By Sandy Swegel
We got a great question from a customer this week about controlling aphids. Her frustration resonates with most of us who garden.
Q. Aphids are terrible, tiny creatures and I fight them every year. I’ve been looking for the best ways to make sure they don’t screw with my garden this time. I thought I had a good way; planting garlic around the plants. “Aphids don’t like garlic,” one link said. “Aphids love garlic leaves, said another one. Soap mixture, Neem oil, rubbing alcohol mixed with soap and water, importing good bugs that love to eat the aphids. I refuse to use chemicals that poison everything, it makes growing organic pretty pointless. Does anyone have any SURE FIRE, tried and true methods?
A. The key to reducing aphids in your garden is to understand their lifestyle. Controlling aphids is like cleaning house. You can’t just clean a house full of people once and expect the house to still be clean a week later if you didn’t keep picking up stuff all week. When you use any treatment you might kill most of the adult aphids that day. But the ones you missed or who were eggs that wouldn’t hatch for another day, are still eating and reproducing. Reproduction is the key to aphid success. Aphids reproduce both sexually and asexually. They lay eggs to survive the winter. And they have life births in warm weather. Each aphid can create up to 100 new aphids per month.
My best sure-fire, tried and true method (or as close to that as one can get) is this:
Accept that you are going to have some aphids. To kill them all, even if possible, means you would also kill all the beneficial insect pollinators and you don’t want to do this.
Understand how aphids die. Warning: graphic content ahead.
It is super easy to kill aphids, which is why plain water spray works great. Aphids feed by attaching to the plant with their mouths. When you spray water on the aphids, the force of the water tears the aphid off the plant. The head and mouthparts stay attached to the plant, instantly killing the aphid. Even just brushing off all the aphids on a leaf with your finger decapitates and kills all those aphids. That’s why you don’t have to poison them….if you can just mechanically remove them.
Be vigilant (every few days) about checking for aphids.
New aphids are hatching in leaf litter or being birthed by the aphids who were hiding out in the weeds next door. You have to spray the aphids every time you see them in large numbers. Each aphid can have dozens of generations…They are baby-making machines. You have to keep after them at least until you see you are no longer getting infestations.
General Advice about aphids.
If you start to watch your aphid population, you will often find that lots of aphids are followed in a week by lots of ladybugs who eat them. Nature does provide a natural balance if you have a healthy garden that supports beneficial insects. If you are aggressively treating aphids with garlic or neem sprays, you are also killing all the other insects that eat aphids.
Learn more about aphids.
You can alter the conditions in your garden that reduce the number of aphids.
Don’t over fertilize. Aphids love nitrogen. Every time you add nitrogen to your plants, you will get a little aphid bloom. Reduce the nitrogen and you don’t have so many aphids.
Encourage earthworms and use earthworm castings. Earthworms produce an enzyme chitinase to help digest their food. Aphids are repelled by chitinase. Unfortunately, the chitinase doesn’t last long enough to be the only deterrent.
Encourage good environmental conditions like air flow and temperature. This works really well indoors. In my greenhouse, I can reduce aphids by keeping a fan going and shading the plants from really hot afternoon sun. Aphids are often in greater numbers on plants that are stressed.
Finally, if you do want to use “organic” sprays, simple soapy water works well. (1 teaspoon per gallon). Some people use the kitchen spray with garlic and Tabasco sauce. I think the science is not clear on neem. It definitely works but it works by disrupting insects hormonal systems and I’m not convinced it doesn’t adversely affect beneficial insects. Some studies say Neem only kills sucking insects. I would try gentler methods first before turning to Neem.