Gray Leaf Spot

Question 1

Gray Leaf Spot

Cuase:

Answer 1

Pyricularia oryzae

Question 2

Gray Leaf Spot

Host:

Answer 2

• Perennial Rye
• Tall Fescue
• St. Augustine

Question 3

Gray Leaf Spot

Sign:

Answer 3

Pyriform conidia with septa

Question 4

Gray Leaf Spot

Symptoms:

Answer 4

• blighted turf with small, irregular lesions with a gray center and purple border
• Rapidly blight the leaf
• Fish Hook - twisting of the leaf

Question 5

Why do you rarely see the leaf lesions from Gray Leaf Spot?

Answer 5

The disease progresses so quickly that the leaves are usually blighted by the time you figure out something is wrong.

Question 6

Gray Leaf Spot

Predisposing Factors:

Answer 6

• Hot Days - Cool Nights
  
  • (**Starts on **First Cold Day of late Summer)
• Excess leaf wetness
  
  • alternating periods of wet and dry
• Excess Nitrogen input
• Tall HOC
• Seedlings
• Using Acclaim herbicide

Question 7

Gray Leaf Spot

At suboptimal temperatures, _____ to _____ degrees, the fungus needs ___ to ___ hours of leaf wetness.

Answer 7

• 68 - 75 degrees
• 21 - 36 hours

Question 8

Gray Leaf Spot

At optimal temperatures, ___ to ____ degrees, the fungus needs only ___ hours of continuos moisture.

Answer 8

• 82 - 90 degrees
• 9 hours

Question 9

What is a good way to tell you are going into the Gray Leaf Spot window?

Answer 9

• First Cold Day of Summer

Question 10

What is a management practice that is most susceptible to Gray Leaf Spot?

Answer 10

Seeding Grass

Question 11

What herbicide will make Gray Leaf Spot worse?

Answer 11

Acclaim

Question 12

Gray Leaf Spot

General Disease Management:

Answer 12

• Lower HOC
• Use resistant varieties
• Blend varieties
• Keep it DRY

Question 13

Gray Leaf Spot

Chemical Control:

Answer 13

• Start in early August
• 14 day intervals
• Continue unti it’s below 68 F
• Tank Mix penetrant and Contact everytime
  
  • ex. DMI & Chlorothalonil