Date of Award

1986

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

Abstract

The effect of tomato fruit size and SGSB density and feeding duration on tomato circumference, weight, and days to maturity, as well as SGSB feeding frequency as indicated by the deposition of stylet sheaths, was quantified. Density and feeding duration had a significant effect on all four damage indices. The interactive effect of density and feeding duration were nonsignificant across all fruit damage indices. Feeding damage induced an early maturity of fruit and thereby reduced fruit size and weight. Both density and feeding duration significantly affected fruit grade. Because of highly significant interactions among grade, density, and feeding duration, the interaction term (bug-days) was used to develop polynomial regression models for the estimation of injury levels. The percentage fruit to be classified as US grade 1, 2, or 3 with a given feeding duration can be estimated with these equations. Among green fruit of varying sizes, SGSB fed less frequently on fruit of intermediate size. The number of stylet sheaths per cm('2) area on tomato fruit was inversely proportional to the size of the fruit. Among mature green and red tomatoes of the same size, SGSB significantly chose green fruit over red fruit and fed longer and more frequently on green than on red fruit. Male SGSB produced significantly more stylet sheaths than females on green fruit. Total feeding time and the mean duration of proboscis insertion were similar in both sexes. Sampling in the morning or afternoon revealed no significant differences in both SGSB within plant dispersion and time consumed in making counts. Strata containing fruit clusters had the lowest coefficients of variation (CV) and the highest mean SGSB counts. The penultimate fruit cluster was the most efficient sampling unit among plant strata. Regression equations estimating whole-plant populations of SGSB from individual fruit clusters were developed. The between-plant dispersion of SGSB fitted a Negative Binomial distribution with a moderate aggregation. A sequential sampling plan using the penultimate fruit cluster as a simple unit was developed to classify SGSB populations into light, moderate, and severe damage levels.

Pages

102

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