soy nemas

7/27/2019 Soy Nemas

http://slidepdf.com/reader/full/soy-nemas 1/36

NEMATODE MANAGEMENT GUIDESOYBEAN

7/27/2019 Soy Nemas


AUTHORS:

David Holshouser, Ph.D. Proessor and Extension Agronomist

Jon Eisenback, Ph.D. Proessor o Nematology

Pat Phipps, Ph.D. Proessor and Extension Plant Pathologist

David Moore Extension Agent

7/27/2019 Soy Nemas


SOYBEANTABLE OF CONTENTSINTRODUCTION 4

SURVEY OF PROBLEM FIELDS 5-6

SAMPLING AND THRESHOLDS 7-11

MANAGEMENT OPTIONS 12-15SOYBEAN CYST NEMATODE 16-18

LANCE NEMATODE 19-20

LESION NEMATODE 21-22

RING NEMATODE 23-24ROOT-KNOT NEMATODE (RKN) 25-26

SPIRAL NEMATODE 27-28

STING NEMATODE 29-30

STUBBY ROOT NEMATODE 31-32STUNT NEMATODE 33-34

NEMATODE MANAGEMENT GUIDE

7/27/2019 Soy Nemas


INTRODUCTION

NEMATODES IN VIRGINIANematodes, or unsegmented roundworms, eed in or onroots o plants. More than 100 species o plant-parasiticnematodes eed on soybean roots, but only a ew are

economically important. In Virginia, most nematodespecies can be ound in the sandier Coastal Plain soils.However, some nematode species can also develop andreproduce on the heavier-textured soils o the Piedmontand Shenandoah Valley. This guide will ocus on thosethat can cause damage to soybeans in Virginia.

Many soybean armers do not realize that nematodesmay be reducing yields by as much as 7 to 8 percent.Thereore management o these pests begins withsampling and determination o the species and numberpresent. I nematodes have been determined to bea threat, certain management practices remain availableto help prevent urther spread and reduce the economiclosses that they cause.

4

7/27/2019 Soy Nemas


SURVEY OF PROBLEM FIELDS

5

In recent years, researchers took more than 1,000 soilsamples in problematic soybean and corn felds in easternVirginia and analyzed them or nematodes. They did notchoose these felds at random, but selected them because o

low productivity or because they showed symptoms that canbe typical o nematode damage. O the “problem” soybeanfelds, 98 percent contained nematodes and 71 percent othe felds showed a moderate to high risk o nematodescausing signifcant yield loss.

7/27/2019 Soy Nemas


SURVEY OF PROBLEM FIELDS

6

RISK LEVELa

LOW % MODERATE % HIGH %

Percentage o

454 soybean feldssurveyed in Virginia

during 2007-2009

where nematodes

were present at low,

moderate or high risk.

Soybean cyst 5 9 22

Lance 48 4 2

Lesion 46 15 2Ring 1 0 0

Root Knot 18 8 9

Spiral 67 8 NAc

Sting 0 0 <1

Stubby Root 24 12 NA

Stunt 57 12 3Fieldb 29 23 47

aRISK LEVELS:

Low = nematodes will not likely cause crop damage.

Moderate = borderline populations in which crop damage may occur

i other actors stress the cropHigh = populations likely to cause crop damage and signifcant yield lossbField risk level takes into account all nematode species present inthat feld. For instance, low to moderate populations o two or morenematode species may result in a high feld risk level.cSpiral and stubby root nematodes usually only cause crop damagewhen other actors are stressing the crop.

