Gliricidia Shoot Borer

📖 Description

Terastia metaspidis — the Gliricidia Shoot Borer — is a pyralid moth whose larvae bore into the terminal shoots of Gliricidia sepium, the versatile nitrogen-fixing tree used across Indian plantations as a shade tree (coffee, cocoa), live fence (coconut, areca nut), and green-manure coppice (tea, pepper, rice bunds). The moth is widely distributed across India’s plantation belts — Coorg and Chikmagalur in Karnataka, Idukki and Wayanad in Kerala, Nilgiris and Anaimalai in Tamil Nadu, and the tea gardens of Assam and Darjeeling — wherever Gliricidia has been planted (estimated 100,000+ ha of Indian plantations have Gliricidia as a component). Adult moths emerge at dusk from pupae inside hollowed-out Gliricidia shoots, mate, and females lay 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, where it feeds for 18–25 days on the soft pith and vascular tissue. The entry hole is small (2–3 mm) and easily missed; the first visible symptom is the wilting and drooping of the terminal shoot 5–7 days after larval entry. By the time wilting is observed, the larva is already deep inside the shoot and beyond the reach of contact insecticides — making the pest difficult to control chemically once established. The larval stage is the damaging stage; mature larvae pupate inside the hollowed shoot in a tough silken cocoon, and the adult moth emerges 10–14 days later through a circular exit hole. The total lifecycle is 35–45 days, allowing 4–5 overlapping generations per year in India’s tropical plantation climate. The economic impact of Terastia on Gliricidia is primarily through deformation of the tree’s architecture — killed terminals force the tree to produce multiple lateral shoots, destroying the single straight bole required for shade-tree use. Heavily infested Gliricidia rows lose 30–60% of their terminals over a single monsoon season, requiring labour-intensive coppicing (cutting back to 30 cm height) to restore single-leader growth. Coppiced Gliricidia takes 18–24 months to regrow to shade-tree height, during which time the main crop (coffee, cocoa, pepper) is exposed to excessive sunlight. The pest is also a problem for the Indian Council of Agricultural Research’s (ICAR) Krishi Vigyan Kendras (KVKs) and the National Bureau of Plant Genetic Resources (NBPGR), which maintain Gliricidia germplasm accessions — infestations in germplasm banks can spread through distribution of infested cuttings to plantation growers. Management is best achieved through IPM — pruning and destruction of wilted terminals (the single most effective cultural practice), conservation of natural enemies (Trichogramma chilonis egg parasitoid, Cotesia sesamiae larval parasitoid), Bt application against neonate larvae before shoot entry, and avoidance of broad-spectrum insecticides that disrupt the rich natural-enemy complex of plantation ecosystems. Genetic resistance is being explored — ICAR-CRIDA (Central Research Institute for Dryland Agriculture, Hyderabad) has identified several Gliricidia accessions with tolerance to Terastia, characterised by harder terminal tissue that resists larval entry.