Using energy budget data to assess the most damaging life-stage of an agricultural pest Mocis latipes (Guenèe, 1982) (Lepidoptera - Noctuidae)

Abstract

There is much evidence to support that Mocis latipes larvae (Guenèe, 1852) are the most dangerous pasture pest and usually cause large environmental losses. However, no studies have been carried out to identify the instars during which this moth causes the most damage to the environment. Here we calculate M. latipes larval energy budget to assess its consumption across all instars and estimate the consumption/amount of plant biomass required to complete its larval development. Assimilation, respiration, consumption, excretion, gross growth efficiency and net growth efficiency were calculated. Pearson correlations were used to identify the best predictors that influenced larval growth and weight. Across all instars consumption increased exponentially, especially during the last phase. M. latipes larvae consumed ca 13.8% of total food from the first to the fifth instar, whereas during the sixth instars these larvae consumed ca 72.6%. Results also show that the best gross growth and net growth efficiency were obtained when larvae reached the fifth instar. The results also show that one larva of Mocis latipes consumes 1.02 g (dry weight) of Paspalum maritimum (Trin) in 19 days. Overall, our results indentified the sixth instar as the most destructive instar of this insect. Thus, once we know the most destructive instars of this pest, measures can be taken to disable M. latipes larval development and consequently stop their increase in plant consumption, reducing ecological and economic damage. This knowledge may eventually lead to reduced agricultural damage and contribute to sustainable farming strategies.