Succulent pests and diseases
Generally there won’t be too many problems with your succulents or cacti...
An example of what to look out for if you think you have Mealybug.
Mealybug is one of them though. They are hunted by ants so if you see ants around your plants you can assume that these little critters are finding a home among your favorite plants. They can accumulate around the base of a plant or can sometimes be just below the soil surface. The bugs themselves are 2 to 3 millimeters long and gray or light brown in color. However if you think you may have an infestation look for white fluffy areas among the leaves.
Remedies: they can be relatively easy to treat and there are several methods for ridding your plants of these pesky little critters. If you catch them early enough it can be as simple as hosing off the plant with a strong water spray. Using a cotton bud soaked in methylated spirits and dabbing the affected area will also kill them. Soapy water (several drops of dish soap to 1 cup water) sprayed onto the plant will kill them. Pyrethrum is also very effective. If you think they are in the soil then soaking your whole pot in a bucket containing an insecticide with a few drops of dish washing liquid will do the trick. Make sure you let the plant dry out completely after using this method. Another option is remove the whole plant from the pot, wash the plant roots and top off well, then re-pot in clean potting medium. Make sure you dispose of the infested soil mix to prevent any re-infestation.
Scale on a Pitaya (dragonfruit) plant
Scale: these little sods are not so easy to just spray and forget. They resemble small whitish/grey like spots over the stem of a plant and can be scraped off quite easily. The best method here is to use the methylated spirits on a cotton bud or a small paint brush with stiff bristles and remove them. Always keep an eye out for them as early prevention is better than trying to control a full blown infestation.
NB: These are the two most common problems with succulents and cacti- they are easy to treat and keep under control. Being vigilant is the best method and catch any infestations early.