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Full Guide on Cactus Diseases, Pests And Treatments

Cactus Diseases, Pests And Treatments

Cacti diseases can affect all Desert plants. Some pests specifically attack certain species. It is important to be aware of the most common pests and diseases, so that you know what to look out for and can take action quickly to stop the spread of disease to your other plants. Treating cactus pests and diseases quickly is imperative to maintain healthy tissue and healthy cacti's roots for your amazing plants to thrive.

Desert Plants

Cacti pests and diseases can be treated with Organic (natural) pesticide, Non-organic plant invigorators, biological controls and synthetic insecticides. At Desert Plants Ltd we believe that avoiding pests and diseases by using good hygiene practices in cultivation, introducing natural enemies and fertilising cactus and succulents should be used first line, to build up their natural defences. Because healthy plants are more resistant to pests and diseases!


If systemic insecticide or contact insecticides are used, this should be used in a minimal and targeted manner. As not only can these treatments be of danger to bees, butterflies or other pollinators, they can also kill of other non-target beneficial insects which are already protecting your cacti from other cacti diseases.

How to treat cactus pests and diseases?

How to treat cactus for mealybugs?

Mealybugs are probably the most common pest encountered by cactus growers/hobbyists. They are microscopic bugs, with a white-cottony appearance and can be a challenge to remove! Quarantine the diseased desert plant as soon as possible.


How to treat cactus mealybugs?

Mealybugs can be treated using these first line methods:


1) Physically remove with damp cotton swabs and spray the entire plant with a high pressure water spray, to blast off any remaining bugs.


2) Spray with soapy water. Kills pests by mode of suffocation.


3) Spray using 70% or less solution of isopropyl alcohol diluted in water. CAUTION: High concentrations or undiluted alcohol solution can cause severe burns or scars to cacti plants. Inhibits pests wax coating and results in fatality.


4) Organic (natural) pesticide such as Neem oil (also a fungicide) can be sprayed onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


5) Non-organic plant invigorators are considered environmentally-friendly pesticides. Contains surfactants and nutrients or fatty acids and algae extracts, which also promote the optimal nutrition of plants. Spray onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


4) Biological controls boost the population of natural predators. The Cryptolaemus montrouzieri ladybird is a natural predator of mealybugs and can be introduced to greenhouses. Both ladybird larvae and adults are able to seek out and destroy mealybugs and their eggs! Another effective predator of mealybugs are parasitic wasps (Leptomastix spp/ Leptomastidea spp and Anagrus spp). These are both available by mail order.

Avoid releasing biological controls for 2+ weeks since last use of insecticides.


If your mealybug infestation is not successfully treated with a first line method, consider using the below as a last resort.


6) Synthetic Insecticides (contact action/systemic action) kill by direct contact or through ingestion of plant materials. Synthetic insecticides should be used with caution as these can damage the environment. They can also destroy other useful predators which may be protecting your cactus or succulent plants from other pests and diseases.


PLANTS IN BLOOM SHOULD NOT BE SPRAYED AS THIS CAN HARM BEES AND OTHER POLLINATING INSECTS.

 


How to treat a cactus for fungus gnats?

Fungus gnats also known as sciarid flies, are fruit fly sized cactus pests that are attracted to damp soil. Although adult flies do not themselves damage plants, they lay their eggs onto the soil which hatch into larvae, which tunnel down into the soil to feed on fungi and plant juices and plant material. This can cause serious damage to cactus seedlings, as the larvae destroy their root system. Fungus gnats can be problematic all year round for indoor plants.


How to treat cactus fungus gnats?

Fungus gnats can be treated using these first line methods:


1) Place sticky card traps around your cactus plants to catch airborne adult fungus gnats.


2) Organic (natural) pesticide such as Neem oil (also a fungicide) can be sprayed onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation. Water soil using Neem oil to kill both larvae and fungus knats.


