Goss s Wilt and Other Crop Diseases

Transcription

1 Goss s Wilt and Other Crop Diseases Paul Esker, Shawn Conley, and Ann MacGuidwin Field Crops Extension Plant Pathologist, State Soybean and Small Grains Specialist, and Nematologist University of Wisconsin-Madison s: paul.esker@gmail.com; spconley@wisc.edu; aem@plantpath.wisc.edu

2 Outline Corn diseases 2011 Goss s wilt where are we at? An introduction to the Oomycete CAP project in soybean Not all nematodes are the same Acknowledgements

3 Goss s wilt where are we at? BIOLOGY AND MANAGEMENT OF GOSS S WILT (SPECIAL THANKS: TED BAY)

4 Improving diagnostics for foliar diseases of corn vs.

5 Goss s wilt Caused by bacterium: Clavibacter michiganense subsp. nebraskensis Foliar fungicides are not effective! Disease originally from the western plains areas of Nebraska and Colorado Google: goss s wilt and corn you will see how much news this disease has generated the past several years Concern: can cause significant yield losses of up to 50 to 80 bushels per acre

6 Confirming Goss s wilt Combination of steps used to verify positive for Goss s wilt/clavibacter michiganense subsp. nebraskensis: Symptoms on leaves and stalks Microscopy (bacterial streaming) Source: UI Plant Clinic Dip stick test for Clavibacter michiganense subsp. michiganense (cross reacts with Cmn) Plating and testing of bacterial colony forming units

7 Impact of Goss s in WI? Several suspect fields were visited In 2011, PDDC received 11 samples (includes IL) Seven were negative Four were positive: Winnebago County Lafayette County (x 2) McHenry County, IL

8 DATCP Seed Corn Tested 58 leaf samples from 271 seed plot acres Goss s wilt confirmed in 20 samples (34%) Found in fields in: Columbia, Dane, Eau Claire, La Crosse, and Rock Counties No Stewart s wilt confirmed in samples

9 Symptoms of Goss s wilt Distinct light tan/yellow to gray lesions, with wavy or irregular margins that follow the leaf veins Within lesions: dark green to black specks or flecks [freckles] Lesions often have shiny appearance due to bacteria oozing onto leaf surface Lesions can coalesce causing whole leaves to be blighted Can have wilting and stalk degradation leading to whole plant death Examine stalk by splitting and looking for an orange to brown color with water-soaked and slimy tissue Can be confused with: Stewart s wilt, NCLB, Diplodia leaf streak

10 Hwy 81, Darlington - Goss Wilt Field 1

11 Adjacent Field

12 Darlington - Goss Wilt Field 1

13 Darlington - Goss Wilt Field 1

14 Fennimore - Northern Corn Leaf Blight Field 1 (w/spider mite damage)

15 Management It all starts with proper diagnosis Avoid introducing the pathogen from field to field work with infected fields last and clean equipment of crop residue thoroughly Make notes of hybrid reaction (resistance is a key management tactic) Cultural practices include: tilling fields immediately after harvest and burying residue Rotate to a non-host crop such as soybean

16 USDA OOMYCETE CAP AN INTRODUCTION TO THE OOMYCETE CAP IN SOYBEAN

17 Stand count is important Reduced stands = reduced yield potential Plant population (30-inch rows) 140k (8 plants/ft) 105k (6 plants/ft) 70k (4 plants/ft) Stand reduction (%) Percent of yield potential 0 (full stand) The reduction in stand was achieved by random placement of 12-inch gaps within rows 2 to 4 weeks after planting (Source: University of Illinois)

18 What affects stand establishment? Compaction Flooding Crusting Seedling diseases Planting depth Cold stress Residue coverage Sidewall compaction Dry soils Herbicide injury Poor seed quality Low germination

19 Seedling diseases Pre- and post-emergent damping off Causal organisms: Pythium species Phytophthora sojae Rhizoctonia solani Fusarium species

20 Oomycetes vs fungi Oomycetes Phytophthora sojae, Pythium species True fungi Fusarium species, Rhizoctonia solani

21 Conditions for disease development Soil moisture Soil temperature Pythium Flooded Cool (50-60 F) Phytophthora Flooded Warm (70s F) Fusarium Wet to dry Cool to warm Rhizoctonia Damp to wet Warm (70-80s F)

22 Survey of soybean seedling diseases

23 Isolates or soil received from 12 states State No. of fields sampled No. of putative oomycete cultures Arkansas Illinois Indiana Iowa Kansas Michigan Minnesota Missouri * 6 0 Nebraska 4 90 North Dakota ** South Dakota *** 6 0 Wisconsin Total Average *Soil samples collected, isolates will be baited; **Not including mid-season isolates; *** Isolates collected being purified

24 Oomycete species diversity 43 Pythium species 2 Phytophthora species

25 Managing soybean seedling disease 1. Good seedbed conditions 2. Seed treatments What's on your seed? available from 3. Resistance

26 Seed treatments Active ingredient mefenoxam/ metalaxyl Phytophthora sojae Pythium species Rhizoctonia solani Fusarium species E E N N azoxystrobin - P F F fludioxonil N N G G ipconazole - P F G pyraclostrobin - P F F trifloxystrobin - P F F E = excellent; G = good; F = fair; P = poor N = none

