Procedure
1. Preparation of rearing basins
The basins (16” dia) used for Corcyra multiplication are thoroughly cleaned with 0.5% detergent wash and rinsing in tap water followed by wiping with dry, clean – used towel and shade drying. Whenever the trays are emptied after a cycle of rearing, they have to be cleaned preferably to 2 per cent formaldehyde and returned to storage until further use. On reuse the cleaning steps are repeated (Fig 2).
2. Preparation of bajra medium for Corcyra
| a. |
The required quantities of bajra grains are coarsely milled and broken into 2-3 pieces in a milling machine. The broken grains are heat sterilized at 1000C for 1 hour to eliminate the residual population of stored product insects viz., Rhizopertha dominica, Sitotroga cerealella, Tribolium castaneum and fungal contaminants. Upon sterilization the grains are cooled under fan in a clean area. The grains are then transferred to plastic basins @ 2.5 kg/basin. |
b. |
Groundnut kernel in required quantity is broken using a pounding machine or a mechanical blender (domestic mixer). Then 100 g of the broken kernel is transferred to each basin and the contents are hand mixed thoroughly. |
c. |
Dry yeast (Bakers) and wettable sulfur is added @ 5g/ basin and the contents are mixed thoroughly. A spray of 10 ml of 0.01-0.05% streptomycin sulfate and mixing of the contents follows this. This medium is used for rearing Corcyralarvae. |
d. |
The number of basins required for egg infestation is calculated and the medium is prepared accordingly. |
3. Preparation of Corcyraeggs
The primary source of Corcyraeggs is reputed laboratories, commercial producers for bulk preparation. If it is intended to begin the production with nucleus colony, the adult moths can be collected from warehouses where the food materials are stored (Fig 3).
| a. |
The eggs used for building up the colony of Corcyrahave to be free from contaminants like the moth scales and broken limbs and not exposed to UV light. |
b. |
The collections of overnight laid eggs are measured volumetrically to ascertain the number of trays that can be infested with eggs. A cc of eggs is known to contain approximately 16000 – 18000 eggs. |
4. Infestation of medium with eggs
The overall production scheme (Fig. 4) involves initial infestation of the cumbu medium with Corcyraeggs in desired quantities. This is accomplished by sprinkling the freely flowing eggs on the surface of the medium in individual basins. Per basin 0.5 cc eggs of Corcyrais infested. The basins are then covered with clean khada cloth and held tightly with rubber fasteners. The basins are carefully transferred to the racks. At a time 84 such basins are stacked in the rack designed at TNAU.
5. Handling the trays during larval development
The larvae that hatch out in 3-4 days begin to feed the fortified Bajra medium. At this stage, light webbings are noticed on the surface. As the larvae grow up they move down. During this period the larvae are allowed to grow undisturbed in the trays. |
