Effects of seed treatment and foliar fungicides on Helminthosporium leaf blight and on performance of wheat in warmer growing conditions

  • Sharma-Poudyal D
  • Duveiller E
  • Sharma R
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Abstract

As the wheat (Triticum aestivum L.) cultivars of
south Asia are susceptible to Helminthosporium leaf
blight (HLB) caused by Cochliobolus sativus and
Pyrenophora tritici-repentis, chemical control through
seed treatment and foliar fungicides could increase
yields. A field study was conducted in 2002 and
2003 to determine the effect of seed treatment and
foliar fungicides on disease and performance of
wheat. Presown seed infection by the pathogen was
determined in a laboratory test. Seed was treated
with Vitavax 200B, Bavistin and Simonis carbendazim
in 2002, and Areestin instead of Simonis carbendazim
in 2003. One and two foliar sprays with
Opus, Allegro, Horizon and Tilt were tested,
along with a control treatment. Cochliobolus sativus
was isolated from 8 and 34% presown seeds in 2002
and 2003, respectively, and no P. tritici-repentis was
found. Seed treatments were not equally effective:
Vitavax 200B increased germination by up to 43%
in both years and reduced seedling infection by
C. sativus in 2003. The foliar fungicides reduced
HLB severity and increased grain yield. Compared
with the control, the highest reduction in area under
disease progress curve (AUDPC) was 53% in 2002
and 63% in 2003. The highest increase in grain yield
over the control due to fungicide spray was 38% in
2002 and 83% in 2003. Grain infection in 2002
(39%) and 2003 (70%) in the control plot was
reduced to 16 and 24%, respectively, thanks to the
application of foliar fungicides. Two fungicide sprays
in most cases did not reduce the AUDPC and grain
infection and increased grain yield any more than
did one spray. The results show that seed treatment
was not effective in reducing HLB severity and
increasing grain yield, but foliar fungicide spray was.
The cost–benefit analysis shows that one spray
could be cost-effective for all four fungicides when
a susceptible cultivar is planted under high HLB
severity.

Author-supplied keywords

  • Chemical control
  • Cochliobolus sativus
  • Pyrenophora tritici-repentis
  • Spot blotch
  • Tan spot

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Authors

  • D. Sharma-Poudyal

  • E. Duveiller

  • R. C. Sharma

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