Transcript Unit 4: Wheat Diseases

Unit 4: Wheat
Diseases
Unit 4: Wheat Diseases
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Rusts
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Three forms can affect wheat (all fungal forms)
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Stem rust
Leaf rust
Stripe rust
Stem Rust
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Most destructive wheat disease
Severe grain shriveling
Unit 4: Wheat Diseases
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Masses of pustules on leaves & stems containing
brick red spores
Rust infested plants transpire much more water
than normal
Spores overwinter in southern U.S.
 Blow north w/ winds
 A rust epidemic in TX can produce a similar epidemic in
ND (when conditions are favorable)
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Lush growth on high N soils are most susceptible
to rust
Unit 4: Wheat Diseases
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Rust can overwinter and/or develop on barberry
bushes
Dusting or spraying infested fields often not
economically effective
Seed-treatment also not effective because its not
a seed-borne disease
Only plant resistant varieties
>275 stem rust biotypes (hard to maintain
resistant varieties)
Unit 4: Wheat Diseases
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Leaf Rust
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Many consider to be more important than stem
rust
Early infection can cause 42-94% yield loss
 Mostly due to less kernels in spike
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Pustules w/ orange-red spores cover leaves and
some stem
Resistant varieties are effective for control
Unit 4: Wheat Diseases
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Stripe Rust
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Not commonly a problem in the Midwest
Smuts
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Flag Smut
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Yield losses of 10-20% in susceptible varieties
Dark stripes on leaves & sheathes
Infected plants are often dwarfed; fail to form
normal heads
Unit 4: Wheat Diseases
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Disease can be carried on the seed and in the soil
Can be controlled w/ seed treatment
Many varieties are resistant
Scab
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Caused by Fusarium spc.
Fungal infection attacks head shortly after
emergence
Can kill or obstruct development of the spikelets
Identified by pinkish-white fungal growth
Unit 4: Wheat Diseases
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Diseased grains
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Shriveled
White
Scabby
Carried on seed and crop residue
Most severe when wheat follows corn
Use seed treatments
Unit 4: Wheat Diseases
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Take-All
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Not common for our area
Has destroyed 10-50% of the wheat crop
Kills plant in the heading stage to grain fill
Plant can turn white
May kill all plants in an area
Root rot occurs & spreads damage
Bottom 1-2” of stem may be black
Unit 4: Wheat Diseases
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Fungus lives in the soil
Must rotate out of wheat, oats, barley, etc. for 2-4
yrs.