Title page for ETD etd-32398-16336

Type of Document Dissertation
Author Langston, David Barnes Jr
Author's Email Address dlangsto@vt.edu
URN etd-32398-16336
Title The Role of Host, Environment, and Fungicide Use Patterns in Algorithms for Improving Control of Sclerotinia Blight of Peanut
Degree PhD
Department Plant Pathology, Physiology, and Weed Science
Advisory Committee
Advisor Name Title
Phipps, Patrick M. Committee Chair
Baudoin, Antonius B. A. M. Committee Member
Hagedorn, Charles III Committee Member
Mozingo, R. Walton Committee Member
Stipes, R. Jay Committee Member
Swann, Charles W. Committee Member
  • disease forecasting
  • sclerotinia
  • peanut
Date of Defense 1998-04-09
Availability unrestricted
An algorithm was developed for assessing disease risk and improving fungicide timing for

control of Sclerotinia blight of peanut, caused by Sclerotinia minor. A 5-day index (FDI) of

disease risk was calculated daily by multiplying indices of moisture, soil temperature, vine

growth and canopy density and summing the values for the previous 5 days. Spray thresholds of

FDI 16, 24, 32, 40, 48 were compared to a 60, 90, 120 DAP (days after planting) schedule and

the standard demand program. Field trials in 1994 indicated that fluazinam (0.58 kg a.i./ha)

applied at an FDI of 32 performed similarly to the demand program and was more efficient than

the DAP schedule. However, the original FDI 32 algorithm triggered sprays 13 days subsequent

to disease onset in 1995, indicating the need for improved vine growth and temperature

parameters as well as DAP-dependent FDI thresholds. Results from 1996 and 1997

demonstrated that algorithms with new vine growth and temperature parameters coupled with

DAP-dependent thresholds performed as well or better than the original FDI 32 algorithm,

demand program, or DAP schedule. Protection intervals of 7 and 14 days improved the

performance of iprodione (1.12 kg a.i./ha) while fluazinam provided protection for up to 21 days

when applied according to the original FDI 32 algorithm. Planting date was evaluated for its

effect on disease and fungicide use patterns. Late planting (20-28 May) delayed disease onset

and reduced early season disease incidence three of the four years tested. When averaged across

planting dates, the original FDI 32 algorithm performed as well or better than the demand

program in 1994 and 1995, as did algorithms utilizing new vine growth and temperature

parameters with DAP-dependent thresholds in 1996 and 1997. Chemicals for altering plant

architecture were compared to defoliation by corn earworm and leaf spot for suppression of

Sclerotinia blight. Chlorimuron (8.8 g a.i./ha) and withholding fungicide for leaf spot control

demonstrated the most significant disease suppression and yield improvement. Results show the

importance of fungicide timing and plant growth and canopy architecture modification for

control of Sclerotinia blight of peanut.

  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
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  apenA.pdf 39.94 Kb 00:00:11 00:00:05 00:00:04 00:00:02 < 00:00:01
  apenB.pdf 8.52 Kb 00:00:02 00:00:01 00:00:01 < 00:00:01 < 00:00:01
  chap1.pdf 35.85 Kb 00:00:09 00:00:05 00:00:04 00:00:02 < 00:00:01
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  chap4.pdf 83.15 Kb 00:00:23 00:00:11 00:00:10 00:00:05 < 00:00:01
  LANGSTONFRONT.PDF 22.90 Kb 00:00:06 00:00:03 00:00:02 00:00:01 < 00:00:01
  vita.pdf 4.59 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01

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