3) Non-organic plant invigorators are considered environmentally-friendly pesticides. Contains surfactants and nutrients or fatty acids and algae extracts, which also promote the optimal nutrition of plants. Spray onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


4) Biological controls boost the population of natural predators. Parasitic Nematodes (steinernema feltiae) are a predator of fungus gnat larvae. These can be purchased in a packet which should usually be kept refridgerated until ready for use. Mix the Nemotides with water following manufacturing instructions and water enough to drench the entire soil. Other predators of fungus gnats are predatory mites (Hypoaspis miles and Macrocheles robustus) and a predatory rove beetle (Atheta coriaria). These biological controls are available by mail order.

Avoid releasing biological controls for 2+ weeks since last use of insecticides.


If your Fungus gnat infestation is not successfully treated with a first line method, consider using the below as a last resort.


6) Synthetic Insecticides (contact action/systemic action) kill by direct contact or through ingestion of plant materials. Synthetic insecticides should be used with caution as these can damage the environment. They can also destroy other useful predators which may be protecting your cactus or succulent plants from other pests and diseases.


PLANTS IN BLOOM SHOULD NOT BE SPRAYED AS THIS CAN HARM BEES AND OTHER POLLINATING INSECTS.

 


How to treat a cactus for aphids?

Aphids are little green sap-sucking insects which excrete a sticky substance and this encourages mould growth. Typically found on soft plant tissue, flower buds or flowers. They are most active in spring or summer, but can be a pest all year round indoors!


How to treat cactus aphids?

Aphids can be treated using these first line methods:


1) Physically remove with damp cotton swabs and spray the entire plant with a high pressure water spray, to blast off any remaining bugs.


2) Spray with soapy water.


3) Spray using 70% or less solution of isopropyl alcohol diluted in water. CAUTION: High concentrations or undiluted alcohol solution can cause severe burns or scars to cacti plant.


4) Organic (natural) pesticide such as Neem oil (also a fungicide) can be sprayed onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


5) Non-organic plant invigorators are considered environmentally-friendly pesticides. Contains surfactants and nutrients or fatty acids and algae extracts, which also promote the optimal nutrition of plants. Spray onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


6) Biological controls boost the population of natural predators. Hoverfly larvae, lacewing larvae and some parasitoid wasps are natural enemies of Aphids and can be purchased and introduced to greenhouses.

Avoid releasing biological controls for 2+ weeks since last use of insecticides.


If your Aphids infestation is not successfully treated with a first line method, consider using the below as a last resort.


6) Synthetic Insecticides (contact action/systemic action) kill by direct contact or through ingestion of plant materials. Synthetic insecticides should be used with caution as these can damage the environment. They can also destroy other useful predators which may be protecting your cactus or succulent plants from other pests and diseases.


PLANTS IN BLOOM SHOULD NOT BE SPRAYED AS THIS CAN HARM BEES AND OTHER POLLINATING INSECTS.

 

How to treat a cactus for thrips

Western flower thrips also known as Thunder flies, are common insects in the UK summer period. They are narrow bodied, typically cream/yellow/brownish in colour, with 2 small wings. Due to their minute size they can be difficult to spot with the naked eye. With the ability to reproduce asexually they can multiply rapidly. There is also no natural predators in the typical household, which can make them just that little bit more challenging.


How to treat cactus thrips?

Thrips can be treated using these first line methods:


1) Physically remove with damp cotton swabs and spray the entire plant with a high pressure water spray, to blast off any remaining bugs.


2) Spray with soapy water.


3) Spray using 70% or less solution of isopropyl alcohol diluted in water. CAUTION: High concentrations or undiluted alcohol solution can cause severe burns or scars to cacti plant.


4) Organic (natural) pesticide such as Neem oil (also a fungicide) can be sprayed onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


5) Non-organic plant invigorators are considered environmentally-friendly pesticides. Contains surfactants and nutrients or fatty acids and algae extracts, which also promote the optimal nutrition of plants. Spray onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


6) Biological controls boost the population of natural predators. Amblyseius cucumeris are natural enemies of numerous Thrips species and can be purchased and introduced to greenhouses. This predator consume Thrips larvae and eggs, which breaks the lifecycle before it grows into an adult insect. For more severe infestations, predators such as Ambylyseius swirskii or the Orius bus can be introduced to destroy adult Thrips.