7/27/2019 Soy Nemas


SAMPLING AND THRESHOLDS

VIRGINIA TECH’S NEMATODE ADVISORY PROGRAMdepends on the cooperation o the agricultural community,extension agents and the Nematode Assay Laboratory.“Assay” means to test, examine, assess, analyze and

evaluate. Proper sampling, completion o appropriateorms and careul laboratory analysis remain necessaryto provide armers with appropriate recommendationson nematode management. The nematode advisoryprogram can help armers avoid costly yield loss due toplant-parasitic nematodes i the steps outlined below are

ollowed.The Virginia Tech Nematode Assay Laboratory currentlyperorms soil and other tests or two dierent purposes:

1. Predictive: The predictive assay determines inematode populations will aect next year’s crop.

A ee exists or predictive samples. Routine assayscost $11 per soil sample, and a routine soil test plusthe testing o cysts on soybean roots cost $19 persample.

2. Diagnostic: The diagnostic assay determines ipoor growth in the current year’s crop is caused by

nematodes. Diagnostic samples can be conducted atno cost.

7

7/27/2019 Soy Nemas



When to Sample: The most appropriate time to sampledepends on the purpose o the sample.

Predictive Assays: Fall sampling provides the mostreliable inormation or predicting nematode problems

or a uture crop. Nematode populations can be highestat the end o the growing season and decline as the soiltemperatures drop. Sample at or immediately ater harvesto previous crop, Sept. 15 to Nov. 15.

Diagnostic Assays: Sample at the onset o symptoms,

during the growing season. Nematodes eed only on livingplants; thereore, sample soil around live plants showingsymptoms. Some nematodes spend part o their liecycle inside the roots, and a more accurate diagnosis onematode damage can be made rom samples includingroots. Also, send another sample rom a healthy plant to

compare population densities.How to Sample: Always sample within the eeder-rootzone– this varies or each crop. Avoid collecting sampleswhen the soil is extremely dry or extremely wet. DO NOTadd water to the soil ater sampling. Take soil samples inareas o common crop history. For example, i one-hal othe feld is planted to soybeans and the other hal to corn,sample each area separately.

8

7/27/2019 Soy Nemas



1. Collect vertical core subsamples o soilwith a soil sampling core or shovel withinthe eeder-root zone (see fgure at right).A 6-inch depth should be adequate.

Nematodes do not occur uniormlythroughout a feld; thus, more than onesubsample must be taken rom the samefeld. The number o subsamples neededdepends on the size o the feld:

– For small felds (ewer than 4 acres),

collect at least 20 subsamples.

– For large felds (more than 4 acres),divide the feld into 4-acre sections. I the feldconsists o several soil types, divide the feld intoas many sections as there are soil types. Collect at

least 20 subsamples rom each section.2. Mix the subsamples in a clean bucket.

3. Place at least 1 pint (500 cc) o the soil mixture intoa nematode soil-sample bag or plastic bag. LABELCOMPLETELY with the armer’s name, address, county,

agent, crop inormation, and feld or sample number.

9

7/27/2019 Soy Nemas



4. Check with your county extension agent or a sampleorm. Complete the orm to send with the samples.Send orms to your nearest Virginia CooperativeExtension ofces at no charge. Soil sample bags may

be available at these ofces, as well; however, quart-size, sealable, plastic bags will also be suitable.

5. Store samples in a cooler or rerigerator until shipping.It is best to ship samples on Monday or Tuesday to avoidthem sitting in a hot U.S. mail room or truck.

6. Mail samples with the appropriate orm, and a checkor predictive assays, immediately to the NematodeAssay Laboratory, 115 Price Hall, Virginia Tech,Blacksburg, VA 24061-0331.

Interpreting Predictive Assays: Predictive nematodesampling use nematode risk thresholds to determine

whether to take action against nematodes. Thesethresholds have been based on results o on-arm testsover several locations and years.

10

7/27/2019 Soy Nemas



The table below lists three levels o risk or yield loss accordingto population densities in a 500-cc sample o soil.Risk thresholds apply only to soil samples collected in latesummer or early all. Soil samples that are collected during

winter or spring always contain reduced levels o nematodesdue to unavorable temperatures and the absence o a hostcrop. Note: I more than one nematode has been ound at the borderline level, the likelihood o a proftable response to a control measure increases.

