Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

First Advisor

T. E. Reagan

Abstract

To facilitate a better understanding of how varietal resistance and predation affect area-wide sugarcane borer populations, several studies were undertaken before the development of a simulation model. The first study was a 3-year investigation into the compatibility and contributions of varietal resistance, arthropod predation and insecticide toward sugarcane borer control. Insecticides were shown to be the predominant management factor preventing plant injury, but varietal resistance appeared nearly as important in terms of sugarcane borer population regulation in sugarcane. The next study assessed a moth production index in addition to the percentage of bored internodes as a tool for quantifying varietal resistance to the sugarcane borer. Resistance ratings based on the percentage of bored internodes were proven to be inadequate estimators of moth emergence due to differences in sugarcane borer survival after entry into the stalk. The third study investigated the fecundity of the sugarcane borer with larval development on four gramineous hosts. A single linear regression on female pupal weight was obtained to predict fecundity regardless of the host for larval development. The simulation model included processes of immature development, oviposition, host-dependent mortality and mortality due to arthropod predation. Varietal parameters in the model were obtained from small-plot varietal evaluations. Percentages of bored internodes were used to compare survival of sugarcane borer eggs until establishment in the stalk among sugarcane cultivars with and without predator suppression. To estimate survival among cultivars, from establishment in the stalk until pupation, a relative survival index was utilized. Simulations showed that differences in moth emergence and total emergence were greatest when there was no exchange of adults among varieties. Simulations indicated that the impact of susceptible varieties on sugarcane borer populations can be mitigated if these varieties are properly dispersed among varieties with greater resistance. Relatively small differences observed in small plot varietal evaluations were magnified during the simulations when amount of adult redistribution among varieties was reduced (i.e. grown in larger continuous plantings). Thus, results obtained from small plot varietal resistance evaluations alone do not adequately address the potential role that varieties may have on pest populations when grown on larger acreages.

Pages

147

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