Flat-backed millipede

Systematic position. Polydesmus inconstans belongs to the order Polydesmida, family Polydesmidae. These small arthropods are known as flat-backed millipedes, which reside in the soil profile and are commonly found in decaying organic matter or humid agricultural environments.

Host plants and damage. This pest primarily attacks germinating seeds and young seedlings of crops such as sugar beets, potatoes, wheat, and various greenhouse vegetables. The millipedes feed on the underground portions of the stem and the roots, leading to plant thinning and reduced vigor in field conditions.

Biology and life cycle. These millipedes favor high moisture levels and environments rich in decaying vegetable material. Females lay eggs in clusters within the soil, encased in protective earthen nests. The development involves a series of molts, where the organism gradually adds body segments until it reaches maturity, with environmental conditions such as soil temperature significantly affecting the speed of their cycle.

Harmfulness. The damage is particularly severe during cold, wet spring seasons, which delay seed germination. During these periods, the seeds remain vulnerable for a longer time, allowing the millipedes to feed on them extensively. This often leads to irregular crop stands and potential total yield losses in localized spots of a field.

Control measures. Integrated pest management involves proper tillage practices to reduce soil humidity and minimize organic debris that attracts the pests. Crop rotation and balanced fertilization are essential. When infestations are high, chemical control using granular soil insecticides or seed treatments containing systemic pesticides is the most effective approach to protect seeds and fragile seedlings during emergence.