The population dynamics and natural mortality of the lesser cornstalk borer, Elasmopalpus Lignosellus, in the peanut agroecosystem and the biology of selected primary parasites

Abstract

The temporal distribution of the lesser cornstalk borer (LCB), Elasmopalpus lignosellus (Zeller), was variable in selected peanut fields during 1975-1977. Three distinct generations occurred in 1975 and 2 in 1976. Generations overlapped in 1977 with the egg population assuming an exponential rate of growth. The density of egg populations was highest in mid-late August of each year. Ecological life tables were constructed from the population data for the generations of 1975-1977. Real mortality (100rx) was variable as indicated by the following values for each life stage: egg and just-hatched larval stage, 49.7-86.8%; medium larval stage 2.3-34.5%; large larval stage, 1.1-26.7%; and pupa, 0-2.9%. Total real mortality for the generations ranged between 87.0-99.9%. A rich fauna of natural enemies was found associated with LCB in peanuts, including 9 species of parasites, 2 pathogens and 3 predator complexes. However, parasitism and disease contributed little to total generation mortality. Parasitism of larvae of medium size based on real mortality ranged from 0.3-2.3% and 0-2.7% for large larvae. Mortality due to disease in the medium and large larval stages varied between 0-6.7% and 0-1.75%, respectively.