11

RISK LEVELa

Risk Thresholds orSoybeans (per 500 cm3 soil)LOW MODERATE HIGH

Soybean cyst larvae 0-20 20-60 >60

cysts 0 - >1

Lance 0-300 300-1,000 >1,000

Lesion 0-100 100-500 >1,000

Ring 0-200 200-700 >700

Root-Knot 0-50 50-170 >170Spiral 0-1000 >1,000 -

Sting 0-10 10-20 >20

Stubby Root 0-90 >90 -

Stunt 0-300 300-1,000 >1,000

Low = nematodes will not likely cause crop damage.

Moderate = borderline populations in which crop damage may occuri other actors stress the cropHigh = populations likely to cause crop damage and signifcant yield loss

7/27/2019 Soy Nemas


9

MANAGEMENT OPTIONS

Prevention and Sanitation: The best management tactics canbe those that prevent the spread o nematodes. Equipment,especially tillage equipment, will spread nematodesrom one feld to another. Reducing tillage has been an

eective means o control. All equipment should be cleanedthoroughly ater coming out o a feld known to be inectedwith nematodes.

Rotation: Crop rotation is the best option or reducingnematodes. However, many nematodes can survive,reproduce and/or increase in numbers in other crops. For

rotation to work, the rotational crop must not be a host to thatparticular nematode. Unortunately, soybeans host nearly alldamaging species. Use the table below to help choose goodrotational crops.

12

7/27/2019 Soy Nemas


9

MANAGEMENT OPTIONS

Acceptable rotations using common crops grown in Virginiaor several nematode species (note that an “X” indicates that the crop is not a good rotational crop).

13

Nematode Corn Cotton Peanut Soybean Perennial Grass Forage

Soybean Cyst X

Dagger X X

Lance X X X X

Lesion X X X X

Ring X X X X

Northern Root-

Knot (RKN)X X

Southern (RKN) X X X

Spiral X

Sting X X X X

Stubby Root X X X X X

Stunt X

7/27/2019 Soy Nemas


9

MANAGEMENT OPTIONS

Resistant Varieties: Variety selection ranks close to rotationas an eective strategy or managing nematodes. One yearo a rotation to a non-host crop may not always be enoughor lasting control. Depending on the nematode species and

one’s crop rotation, variety selection may be the only option.Integrating a resistant variety with eective rotation will resultin a greater response than just one tactic.

For instance, a rotation o corn rotated with a resistantsoybean variety then rotated back to corn means that thenematode has nothing to eed on (excluding weed hosts) or

three years. Beore purchasing seed, armers should reviewlocal reports o cultivar perormance and characteristicsor their region. Most soybean varieties have soybean cystnematode resistance and a ew have root-knot nematoderesistance. Check seed-company guides or contact your seedprovider or a list a nematode resistance and other traits.

14

7/27/2019 Soy Nemas


9

MANAGEMENT OPTIONS

Nematicides: The need or a nematicide should be based onthe previous site history and on the results o a soil test or thepresence and level o plant pathogenic nematodes.

Nematicides Registered or Use on U.S. Soybeans:

15

Nematode NematicideCommon Name

NematicideTrade Name

Rate Remarks

Root-knot,lesion,stubbyroot

abamectin +thiamethoxam +ungicidemixtures

clothianidin +Bacillus frmus

(systemic insec-ticide +biological seedtreatment)

aldicarb

AvictaCompleteBeans

Poncho/Votivo(protects seed

and seedlingsagainst early-season insectand nematodedamage)

Temik 15G

0.15 mgai/seed

0.13 mgai/seed

5.5 oz/ 1,000 t.

o row

Only or use as aseed treatment inSyngenta-certifedtreatment acilities.

Apply only as aseed treatment

according to labeldirections. Not oruse as a hopperbox or other treat-ment in on-armapplications

Apply to seedurrow at plant-

ing. Maximum userate is 7 poundsper acre. See labelinstructions toprotect ground-water and wells.

