Erythrina Shoot Borer

📖 Description

Terastia prosopealis — the Erythrina Shoot Borer — is a pyralid moth closely related to Terastia metaspidis (the Gliricidia Shoot Borer) and sharing the same genus, host-shoot-boring habit, and Indian plantation ecosystem. The pest is widely distributed across India’s coffee belt — Kodagu, Chikmagalur, and Hassan in Karnataka; Idukki and Wayanad in Kerala; Nilgiris and Anaimalai in Tamil Nadu — wherever Erythrina (Dadap) is grown as a shade tree for Robusta coffee. Erythrina lithosperma is the single most important shade tree of Indian Robusta coffee plantations, providing the regulated 30–50% shade that Robusta requires for optimal berry set, bean size, and beverage quality. Adult moths emerge at dusk from pupae inside hollowed-out Erythrina shoots, mate, and females lay 100–180 eggs singly or in pairs on the underside of terminal leaflets. Eggs hatch in 4–5 days, and the neonate larva immediately bores into the tender terminal shoot. The larva feeds inside the shoot for 20–28 days on the soft pith and vascular tissue, moulting 5 times. The first visible symptom — wilting of the terminal shoot — appears 5–7 days AFTER larval entry, by which time the larva is deep inside and beyond the reach of contact insecticides. Mature larvae pupate inside the hollowed shoot in a tough silken cocoon; the adult moth emerges 12–16 days later through a circular exit hole. Total lifecycle 40–50 days, with 4–5 overlapping generations per year in India’s tropical plantation climate. The economic impact on coffee is significant — heavily infested Erythrina rows lose 40–70% of their terminals over a single monsoon season, requiring labour-intensive coppicing to restore. Coppiced Erythrina takes 18–24 months to regrow to effective shade-tree height, during which time Robusta coffee bushes are exposed to excessive sunlight, reducing berry set, bean density, and cup quality. The Coffee Board of India estimates annual losses from Erythrina Shoot Borer at ₹50–80 crore across the Karnataka and Kerala Robusta belts. Management is best achieved through IPM — pruning and destruction of wilted terminals (the single most effective cultural practice, removing 60–80% of the larval population when practised weekly during peak activity), conservation of natural enemies (Trichogramma chilonis egg parasitoid, Cotesia sesamiae larval parasitoid), and Bt application against neonate larvae. Genetic resistance is being explored — the Central Coffee Research Institute (CCRI, Balehonnur) has identified several Erythrina accessions with tolerance to Terastia, characterised by harder terminal tissue that resists larval entry, and these are being propagated for distribution to coffee growers.