Document Type

Thesis - University Access Only

Award Date

1995

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Billy W. Fuller

Abstract

Artificial infestations of non-viruliferous bird-cherry oat, Rhopalosiphum padi (L.), and English grain aphids, Sitobion avenae (F.), were applied to spring wheat, Triticum aestivum (L.), under laboratory and field conditions. An aphid-free control and three levels of aphid infestation at 30, 60 and 120 aphids per plant were maintained and evaluated for differential plant responses to aphid feeding in the laboratory during phenological spring wheat growth stages of boot, anthesis and dough. Least significant difference analyses for bird-cherry oat aphid determined significant differences (P < 0.01) among treatments concerning mature plant height, spikelet number, seed yield and total seed weight per head for the duration of boot. Observed trends suggest that aphid feeding influences have an additive effect for these variables. Significant differences (P < 0.01) regarding variously maintained English grain aphid populations exhibited greater variability over growth stages with no defining trends in plant response. Simple linear regression techniques V revealed similar results with aphid populations unmaintained at identical departing aphid densities. Significant negative (P < 0.01) slopes concerning R. padi were observed for seed yield and seed weight for the duration of boot. Non-significant relationships (P > 0.05) were detected for English grain aphid regardless of growth stage with the exception of average seed weight (P < 0.01) at boot. Artificial infestations of aphids produced varying population densities in a field cage study during late-boot through early-milk stages of crop development. Additional plots were infested with aphids at late-milk through hard-dough growth stages. Yield components including seed yield, number of heads, total seed weight and average seed weight were evaluated by multiple linear regression analyses. Significant negative linear slopes (P < 0.01) regarding aphid populations of both species were determined for earlier development. Aphid feeding affected average seed weight most since aphid densities were designated as the primary regressor in r-square analyses. Non-significant (P > 0.05) relations were found between aphid populations and yield components during late growth stages of spring wheat. Seed yield losses of 8.6% for R. padi at 37.5 aphids per tiller can be expected according to the model during late-boot through early-milk stages.

Library of Congress Subject Headings

Wheat -- Diseases and pests -- South Dakota
Wheat -- Yields -- South Dakota
Aphididae -- South Dakota

Format

application/pdf

Publisher

South Dakota State University

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Rights Statement

In Copyright