Platygaster oryzae Cameron

Platygaster oryzae is a maggot-puparium parasitoid of Pyricularia oryzae parasitism levels reach very high, some-time nearing 100 per cent.

O. oryzae is multiplied in the glasshouse or insectary. It is reared on rice plants placed in a cage measuring 105 x 110 x 90 cm with glass or nylon mesh (30 mesh/cm). The front door opening is fitted with glass. The cage is fixed on a galvanised iron frame 20 cm high with 42 pots 15 cm deep and 15 cm wide containing three plants each. Three cages are grouped together and placed in an aluminum tray (20 x 400 x 400 cm) supported by six metal legs on concrete blocks at the bottom of the tray. The water level is maintained at 5 cm level to ensure adequate moisture in the pots. All the trays are connected to a water supply line with automatic valve fixed to fill the trays regularly. Mist blowers are fixed which maintain relative humidity between 90% and 100% for 96 h following the beginning of oviposition by the females.

Seeds of TN 1 variety or any other susceptible variety are sown in 15 cm plastic pots filled with sandy soil. The seedlings are thinned after 20 days to three plants per pot. O. oryzae adults less than 24 h old, are released in a cage 5 days after the rice plants are thinned. These adults are allowed to oviposit on the rice plants for 48 hrs. 75% of the eggs are laid by the females of O. oryzae during the first night after emergence. Upon emergence the adults are aspirated into a tube by disturbing the rice plants. The adults are collected upto a week. Males are smaller and have long and curved antennae, while females have short antennae. The life cycle is completed in 19-39 days.

The O. oryzae infested plants are exposed to P. oryzae females in batches which lay eggs, but the larval development is slow and finally the parasitoid emerges from the mature larvae or sometimes puparia. A single individual develops in each host. The rearing of P. oryzae is being further improvised.