Unit 4: Wheat Diseases

Unit 4: Wheat Diseases Rusts

Three forms can affect wheat (all fungal forms) Stem rust Leaf rust Stripe rust

Stem Rust Most destructive wheat disease Severe grain shriveling

Unit 4: Wheat Diseases 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) Lush growth on high N soils are most susceptible

to rust

Unit 4: Wheat Diseases 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 Leaf Rust

Many consider to be more important than stem rust

Early infection can cause 42-94% yield loss Mostly due to less kernels in spike

Pustules w/ orange-red spores cover leaves and some stem

Resistant varieties are effective for control

Unit 4: Wheat Diseases Stripe Rust

Not commonly a problem in the Midwest

Smuts Flag Smut

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 Disease can be carried on the seed and in the soil Can be controlled w/ seed treatment Many varieties are resistant

Scab 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 Diseased grains

Shriveled White Scabby

Carried on seed and crop residue Most severe when wheat follows corn Use seed treatments

Unit 4: Wheat Diseases Take-All

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 Fungus lives in the soil Must rotate out of wheat, oats, barley, etc. for 2-4

yrs.