Phyllanthus Leaf Webber
Diedra rubricosa
Chewing Insects Moderate Risk 20–25 mm wingspan (adult); 18–22 mm (mature larva)
📖 Description
Diedra rubricosa is a pyralid moth whose larvae web together leaves of Phyllanthus species in India. The species is a chronic defoliator of aonla orchards in Rajasthan, Gujarat, and Uttar Pradesh, with peak activity during the cool dry winter months (November–February) when humidity is low and new leaf flush is mature. Outbreaks are most severe in poorly managed orchards where pruning is neglected. Though direct yield loss is moderate (10–15 % in heavily infested orchards), the cosmetic damage to the outer canopy reduces orchard aesthetic value and may indicate broader neglect.
⚠️ Symptoms to watch for
- Larvae web together terminal leaves with silk, forming conspicuous dirty-white webbed masses on the outer canopy
- within the web, larvae feed on the leaf lamina, leaving only midribs and major veins
- heavily infested trees show characteristic 'burnt' appearance of the outer canopy by late winter
- severe infestation reduces fruit set and quality the following season.
🩹 Treatment
- Remove and burn webbed leaf masses during winter (December–February) — this single cultural practice can reduce infestation by 60–70 %.
- Spray lambda-cyhalothrin 5 EC at 0.5 ml/L or emamectin benzoate 5 SG at 0.3 g/L at 30-day intervals during the active season (November–March).
- Apply Bacillus thuringiensis var. kurstaki at 1 g/L against early-instar larvae before webbing becomes extensive.
🌿 Organic treatments
- Remove and burn webbed leaf masses weekly during winter.
- Spray Bacillus thuringiensis var. kurstaki at 1 g/L plus sticker at first sign of webbing.
- Apply neem oil (1 % Azadirachtin) at 5 ml/L.
- Release Trichogramma chilonis at 50,000/ha against eggs.
- Spray Beauveria bassiana at 5 g/L in humid weather.
🧪 Chemical treatments
- Lambda-cyhalothrin 5 EC (0.5 ml/L), emamectin benzoate 5 SG (0.3 g/L), or chlorantraniliprole 18.5 SC (0.3 ml/L).
- Apply as a high-volume spray to penetrate the webbed masses — use a wetting agent for better coverage.
🛡️ Prevention
- Prune the outer canopy in late October before oviposition begins to remove preferred oviposition sites.
- Remove wild Phyllanthus hosts from orchard boundaries.
- Avoid interplanting aonla with star gooseberry.
- Maintain balanced nutrition — nitrogen-deficient trees are more susceptible.
🪴 Affected plants
- Phyllanthus species including Phyllanthus emblica (aonla) and Phyllanthus acidus (star gooseberry / Harfarauri)
- also recorded on aonla cultivars 'NA-7', 'Kanchan', and 'Banarasi' in mixed orchards.
🦋 Natural predators
- Trichogramma chilonis (egg parasitoid)
- Apanteles spp. (larval braconid parasitoid)
- predatory bugs (Anthocoridae — Orius spp.)
- lacewings (Chrysoperla zastrowi sillemi)
- and birds (Parus major, Aegithalos concinnus) that tear open webs to extract larvae.
🌱 Host plants
- Phyllanthus emblica (aonla), Phyllanthus acidus (star gooseberry).
- Other Phyllanthus spp. may serve as wild reservoirs.
🔄 Lifecycle
- Egg (5–7 days, laid in clusters of 10–20 on tender leaves) → Larva (25–35 days, 5 instars, web-building) → Pupa (10–14 days, inside the web or in soil) → Adult (10–15 days).
- Multivoltine — 3–4 generations during the November–March active season.
📅 Season
- Active November–March (cool dry winter); peak activity December–February.
- Inactive during the hot dry season (April–June) when trees are leafless and during the monsoon (July–September) when high humidity favours disease.
🔎 Appearance
- Adult is a small pyralid moth with yellow-ochre forewings marked with two darker transverse lines and a darker discoidal spot; hindwings are pale grey with a darker border; at rest wings are held tent-like.
- Larvae are cylindrical, pale yellowish-green with a darker green dorsal stripe, dark head capsule, and sparse pale setae; mature larvae reach 22 mm.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian aonla tract (Rajasthan — Pratapgarh, Chittorgarh; Gujarat — Banaskantha, Mehsana; Uttar Pradesh — Pratapgarh, Varanasi).
- Also reported from Sri Lanka, Myanmar, and Thailand.
Have an Insect to Identify?
Upload or take a photo of an insect on your plant and our AI will identify it and recommend treatments.
📷 Diagnose from Image