Hi Dr. Myers,

How do I get rid of these persistent pests(root aphids). I have tried
several organic pesticides including neem oil and potassium salts with no
effect on them.

Some of the same things that work for 'normal' aphids will work on root aphids see my post on aphids

There are several options, none are fool proof. First, there is a fungus that kills insects (Beuveria bassiana) This is sold under two brand names that I know of, (any readers please let me know if you know of others) Botinigard and Naturalis. This fungus is mixed with water and sprayed on the plants making direct contact with the aphids is important. This is one reason root aphids are so hard to control; there are so many nooks and crannies in soil and other mediums that almost any treatment is bound to miss a few pregnant females. In fact, one study I read showed that the number one reason for difficulty controlling root aphids is lack of proper application of the chemical or pathogen. I should mention too that the finer the mist the better. Also, since this fungus gets on the skin of aphids, and aphids that are growing rapidly can shed their skin every 3-5 days you should reapply the fungus every 3-5 days. In Europe they use a fungus Verticillium lecanii with much success. I think this is still in the process of being approved by the EPA, but you could do a search for it.

Second, you can apply chemicals like Neem, pyrethrum etc. to the roots and above ground parts of plants. For root aphids it is recommended you soak the root balls in an insecticide for 5 minutes. There are studies that show soaking in any insecticide for less than 5 min. will result in far less than 100% dead (you don’t fix the problem) so soak longer rather than shorter.

You could also try and not use insecticides by soaking plants for several hours in dish soap as I recommended in my post about general insect care

If you see them in clusters (aphids tend to be gregarious) you have a major infestation and maybe a very serious problem. Large clusters mean you have a chance to have winged aphids, which can fly to new plants anywhere in your grow room, green house, home or garden. The bigger and older the grouping, the greater the chance of winged aphids in your area.

Biological control is possible for these aphids as well. Before you buy predatory insects/organisms look at the shipping routes, release rates and timing. Mail is susceptible to very cold, maybe freezing temperatures. Also, some predators are better than others depending on what species of aphid you have. If you can figure out the species you will have more success.

There is a predatory aphid midge (Aphidoletes aphidimyze) that eats over 60% of all aphid species. The midges are shipped as larvae and 2-3 larvae are put on each plant. This midge likes humid conditions so cutting down on the exhaust fan or putting in a humidifier to increase humidity will increase its success, but watch out for mold.

The last result is to start over with seeds after you sterilize everything with hydrogen peroxide or bleach and a good hot soapy wash. If you can't start from seed you could try cuttings, but they may have aphids on them (root aphids are not always on the roots) So, you must soak any cuttings in insecticidal soap or in dish soap for a long time. This will kill many plants but you need to make sure you are not just starting over with the same problem. As with all insect infestations, prevention is better than a cure, so think about how you go them. I know many people have gotten insects by buying top soil. I try to NEVER buy top soil if it is stored outside for long periods. It is easy for soil gnats or root aphids to get into it and into your garden.

I hope this helps, Let me know if anything works, I’d like to help other readers in the future with specific results.

Good Growing
Dr. E. R. Myers

1 comment:

Anonymous said...

Good article. I have had root aphids for almost 2 years. HIt em with everything from Azamax to pyrethrin to Botanigard. Botanigard ES works best out of everything. RA suck!!!!!