Document Type

Thesis - University Access Only

Award Date

1998

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Laurence D. Chandler

Abstract

In 1996 and 1997, field locations were chosen at the USDA-ARS Eastern South Dakota Soil and Water Fann, Brookings, SD to determine the impact on grain yield from these two pests in various treatment combinations on three hybrids of field com with 87, 97, and 106 day maturities, respectively. Three infestation levels of WCR (0, 600, 1600 eggs/30.5 cm row), and four ECB infestation regimes (no infestation, early season, late season, early and late season) were used. The 97 day hybrid (early & late ECB infestation) had the most tunneling (4.575 in), and the 106 day hybrid (no ECB infestation) had the least amount of tunneling (0.05 in) for all comparisons made. There was more ECB tunneling for all three hybrids with WCR treatments in 1996 than 1997. On average, the 97 day hybrid received more tunneling (0.5 - 1.0 in) than the other two hybrids. In 1996, root ratings were lower for the 87 and 97 day hybrid plots which received no ECB infestation than for those that received the early infestation. Overall, the 106 day hybrid had the lowest root ratings of the three hybrids for both years. In 1996, the 1600 WCR egg infestation rate with the early ECB infestation had a root rating (4.6) that was significantly higher than any of the other treatments for both years. Rainfall differences between the two years and the amount ofECB tunneling are two factors which likely caused this. In 1996, all three com hybrids which received both infestations of ECB had yields that were lower than those that received no ECB or only one infestation. The 97 day hybrid had significantly higher yields than the other hybrids for all ECB infestation regimes. The 87 day hybrid had significantly lower yields for all treatments. In 1997, the early season infestation had more of a negative impact on yield than the late season infestation. The 97 day hybrid had the highest yields regardless of the ECB infestations. In 1996, the 97 day hybrid had the highest yields and the 87 day hybrid had the lowest yields for all three WCR infestation rates. No significant differences were found between the 600 WCR infestation rate and 1600 infestation rate for all three hybrids. In 1997, all three hybrids had yield reductions from the 600 WCR infestation rate and the 1600 infestation rate. The 97 day hybrid had higher yields overall, for both years. Step-wise regression analysis for 1996, showed that for every unit change on the root rating scale, a grain yield loss of 4.36 grams/ear (-3.5%) occurred. The following year, the yield loss was 8.46 grams/ear (-6.6%) for every increase in the root rating scale. In 1996, for every inch of com borer tunneling there was a yield reduction of 1.55 grams/ear (-1.2%), and 5.8 grams/ear (-4.5%) in 1997. The data shows that for this experiment, WCR had more impact on yield than did ECB, and there was a greater yield reduction from both insects in 1997 than in 1996. The com hybrid with the 97 day maturity had higher yields even though it received the most damage from the two insects when compared to the other two hybrids. In this experiment, root ratings showed a significant interaction between WCR and ECB, with year of the experiment being important because of environmental factors. A survey of ECB larval parasitoids was conducted in eastern South Dakota in 1995 and 1996. The purpose for this survey was to identify parasitoids ofECB. ECB larvae were extracted from com plants twice during the growing season from four counties in eastern South Dakota. In 1996, 12% ofECB larvae were parasitized, and 4% in 1995. Species encountered included; Macrocentrus grandii Goidanich, Eriborus terebrans (Gravenhorst), and Sympiesis viridula (Thompson). This survey showed great variability between years and locations for these parasitoid species and their numbers.

Library of Congress Subject Headings

Hybrid corn -- Diseases and pests
European corn borer
Western corn rootwarm

Publisher

South Dakota State University

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Rights Statement

In Copyright