Author

Karen Cameron

Document Type

Thesis - Open Access

Award Date

1982

Degree Name

Master of Science (MS)

Department

Plant Science

First Advisor

David D. Walgenbach

Abstract

Corn rootworms are the major economic insect pests of corn produced in the Midwest. Economic loss to the grower is through yield reduction caused by larval and adult damage and the cost of insecticidal control measures. Larval damage to corn roots is by tunneling in the roots and damage to the cortical parenchyma. Most of this damage occurs in late June and in early July. Brace root feeding by the larvae can cause the plant to lodge. Adults also damage corn by feeding-on all above ground portions with primary damage to silks and tassels. This feeding disrupts pollination resulting in improper filling of ears and subsequent yield reduction. Three species of corn rootworms are present in South Dakota: the northern corn rootworm (NCR), Diabrotica longicornis barberi Smithand Lawrence; the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte; and the southern corn rootworm (SCR), Diabrotica undecimpunctada howardi Barber. The SCR is not a significant pest of corn in South Dakota as it is unable to overwinter and migrating adult populations are generally low until late in the season. The NCR and the WCR have been major problems the past two decades. The WCR causes the majority of the damage in continuous cornfields and the NCR in continuous and first year corn. Northern corn rootworms were first recognized as being damaging to corn in 1880 by Charles Riley (Hill et al. 1948). The WCR were found to damage continuous corn in Colorado in 1909 (Gillette 1912). Tate and Bare (1946) reported the WCR in Nebraska in 1929. Economic populations of the WCR were not common in Nebraska until 1961. Rootworm resistance coincided with the spread of WCR from Nebraska to Ohio. Gravid adult WCR and NCR females lay their eggs in the soil of cornfields during late summer and fall. A minority of the eggs are deposited in fields containing crops other than corn or in ditches where weeds and flowering plants are present. Rootworms overwinter as diapausing eggs and hatch in early June. Pupation begins in late June and early July. Adult emergence begins about 10 to 14 days thereafter. Emergence continues throughout July and August and into early September. The insect targeted in the laboratory and in artificial infestations was the WCR and both WCR and NCR in the field associated with continuous corn production. The objective of this research was to determine if ammonia affected mortality of the WCR in the laboratory, and the effect of rates and placement of aqua ammonia and anhydrous ammonia on survival of post diapause WCR eggs in the soil in the field.

Library of Congress Subject Headings

Ammonia -- Physiological effect
Corn -- Diseases and pests
Western corn rootworm

Format

application/pdf

Number of Pages

62

Publisher

South Dakota State University

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