Nutritional studies of the rice stem borer,Chilo suppressalis Walker, and its mass rearing

Abstract

The nutritional requirements of the rice stem borer,Chilo suppressalis Walker were studied by rearing on synthetic food media in relation to the constituents of the rice plant. The larvae required amino acids, vitamins, carbohydrates, cholesterol, minerals and water extract of the rice plant for their growth. Among amino acids, arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophane and valine were indispensable for the growth, and these amino acids could not be synthesized in the larval body. Among vitamines, thiamine, riboflavin, nicotinic acid, pyridoxine, Ca-pantothenate, folic acid, biotin, cholin chloride and ascorbic acid were essential for the growth. Cholesterol is the only essential nutrient among fat-soluble factors. Fructose, glucose and sucrose showed high nutritive values among carbohydrates. Addition of the water extract of the rice plant to the media improved the development of the insects, but the excess amounts of it resulted inhibition of the growth. Two aromatic acids, benzoic and salicylic acids, were isolated as the growth inhibitory substance.

p-methyl acetophenone isolated from the rice plant seemed to play an important role for the attraction of the insect.

Mass rearing of the rice stem borer in a laboratory was carried out on two kinds of foods: living rice plant seedlings and synthetic food media. The rearing the insects on rice seedlings is easy if rice seeds are available. The rearing on synthetic food media is modified to simplify from these for the nutritional study. The rearing practices, merit and demerit of both methods are discussed.

Résumé

Les besoins nutritionnels deChilo suppressalis ont été examinés par élevage sur milieux artificiels en relation avec les constituants du riz. Les larves exigent 10 acides aminés, 9 vitamines, des hydrates de carbone (fructose, glucose et sucrose), du cholestérol, des sels minéraux et de l’extrait aqueux de riz pour leur croissance. L’addition d’extrait de riz accélère le développement des larves mais un excès détermine une inhibition de la croissance due à deux acides aromatiques, les acides benzoïque et salicylique. La p-méthyl acetophenone isolée du riz semble jouer un rôle important pour l’attraction de l’insecte.

L’élevage en masse du foreur a été effectué avec deux types d’aliments: des jeunes plants de riz et des milieux artificiels. Les avantages et inconvénients des deux techniques sont discutés.