Spider mites can be some of the most damaging pests in a cactus collection. These little devils thrive in hot dry conditions. Which, surprise, surprise is also the favoured conditions of most cacti. Due to their extremely small size they are hard to detect until the damage has already been done. †
This is a Echinopsis chamaecereus plant that had begun to show signs of spider mite damage. On closer inspection with a magnifying glass I detected little red mites crawling over the damaged section of the plant. Here you can clearly see the extent and particular way they damage the plants. One side was left unscathed, the other was not so lucky.
They reproduce extremely fast. A fresh egg can hatch in as little as 3 days, and become sexually mature in as little as 5 days. One female can lay up to 20 eggs per day and can live for 2 to 4 weeks, laying hundreds of eggs. This ridiculous reproductive rate can allow spider mite populations to become resistant to insecticides, so chemical control methods can become ineffective when the same pesticide is used over a prolonged period. To treat spider mite infestations with chemicals often requires multiple treatments of different sprays. Most of which are harmful to the environment and also to your cacti. It has been my experience that cacti are quite sensitive to chemical sprays and insecticidal soap. I have had many issues in the past with chemical burns and photosensitivity. (Sun burn)
After much futility and heart-break trashing plant after plant that had either succumbed to the sprays or the mites I figured there must be a better way. It turns out, there is.
Meet the Predator
Phytoseiulus persimilis is a natural predator mite of the red spider mite and two-spotted mite. This little brutalisk is capable of devouring up to twenty young or seven adult mites each day and under optimum conditions can multiply twice as fast as the little devil mites. The maths says it all. They destroy and out-compete the spider mites one by one leaving your collection completely pest free.
But arenít you just replacing one problem with another? †Not necessarily as the predators have a rather morbid side in that after devouring their food source they begin to starve. This leads to cannibalism and eventual extinction from the collection.
There are two methods of employing mites to do your dirty work. One is the above mentioned genocide/suicide style or my preferred method which is to establish a healthy population of predators in my collection and in the surrounding yard. By having them in the vicinity of my collection they will always be ready to consolidate and brutally quell any spider mite uprising. Also it helps to keep the garden free and healthy of unwanted pests.
Another significant benefit of the predators that is worth mentioning is that they can get to places that sprays just canít reach. If you have any big clumps or particularly hairy cacti, sprays will never treat the whole plant. But, the little predators can climb through the hair and under the pups.
So upon learning this information I settled on using nature to look after my collection. I purchased a bucket of 10,00 mites from an Australian company for around the $100 dollar mark. It is quite a bit more expensive than buying a bottle of death sauce from the local hardware store but considering the benefits, the cost is easily justified.
Here you can clearly see the little hunters roaming around the tub.
It is best to store them in the fridge until you are ready to use them as they are extremely active and once the lid is open they get everywhere and climb on everything. But remember they have a very short shelf life so it is best to use them 1-2 days after receiving them. They come on bean leaves and all you have to do is scatter them around your collection and yard. They will climb off the leaves and get straight to work.
After inspecting the plants the next day it is very easy to see them crawling all over the place. I am very happy with my little bugs of doom and would highly recommend using biological control over sprays.