Adult moths are small, with a wingspan of 6–7 mm, displaying a mix of orange, white, and gray-black patterns. Females lay eggs on the undersides of soybean leaves, and larvae develop through five instars.
Early instars feed on leaf sap, creating serpentine mines that later expand into whitish blotches. Older larvae consume leaf tissue, forming tentiform mines where pupation occurs. Under controlled conditions at 25°C, development from egg to adult is roughly 25 days.
Larval feeding reduces photosynthetic capacity, primarily affecting mid- to lower-canopy leaves. Scouting should focus on field edges near wooded areas, where the characteristic tentiform mines are visible.
While no specific economic thresholds for M. morrisella exist, general soybean defoliation thresholds 30% during vegetative stages and 20% during reproductive stages can serve as interim guidance.
Management approaches are in development. Field studies indicate that insecticides with translaminar activity can suppress larval populations and damage.
Additionally, some soybean cultivars may be less attractive for egg-laying or less suitable for larval survival, suggesting potential for resistance breeding.
Ongoing research aims to refine scouting protocols, establish economic thresholds, and develop effective control strategies to limit yield losses from this new soybean pest.
Photo Credit: istock-oticki