The Effects of Soil Moisture on the Pupation, Survival, and Emergence of the Tomato Leafminer, Tuta absoluta

The tomato leafminer, Tuta absoluta (Meyrick), is a globally invasive lepidopteran pest whose pupal stage commonly occurs within or at the soil surface. Soil moisture is a primary abiotic driver shaping soil microhabitats and therefore likely to influence pupation behavior, pupal survival and emergence. We quantified how six controlled soil moisture levels (0%, 20%, 40%, 60%, 80% and 100% saturation, wet-weight basis) affect pupation site selection, pupation depth, pupal survival and emergence under laboratory conditions, and performed a four-choice moisture preference assay. Larvae preferentially selected shallow soil layers (0–1 cm) and showed a marked behavioral preference for relatively low moisture (20–40%); maximum emergence (83%) occurred at 20% moisture. Both extreme drought (0%) and high saturation (≥80%) strongly reduced survival and emergence. These unimodal responses indicate that soil moisture constrains T. absoluta recruitment and may be exploited as a target for ecologically based control. The results provide a quantitative basis for soil-moisture-oriented IPM tactics and identify field validations and formulation/timing optimizations required to translate laboratory findings into practice.