Cashew Stem & Root Borer
Plocaederus ferrugineus
📖 Description
Cashew Stem & Root Borer (CSRB) is the most destructive pest of cashew across the Indian subcontinent, particularly in Kerala, Karnataka, Goa, Maharashtra, Andhra Pradesh, Odisha, and Tamil Nadu. Adult female beetles lay eggs in bark crevices near the base of the trunk. Newly hatched larvae bore into the bark and tunnel extensively through the stem and roots, feeding on the inner bark and sapwood. Tunnels fill with frass and gum, and damaged trees show yellowing, wilting, and dieback before dying suddenly in advanced stages. The pest’s hidden internal feeding makes chemical control difficult — manual extraction of larvae with a hooked wire is the most effective control method. Early detection and intervention are critical because severely infested trees cannot be saved. Orchards can be completely lost within 2-3 years if CSRB is not managed.
⚠️ Symptoms to watch for
- Yellowing and wilting of leaves, oozing of gum and frass from holes in the trunk and roots, dead bark peeling off to expose tunnels, dieback of branches, sudden death of trees in advanced stage, complete plantation loss possible in 2-3 years if unmanaged, yield loss 30-100%
🩹 Treatment
- Manually extract larvae from tunnels with a hooked wire, apply Beauveria bassiana paste on wounds, drench soil with chlorpyrifos, destroy infested trees, swab trunk with neem oil
🌿 Organic treatments
- Manually extract larvae from tunnels with a hooked wire (most effective), apply Beauveria bassiana paste on freshly opened wounds, apply Metarhizium anisopliae in soil around base, drench soil with neem oil 5 ml/L, swab trunk with neem oil + paste, apply neem cake @ 250 g per tree, remove and burn severely infested trees before adult emergence
🧪 Chemical treatments
- Drench soil with Chlorpyrifos 20 EC @ 5 ml/L per tree, swab trunk with Monocrotophos 36 SL paste (5 ml + 5 ml water + 90 g clay), Fipronil 5 SC @ 4 ml/L drench, apply Carbofuran 3G @ 50 g per tree in soil, Bifenthrin 10 EC @ 2 ml/L drench
🛡️ Prevention
- Inspect orchards weekly for early signs (oozing, frass), manually extract larvae early before extensive damage, swab trunks with neem oil paste preventively, maintain orchard sanitation, avoid injuries to trunks and roots, remove and burn severely infested trees before adult emergence, plant resistant varieties where available, avoid waterlogging around tree base, intercrop with repellent plants like neem or marigold
🪴 Affected plants
- Cashew (primary), Occasionally Other Anacardiaceae
🦋 Natural predators
- Birds (woodpeckers), Predatory Beetles, Ants, Spiders, Entomopathogenic Fungi
🌱 Host plants
- Anacardium occidentale
🔄 Lifecycle
- Female lays 80-200 eggs in bark crevices near the base of the trunk.
- Eggs hatch in 6-10 days.
- Larvae tunnel through stem and roots for 4-7 months, passing through 8-10 instars.
- Pupation occurs in a pupal cell inside the wood, lasting 15-30 days.
- Adults live 30-60 days and are nocturnal.
- Total life cycle 6-9 months; 1-2 generations per year.
📅 Season
- Year-round, adult activity peaks Apr-Sep during warm humid period
🔎 Appearance
- Large, reddish-brown longhorn beetles with long antennae (longer than the body in males).
- Larvae are creamy-white, legless grubs with a brown head, growing up to 50 mm, found tunneling in cashew stems and roots.
💥 Damage level
- Severe
🔁 Reproduction rate
- Slow
🗺️ Geographic regions
- Indian Subcontinent
- Southeast Asia
- East Africa
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