Presentation is loading. Please wait.

Presentation is loading. Please wait.

Unit 1: Corn Diseases.  Corn Smut Caused by fungus: Ustilago maydis Most widely recognized corn disease Symptoms:  Complete barrenness in most plants.

Similar presentations


Presentation on theme: "Unit 1: Corn Diseases.  Corn Smut Caused by fungus: Ustilago maydis Most widely recognized corn disease Symptoms:  Complete barrenness in most plants."— Presentation transcript:

1 Unit 1: Corn Diseases

2  Corn Smut Caused by fungus: Ustilago maydis Most widely recognized corn disease Symptoms:  Complete barrenness in most plants Result:  Reduced grain development  ~30% yield loss

3 Unit 1: Corn Diseases Appears as galls on both the ear and stalk  White at first, but develop into dark lesions w/ dark spores inside whitish membrane Galls break and scatter spores  Found on: Ears Near midrib of the leaf Nodal buds on the stem More likely to attack vigorous growing plants Not poisonous to livestock

4 Unit 1: Corn Diseases Smut organism lives in the soil  Seed disinfection or treatment is ineffective, except to prevent spread to new fields Treatment:  Crop rotation  Don’t spread manure smut infested manure on fields  Many resistant hybrids

5 Unit 1: Corn Diseases  Head Smut Galls on ear and tassels  Entire destruction of these structures Mostly affects Southwestern & Pacific Coast states Also caused by fungus living in the soil, or on seed Galls dispense spores just as corn smut

6 Unit 1: Corn Diseases Control:  Rotate field out of corn for 2 years  Used treated seed to prevent infestation into other fields Most field corn hybrids resistant, sweet corn varieties are susceptible

7 Unit 1: Corn Diseases  Root, Stalk, & Ear Rot Effects:  Reductions in field stand  Reductions in plant vigor  Chlorosis  Barrenness  General blighting of the plant  Rotting of the ear

8 Unit 1: Corn Diseases Caused by fungal infestations:  Ear rot: Gibberella, Fusarium, Aspergillus, & Pythium spcs.  Root rot: Pythium, Gibberella, Diplodia spcs.  Stalk rot: Fusarium, Gibberella, Diplodia  Stalk Rot Genetic resistance not available

9 Unit 1: Corn Diseases Problems tend to occur under certain conditions  Symptoms prevalent when plant is stressed Stresses:  High N w/ low K  High moisture mid to late season after dry early season  High moisture stress early in season & during grain fill  High leaf disease pressure  Insect damage  Select hybrids resistant to the above stresses & have good soil fertility

10 Unit 1: Corn Diseases  Ear rot Can continue growth and damage after corn is harvested Mold damage to corn when moisture of grain in storage is >14% Rot and darkening of the corn embryo (called Blue Eye) Nearly all organisms are carried on decaying corn residues or in the soil

11 Unit 1: Corn Diseases Some also carried on the seed Molds are typically evident on the ear Can also observe dark bodies on outside or inside of old stalks  Root rot Develops on infested kernels Crown roots rot, weak plants die Subcrown roots appear dry, brown instead of healthy white

12 Unit 1: Corn Diseases Little evidence that root rot fungi advance up the stalk Most serious under dryland conditions  Stalks will die and fall Prevention:  Use disease-free treated seed  Plant at proper soil temperature  Balance soil nutrients  Plant resistant hybrids

13 Unit 1: Corn Diseases Chemical seed disinfectants are effective  Captan, metalaxyl, fludioxonil  Increase yield, stand, vigor  Leaf Diseases Northern Corn Leaf Blight  Infection of the lower leaves  Boat-shaped, grayish lesions  Spread to other leaves in cool, damp weather  Can cause leaf death

14 Unit 1: Corn Diseases  Treatment: Use resistant hybrids  Has caused losses mostly in the East & South Significant damage as far West as NE Southern Corn Leaf Blight  Usually not considered a problem  Major infestation in 1970 w/ major losses throughout corn belt  Needs warm, moist weather to flourish  Lesions form on leaf, ear shanks, husks  Can infect the ear

15 Unit 1: Corn Diseases Gray Leaf Spot  Problem since 1925 from Atlantic states to eastern corn belt  Cool temps w/ prolonged overcast days  Lesions can be confused w/ other blight diseases Mature lesions are rectangular restricted by leaf veins Signified by yellow halo Lesions can join causing blight of large portion of the leaf

16 Unit 1: Corn Diseases Stewart’s Wilt  Found throughout the Corn Belt  Carried by the corn flea beetle  Symptoms: Long, water-soaked lesions that can extend the length of the leaf Leaves turn necrotic Goss’s Wilt  Water-soaked lesions forming next to leaf veins  Stalks can be discolored

17 Unit 1: Corn Diseases  Affected plants can be stunted and die at any stage  Bacterium overwinters in corn debris near soil surface and in the seed  Next time— Quiz!


Download ppt "Unit 1: Corn Diseases.  Corn Smut Caused by fungus: Ustilago maydis Most widely recognized corn disease Symptoms:  Complete barrenness in most plants."

Similar presentations


Ads by Google