27 Acknowledgements Extension Network Oomycete collections NIFA funded 2011 to 2015 NCSRP and USB funding 2012 to 2014 MSU - Project GREEEN funded 2011

28 Not all nematodes are the same! NEMATODES AFFECTING CORN AND SOYBEAN

29 Nematodes out number every other type of animal on earth 4 out of every 5 animals alive today are nematodes! Members of the phylum Nematoda are diverse for their habitat, life history, and physical characteristics. feeds on insects feeds on microorganisms feeds on plants

30 Nematodes that live in soil are microscopic and transparent. The majority of soil-dwelling nematodes play important roles in decomposition and nutrient cycling so are beneficial to plants. Acrobeles, <.5 mm in length, feeds on bacteria Close up view reveals a sensory organ that enables nematodes to locate food.

31 Plant feeding nematodes have sucking stylet mouthparts. The shape and size of the stylet is related to how and where the nematode feeds. D

32 Soybean cyst nematode 2011 Sampling and testing program funded by WSMB 496 kits sent to growers from which 25% had soil samples submitted 64% were negative for SCN 45 samples positive for SCN and average egg count of 2027 eggs/100 cc soil (high was 10,050 eggs/100 cc)

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34 Management Recommendations Rotate, rotate, rotate Use of nonhost crops Rotate with resistant varieties Rotate the resistant varieties you use Rotate with tolerant or susceptible varieties only if SCN numbers low Relieve stress through good weeds, water, and soil fertility management Monitor SCN populations through periodic sampling and monitor how numbers change ide_5thed.pdf

35 Common Scientific Name Name (genus) Location Damage Potential Needle Longidorus soil high Lesion Pratylenchus soil & roots moderate - high Dagger Xiphinema soil moderate - high Stubby Root Paratrichodorus soil moderate - high Lance Hoplolaimus soil & roots low - moderate Spiral Helicotylenchus soil low - moderate Stunt Tylenchorhynchus soil low - moderate Ring Criconemella soil low - moderate Pin Paratylenchus soil low Limited distribution in Midwest: Sting Belonolaimus soil high Root Knot Meloidogyne soil & roots moderate high

36 Ectoparasitic genera remain in the soil and do not infect roots: Needle, Stunt, Dagger, Stubby Root, Spiral Some, like needle, prefer root tips. Others, like stunt, feed any where along the root

37 Endoparasitic genera infect roots so are found in both soil & roots. Lesion and Lance Nematology: UC-Riverside Lesion nematode feeding inside a root cortical cell Greg Tylka Stained Lance nematodes in the root cortex

38 2008. Syngenta Crop Protection, Inc., Greensboro, NC. #s detected None Low Medium High No Data A survey of 2179 corn fields in showed 99% were infested with plant-feeding nematodes.

39 Corn survey results for Wisconsin 2007 Range represents nematodes per 100 cc soil (and root fragments in that volume) nematode # positive % positive range % > threshold threshold (/100cc) root lesion needle dagger lance stunt spiral pin ring stubby root cyst not a corn pest root knot not a corn pest

40 How do you diagnose a nematode problem? Nematode damage can be difficult to spot in the field patchy, obvious for only a short time, and similar to damage caused by other factors. Some you can see Some are only detected by a yield monitor.

41 Assays for SCN DO NOT recover nematode pests of corn SCN cysts have a much larger diameter than worm-shaped nematodes so the sieves used to filter them from soil send nematode pests of corn down the drain! Nematodes that live in roots are recovered by incubating roots. This method does not work for SCN so is not part of the SCN assay.

42 Symptoms : Fast yes / Reliable no Other factors cause similar symptoms. May only be evident for a short time. Are difficult to discern in the field. Yield reduction might be the only symptom. Nematodes kill roots or stunt root and plant growth, and affect carbohydrate partitioning, robbing some plant organs of nutrients.

43 Putting symptoms to good use: Start with the field: Is there a patchy pattern to the symptomatic areas in the field? Tamra Jackson, NE

44 Carefully dig plants from the perimeter of the symptomatic area any time before the crop reaches V6. Don t stop there collect a soil sample.

45 Collect a soil sample. Sample in the row at an angle the goal is to intersect roots so the sample contains both soil and roots. More cores = better sample. Would you predict yield based on one plant?

46 Assays for nematode pests of corn rely on nematodes being alive. Avoid throwing, crushing, or heating the sample. Include a symptomatic root system with the sample or at least the seminal roots. Develop a relationship with a reliable nematode diagnostic lab most land grant universities offer this service or there are a number of private labs that offer good nematode diagnostics.

47 Nematodes begin feeding on roots before plants emerge. Early season damage has long term impact. V1 V2 nematode tracks on agar Nematodes have nervous and muscle systems that enable them to locate roots as soon as they appear.