Soybean cyst nematode remarks: Use o nematicides alone or control osoybean cyst nematode has not been recommended. A our-year rotation that

alternates resistant and susceptible varieties with nonhost crops is needed.Application o Temik® 15G at 3 to 5 ounces per 1,000 eet o row in urrow maysuppress nematode damage.

7/27/2019 Soy Nemas


SOYBEAN CYST NEMATODE (SCN), the most commonsoybean nematode in Virginia, can be most problematicin continuous soybeans. Several types or races have beenidentifed. Farmers need to know the race o the nematodeinecting their felds in order or control measures to beeective. Although resistance to race 3 o this nematode hasbeen placed into most soybean varieties, ewer have resistanceor races 1 and 2. Additionally, several felds in Virginia have

been identifed as containing race 4 SCN. Only one commercialvariety available has been identifed as providing resistance tothis race.

LIGHT MICROGRAPH OF FEMALES AND CYSTS OF THE SOYBEAN CYST NEMATODE, Heterodera spp.

OVERVIEW

15

SOYBEAN CYST NEMATODE

16

7/27/2019 Soy Nemas



Above-ground symptoms can include stunting and yellowing,but 15 to 20 percent yield losses can occur even when there

can be no above-ground symptoms. Stunting and yellowingactually reveal a long-term problem that has aected yield overseveral seasons. Yellowing resembles the symptom associatedwith Mn defciency in soybean. Below ground, nodule ormationand the nitrogen fxation in these nodules can be reduced withsubstantial populations. Because symptoms can be nondescript,

diagnosis must be based on the white or yellow emalesattached to the roots.

Rotation and the use o resistant varieties are the only eectivemanagement strategies or SCN. Although an aldicarb insecticide will

reduce damage to roots early in the season and reduce yield loss, itdoes not reduce end-o-season populations. Furthermore, the newerseed treatments have not proven to be a replacement or aldicarb.

Long-term management o SCN depends on:

1. Early-season soybean vigor

2. Reducing SCN levels in the soil3. Preserving resistant varieties

MANAGEMENT

SYMPTOMS

17

7/27/2019 Soy Nemas



To meet these goals, the ollowing our-year rotation mustbe put into place:

1. Year 1 – non-host crop

2. Year 2 – resistant soybean variety

3. Year 3 – non-host crop

4. Year 4 – susceptible soybean variety

A 3-year rotation can be used in areas with low to moderaterisk o crop damage: Year 1 – non-host crop; Year 2 – resistant

soybean variety; and Year 3 – susceptible soybean variety.

18

7/27/2019 Soy Nemas


LANCE NEMATODE has been ound throughout Virginiain many soils, but has been rarely ound in great enoughnumbers to cause yield reductions. Still, lance nematode hasbeen identifed as the reason or poor growth in several feldssurveyed in Virginia during 2007 to 2010.

It must be noted that three species o lance nematode havebeen identifed, one o which (the Columbia lance nematode)can cause severe injury. The Columbia lance nematode has

not been reported in Virginia.

LIGHT MICROGRAPH OF A MALE AND FEMALE LANCE NEMATODE, Hoplolaimus app.

OVERVIEW

19

LANCE NEMATODE

7/27/2019 Soy Nemas


LANCE NEMATODE

Stunted plants will be the primary symptom o lancenematode. Under damaging inestations and where

subsurace compaction has been present, great numbers osecondary and tertiary roots are produced and coincide withtaproot necrosis.

Planting early (mid-April/early-May) may help avoid optimaltemperatures or inection and reproduction o the nematode.Aldicarb can help prevent yield loss. Subsoiling will be advisedto alleviate hardpans.

