Here’s a quick guide to help you establish your own environmental habits to help keep your succulents pest and disease free as possible.
Scale: Watch out for these fuzzy, furry insects. They quickly multiply on cacti and will leave a scar behind even after you’ve removed it. Scale seem to prefer shade and they may occupy every open space on the shady side of the plant and leave the sunny side untouched. How to treat scale: Physically remove the scales from the plant by using your finger nail, tweezer or a garden hose to spray them off. Make sure to get down in the cracks and under the spines of your cacti. Once you have removed them & to prevent repeated outbreaks treat your plant with a systemic insecticide. For a systemic to work though the plant must be growing and taking in water and nutrients at the time so apply the systemic once at the onset of the growing season and keep an eye on the plant and physically remove the scale again while you wait for the systemic to take affect. Left untreated scale will spread to other nearby succulent plants.
Mealy bugs: Mealybugs affect the plant tissue and they like to hide out in between the ribs and the tubercles and they live under the soil sucking on the roots. There are even mealy bugs that live on the spines of the cactus and suck the plant juices through the spines. They are known for being difficult to get rid of and it’s nearly impossible to do so without the use of a systemic pesticide. Contact insecticide to will kill mealybugs, but it has be added in a fairly high concentration due to the protective covering that the insect makes for itself. Also, contact insecticides are risky due to their oily make up. This can cause the plant epidermis to burn in the sunlight. For best results, after physically removing the mealybugs with a toothbrush or high-pressure water spray, it is best to treat the plant with a systemic insecticide. This should be applied only when the plant is growing or it will not be taken into the plant tissues. It is also not a bad idea to treat your plants at the onset of the growing season to prevent mealybugs from getting a start. Mealybugs also affect different areas of the plant, unlike scale and other pests, it’s always wise to check the entire plant when they are detected. So make sure to check down in the joints of the plant and unpot the plant and check the roots.
Red spider mite: They’re actually not spiders at all, but mites. They make a spider-web like silk and whatever plant they are attacking. They’re extremely small and depending on your eyesight you might not even be able to see them. Now real spiders will make webs on cacti so don’t panic the first time you notice a silky web. If the way up belongs to spider mites, you will see the plant turning dry brown especially where ever there is a new growth at the apex of the plant. Spider mites love the fresh new growth and will always attack the tender parts first. Eventually they will eat the entire outer layer off your cactus which will kill it if left untreated. After spider mites are killed off, the plant will continue to grow from the top and as it does the area damage from the mites will move down the plant. The damaged areas will never look healthy again and you will have to wait for the plant to grow out of it. If you get a new plant that is dry brown around the bottom, it is likely one that has survived a spider mite attack and started to grow out of it. If you even suspect spider mite damage on your succulent or cacti, quarantine all infected plants immediately. Treatment with some form of pesticide is the only cure. So look for a pesticide this specifically states control of spider mites on the label. Multiple treatments will be required as the eggs will not be killed by the pesticide. Typically, re-application will need to be done every week or so depending on the temperature. At higher temperatures, the mites reproduce faster and more frequent treatment will be necessary. Since most pesticides will create a phototoxic reaction on the plant’s epidermis, it is best to keep your plants out of direct sunlight after treatment for several weeks. Because spider mites are difficult to detect until they have done a lot of damage and because of their small size, a systemic pesticide is typically not a useful treatment. Too much damage will be done before the systemic could take affect. Using a systemic as a preventative measure is a good idea but mites are not insects and are not controlled as easily with insecticide. Also it’s a good idea to spray the area surrounding the affected plants and to pay close attention to uninfected plants. The chances are good that the spider mites have been on the move before you noticed them.
Slugs and snails: They’re a problem only when the conditions are right(warm & moist). They’re very seasonal and because they are prone to dry out they wait until night to come out of hiding. If your garden has optimal conditions they can exist in very large numbers. Although these animals are very soft they can crawl on harmed right across the top of the spines on your cactus to get to the part they want to eat. They prefer the softer new growth of cacti and seldom bother with the older growth. On the cactus Stamms these great off the top layer of the tissue as they go. This leaves behind a rounded patch of expose tissue that quickly scabs over. They love flower buds and they will eat all of them before touching the stem. On your potted plants, lift the pots and check underneath them. Any cool or shady spot is a good hiding spot for them and they don’t go too far from where they had their last meal. Going out at night with a flashlight, is another way to physically get rid of them. On a larger scale, you can always use a snail or slug bait. They are repelled by copper although that isn’t cheap. You can also use some liquid treatments and put a circle around each pot or plant so that when they start to cross this they will die afterwards. Then when the sun comes up they will dry out and there will be nothing left but their shells.
Worms and Caterpillars: There are a few moth species whose caterpillars will eat some succulents and cacti species. Especially if you have an Opuntia. Typically a moth will lay its egg in a protected spot somewhere on the cactus. Then, when the egg hatches, the caterpillar starts eating its way through the plant. In some cases, the caterpillar will be eating on the inside of the stem unseen by the gardener. Cactus moths are easy to spot and kill.
Aphids: These little green insects will gather on soft plant tissue and suck the plant juices. On a succulent or cacti they normally only affect the flower buds or the flower themselves. You normally see them on very soft, new growth. If you have ants on your plants, be on the lookout for aphids as they are often brought in by the ants. To get rid of them spray them off with a high-pressure water hose just be careful to not damage your plants in the process.You might have to do this several times. If the problem persists, spray the infected part with soapy water. If this still doesn’t work, then a systemic insecticide is recommended, but once again take into consideration the plant’s epidermis.
Fungal attacks: If you noticed rust colored or black spots surrounded by dry brown sections on the stand love your cactus or succulent that means that something is eating up your plant. Right is sometimes a fungus eating up the dead plant tissue but in that case something else triggered the start of tissue death. In a true fungal attack, there is a fungus growing inside the plant tissue that kills it as it goes. That’s why it turns brown and dry. Fungal attacks are hard to stop. The best option is to find any uninfected stem and just propagate a new plant from it and throw the rest of the plant away.
Rot: Right usually starts from the bottom up. Often the roots will rot off first, but the plant body will appear fine. Sometimes you’ll see the top section of the plant rot first. You will normally see this when the cells fill up with water and then they burst open. After the cell wall is ruptured, the cell dies. If a group of cells die from this, it is the perfect place for rot to settle in. You’ll deal with rot more than anything else and that’s because succulents and cacti are mostly water-filled fleshy tissue. This is just the type of environment that bacteria and fungi thrive in. In proper conditions, rot does not occur because the moisture in the environment is low. In the wild, most succulents grow in rocky, fast draining soil, and high temperatures. While the amount of moisture a succulent can tolerate varies from species to species, as a general rule rich soil with a high organic content that is continually damp will rot pretty much any succulents, especially if the temperatures are low.