Root Aphids

Root aphids are typically pale or waxy-coated, distinguishing them from the more variably coloured foliar aphids, and are found clustered on roots or the below-ground portion of stems when soil around affected plants is carefully disturbed.

Above-ground signs are often the first clue: plants that wilt or appear stunted despite adequate soil moisture, sometimes with ants visibly active around the base of affected plants tending the colony below.

Like foliar aphids, root aphids can reproduce rapidly through asexual reproduction under favourable conditions, allowing underground colonies to expand quickly once established on a host root system.

Some species alternate between root and foliar feeding at different life stages or times of year, while others remain root-associated throughout, often assisted in colonisation and protection by mutualistic ants.

Root feeding reduces the plant’s capacity to take up water and nutrients, producing wilting, yellowing, and stunted growth that can be mistaken for drought stress or nutrient deficiency until roots are inspected directly.

Host crops include lettuce, maize, and sorghum, among other crops where root aphid colonies can establish on the root system.

Because root aphids are hidden below ground, monitoring relies on inspecting the roots of wilting or stunted plants, watching for associated ant activity at the plant base, and soil sampling in fields with a history of root aphid pressure.

Root aphid management fits within integrated pest management, combining several tactics rather than relying on any single approach.

• Rotate away from known host crops where root aphid pressure has been identified
• Manage ant populations that protect and spread root aphid colonies where they are a contributing factor
• Support soil biology and organic matter that favour natural predators and pathogens of soil insects
• Inspect roots of wilting or stunted plants to confirm root aphids before assuming other causes