Cochineal vs Cactus

When you look at the white spot covering on Opuntia, do you think it's from fungus or insect?  The answer is from an insect infestation. The white sticky mounds are the housing for cochineal bugs (also known as mealy bugs.  


 The white sticky mounds are the housing for cochineal bugs (also known as mealy bugs)  All of the host plants of cochineal colonies were Opuntia species. Cochineal feed on plant moisture and nutrients.

Like the aphid (a related insect) the female drives her tubular proboscis through the cactus skin, where she will remain affixed for the rest of her life, sucking out the juice.  Simultaneously, she produces a white, waxy, fungus-looking coating that will help protect her from predatory insects and birds and shade her from the desert sun.  However, she sometimes fall prey to a rare carnivorous caterpillar and more commonly, to our good friend, the ladybird beetle.  Over time, a heavy cochineal infestation can kill its resident plant. 

However, Cochineal has industrially important insects because Cochineal can produce scarlet, orange, and other red tints. The  colors are produced from carminic acid which is today primarily used as a natural dyeing for food, pharmaceutical and cosmetics industries .  And seriously, there are cochineal farms for export in some countries such as Peru, Australia, Mexico, Chile.

If you don't want cochineal on your healthy plants, it’s suggested to treat  the damaged areas by scrubbing them with insecticidal soap or unscented dish soap. In small areas you can scrub with a tooth brush but for larger areas it is best to use a long handled brush. Or you can just spray all of the surfaces of the prickly pear pads thoroughly using a power nozzle attached to your hose and then thoroughly spray with a solution of spectraside and insecticidal soap. Do not rinse after applying the spectraside and insecticidal soap.

source: http://www.desertusa.com, http://www.thecactusdoctor.com, http://en.wikipedia.org

What to do when cactus is rotting???

The before picture. 
when my mammillaria was still healthy in the big pot

Thailand is in the rain season now and some cacti in my garden were also rotten.  At this time, it happened with my favorite mammillaria which became rotten and I just noted it recently.  So I think it’s important to fight with rotting seriously although before that, I led the plant rot without do anything. Here is the way to do that and hope it’ll be helpful when you have same trouble like me.

• How do we know or notice that the cactus is rotting?

The brown base of can mean that the plant is aging (become woody) or rotting. To tell the difference, touch the base and see if it is hard or flabby/soft. Hard means everything is OK. But, it’s soft, it means that plant is rotting and it must be treated with care.  

Here is after picture.  It was so soft and I had to cut some rotten part out and dried the rest for 3-4 days together with the rotting aloe

• Can I still save the rotting cactus? 

The second way to save a rotting cactus is to simply cut of its top.  Using a sharp knife cut off the top of the plant.  After that, let’s it dry for a 2-7 days. Once dry, set about 1/2 the plant into potting mix/perlite or cactus mix/perlite.

Do not water too much. Just enough to make the soil to become a little humid. Over watering at this point could cause rot again. With luck and the right conditions it will start to root. Once it develops its own roots, the watering can be increased.  Establishing the new roots may take several days or weeks depending on the condition of plant and care.

I put them on top of pot with 100% perlite

After several days with humid from rain, the new root came out finally! 

Another option is to take a cutting or two for grafting which need skill & experience to do that.

• What if my cactus is rotting from the top? What shall I do?

If a cactus is rotting from the top you need to act immediately before more of the cactus rots. Just like as if it is rotting from the base, carefully cut off the top of the cactus that is rotting. Dispose of the cactus top.

As for the bottom, clean it with a spray to make sure it does not catch the top's disease. Change the soil unless it looks as if the cactus can't take a repot. The remaining cactus should now be healthy. After a few weeks of extra care, start caring for it as for a normal cactus. It will not grow a new top or increase in height but it will grow branches which will grow.

Source: http://www.botanicalgarden.ubc.ca,  http://www.alexandgregory.com/

Cactus vs Fungus

Here are the fungus found normally in cactus.

1. Cactus Anthracnose (fungus – Colletotrichum (Gleosproium) spp): This disease affects several kinds of cacti, cereus, echinocactus, mammillaria, and particularly, opuntia (prickly pear). Infection results in a rather moist light brown rot that shows many light pink pustules on the surface. Spots are small at first, later enlarge, and become covered by the small spore-producing pustules. 
Large areas may be affected, sometimes destroying entire plants. No satisfactory control is available, other than removing and destroying diseased cladodes as soon as noticed. In the greenhouse, soil from infected plants should be removed and benches disinfected. Spraying with a copper fungicide may help in checking this disease.

2. Scorch or Sunscald (fungus – Henersonia opuntiae): This disease is common and

serious on prickly pear cactus (opuntia). Spots at first are distinctly zoned, later enlarging until entire cladodes turn a reddish-brown and finally die. The center of the disease area is grayish-brown and cracked. Other fungi may be present in the diseased area. No practical control has been developed.

3. Cotton Root Rot (fungus – Phymatotrichum omnivorum): Several members of the

cactus family are susceptible to attack by the cotton root rot fungus. Infected plants die.  When pulled from the soil the brown strands of the fungus can be found growing on the root surface. No control practice is available.

4. Scab (physiological): Particularly common on prickly pear cactus. Rusty colored, corky areas appear on the stems. Scab is thought to be a form of edema, resulting from over watering and poor ventilation. Increase light and decrease humidity for control.

What to do when cactus are infected?

•        Quarantine and remove infected plant material.  
•        Repot and cut off the infected area if it’s not severe and it’s possible to cut.  Cut behind the infection so that you can throw the fungus away entirely.  If it’s severe, destroy affected plants and their pots.
•         Set the environment of your greenhouse or garden to be more appropriate for the cactus.  The causes of fungus are sometimes poor ventilation, light or humidity.
•          Dust the both infected and healthy plant with Bordeaux mixture or another fungicide.  

Preventing the fungus 

1. Back the basic, pay attention and take care of your plants closely.  Mostly, the infection can invade your garden when you don’t have time to check or care the cactus.  (This case ever happened with me, too)

2. Get rid of the fungus/infection as soon as you find it.  The earlier to figure the fungus, the easier to control it.

3. Giving more time to spray the fungicide (every one or two weeks), repot and fertilize the plants.

Every plant is same; cactus, succulent, orchid, rose or else.  If you take care of it well, it will grow up greatly and make you proud. 


If you have any comment or question, please feel free to contact me :)

Cactus Diseases

Although we take care of our cacti carefully, it is perfectly sure that our plant will not have any diseases. And when they happen, it will be a serious problem because it can cause the plant die if we don't know how to deal with the disease properly. Today I also give you information of some diseases that always see.




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. Cold temperature and plant wounds exasperate 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.

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 exasperated by hot weather and lack of water, so, make sure the plant is properly watered.