Grainage is where disease is either excluded or passed on. Mother moth examination is the only reliable pebrine test, and the moth stage is the only stage at which it works — a cocoon infected in the fifth instar still looks sound, so appearance can never substitute for the microscope.
Seed cocoon selection and preservation
- Larvae uniform in size through rearing; cocoons taken from the peak ripening date (bhor pok), compact and uniform.
- Muga: female ≥ 6.0 g, male ≥ 4.0 g. Eri: female ≥ 3.0 g, male ≥ 2.5 g.
- Transport in cooler hours in shelved bamboo baskets so cocoons neither overlap nor bruise.
- Preserve in a cocoon cage in a single layer or as a garland, cool and well ventilated, at 27–29 °C and 70–80 % RH.
Grainage operations
| Operation | Practice |
|---|---|
| Layout | Cocoon preservation room 30 × 20 ft and egg-laying room 40 × 15 ft; hall cleaned and disinfected with 5 % bleaching powder one week ahead, freed of ants, lizards and uzi maggots, sealed airtight 2–3 days, then opened. |
| Emergence | About two weeks after cocoon formation; males emerge ahead of females. Hold the hall at 26–28 °C. Fresh moths sit motionless 1–2 hours and must not be disturbed. |
| Sorting | Reject deformed, darkened or weak moths before pairing. |
| Pairing | Equal numbers of males and females in trays or cages by about 16.00 hours. Allow at least six hours before decoupling. Females emerging in the evening usually do not mate that night. If males are short, reuse decoupled males after 2–3 hours rest. |
| Tying | Hold the coupled female by the right hind wing and tie her to the kharika — a straw or twig bundle about 8 inches long — with cotton thread. |
| Laying | Three days only. A muga moth would lay over 6–7 days in the wild; limiting to three keeps hatching uniform and excludes disease from weak late-hatched larvae. |
| Egg sterilisation | After examination, surface-sterilise in 2 % formaldehyde, then soap solution and fresh water. |
Mother moth examination
The moth stage is the best stage for detecting pebrine. Examination is by two persons, cross-checking.
| Step | Operation |
|---|---|
| 01 | Macerate. Crush one moth in a mortar with 10 ml K2CO3 — 0.8–1.0 % for muga, 0.6–0.8 % for eri. |
| 02 | Settle. Transfer to a tube, preferably plastic; stand 3–5 minutes so debris floats clear. |
| 03 | Filter and centrifuge. Filter through 2–3 thin layers of absorbent cotton; spin 5 minutes at 3,000 rpm. |
| 04 | Disperse. Decant; disperse the sediment in 0.8 % (muga) or 0.6 % (eri) K2CO3, or 2 % KOH. |
| 05 | Read. Two smears per sample, five fields per smear at 600×; record intensity by spores per field. |