Mosquitoes are the winners in the global warming climate, thriving for longer periods of time in areas that are warmer and more humid. There are about 3000 species worldwide, about 200 mostly-harmless mosquito species in the US, and about a dozen that are bad actors capable of spreading diseases like zika, West Nile, malaria, chikungunya, and dengue. When I saw a gardening article about plants that repelled mosquitoes, I questioned the veracity of its claim. If it were really that simple, we would all have marigolds, lantana, catnip, calendula, lavender, rosemary, sage, thyme, lemongrass, basil and garlic planted near our doors and outdoor eating areas. It turns out that the research was not conducted on the plants sitting on your patio or in your garden, but on the plants' extracts and oils, and these oils and extracts don't all come from the plants' flowers and/or leaves. If you like these plants, grow them for their scent and their beauty, but not for any mosquito-repellency.
The bottom line for repelling mosquitoes is the same:
- Drain any standing water. I routinely drain plant saucers and invert buckets and containers that could hold water. For any large containers that I can't drain easily, I use a Mosquito Dunk. These resemble flat donuts. They are specific mosquito larvae killers, meaning they don't harm anything else. I do have to remember to replace them every 3 or 4 weeks or as long as any water remains.
- Check screens for any holes, fix them and make sure to latch all screens.
- Wear light-colored, loose clothing to keep them from getting to your bare skin.
- Consider using a fan with a strong breeze near where you're relaxing to keep them away from you.
- Use a repellent that has been approved by the Environmental Protection Agency. Those lasting the longest after application contain DEET. The EPA has okayed repellents containing picaridin and PMD (oil of lemon eucalyptus). The EPA has also given their approval to plant-based repellents containing catnip (catmint) oil and 2-undecanone which is made from wild tomato plant stems and leaves. These plant-based products are not effective for as long as DEET, but work well for the first few hours after they are applied.
For more information, please see UC ANR Publication 7451, Pest Notes: Mosquitoes https://ipm.ucanr.edu/PMG/PESTNOTES/pn7451.html