MANAGEMENT

SYMPTOMS

20

7/27/2019 Soy Nemas


LESION NEMATODES HAVE BEEN FOUND THROUGHOUTVIRGINIA AND ATTACK A NUMBER OF CROPS AND WEEDS.Lesion nematodes can be identifed as small nematodesoccurring on a wide range o soil types. Occasionally thesenematodes can be ound in great-enough numbers to cause ayield reduction in Virginia felds.

LIGHT MICROGRAPH OF A FEMALE LESION NEMATODE, Pratylenchus spp.

OVERVIEW

21

LESION NEMATODE

7/27/2019 Soy Nemas


LESION NEMATODE

Under heavy inestations, stunting and yellowing o plantswill occur; however, crop losses rom lesion nematode can

occur without any observable symptoms above ground.Feeding rom lesion nematodes causes dark lesions and anoverall browning o the roots. Roots may appear short andstubby on the tips. The outer two layers o cells (epidermisand cortex) can slough away rom the roots on severelyinected plants. Nutrient and soil moisture stress intensifes

yield loss.

Varieties vary in their susceptibility to lesion nematode, butew companies list (or know) this trait in publications.The wide host range o this nematode makes rotation lesseective, but rotating to perennial grass crops may bebenefcial. Nematicides may reduce early-season injury.

MANAGEMENT

SYMPTOMS

22

7/27/2019 Soy Nemas


RING NEMATODE has been the least common nematode in

Virginia Tech surveys. Relatively high numbers must be oundto cause yield reductions.

LIGHT MICROGRAPH OF A FEMALE RING NEMATODE, Mesocriconema spp.

OVERVIEW

23

RING NEMATODE

7/27/2019 Soy Nemas


RING NEMATODE

Symptoms caused by ring nematodes are nondescript.Generally they may cause some stunting o the plants, but

their major eect is on overall yield, especially in seasons thatinclude long periods o drought.

Management o ring nematodes can be best achieved bycrop rotation and other cultural practices because they arenot very pathogenic and have minimal economic impact.Sources o resistance remain unknown, and nematicides canbe too costly to provide a good return on the investment.

MANAGEMENT

SYMPTOMS

24

7/27/2019 Soy Nemas


RKN has been identifed as one o the most problematicnematodes in Virginia and attacks a number o commonly

grown crops. Four species o this nematode are commonlyound in Virginia: southern RKN, northern RKN, Javanese RKN,and peanut RKN. Northern and peanut RKN can be usually oundin our peanut-growing regions, whereas southern and JavaneseRKN is most common in our traditional corn, small-grain andsoybean regions. Southern RKN has become more established

where cotton has been rotated with soybeans. Some feldscontain mixtures o more than one species o RKN.

GALLING CAUSED BY SOUTHERN ROOT-KNOT NEMATODE

OVERVIEW

25

ROOT-KNOT NEMATODE (RKN)

7/27/2019 Soy Nemas


ROOT-KNOT NEMATODE (RKN)

The main symptom o RKN includes the presence ogalls, or swelling on the inected roots. Water and nutrient

movement through the plant can be greatly disrupted or eveninhibited. As a result o this disruption, inected plants willbecome yellow and stunted, and wilt during the hot partso the day. On moderately and heavily inested felds, plantsmay mature one to two weeks earlier than normal. Spread oRKN can be generally in the direction o tillage; thereore, oval

patches that run parallel to the row are common.

Eective crop rotation or root-knot nematodes can bedependent upon identifcation o the species that arepresent in the feld. The Virginia Tech Nematode Diagnostic

Lab provides this service. This can only be done on specialrequest. Rotation options have not been identifed. Varieties withresistance to southern RKN can be available and remain a crucialmanagement tactic. Note that this resistance is not always complete and the addition o an in-urrow or seed treatment nematicide will usually increase yields over either tactic alone. Double-cropping soybeans, due to a lack o ood source or RKNduring May and early June, may reduce RKN numbers.

