Insecticidal effect of diatomaceous earth formulation against Pear lace bug, Stephanitis pyri (Fabricius, 1775) (Hemiptera: Tingidae)

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The pear lace bug, Stephanitis pyri (Fabricius, 1775) (Hemiptera: Tingidae), is an economically important pest of pome fruit trees. This study was conducted under controlled laboratory conditions to determine the insecticidal efficacy of Detech® WP 95 against the nymphal instars and adults of S. pyri. Experiment was carried out on apple, Malus domestica Borkh. (Rosales: Rosaceae) leaves using aqueous DE suspensions at three concentrations (2.5, 5, and 10 g/m²), and mortality was recorded daily from the first to the fifth day after treatment. 100% mortality was achieved within 24h in all treatments with 1st nymphal instars, indicating a high susceptibility of early instar nymphs to DE exposure. In the 5th nymphal instar, at a rate of 2.5 g/m², mortality increased from 70 to 100% on the third and fifth day, respectively. At 5 g/m², mortality was 80% on the second day and 100% on the third day of the treatment. Overall, mortality was positively correlated with both exposure time and DE concentration. Lethal time (LT₅₀) value for adults at the lowest concentration was 1.29 days, which was lower than that of fifth-instar nymphs (2.56 days). In conclusion, DE shows significant toxicity against S. pyri and highlights its potential as a natural insecticidal agent in integrated pest management programs.