Chelonus blackburni Cameron

Chelonus blackburni is a parthenogetic egg - larval parasitoid introduced from Hawaii, USA which is the natural home of this parasitoid. C. blackburni has a fairly wide host range but in India the common meal moth Corcyra cephalonica Stainton and potato tuber moth Phthorimaea operculella (Zeller) have often been used for multiplication of this parasitoid. It could also be multiplied successfully on Achroia grisella (Fabricius) and Spodoptera exigua (Hübner). C. blackburni has been used for the biological suppression of P. operculella in Maharashtra, cotton pests viz., Earias vittella (Fabricius) in Karnataka, Earias insulana (fabia) Stoll, in Maharashtra, Pecinophora gossypiella (Saunders) in Maharashtra and polyphagous Helicoverpa armigera (Hübner) on cotton and other host plants in many states. It is becoming an important component of IPM systems on potato, cotton, etc.

A set of 1500 eggs of potato tuber moth (PTM) laid on a cloth are stapled to a card. This card containing 0-24 hr old eggs is exposed to 30 Chelonus blackburni adults. The card is inserted through a side opening of a container used for Chelonus blackburni production. The plastic container (14 cm x 11 cm) is converted into C. blackburni rearing unit by cutting windows and fixing plastic mesh for aeration. Two cotton swabs, one soaked in 50% honey solution and the other in drinking water are also placed inside from the side opening which is closed tightly with a cloth covered cotton plug. The PTM egg card after exposing to C. blackburni fot 24 hrs is removed and placed on punctured potatoes. The potatoes are punctured by the method as described under PTM production procedure. This provides more entry points for PTM larvae and kept in a similar plastic container as described for exposure to C. blackburni. The bottom of this container is lined with sterilized sand. In 25.8±1.6 days time, adults start emerging from the cocoons formed in sand at the bottom of the cage or sometimes inside potatoes after completing development on potatoes. The adults live for 22.6±8.4 days and their fecundity is about 287.9±103.

The parasitoid could also be reared on Corcyra cephalonica by adopting the same procedure except that after exposing the Corcyra egg card for 24 hrs the parasitized eggs are transferred into a plastic container (20 x 15 cm) containing 1 kg of broken- sterilized grains of sorghum. The parasitoid develops in 42.5±3.5 days. The adults live for 18.8±5.5 days and the female lays 248.7±53.5 eggs.

The parasitoid can also be successfully reared on Achroia grisella (Fabricius) which is produced on artificial diet. Achroia grisella develops in 39.5±2.1 days as compared to Corcyra cephalonica which develops in 50.5±4.1 days. The most favoured host is Phthorimaea operculella which completes development in 24.7±2.0 days. The parasitoid on A. grisella completes its development in 36.4±3.5 days, the progeny produced lives 20.1±4.1 days, the female produces 365.2 ± 55.6 eggs.

The most popular method of production of C. blackburni is to produce it on PTM eggs.