Almond Wasp
Eurytoma amygdali
Borers, Mining & Weevils Insects High Risk 6–8 mm (adult female); 4–6 mm (male)
📖 Description
Eurytoma amygdali is a specialist chalcidoid wasp whose larvae develop exclusively inside almond kernels. The species is a chronic constraint on almond production across the Mediterranean basin, the Middle East, and the Himalayan almond belt of India (Kashmir, Himachal Pradesh, Uttarakhand). Indian almond acreage is small (~40,000 ha) but high-value (₹800–1,200/kg in-shell at 2024 prices), so even modest infestations carry disproportionate economic impact. A single female lays 20–40 eggs by drilling through the hull and shell with her ovipositor, depositing one egg per nut. The larva consumes the entire kernel over 25–35 days, then pupates inside the shell. There is one generation per year, with adults emerging in the following spring synchronised with almond bloom.
⚠️ Symptoms to watch for
- Infested almonds drop prematurely from the tree 4–6 weeks after petal fall; exit holes (1–2 mm diameter) are visible on the hull and shell when fallen nuts are cut open; kernels are hollowed out and filled with frass and a single larva; affected orchards show characteristic carpeting of dropped nuts under trees by early summer.
🩹 Treatment
- Collect and destroy all fallen nuts daily during the drop period (April–June) to break the lifecycle — this single cultural practice can reduce infestation by 70–80 % over two seasons. Install pheromone-baited yellow sticky traps at 4 traps/ha from pink-bud stage to monitor adult emergence. Apply chlorpyriphos 20 EC at 2 ml/L or lambda-cyhalothrin 5 EC at 0.5 ml/L at husk-split stage if trap counts exceed 5 adults/trap/week.
🌿 Organic treatments
- Burn or deep-bury (≥50 cm) all fallen nuts within 24 hours to prevent larval pupation in soil. Spray neem oil (1 % Azadirachtin) at 5 ml/L at petal-fall and again at 30-day intervals. Release Trichogramma embryophagum parasitoids at 50,000/ha during peak adult flight to target eggs. Apply Beauveria bassiana (1×10^9 CFU/g) at 5 g/L as a hull spray at husk-split.
🧪 Chemical treatments
- Chlorpyriphos 20 EC (2 ml/L), lambda-cyhalothrin 5 EC (0.5 ml/L), or thiacloprid 240 SC (0.5 ml/L) at husk-split stage. Repeat after 15 days if pest pressure persists. Always apply in the evening to protect pollinators.
🛡️ Prevention
- Plant late-husk-split cultivars such as 'Ferragnès' or 'Ferraduel' that escape peak wasp flight. Avoid interplanting almond with apricot or peach. Maintain clean orchard floor — no weeds or debris that shelter pupae. Spray kaolin clay (Surround WP) at 3 % w/v at petal-fall to deter oviposition.
🪴 Affected plants
- Almond (Prunus dulcis) is the primary host; occasionally infests related Prunus species such as apricot and peach in mixed orchards where almond is the dominant crop.
🦋 Natural predators
- Eupelmus urozonus (ectoparasitoid of larval/pupal stage, 10–30 % parasitism in unsprayed Kashmir orchards), Pnigalio mediterraneus (eulophid ectoparasitoid), Eurytoma plotnikovi (hyperparasitoid), and generalist predators including anthocorid bugs (Orius spp.) and spiders (Thomisidae) that consume adults on foliage.
🌱 Host plants
- Prunus dulcis (almond — primary host, all commercial cultivars susceptible). Occasionally on Prunus armeniaca (apricot) and Prunus persica (peach) in mixed Himalayan orchards.
🔄 Lifecycle
- Egg (8–12 days, inside kernel) → Larva (25–35 days,Kernel feeding) → Pupa (180–220 days, overwintering inside the shell on the orchard floor) → Adult (10–15 days, emerging at bloom).
- Univoltine (one generation per year).
📅 Season
- Adult emergence and oviposition: March–April (bloom to petal-fall).
- Larval feeding: April–June.
- Pupation: June onward.
- Overwintering pupal stage: July–February inside fallen nuts on the orchard floor.
🔎 Appearance
- Adult wasps are shiny black with a slightly elongated, laterally compressed abdomen; legs are reddish-brown with darker femora; wings are clear with a smoky stigma.
- Females carry a conspicuous ovipositor used to drill through the hard almond hull and shell.
- Larvae are legless, creamy-white grubs up to 8 mm long with small brown mandibles, found feeding singly inside the developing kernel.
💥 Damage level
- Severe
🔁 Reproduction rate
- Moderate
🗺️ Geographic regions
- Indian Himalayan almond belt (Kashmir
- Himachal Pradesh
- Uttarakhand); also reported from Mediterranean basin (Spain
- Italy
- Greece
- Turkey)
- Middle East (Iran
- Lebanon
- Syria)
- and Central Asia (Afghanistan
- Tajikistan).
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