Document Type

Thesis - Open Access

Award Date

1985

Degree Name

Master of Science (MS)

Department

Plant Science

First Advisor

David D. Walgenbach

Abstract

The northern corn rootworm, Diabrotica 1ongicornis barberi Smith and Lawrence (NCR) and the western corn rootworm D. vtrgifera virgtfera·LeConte (WCR) are the two species of rootworms of economic importance in South Dakota corn fields. NCRs infest both first year corn fields and continuous corn whereas WCRs generally infest continuous corn fields. Damage can occur from larval feeding on roots which inhibits nutrient and. moisture uptake, increases propensity for lodging or by adult feeding on silks which causes losses in pollination and seed set. Adult emergence begins in early July and continues until early September. Female rootworm adults mate and then lay eggs in cracks in the soil. Rootworms overwinter as eggs in the soil with egg hatch occurring in June and continuing until early July. The larval stage of the rootworm feeds on corn roots until pupation occurs in August. One generation of rootworms per year occurs in South Dakota. Control of rootworms is attempted through application of granular insecticides at planting and crop rotation. Yield increases from the use of insecticides was first shown by Cox and Lilly. Resistance to insecticides was first noted in Nebraska and recorded by Ball and Weekman. Crop rotation is the first recommendation by extension entomologists in the North Central Region. Root ratings developed in 1971 by Hills and Peters are the standard for checking insecticide efficacy. Using this rating system and pooled agronomic and edaphic factors, Turpin et al, determined a rating of 2.5 as the economic injury level. No investigations have been published that correlate root ratings to yields on an individual plant or field basis. With this in mind, the objectives of my research were three fold. The first objective was to assess corn root damage by Diabrotica larvae and their relationship to corn yield losses; secondly, to determine if correlations exist between corn root damage ratings and yields; and third to potentially serve as an insight for establishing a method of damage rating that will provide a positive correlation between root ratings and yields on a field basis.

Library of Congress Subject Headings

Northern corn rootworm
Corn -- Diseases and pests
Corn root rot

Format

application/pdf

Number of Pages

122

Publisher

South Dakota State University

Rights

No Copyright - United State
http://rightsstatements.org/vocab/NoC-US/1.0/

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