Avoid releasing biological controls for 2+ weeks since last use of insecticides.


If your Thrips infestation is not successfully treated with a first line method, consider using the below as a last resort.


6) Synthetic Insecticides (contact action/systemic action) kill by direct contact or through ingestion of plant materials. Synthetic insecticides should be used with caution as these can damage the environment. They can also destroy other useful predators which may be protecting your cactus or succulent plants from other pests and diseases.


PLANTS IN BLOOM SHOULD NOT BE SPRAYED AS THIS CAN HARM BEES AND OTHER POLLINATING INSECTS.

 

How to treat a cactus for scale bugs

Cochineal scale insects appear as raised blotches of grey dust or cottony appearance! These cacti pests are otherwise not visible to the naked eye, with no apparent movement observed. The scale insects mainly affect the Opuntia cactus plant species. Interestingly these bugs (also known as Dactylopius coccus) have been historically harvested on Opuntia cacti pads in Mexico and South America, to create a crimson red dye!


How to treat cactus scale bugs?

Scale bugs can be treated using these first line methods:


1) Physically remove with damp cotton swabs and spray the entire plant with a high pressure water spray, to blast off any remaining bugs.


2) Spray with soapy water.


3) Spray using 70% or less solution of isopropyl alcohol diluted in water. CAUTION: High concentrations or undiluted alcohol solution can cause severe burns or scars to cacti plant.


4) Organic (natural) pesticide such as Neem oil (also a fungicide) can be sprayed onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


5) Non-organic plant invigorators are considered environmentally-friendly pesticides. Contains surfactants and nutrients or fatty acids and algae extracts, which also promote the optimal nutrition of plants. Spray onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


If your Scale bugs infestation is not successfully treated with a first line method, consider using the below as a last resort.


6) Synthetic Insecticides (contact action/systemic action) kill by direct contact or through ingestion of plant materials. Synthetic insecticides should be used with caution as these can damage the environment. They can also destroy other useful predators which may be protecting your cactus or succulent plants from other pests and diseases.


PLANTS IN BLOOM SHOULD NOT BE SPRAYED AS THIS CAN HARM BEES AND OTHER POLLINATING INSECTS.


How to treat your cactus for red spider mites?

Red spider mites, initially present as small yellow or brown spots. High infestations can display tiny red silk-like spider web. Bare in mind that they are minute and difficult to see with the naked eye, you may therefore notice signs of damage to the plant first. Spider mites suck plant's juices from cacti and succulents, causing significant damage over time


How to treat cactus red spider mites?

Red spider mites can be treated using these first line methods:


1) Physically remove with damp cotton swabs and spray the entire plant with a high pressure water spray, to blast off any remaining bugs.


2) Spray with soapy water.


3) Spray using 70% or less solution of isopropyl alcohol diluted in water. CAUTION: High concentrations or undiluted alcohol solution can cause severe burns or scars to cacti plant.


4) Organic (natural) pesticide such as Neem oil (also a fungicide) can be sprayed onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


5) Non-organic plant invigorators are considered environmentally-friendly pesticides. Contains surfactants and nutrients or fatty acids and algae extracts, which also promote the optimal nutrition of plants. Spray onto the entire plant as a treatment and on a regular basis as a preventative (e.g. every 7-14 days in grow season). Kills pests by mode of suffocation.


6) Biological controls boost the population of natural predators. Phytoseiulus persimilis (supplied in shaker bottles), Amblyseius californicus (available in bottles or sachets) and Atheta coriaria beetle (available by mail order) are natural enemies of Red spider mites which can be introduced to a greenhouse to seek out and destroy Red spider mites.

Avoid releasing biological controls for 2+ weeks since last use of insecticides.


If your Red spider mites infestation is not successfully treated with a first line method, consider using the below as a last resort.


6) Synthetic Insecticides (contact action/systemic action) kill by direct contact or through ingestion of plant materials. Synthetic insecticides should be used with caution as these can damage the environment. They can also destroy other useful predators which may be protecting your cactus or succulent plants from other pests and diseases.


