Dear Dan, I wrote in a while ago to see if you would do an article on root aphids but haven’t seen one. I believe these are more common than people think, especially soil growers. They hide on the outside of the roots, so unless you pull it out to observe it, you don’t see them until they are winged and flying around. The problem then is that most people probably write them off as fungus gnats.
I’ve used Azamax soil drenches, pyrethrin sprays and dips, and more and they are still around after almost 2 years! What gives with these things? There’s not alot of info out there on them. – Ben in RI
Sadly, I’ve been hearing more and more about these unique and persistent pests. Root aphids reproduce so rapidly that some growers say they’re “born pregnant and die pregnant.” As you noted, they’re also often misdiagnosed as fungus gnats, and traditional treatments such as Azamax and Gnatrol won’t work to treat them. They’ve also been found in every kind of growing medium from soil to coco to hydroponic ones such as rockwool and grow rocks (expanded clay pellets). They’ve even been seen in aeroponic and DWC systems where roots dangle in mist and nutrient solution only.
Getting rid of root aphids requires a combination of efforts. Rotate your pest control regimen daily using neem oil, pyrethrins and other organic insecticides and being sure to treat the medium as well as the plant. There’s also a promising product called Botanigard made up of a fungus that attacks aphids, whiteflies and thrips.
The best way to avoid getting root aphids altogether is to isolate any new clones and avoid bringing pathogens or infected plants or soils into your grow space. Always check out the leaf surface, underneath all leaves and the top layer of your medium for signs of bugs and treat them immediately upon discovery.