Document Type

Thesis - University Access Only

Award Date

2003

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Michael A. Catangui

Abstract

Insect defoliation of soybean Glycine max L. during flowering and pod fill reduces leaf area, delays maturity, and reduces yield. Scouting for insect damage in large fields is time-consuming and costly. Alternate methods are needed to reduce scouting time and costs. The objective of this study is to evaluate the use of aerial imagery in diagnosing damage caused by grasshopper, Melanop/us spp., and bean leaf beetle, Ceratoma trifurcata Forster, during vegetative, flowering, and pod fill stages. Five simulated defoliation treatments were compared, ranging from no defoliation to complete defoliation. Leaf area was obtained from whole plants harvested from the field. Aerial and radiometer images were collected on different dates. Artificial defoliation of 38%-90% was detectable in the aerial images. Yield results were influenced by the extent and timing of damage. The largest yield reduction (27.45%) in 2000 occurred with defoliation at pod fill. Other yield losses were 17. 75% at 90% defoliation and 8% at 45% defoliation at flowering. The largest yield reduction in 2001 occurred with 87 .13% defoliation at R6 soybean growth stage resulting in a yield loss of 71.55%. The smallest yield reduction occurred with 35.6% defoliation at V6 soybean growth stage with a yield loss of 2.6%. Analysis was conducted on the relationship between the defoliation treatments and NIR pixel values. The NIR pixel values collected were significantly correlated with percent defoliation. Low percent defoliation was associated with high pixel values, and high percent defoliation was associated with low pixel values. Plants with more leaves produced higher yields, pixel values, and reflected more NIR energy. As plant biomass decreased, visible energy reflectance increased, and NIR energy reflectance decreased. Significant yield reductions due to artificial defoliation were noted at R4 and R6 soybean growth stages. Spatial analysis of IKONOS satellite imagery combined with field data provided spatial maps of the soybean field. Further statistical analysis indicated significant correlation between mobile insects and yield, and immobile insects and percent defoliation.

Library of Congress Subject Headings

Soybean -- Diseases and pests -- Remote sensing
Defoliation -- Remote sensing
Aerial photography in agriculture
Insect pests -- Control

Publisher

South Dakota State University

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Rights Statement

In Copyright