PLANTS IN BLOOM SHOULD NOT BE SPRAYED AS THIS CAN HARM BEES AND OTHER POLLINATING INSECTS.


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

One of the most common causes for wet rot is over watering. However; another cause which is often overlooked is the drainage quality of the soil mix. If your soil mix takes days or weeks to dry, the roots will be sitting in constant damp which significantly increases the risk of rot. A good cactus soil mix is imperative, to prevent the build up of harmful bacteria that can penetrate into the cactus plant tissue.


Dry rot is caused by a fungi such as Diplodia or Phyllosticta concava. It can be identified as either black sots or protruding brown/rust colored spots. Good hygiene is an important step to take, especially when trimming, pruning, cutting or grafting cacti to prevent the introduction of bacterial and fungal infections.

Good drainage cactus soil mix

Cactus Rot Prevention

Most cacti should receive little to no water in winter, as they are likely going through a dormant period. With no active growth the roots will not need to absorb water from the soil. It is also important to note that under watering cactus in Summer can also be harmful, as the plant roots system will become dried out and unable to absorb moisture when needed.


How often to water cacti?

How to spot if your cactus is rotting?

If your cactus is suffering from wet rot, it will likely be rotting from the stem and become soft and mushy. In comparison a cactus suffering from dry rot typically occurs further up the plant and can appear as a hardened dark brown or black patch. It is important to note that many cactus develop a corky stem and this is a natural ageing process. If the bottom of the cactus is soft and mushy, this is wet rot. If the bottom of the cactus is hard, this is natural corking.


Signs of cactus rot


Corking of a cactus vs. sunburn (phototoxicity)

As the cactus grows and stores more water, it will become top heavy. It is thought that corking provides strength, helping to keep the cactus achored, growing upwards. Therefore, corking occurs at the bottom of the stem.


Although cacti come from hot arid climates in their natural habitat, cacti grown in the UK will not be climatised to the same conditions. Similarly cacti which have been imported, will become accustomed to their new environment. This means that they may be less tolerant of hot weather fluctuations and more likely to burn in extreme heat waves.


Cactus corking

How to treat sun burnt cactus

Remove the cactus from direct sunlight as soon as suspected and allow the plant to recover. Gradually reintroduce the cactus to low level light exposure, for short periods of time. This step is important to help the plant build up some immunity.


How to prevent sun burnt cactus

Cactus seedlings will be less tolerant of extreme heat and should be provided with some screen. An easy way to protect seedlings is to gently place a newpaper sheet ontop! Alternatively, for larger cacti cover with a shade cloth in the hottest part of the day. If you notice that your cacti is becoming red, this can be a sign of sun stress.


Common Factors That Lead To Cactus Pests And Diseases

Over watering your cacti plants or poor drainage medium is probably the most contributing factors for rot, caused by bacteria and fungi. It is important to note that fungal spores can also be spread via wind or rain splashing from other infected plants. Damp soil may also attract mealybugs, fungus gnats, and aphids. However, on the flip side Thrips and Red spider mites hate damp and are much more attracted to plants grown in dry soil!


It is also important not to overlook the importance of fertilising your desert plants once or twice per year minimum. This can help promote structural strength of a plant, movement of water, nutrients and carbohydrates throughout the cells of the cactus plants. All of which will promote healthy plants.

How often to fertilise cactus?

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

The majority of cactus and succulent plants aren't frost hardy. The first signs of frost damage can be softened tissue which can start to appear white. This will later turn black with rot. It is possible to save your cacti but trimming off any frost damaged rot and allowing the cacti time to recover. As the UK is known for its humid temperature oceanic climate, it is best to keep most cacti in a heated greenhouse or indoors over the winter period to avoid the risk of frost damage.


How to protect cactus from rot?


How to treat Slugs and Snails?

Slugs and snails are very common pests in the UK and particularly can be a challenge in outdoors greenhouse enclosures. It is best to physically remove these from the area. Copper strips or tape can be applied to the bench legs, this can be a preventative measure to repel these pests.


Do slugs eat cactus?


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