In the first issue of Pest Busters, we talked about how you can solve a lot of problems by improving your soil with organic matter and by proper watering and fertilizer techniques. If you missed it, check out the Introduction on the previous page of this site.
So, you've done all that and now you think you have aphids. First, make sure you identify them as definitely being aphids. Don't know what they look like? Check out this page full of aphid pictures. Some aphids can be light green or yellow and others can be brown, black or even red. They are so tiny that it is sometimes hard to tell you even have them until you see a whole stream of them lined up on the stems of the plant. Aphids basically suck the juices out of a plant or they can even inject toxins into the plant which cause distorted growths and other problems. Aphids rarely kill a healthy plant, but their numbers do need to be monitored so that they don't get out of control. They will leave a sticky substance called "honeydew" on the plant which can attract ants, so if you see a lot of ants attracted to one particular area of your garden, you may want to look for aphids.
Once you have correctly identified the critters as aphids, you can then begin your attack on them. The best control is to use natural predators to control them. Lady beetles, parasitic wasps, lacewings, and syrphid flies are your best bet. If you have stopped using chemical pesticides and fertilizers on your gardens, you should have a good supply of these good guys in your yard and you will need to do nothing, but in case you don't, lady beetles can be purchased online or at a good nursery.
Aphids are susceptible to fungal diseases when it is hot and humid, so take comfort in the fact that aphid season is mainly in the spring and early summer in most areas. Start checking your plants once or twice a week in early spring when growth is rapid. If you only see a few on a stem or two, blast them with a sharp spray of water from your garden hose. I like to wear a rubber glove and wipe down the stems as I am spraying them with water. Check under leaves as they love to hide. You want to pay special attention if you see aphids on young seedlings as the plants are not strong enough to withstand the aphids.
High levels of nitrogen fertilizer seem to help the aphids to breed, so that is all the more reason to only fertilize with organic slow release fertilizers or compost.
If you feel you must you a pesticide, use the least offensive method first and try not to use it near any beneficial bugs, such as wasps or bees (our most prized pollinators). Without the beneficial insects, the bad insects would destroy all our plants.
The least offensive (besides spraying with water), would be a homemade insecticidal soap. The recipe is simple.
- 1 tablespoons of soap
- 1 quart of warm water
Make sure that you are using a soap and not a detergent. Some good choices would be Dr. Bronner's Pure-Castile Soap or Fels Naptha. Use a distilled water or water that has been filtered as this will allow the soap to stick to the surface better. If you are using one of the bar soaps listed, shave off what you need and dissolve in warm water. The soap mixture must come in contact with the insects in order to work, so don't spray the whole plant down. Some plants can be sensitive to this mixture, so test it on a leaf first, wait 24 hours and then apply it to the problem areas if your plant if it doesn't seem to be adversely affected by the spray. It is also best applied on a cloudy day or very early morning when the plant surface will not be "burnt" by the sun. Apply once a week, as needed, no more. And again, I cannot stress this enough, only apply it to the aphids themselves as the soap will not work otherwise.
Neem Oil is also a good alternative if for some reason the insecticidal soap is not working. But to be honest, the soap mixture works the best for me on most pests. I mix Dr. Bronner's with water as that is what I have on hand and it seems to work the best anyway.