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Fundamentals of Corn Pathology Paul Vincelli University of Kentucky.

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Presentation on theme: "Fundamentals of Corn Pathology Paul Vincelli University of Kentucky."— Presentation transcript:

1 Fundamentals of Corn Pathology Paul Vincelli University of Kentucky

2 Disease triangle What are some factors that favor disease development in KY corn production?

3 Corn residue can favor certain diseases What is the most practical way to kill out pathogens surviving in corn residue? Spores of gray leaf spot fungus

4 Almost all disease management in corn is preplant.

5 Leaf diseases

6 Gray leaf spot

7 Hybrid differences Leaf blighting

8 Northern leaf blight Image by K. Leonard and E. G. Suggs Courtesy of the American Phytopathological Society

9 Large, coalescing lesions of NLB

10 Susceptible and resistant reactions to Northern leaf blight Image by K. Leonard and E. G. Suggs Courtesy of the American Phytopathological Society Susceptible hybrid Chlorotic lesion Reaction (Ht resistance)

11 NLB: Susceptible vs Ht resistance

12 NLB: susceptible (R) vs Ht resistance (L) Henderson County, 2004

13 Lodging from Severe NLB Courtesy Bill Meachum, Pioneer

14 Rusts Southern rust Common rust Rust spores

15 Brown spot

16 Purple leaf sheath

17 Holcus spot

18 Infection of foliage by bacteria Fire blight

19 Stalk rots

20 Anthracnose lower stalk rot in mature plants

21 Anthracnose top dieback G. Munkvold

22 Diplodia stalk rot

23 Gibberella stalk rot

24 Gibberella (left) and Diplodia (right) stalk rots

25 Stalk rot = disintegration of pith Charcoal stalk rot

26 Factors that Enhance Corn Stalk Rots High plant populations High nitrogen rates High levels of leaf disease

27 High-yield production can favor stalk rots

28 Seedling diseases

29 Pythium damping off Data of Woltz and TeKrony Karen Rane, Purdue U.

30 Anthracnose in seedlings

31 Other Diseases

32 Common Smut

33 Maize dwarf mosaic

34 Maize chlorotic dwarf virus

35 Crazy top

36 Ear and kernel rots Mycotoxins

37 Diplodia fungus

38 Diplodia ear rot

39 Fusarium ear rot: Fumonisins

40 Gibberella ear rot Produces zearalenone and DON

41 Aspergillus ear rot: Aflatoxins

42 Extension publications on mycotoxins

43 Maximum Fumonisin Levels Recommended by US FDA Intended use Max fumonisins (FB 1 +FB 2 +FB 3 ) Equids and rabbits5 ppm (no more than 20% of diet) Swine and catfish20 ppm (no more than 50% of diet) Human foods2-4 ppm

44 Corn with 26 ppm fumonisins

45 FDA Aflatoxin Action Levels Action Level (parts per billion) CommoditySpecies 0.5MilkHumans 20Any food except milk Humans 20FeedLivestock* *Exceptions for breeding cattle, breeding swine, mature poultry, finishing swine, & finishing beef cattle

46 Factors That Enhance Corn Ear and Kernel Rots and Preharvest Mycotoxin Accumulation Hot, dry weather during silking or grain fill Delayed harvest Injury to kernels (insects, birds) Hybrids with ears at maturity that are: - upright - incomplete husk coverage

47 Crop stress can favor preharvest mycotoxin contamination Fusarium ear rot Aspergillus ear rot

48 Harvest management can influence postharvest accumulation of mycotoxins

49 Reducing risks of mycotoxins in storage Adjust combine for minimum kernel damage Dry below 15.5% within 24-48 hours of shelling Clean storage facilities and control insects Aerate and check for heating and crusting

50 Testing corn samples UK Grain Quality Testing Lab Attn: Michael D. Montross Biosystems & Agricultural Engineering 128 Barnhart Bldg. University of Kentucky Lexington, KY 40546-0276 Voice: (859) 257-3000 X106 Fax: (859) 257-5671 Email:

51 Headline 6 fl oz, Quilt 14 fl oz, Stratego 10 oz 63 out of 168 = 38% of the time had a yield increase of 6 bu/A or greater. Mean = 3 bu/A increase over the untreated

52 Overall Yield Response University (68) and On-Farm (121) Trials *Assumes $3.75/bu corn and $20/ac for fungicide. Break-even response = 5.3 bu/ac Overall yield advantage: 8.7 bu/ac Percent wins: 79% Economically beneficial*: 60% Average net return: $12.63/ac (121 hybrids from 20 companies) PIONEER SUMMARY

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