Casuarina Stem Borer

📖 Description

Casuarina Stem Borer (Sahyadrassus malabaricus), also called Casuarina Wood-Borer, Malabar Swift Moth, or Giant Casuarina Borer, is a serious boring pest of casuarina (Casuarina equisetifolia — one of India’s most important coastal agroforestry trees, used for fuelwood, pulpwood, windbreaks, and coastal erosion control) across the Indian subcontinent, particularly severe in the major casuarina-growing belts of Tamil Nadu (Cuddalore, Nagapattinam, Tiruvarur, Thanjavur, Pudukkottai, Ramanathapuram — India’s largest casuarina-producing state, with over 100,000 hectares of coastal plantations), Andhra Pradesh (Nellore, Prakasam, Guntur, Krishna, East Godavari, West Godavari, Srikakulam, Vizianagaram, Visakhapatnam — second largest), Odisha (Puri, Cuttack, Balasore, Bhadrak, Ganjam, Jagatsinghpur — coastal districts), West Bengal (Purba Medinipur, South 24 Parganas, North 24 Parganas — Sundarbans region), Karnataka (Uttara Kannada, Udupi, Dakshina Kannada — coastal districts), Kerala (Kollam, Alappuzha, Thrissur, Kasaragod — coastal districts), Maharashtra (Ratnagiri, Sindhudurg — coastal districts) and Gujarat (Junagadh, Amreli, Bhavnagar, Surat, Valsad — Saurashtra and south Gujarat coast) where India has the world’s largest casuarina plantation resource (over 500,000 hectares of casuarina plantations, mostly in coastal areas, producing over 5 million tonnes of pulpwood and fuelwood annually — casuarina is a critical multipurpose tree in Indian coastal agriculture, used for paper pulp (mill demand), fuelwood (household demand), poles (construction), windbreaks (coastal protection), and as a nitrogen-fixing agroforestry species in coastal saline soils where few other trees grow, and India’s casuarina plantation industry is worth over ₹1,500 crore per year). The pest is unusual among casuarina pests because (a) it is one of India’s largest moth species (wingspan up to 110 mm) — but despite their size, the adults are short-lived (5-10 days) and rarely seen, (b) the female lays 500-1000 eggs on the bark of the host tree or drops them in flight — meaning a single female can infest multiple casuarina trees, (c) the young larvae feed on the bark and sapwood before boring into the wood — where they construct large tunnels (up to 15 mm diameter) that can completely hollow out the trunk, making the tree vulnerable to wind breakage, (d) the larvae are protected from contact insecticides and most natural enemies inside the wood — requiring insecticide injection into bore holes or entomopathogenic nematodes for effective control, (e) the pest has a long life cycle (1-2 years per generation) — meaning infestations can persist for multiple years before being detected, by which time the damage is often severe, (f) the larvae girdle the trunk by feeding on bark and sapwood in a ring around the tree — cutting off sap flow and killing the tree above the girdle, AND weakening the trunk at the tunnel site so the tree snaps in strong winds (a major economic damage in coastal casuarina plantations where strong monsoon winds are common), (g) the damaged tissue is often invaded by fungal pathogens — causing wood rot that further reduces pulpwood quality, and (h) the pest is particularly severe in coastal plantations (where casuarina is mostly grown) — making area-wide management difficult across fragmented small-scale plantations. IPM with borer-free seedling certification (most critical preventive measure), light trap monitoring (useful for early detection of moth activity), biological control (Beauveria bassiana and Metarhizium anisopliae — entomopathogenic fungi injected into bore holes kill larvae inside tunnels; Steinernema carpocapsae entomopathogenic nematodes — highly effective against borers inside tunnels, seeks out larvae in the wood; conservation of native parasitoids Bracon and Apanteles by avoiding broad-spectrum insecticides; conservation of woodpeckers which feed on larvae inside wood), neem-based sprays and trunk pastes, need-based insecticide injection into bore holes (Dichlorvos is most effective — fumigant action; Monocrotophos is systemic), trunk banding with polythene sheet coated with grease (most effective preventive measure for high-value trees), and orchard sanitation provides effective and sustainable control. The pest is a particular concern for Indian casuarina growers because (i) casuarina is a high-value agroforestry crop — even slight borer damage reduces both pulpwood and fuelwood value, (ii) the tree is grown as a 4-6 year short-rotation crop — so borer attack can completely destroy a plantation, with economic losses of ₹50,000-1,00,000 per hectare, (iii) the crop is grown mostly in small-scale coastal plantations with limited access to IPM knowledge and insecticide injection equipment, and (iv) the crop is grown in cyclone-prone coastal regions where wind breakage of borer-weakened trees is a major economic risk — entire plantations can be lost in a single cyclone. Climate change with warmer conditions and more frequent cyclones is expanding the pest’s range and severity.