Entomology, Department of


Date of this Version

Spring 5-2012


DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Entomology, Under the Supervision of Professors Thomas E. Hunt and Robert J. Wright. Lincoln, Nebraska: May 2012

Copyright (c) 2012 Silvana Vieira de Paula Moraes


Western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a native pest of dry beans (Phaseolus vulgaris L.) and corn (Zea mays L.), and historically distributed in the western United States. The insect’s recent expansion eastward is documented since 1999. The species is univoltine, the adults typically emerge in the middle of July, lay eggs on corn leaves, and the larvae feed on different corn tissues. In the fourth instar, larvae start colonization of the ear where they feed on kernels. There is a narrow window for management and early detection of the pest in the field is essential. Larval feeding and dispersal of early larval instar studies of western bean cutworm are necessary to improve the understanding about how feeding requirements affect larval survival and establishment on the corn plant. A refinement of economic injury levels (EIL) and economic thresholds (ET) are also required for management decision-making. Studies during 2008 - 2011, across three ecoregions of Nebraska, had the following objectives: (1) developing a binomial sequential sampling plans for egg masses, (2) determine the feeding behavior and dispersal of the early instars on corn, and (3) development of EILs and the ETs that incorporate the dynamics of corn price, management cost, and pest survival. The results from the present study demonstrated that the binomial sequential sampling plans developed significantly reduce the effort required for effective management of this pest, reducing sampling effort from 100 plants sampled to an average of 38 to 41 plants sampled per field. The results indicate low larval survival of this species and that the early instars of western bean cutworm are the critical stage for establishment in corn. A behavior of initial larval movement toward the tassel was observed. The overall mean yield loss one western bean cutworm larva per plant was 945.52 kg/ha (15.08 bu/acre), based on 74,100 plants/ha. The ETs are expressed in percentage of plants with at least one egg mass, incorporate larval survival that was observed across three locations in Nebraska.

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