I'm new to growing edible plants and have been trying my hand at cultivating various herbs from seeds. However, I've been facing a variety of pests, particularly fungus gnats and aphids, and I've even dealt with spider mites and mealybugs on my houseplants. I created a spray using a recipe I found that includes neem oil, peppermint castile soap, and isopropyl alcohol, which has helped reduce the aphid population and significantly decreased the fungus gnats. But after using the spray, some of my herbs, especially my dill and basil, have developed black, shriveled spots on their leaves. My cilantro and parsley seem okay though. Given that I'm in Michigan and all my plants are indoors under grow lights during winter, I'm looking for effective ways to control pests on my herbs. It feels like an ongoing battle with pests, and I'm feeling a bit overwhelmed.
3 Answers
It sounds like the alcohol in your spray might be dehydrating the leaves, which could explain those black spots. Maybe try removing the alcohol and increasing the water content instead? That could make a difference without stressing your plants too much!
Make sure to check that your herbs are getting the right nutrients too! Sometimes stressed out plants can attract more pests. You might want to add a layer of sand on top of the soil to help with those gnats since they need access to the soil. I also recommend bottom watering to prevent over-saturation, which can really help reduce fungus gnats. Trimming off any unhealthy leaves will also encourage new growth. Just remember that herbs can grow year-round, but they go through growth phases, so don't worry if you hit a few bumps along the way!
Also, ensure that the neem oil you're using is safe for edibles and labeled for indoor use. Not all neem products are the same, and some might harm your herbs. It's worth double-checking before spraying again!