48 log(rl + 1) per gm Root (dry wt) Root lesion nematodes are highly concentrated in the seminal root system: these roots provide inoculum for the life of the corn plant. Kansas Wisconsin Seminal Adventitious Linear (Seminal) Linear (Adventitious) Days After Planting

49 At what point should nematode population densities be managed? Crop rotation is the cornerstone of proactive nematode management because it helps prevent population explosions of some nematode pests. Reactive management based on risk assessment: - #s in samples vs. damage thresholds* * #s in sample affected by sample quality, when it was collected, and assay methods used by the lab

50 Case Study: What I consider when estimating the risk potential of Root Lesion nematodes Quality of the sample: Is it representative? (multiple cores across field) Soil: 12 Organic fraction: 51 How old are the root fragments in the sample?

51 Yield (bu/acre) Threshold values are based on samples collected at or close to planting P = 0.02 R 2 = Root lesion numbers predict corn yield in a sandy soil in WI RL per 100 cc Soil 17 DAP (5/29/08)

52 For late summer or fall samples we project what population densities will be the following spring. Data are from 5 depths 3-18 Populations increase while the crop is growing And decline in the fall until the ground freezes

53 68 samples from corn fields were submitted for nematode analysis during June 2010 (WI) 96% were positive for Root Lesion nematode # Root Lesion / 100 cc Soil (including root fragments) No. of Samples % of Samples Root Lesion Risk Potential for This Corn Crop Root Lesion Risk Potential for Corn Next Year none none slight moderate moderate high > 200* high high * Actual counts ranged from 220 to 1077 Moderate high risk for Needle 3 samples (> 10) Lance 3 samples (> 150) Stunt 1 sample (> 300) Spiral 1 sample (> 500)

54 Nematodes can be recovered at any time of year. When you collect the sample should be based on why you re doing it. corn up to V6 detect a nematode problem in a field that has not been sampled before evaluate efficacy of corn seed treatments In the late summer or fall before corn check nematode population densities to decide if a seed treatment is needed

55 What management options are available? Outcome Limit food availability Interrupt life cycle Encourage antagonists Kill nematodes Kill / immobilize Immobilize / kill There are no rescue treatments for nematodes! Practice rotation, weed control tillage organic amendments soil fumigants Counter nematicide New seed treatments Avicta Votivo

56 Seed treatments Materials are lethal to nematodes Avicta: Abamectin already in use for animals. Votivo: Bacteria Bacillus firmus works in the lab But to kill nematodes you need the right dose in the right place at the right time Seed placement supported by data Dose??? Even sublethal exposure may confuse or paralyze nematodes, protecting young plants

57 Many trials have showed trends of increased yield, but few have shown a statistical advantage for seed treatments. Why???

58 How do you evaluate the success of nematode management practices? Do an experiment!!! Using: A valid comparison (control). The goal is that the control differs from the treatment by only one feature. Example: A clean comparison of seed treatment products would use the same corn hybrid. Replication because the distribution of nematodes in the field is patchy.

59 See this online publication for information about conducting in-field experiments Sampling for Plantparasitic Nematodes in Corn Strip Trials Comparing Nematode Management Products php/diagnosticguide/2011/nematode/

60 Fields that are good candidates for nematicide seed treatments Have infestations of corn nematode pests that have been verified by soil testing Evident that the infested areas are large enough to impact yields (if not, consider site-specific use) Been sampled in at least the last five years (preferably more frequently) to verify that population densities warrant treatment

61 Seed treatments NOT should be used As a preventative measure Repeatedly if nematode pressure remains high, supplement with additional measures. Overuse could accelerate pesticide resistance As a means to control fungal diseases of roots

62 Summary: What s the normal status of a field for nematodes? Most pest nematodes are native. Manage fields to prevent population explosions. Use nematicides when explosions are imminent or have already occurred. How do you diagnose a nematode problem? By soil testing. Use other measures to supplement, not replace, soil testing.

63 At what point should nematode population densities be managed? When population densities have potential to reduce yield. In evaluating how much yield you need to recover, don t forget about the risk of accelerating pesticide-resistance in the nematode population. What management options are available? Historic recommendations like crop rotation remain valid plus there are new seed treatments How do you evaluate the success of a nematode management tactic? On-farm experiments are the gold standard

64 Acknowledgements UW-Plant Pathology: Amanda Zimmerman, Alex Buesing, Ben Williams, Jessie Mayry, Mai Neng Kha, Bryan Winters, Seth Davis UW-Madison: Bryan Jensen, Shawn Conley, Joe Lauer, John Gaska, Mark Martinka, Craig Grau UW-Extension: Bill Halfman, Mike Ballweg, Greg Blonde, Joe Bollman, Jerry Clark, Bob Cropp, Carl Duley, David Fischer, Richard Halopka, Matt Hanson, Steve Huntzicker, Richard Proost, and Trisha Wagner and their local grower cooperators UM-Extension: Fritz Breitenbach, Lisa Behnken, Matt Bicknell, Ryan Miller, and Jerry Tesmer

65 Acknowledgements Iowa: Alison Robertson and Daren Mueller Illinois: Carl Bradley Indiana: Kiersten Wise Ohio: Pierce Paul Minnesota: Dean Malvick Michigan: Martin Chilvers Ontario: Albert Tenuta

66 Acknowledgements U.S. Wheat Barley Scab Initiative