To the best of our ability to discern (with the help of the Google Extension Service), we have aphids. We noticed some dark colored insects flying around initially.
From Natural Living, I learned that of the more than 4,000 species of aphids, about 250 are a danger to crops. Sometimes called plant lice, these pests pierce the stems of plants to suck out nutrient-rich sap. In the process, they spread viruses and secrete a fluid that attracts sooty molds that can cover a plant's leaves and block the sun. The viruses they carry can kill potatoes, citrus fruits and grains.
There was some good news in this article -- and some bad news. There are a number of things you can do to deter or get rid of them -- but some don't work in a water-starved area and others we've tried and we still have an infestation. Here were the suggestions:
- Physically removing the bugs. This means brushing them off (probably with the tomato buds), pinching them off the leaves and stems (ICK!) or clipping off infested branches and tossing them into a bucket of soapy water.
- Washing them away with a hose and sprayer. Not an option in our drought-hobbled world.
- Spraying them with water and a mild detergent. We tried this and will talk about it more later.
- Spraying with neem oil. It is mixed with water and sprayed on the plant stems and leaves. It will also work against mealy bugs, cabbage worms, beetles, leafminers, ants and caterpillars as well as many types of fungus. Neem is an evergreen tree that grows in India and has been introduced to other tropical areas. It has a bitter taste and a garlicky-sulfurous smell. It repels insects; interferes with their feeding and their hormone system, making it harder for them to grow or lay eggs. It doesn't last long, so it has to be applied regularly, but is safe for other creatures in the garden. A four-ounce bottle of cosmetic-grade neem oil sells for $5 to $10 on Amazon.com.
- Spraying with essential oils. Mix equal parts (about four to five drops each) of thyme, peppermint, clove and rosemary essential oils in a sprayer bottle with water. Shake well and spray the contents over the plant, covering all surfaces. This supposedly kills most garden pests as well as their eggs and larvae. We're planning on giving this a try.
- Bring in beneficial insects like lady bugs or hover flies. One year, we bought lady bugs, but they have no loyalty. They flew out of the garden and into someone else's yard almost as soon as we set them free. You have to attract hover flies to a garden by planting fragrant herbs such as garlic, catnip and oregano. Herbs like clover, mint, dill, fennel and yarrow also attract ladybugs and lacewings. At different times we've had yarrow, garlic, dill and we have a nice sized bed of oregano. None of these things seemed to have an effect. The feral cats that the next door neighbors feed is the bane of our garden. They view the plot as a luxurious cat box. We definitely will NOT be planting catnip.
- Attract bug-eating birds. Natural Living suggests wrens, chickadees and titmice, none of which live in suburban Van Nuys; they wisely prefer the cooler woodland areas of the hills and mountains. Natural Living suggests building bird houses and bird feeders. All I can see are squirrels fighting with crows, seagulls, pigeons and sparrows for the food with the feral cats swirling below. This idea isn't on the viable list.
- Planting members of the allum family such as garlic and onions. We've had both in the garden at different times with no particular effect on the pest population.
- Using companion plants to repel pests. All of our tomato plants are ringed by marigolds. An 18-inch high marigold bush doesn't stand much of a chance against a six-foot plus tomato plant.
- Planting zinnias, dahlias, cosmos and asters away from the vegetables. The strategy here is that the aphids like these plants and will head for them in preference to the vegetables. I'm not sure if the aphids don't harm these plants or if you end up with a bed of dying flowers. At any rate, we're a season too late for this idea.
The smaller tomato plant, which suffered the most from the invasion, is probably ready to be pulled out and thrown into the trash. (Unless we want the same tomatoes next year, we can't put it in the compost pile.)
At the moment, it seems to be a battle between the aphids and gravity to keep the biggest tomato plant growing.