Many growers turn to biological control agents (BCAs) to effectively control foliar aphids; why should root aphids be any different? The difference lies in location, location, location! Root aphids tend to infest the entire container profile. Wherever plant roots are found, root aphids will follow. Root aphids hide out in any available crevice, providing a seemingly endless source of re-infestation. These deep colonies are the sticking point for most BCAs. Nevertheless, many growers have heard rumors of success with various BCAs. This tech tip will examine a few such BCA/root aphid relationships.
Stratiolaelaps scimitus (Hypoaspis) mites
Hypoaspis miles, also known as Stratiolaelaps scimitus, is a soil-dwelling predatory mite with the ability to survive for long periods of time in the crop media. Their primary prey consists of fungus gnats, shore flies, and thrips pupae. This BCA reproduces in high numbers, quickly establishing populations. Hypoaspis mites have been observed feeding on root aphids, but their limiting factor is physical access. Hypoaspis mites are only active in the top and bottom inch of container media. Deeper aphid colonies will remain untouched, providing new waves of pests as these colonies continue to feed on plant roots and reproduce.
Nematodes
Nematodes for use as biological controls have been established as an easy and effective tool for growers to use. From fungus gnats and shore flies to thrips pupae, their efficacy is well understood. Nematodes have the advantage of being able to be drenched into media, though typical nematode applications only target the top two inches of soil. Nematologists confirm that certain species of beneficial nematodes, specifically Heterorhabditis bacteriophora, have the capability to harass and infect root aphids, but their capacity to kill is far outpaced by the root aphids’ speed of reproduction.
Dalotia/Atheta/Rove beetle
Rove beetles are media-dwelling insects that help growers manage shore flies, fungus gnats, thrips pupae, springtails, and other soil-dwelling pests. They are aggressive feeders, spending most of their time at media-level but adults may fly around at night in search of prey. Being a generalist predator, they may indeed prey upon root aphids that they encounter, but their contact is limited. Dalotia beetles dwell primarily in the top ½ inch of soil or media, again leaving deeper hidden colonies of aphids untouched.
So, what DOES work?
Our current recommendations fall back on full-pot-volume drenches of biopesticides and insect growth regulators. Specifically, the combination of B. bassiana fungal spores with an azadirachtin product has shown some level of control in production environments. Drenches target root aphids while sprays control foliar aphids and fliers. A tank mix and weekly spray/drench of these products can go a long way toward achieving or maintaining control of both root and foliar aphid species. For more information contact your local Griffin rep or the GGSPro team.
| Product Name | Item Number | |
|---|---|---|
| BotaniGard WP | 70-12521 | |
| BotaniGard ES | 70-12511 | |
| BioCeres | 70-1245 | |
| Velifer | 70-9540 | |
| AzaGuard | 70-1225 | |
| Azatin O | 70-12301 | |
| Molt-X | 70-2410 | |
| Aza-Direct | 70-1222 |
