Crop Loss Assessment on Jajor Mungbean Pests in Rice-Based Cropping Systems

Abstract

Yield-loss relationships study for major insect pests on mungbean grown in the rice-based cropping systems at different growth stages by using single plant method was conducted at Chainat Field Crops Research Centre and farmer’s field of Amphoe Sunburi, Chainat province. The observations on damage-density were made at weekly intervals starting from vegetative through harvesting stages. The observed plants were harvested separately and the seed weight per plant determined. The informations obtained were statistically analyzed by a stepwise multiple regression procedure. The results indicated that the infestations occurred during vegetative stages had no impact on yield at all. However, the infestation of cutworm (Spodoptera litura Fabricius) and thrips (Megalurothrips usitatus Zehntner) during the end of vegetative of pod filling stages were negatively correlated to grain yield significantly and resulted in yield reduction approximately by 0.3-0.5 and 0.3-0.4% per percent infested leaves respectively. Subsequently economic-injury levels were, therefore, established to be 16 and 30% infested leaves for cutworm an thrips respectively.