Introduction
Spring is in full swing for most of the temperate regions in the United States. For many, that means starting seedlings and purchasing flowers/vegetables at nurseries or online. One risk that many do not account for is the increased risk of bringing in pests from another greenhouse or field into your own garden or home. One of the most notorious pests out there in the gardening world is referred to as spider mites. Spider mites are members of the Tetranychidae family, which consists of about 1,200 species. The mites vary in color and size, but are most commonly seen on the underside of the leaf with a silky, web like structure for protection (hints the name spider mites).
Recently, I gifted someone a succulent plant I got from a local nursery. The plant was a string of pearls plant, and all seemed well until the person I gifted the plant to repot the plant, then let a few days pass. Later, they called me and told me that the plant that they had been gifted was covered in little webs and had some slight damage being done to the meaty portions of the plant. Since the mites are so small and difficult to see, it makes spreading the pests very easy and treatment of the issue more difficult than you would think.
I hope to transfer what I have learned while dealing with the issue to you, the reader, as these mites can bring chaos into your indoor and your outdoor vegetable gardens if not kept in check. I feel that to thoroughly address the issue you must understand the life cycle of the mite, be able to correctly identify the mite, understand the niche it utilizes and how it harms the plant(s) (both indoor and outdoor), and lastly, how to treat your plants to get rid of the mites.
1. Understanding The Mite Life Cycle
There seems to be some correlation with hot dry weather and the increased occurrence in regards to the numbers of the mite that may be infecting your plant, so keep that in consideration when growing desert plants. These bugs have very quick life cycles and generation rates, this is important to understand as they can grow exponentially in a relatively short amount of time. Some species within the family are able to hatch in only a few days and become sexually mature a few days after that. To spread to other parts of plants or whole new plants as a whole the mites use their silky strands to help connect them or be blown astray by the wind. This is why it is important to destroy any structures you see made on your plants as to help prevent and reduce further spread. One female can lay up to 20 eggs a day and live for a few weeks, this showcases how much their population can increase in a relatively short amount of time.
Picture of Red Spider Mite by Egor Kamelev
2. Identifying The Mite
Since these little guys can reproduce so quickly and it is important to solve the issue in a timely manner, you may be wondering what they look like and how to spot them in your plants. Well, I hate to break it to you, these mites are very small. If you aren’t actively looking for pests on your plants you may never see them and always overlook them. They look like dust on the leave of your plant, which for those of us who have kept plants indoors for years, you are used to the idea that plants can surely develop a layer of dust if you are like me and never dust your house and don’t have constant fans running on your plants at all times. Since there are so many different kinds of mites that eat plants in a similar fashion there aren’t too many physical characteristics outside the dustiness looking layer and the web creation. I also had spider mites in some of my basil plants that I propagated from last summer and they had what I thought were spiders on them, but in the webs you could see these tiny little blobs just move around and that is what sounded off a siren that I personally was harboring and potentially spreading spider mites.
3. The Mite's Impact on Plants
The University of Nebraska-Lincoln wrote an article describing the impact of spider mites on plants/crops titled, Identifying Spider Mite Damage and the Species Responsible, by Robert Wright, Julie Peterson, and Tom Hunt. They describe the mites impact when they write, “Mites damage crops by piercing plant cells with their mouthparts and sucking the plant juices. The first evidence of mite feeding — which usually can be seen on the top of the leaf — is a yellow or whitish spotting of the leaf tissues in areas where the mites are feeding on the lower leaf surface. Because many other things can cause similar discoloration, it is important to check leaves closely to make sure mites are actually causing the damage. Leaf discoloration caused by mite feeding can be easily identified by checking the undersurface of leaves for the presence of mites, eggs and webbing”. Basically the mites are eating your plants by sucking out the carbohydrates and water in the leaves that the plants have accumulated in their cells.
The reason why this is a big deal is that over time if paired with other environmental factors and increased rates of plant damage it can stress out the plants so much that the entire leaf dies. This is a problem in the long term if you are in the business of selling plants, growing crops, or are striving to keep the highest quality of plants in your selection. If a lot of leaves begin to become infected with the pest and die due to prolonged amounts of herbivory the plant can’t produce as much energy overall. This reduces the plants overall potential energy allocation towards fruit/vegetable production and overall plant growth/expansion in some cases.
4. How to Treat Your Plants
There are a few ways to treat your plants for mites. Some require no use of pesticides; others require some use of organic or over the counter pesticides. Sometime if this doesn’t work you may just have to quarantine or remove the plants that are infected and try to grow more plants elsewhere in a new location or in a spot with more plant diversity. Obviously beyond prevention, one of the most common ways to treat spider mites can be as simple as using either a cloth or rough spray to blow the mites off of the plant. This is beneficial as the mites don’t like wet environments and are relatively small and easy to blow off of plant(s).
The next method expands on the previous method but uses other chemicals to help push out and kill the mites. Some people prefer to use a 1 quart ratio of water to 1tsp of dish soap. Another method similar to this is the use of a hydrogen peroxide solution and water, or a mixture of rubbing alcohol and water. Typically if you go this route you put one of the solutions that you choose into a spray bottle and thoroughly spray/mist down the needed plans every 2-3 days for 2-3 weeks depending on how your results are working.
I have also heard of people using certain types of essential oils to naturally push out the pests. I personally don’t know how well this method works, but when I was working around greenhouses I recall hearing them refer to essential oil treatments for pests. Another organic method of removing mites is the use of one of the species of predatory mites called persimilis and fallacis. These mites predominantly only attack spider mites and keep them in check, they even help keep thrips in check, it is a win-win. You can also use lady bugs to reduce spider mite populations and attract them naturally through habitat creation with various herbs and flower species. This takes time though and may slow down your efforts or cause too much damage to be done before they arrive naturally. You could also buy ladybugs in bulk online too.
One last organic method is the use of neem oil. I hear that neem oil is relatively effective in removing the mites from your plant(s). Neem oil is oil created from pressing fruits and seeds from a tree referred to as the neem tree. The chemical defense of this tree is potent against various types of insect herbivory (plant predation)/granivory (seed predation). It is commonly recommended in various gardening forums and is known to work for most small-moderate scale applications.
Conclusion
Spider mites are a gardener’s pain the neck, they cause extra hassle and more work to ensure yield and the health of your plants. It is important to watch out for the signs of this mite in your grow room and in your garden, especially when bringing in new plants from other greenhouses and nurseries. You have to be quick acting otherwise you may find it hard to play catchup behind the little guys. I hope you try out some of the methods I described above and cure your issue if/when you ever run into the issue of dealing with the infamous spider mites.
Works Cited
Wright, Robert, et al. “Identifying Spider Mite Damage and the Species Responsible.” CropWatch, University of Nebraska-Lincoln , 17 Oct. 2022, https://cropwatch.unl.edu/2016/identifying-spider-mite-damage-species-responsible#:~:text=Mites%20damage%20crops%20by%20piercing,on%20the%20lower%20leaf%20surface.