SEX-SPECIFIC INFESTATION AND LARVAL STAGE STRUCTURE OF Tirathaba mundella IN OIL PALM INFLORESCENCES

Tirathaba mundella is a pyralid moth whose larvae infest oil palm inflorescences, causing bunch failure.This study quantified sex-specific infestation patterns and larval stage compositions of T. mundella on peat-grown palms.Over 20 weeks, 882 inflorescences (441 females; 441 males) were harvested from the Jobenar Raya Estate in Sarawak, Malaysia.Larvae were dislodged, counted, and assigned to five instars.Infestation incidence was greater in female inflorescences (27.9%; 123/441) than in male inflorescences (8.2%; 36/441), yielding a risk ratio of 3.42 (95% CI: 2.41-4.83).Among infested inflorescences (n = 159), multinomial logistic regression revealed a strong shift in stage structure by inflorescence sex (likelihood ratio χ² = 1578.9,df = 4, p < 0.001).Females were enriched for later instars (Stage 4-5), whereas males were dominated by early instars (Stage 1-2).These results indicate that female inflorescences serve as the principal developmental sites that sustain advanced stages, whereas male inflorescences may act as transient sites for early-stage establishment.Surveillance and control should prioritise female inflorescences and incorporate male inflorescences into sanitary pruning.Future work should determine whether larvae migrate between inflorescence types or whether dual-site oviposition with differential survival underlies the observed pattern, thereby improving the timing and efficiency of integrated pest management strategies.