Black soldier fly frass — the manure, shed skins, and leftover food from insect farming — reduced leaf damage from insect pests by 38 to 45 percent when used as a soil amendment in soybean fields. Published in the Journal of Environmental Quality (Arkansas Agricultural Experiment Station, 2026), the study compared frass to poultry litter across irrigated and non-irrigated soybean and switchgrass systems. The pest-resistance effect is the first field-condition demonstration that insect frass can enhance a plant's defense against herbivory.
The nutrient efficiency was equally striking. Low application rates of frass produced two to four times greater nutrient efficiency than either high frass rates or poultry litter, delivering similar yields with lower inputs. Less amendment, same crop. The standard agricultural logic — more fertilizer, more growth — inverts: the frass at low concentration does something that additional frass or alternative amendments don't replicate.
The researchers can't fully explain it. Their hypothesis: plant-growth-promoting microbes present in insect frass but absent in poultry litter. The frass isn't just a nutrient source. It's an inoculant — it introduces microbial communities that either stimulate plant defense pathways or improve nutrient uptake or both. The “something else” is the interesting part: a byproduct from one agricultural system (insect farming) carrying beneficial microorganisms that enhance a different agricultural system (row crops).
The industrial framing treats insect farming and row crop agriculture as separate supply chains. Frass is a waste product from the first, a potential input to the second. But the microbial connection suggests they're parts of the same system — the insects cultivate soil microbes as a side effect of their metabolism, and those microbes are what the soil was missing. The waste product isn't waste. It's the connection between two halves of a cycle that industrial agriculture separated.