Institute of Ag Professionals

Transcription

1 Institute of Ag Professionals Proceedings of the 2009 Crop Pest Management Shortcourse & Minnesota Crop Production Retailers Association Trade Show Do not reproduce or redistribute without the written consent of author(s).

2 SOYBEAN AND CORN DISEASES KNOW THEM AND THEIR RISKS Dean Malvick Department of Plant Pathology University of Minnesota, St. Paul

3 OUTLINE General Information Disease Risks for Corn and Soybean Disease Diagnosis

4 REVIEW OF CROP DISEASE PROBLEMS IN MINNESOTA IN 2009 Corn Stalk Rot Northern Corn Leaf Spot Goss s Wilt Eyespot Ear molds Soybean White Mold Brown Stem Rot Rhizoctonia Root Rot Pod and Stem Blight SCN

5 PUTTING IT ALL TOGETHER DISEASE DISEASE Poor weather DISEASE Planting YIELD Scouting Diagnosis Good variety Good growing conditions Importance in your situation Disease priorities for management Variety selection

6 THREE KEY FACTORS THAT AFFECT RISK OF CROP DISEASE SUSCEPTIBLE PLANT MANAGEMENT -tillage -planting date -seeding rates PATHOGEN PRESENCE -various fungi FAVORABLE ENVIRONMENT -Wet; cool, hot, dry

7 What are major disease risks in MN that can cause large (>25%) losses? Corn > stalk rot > Common rust? > Future - Gray leaf spot? Soybean > SDS > Phytophthora rot > White mold >Brown stem rot

8 CORN DISEASES Corn diseases throughout the season

9 CORN GROWTH STAGES Source of Figure University of Illinois Critical time for foliar disease : Tasseling +/- 2 wks Tasseling Silking

10 Corn Leaf Diseases Foliar/leaf diseases Anthracnose Common rust Eyespot Gray leaf spot Northern corn leaf blight Northern corn leaf spot Goss s Wilt

11 Corn Anthracnose Disease Cycle (Bergstrom and Nicholson, Plant Dis. 1999) ANTHRACNOSE Leaves and Stalks

12 ANTHRACNOSE RISK FACTORS Infested corn residue Cloudy, overcast weather corn is more resistant under high light intensity Extended periods of high humidity required for sporulation Rain: raindrops disperse spores (conidia) Warm temperatures (78 86F) Stress from other pests root lesion nematodes *severe infestations of European corn borer

13 GRAY LEAF SPOT Most serious leaf disease of corn in the U.S. Caused by the fungus Cercospora zeae-maydis Yield reductions up to 44% reported in the Midwest and 24 to 69% in Virginia

14 GLS RISK FACTORS Prolonged high humidity (>95%, >24 HR) Warm temperatures (70-85 F) Protected fields Large amounts of corn crop residue Late maturing hybrids Susceptible hybrids

15 COMMON RUST

16 COMMON RUST RISK FACTORS Favored by: Moderate temperatures (61-76F) High humidity (greater than 95%) Epidemics in southern U.S. and Mexico Inhibited by: High temperatures (over 85F) Usually develops in MN late in season

17 NORTHERN CORN LEAF BLIGHT 1 to 6 inch long cigar-shaped gray-green to tancolored lesions on the lower leaves. Symptoms on resistant cultivars: small chlorotic or necrotic spots

18 NORTHERN CORN LEAF BLIGHT RISK FACTORS Cool and wet weather Corn residue from previous crop on soil surface Susceptible hybrids

19 EYESPOT

20 EYESPOT RISK FACTORS Seed production fields with very susceptible inbreds. Cool and humid weather Corn-on-corn field with minimal tillage Hybrid susceptible to eyespot

21 GOSS S LEAF BLIGHT WESTERN MN 2009 Special thanks to the photographer

22 GOSS S LEAF BLIGHT RISK FACTORS Can cause leaf blight and seedling blight Corn debris from previous crop on soil surface Warm and wet weather Injury to leaves by wind-blow sand/soil Hail Infested seed

23 NORTHERN CORN LEAF SPOT Ohio State University Risk factors: Wet weather Infested crop residue on soil surface

24 ANTHRACNOSE: STALK ROT PHASE

25 GIBBERELLA STALK ROT Photos courtesy D. White

26 FUSARIUM STALK ROT

27 STALK ROTS RISK FACTORS Stress on the corn plant Stalk debris on soil surface or buried Corn on corn minimal rotation susceptible and high-yielding hybrids leaf disease and grasshopper damage high plant populations early maturation water stress high fertility, especially very high N low N, low K and low P

28 EAR ROTS AND MYCOTOXINS Diplodia Ear Rot D. maydis no toxins in US Giberella Ear Rot G. zeae zearalenone Penicillium Ear Rot ochratoxins Aspergillis Ear Rot (A. flavis) aflatoxin Fusarium Ear Rot (F. moniliforme, F. proliferatum, F. subglutinans) fumonisins

29 Fusarium ear rot >most severe when hot, dry weather occurs at or just after flowering. Aspergillis ear rot >favored by hot weather and low soil moisture

30 CLADOSPORIUM AND TRICHODERMA EAR ROTS COMMON IN MINNESOTA IN NOVEMBER 2009

31 FIELD GUIDE TO CORN DISEASES This Field Guide to Corn Diseases is an extensive guide to identification of common corn diseases in the United States. Disease identification and management will be aided with the brief descriptions and multiple color photographs for the 56 different diseases that are included in this guide. Can be orderd via the internet: shop.extension.umn.edu Or call:

32 SOYBEAN DISEASES Soybean diseases throughout the season

33 What are major disease risks in MN that can cause major (>25%) losses? Soybean > SDS > Phytophthora rot > White mold >Brown stem rot > SCN?

