on woody stems and crawlers hatch in spring. These suck juices from soft spots on your plants, causing distorted growth and weakening the plant. As crawlers suck on the leaves, they develop a waxy coating that protects them. Feeding crawlers mostly stay in the same spot unless moved to another plant by ants.
Ants covet the juice (honeydew) produced by feeding mealybugs and aphids, protecting the pests in their symbiotic relationship. Alcohol or horticulture soap spray dissolves the protective exoskeleton, eliminating the pests. Again, more than one treatment may be needed. Alcohol is available in handy spray bottles. Both 50% and 70% types work for treating pests.
Don’t let these pests of succulents or cacti keep you from enjoying your plants. Learning what to look for and how to treat them is all you need to keep these plants looking their best.