Last year was the first time I experienced a lot of spider mite damage on some of the plants in my garden. Let me tell you, it’s not fun.
I went on a mission to figure out how to get rid of spider mites and prevent them from ravaging some of my rosemary plants this season. Let’s get into it!
What Are Spider Mites?
Red spider mites are very small red bugs (i.e. arachnids) that are reddish-orange color as adults and green color as nymphs. They originated in South America, but are now found all over the world (fun!).
Spider mites usually speak during the early summer, and they thrive in the hot and dry weather which is when their populations seem to explode. They are hard to get rid of because they can move around via wind, water, and on the clothes of gardeners and farmers.
They create these massive nests on plants and the infected leaves will eventually turn brown and die.
How to Get Rid of Spider Mites on Rosemary Plants
If you already have an issue with spider mites, let’s walk through a few ways to kill mites and salvage your healthy plants. Number 5 is questionable, and not my favorite, but I wanted to be thorough.
1. Spray the Leaves With Water
One of the best ways to help reduce a spider mite population is by spraying the leaves with a harsh stream of water. This can knock them off the plant, but make sure you don’t spray them onto nearby plants as this won’t really help.
Make sure you spray the underside of the leaves as well because this is where spider mites will lay eggs and can hide.
2. Neem Oil
Neem oil is another option for helping to control spider mites and it is my favorite. Unlike some other options, neem oil can attack eggs and larvae as well as adults, so it’s more effective on a broad scale.
Neem oil is effective at controlling populations, even after the initial application as the oil can get into the soft-bodied insects and cause damage.
You want to reapply about every 2 weeks, but that’s a lot less than some other methods of controlling mites.
3. Horticultural Oil & Soaps
Ultrafine horticultural oil sprays can be effective for removing spider mites on contact, but make sure to thoroughly spray the plants as they work on contact. Apply in the morning, or when the weather does not get above 75 degrees Fahrenheit.
Horticultural oils and soaps are a great option, but just know that once these dry they don’t help at all, so it’s really the initial contact with the pests that will kill spider mites.
These don’t work on spider mite eggs, so you want to re-apply after 2-3 days once those eggs have all hatched.
4. Hot Pepper Spray
You can also make a hot pepper spray to spread around the leaves and underside of leaves as this will kill many of the mites. Add about 80 grams of red pepper or chili powder to a gallon of water (or 20 grams to a liter) and spray the plants thoroughly.
5. Diatomaceous Earth (But….)
Diatomaceous earth is a powdery substance that I loved when I first started gardening. It is effective at removing a lot of pests you don’t want in your garden.
Diatomaceous earth essentially gets into the exoskeleton of its target and dehydrates it, eventually killing the pest anywhere between 1-5 days after application.
The great thing is that food-grade versions of this are non-toxic to humans. But the bad thing about diatomaceous earth is that it can also kill beneficial insects like ladybugs, lacewings, butterflies, and the coveted honeybee.
Not only are these generally beneficial in the garden, but they are some of the natural predators of the spider mite, so you don’t want to harm them as it could increase the infestation instead of having the opposite effect.
I no longer use diatomaceous earth because of this.
How to Prevent Spider Mites
Preventing spider mites in the first place is important for reducing the annoyance of spider mites taking over your rosemary plant.
Check Your Plant Regularly
Spider mites usually start appearing on the lower leaves of plants, working their way up as they need more space. This is a great place to start your search when you check for spider mites. The underside of leaves is where you’ll initially find spider mites on your plants.
While they can be hard to see with the human eye, you can use a magnifying glass or small hand magnifier to check the leaves for spider mites.
Remove Infested Plants After Harvest
If you had a spider mite infestation during the garden season, make sure you’re getting rid of those crops altogether. You can burn them, or find other creative ways to destroy them, but whatever you do, don’t put them in the compost pile.
Spider mites can overwinter and will come back next year, so this is just adding their eggs and nests to the soil you’ll use next year, spreading them around even more. No thank you!
Control Weeds in the Garden
Weeds are the bane of any gardener, and while it’s an annoying job, it’s super important to keep them at bay because they house many pests, including spider mites. Weed management is said to reduce the risk of them overwintering and traveling throughout the garden.
Solanum Nigrum, or black nightshade, is a regular host for spider mites, so if you have these in the garden, it’s important to keep them under control.
Frequently Asked Questions About Spider Mites
Can I Eat Rosemary That Had Spider Mites?
Yes, spider mites are edible, so certainly you can eat rosemary that had spider mites on it. Because the mites can cause rosemary leaves to crack, you might want to remove the piece of the rosemary that was affected in case those cracks let in other issues.
Do Spider Mites Lay Eggs in the Soil?
Female spider mites will overwinter in plant debris and fallen leaves, so it’s important to clean up the garden after the season is over.
Do Spider Mites Hurt Rosemary?
Spider mites can severely damage a rosemary plant if left unchecked. You will start to see white or yellow spots on your rosemary plants, and eventually, the leaves will begin to die. Spider mites feed on the chlorophyll in the cells of the leaf, which is what causes those discolored spots in the first place.
Once the population grows enough, you’ll start to see the webbing around the leaves and you’ll know your problem is a little more serious.
Using neem oil or spraying your leaves when you find spider mites can help mitigate the damage of a population.
Does Rosemary Oil Repel Spider Mites
Rosemary oil is often used to repel spider mites, however, it’s not been fully proven to work. There are still cases where rosemary can get infested with spider mites.