34 D. Malvick University of Minnesota SOYBEAN GROWTH STAGES Critical time: Bloom through pod fill Source: University of Illinois Extension Source of Figure University of Illinois 3 developed trifoliates (leaf edges don t touch) Beginning bloom* Beginning pod* Beginning seed* * Found at one of upper 4 nodes on main stem

35 D. Malvick University of Minnesota YIELD LOSS FROM SOYBEAN DISEASES RESULTS FROM: Plant death Root and stem dysfunction Loss of leaves and leaf function Premature defoliation Increase in number of unfilled pods/plant Decrease in # of seeds/plant Decrease in seed weight Decrease in germination of seed

36 D. Malvick University of Minnesota STEM DISEASES LATE SEASON DISEASES Brown Stem Rot (BSR) White mold Stem canker Pod and stem blight Anthracnose

37 D. Malvick University of Minnesota BROWN STEM ROT (BSR) COMMON AND DAMAGING PROBLEM IN MANY AREAS IN MN IN 2008 AND 2009

38 D. Malvick University of Minnesota BSR: STEM BROWNING BUT NO FOLIAR SYMPTOMS

39 D. Malvick University of Minnesota EFFECTS OF BSR : PREMATURE DEFOLIATION Row with BSR

40 BROWN STEM ROT RISK FACTORS Cool temperatures (60-80 F) during pod fill - whereas, temperatures > 80F suppress symptoms. Leaf symptoms often most severe when: - wet soil near saturation at flowering/pod fill (R1-R6) & dry soil during maturation (R6-R8 stages) Short rotations Ineffective resistance Soybean cyst nematode ph <6.5

41 D. Malvick University of Minnesota WHITE MOLD IN SOUTHERN MN

42 WHITE MOLD RISK FACTORS HIGH MOISTURE DURING FLOWERING STAGES COOL TEMPERATURES DURING AND AFTER FLOWERING STAGES CROP ROTATON <3 YEARS OUT OF SOYBEAN OR OTHER HOST CROPS FIELD WITH HISTORY OF WHITE MOLD HIGH FERTILITY ESPECIALLY MANURE HIGH WEED POPULATION IN FIELD HIGH PLANT POPULATION HIGHLY SUSCEPTIBLE SOYBEAN VARIETY

43 STEM CANKER D. Malvick University of Minnesota

44 D. Malvick University of Minnesota ROOT DISEASES SDS Phytophthora rot Fusarium root rot Rhizoctonia root rot SCN

45 D. Malvick University of Minnesota SDS in southern Minnesota soybean field.

46 D. Malvick University of Minnesota SDS SYMPTOMS AT DIFFERENT STAGES OF DEVELOPMENT ON SOYBEAN LEAVES

47 BSR VS SUDDEN DEATH SYNDROME (SDS) SDS BSR No browning of pith in stems D. Malvick University of Minnesota

48 SDS RISK FACTORS Susceptible soybean varieties Early planting cool wet soil after planting Field history of SDS Compacted soil, poor drainage High SCN populations High yield environments Heavy rainfalls through June and to mid-july

49 PHYTOPHTHORA ROT OF SOYBEAN Phytophthora sojae Kills soybean plants at all growth stages. Outbreaks of Phytophthora Rot are generally associated with water-saturated soils Wrather, Univ. of Missouri

50 D. Malvick University of Minnesota PHYTOPHTHORA ROOT ROT RISK FACTORS Varieties without major resistance genes: Rps1K, Rps1c, Rps6, or Rps3 Varieties with low tolerance (partial resistance) Poor soil drainage Frequent rainfall in the first month after planting Warm wet soil for extended periods History of disease in field

51 RHIZOCTONIA ROOT ROT D. Malvick University of Minnesota

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53 RHIZOCTONIA ROOT ROT RISK FACTORS Wet to moderately-wet soil Warm conditions Crop residue P and K deficiency ph unfavorable for soybean Physical damage to soybean plants

54 SOYBEAN DISEASES WEB SITE:

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56 DIAGNOSIS OF CORN AND SOYBEAN DISEASES Field Identification Laboratory Diagnosis

57 FIELD DISEASE IDENTIFICATION Symptoms - Lesions, Flecks, Streaks, Canker, Rots, Spots, etc... Signs - Spores, Ooze, Cysts, Particles, Mushrooms, etc. Field Patterns Time of appearance Field History

58 LABORATORY DIAGNOSIS Culturing Advanced Techniques One example is DNA analysis

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60 SOYBEAN ROOTS AND STEMS CONTAIN MANY DIFFERENT KINDS OF FUNGI

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62 DNA TEST TO CONFIRM SDS Plant With SDS Plant Without SDS We are using similar methods for BSR, Stem Canker, and Phytophthora

63 FINAL POINTS Disease is a significant factor in corn and soybean production Weather drives disease (and yield) One more diseases are favored by any weather conditions ranging from very hot and dry to very cool and wet. Scouting and disease identification in mid August can be very beneficial in managing corn and soybean diseases A proper diagnosis can be extremely valuable Common risk factors: wet weather in July, very dry weather in August, cool and wet May, poor drainage and compaction, no crop rotation, crop residue on soil surface