MANAGEMENT

SYMPTOMS

26

7/27/2019 Soy Nemas


Spiral nematode will only cause yield reductions in soybeanswhen very high numbers have been present and the crophas been stressed with environmental or other conditions. Still, this nematode can be very common in surveyed felds.Very high numbers have been ound in some felds, which, incombination with other nematodes present, resulted in control

recommendations.

LIGHT MICROGRAPH OF A FEMALE SPIRAL NEMATODE, Helicotylenchus spp.

OVERVIEW

27

SPIRAL NEMATODE

7/27/2019 Soy Nemas


SPIRAL NEMATODE

The symptoms caused by spiral nematode have been minimaland may only show as a reduction in yield potential, especially

during growing seasons with long periods o drought.

Management o spiral nematodes can be difcult to achieveand usually not proftable because their impact has been

minimal.

MANAGEMENT

SYMPTOMS

28

7/27/2019 Soy Nemas


Sting nematode, one o the least common and problematic othe nematodes, has been ound in Virginia. Still, relatively lownumbers o these nematodes can cause substantial damage to

soybeans. They have larger bodies than other nematodes, havea wide host range and generally occur on very sandy soils.

LIGHT MICROGRAPH OF A FEMALE AND MALE STING NEMATODE, BELONOLAIMUS SPP.

OVERVIEW

29

STING NEMATODE

7/27/2019 Soy Nemas


STING NEMATODE

Above-ground symptoms include stunting and yellowing.Dark, sunken lesions frst appear along the root axis and root

tips, and then enlarge to girdle the roots or extend longitudinallydown the root axis. Girdled roots can break o, giving a stubbyroot appearance. Root prolieration will occur above the pointso attack, resulting in a characteristic multi-branched rootappearance o plants inected with sting nematode.

One eective tactic to manage sting nematodes is to avoidplanting in very sandy soil. They can only be a problem inareas with greater than 80 percent sand and less than 10percent clay. Nematicides may be cost-eective, especially ithey are placed in areas o the feld with very sandy soil.

MANAGEMENT

SYMPTOMS

30

7/27/2019 Soy Nemas


Stubby root nematode has not been ound in very many feldsin our survey, but where it has been ound, its numbers havebeen great enough to warrant control measures, especially withother nematodes present.

LIGHT MICROGRAPH OF A FEMALE STUBBY ROOT NEMATODE, Paratrichodorus spp.

OVERVIEW

31

STUBBY ROOT NEMATODE

7/27/2019 Soy Nemas


STUBBY ROOT NEMATODE

Stubby root nematodes may reduce overall growth o the plantand yield, especially during growing seasons with long periods

o drought.

Practices that minimize the impact o stubby root nematodescan be economically viable but have not been available. Crop

rotation and other cultural practices may be helpul in reducingtheir number; however, nematicide application usually costsmore than the beneft that can be achieved.

MANAGEMENT

SYMPTOMS

32

7/27/2019 Soy Nemas


Stunt nematode has been commonly ound in Virginia soybeanfelds and oten at levels great enough to warrant control,especially i the crop has been under stress.

LIGHT MICROGRAPH OF A FEMALE AND MALE STUNT NEMATODE, Tylenchorhynchus spp.

OVERVIEW

33

STUNT NEMATODE

7/27/2019 Soy Nemas


STUNT NEMATODE

Stunt nematodes may reduce overall plant size and yield;however, the population has to be high and the growing

season must contain long periods o drought beore thiseect is evident.

No eective management practices are available or reducingthe populations o stunt nematodes other than crop rotationand other cultural practices.

MANAGEMENT

SYMPTOMS

34

7/27/2019 Soy Nemas


FARM LEADERS o the national soybean checkoinitiated the Inormation and Technology Transerproject, a collaborative eort between the soybean

checko, numerous state soybean boards andtheir respective land-grant universities to distributechecko-unded and other critical productionresearch inormation to help soybean armersimprove their proftability. This guide is part othis eort. The United Soybean Board neither

recommends nor discourages the implementationo any advice contained herein, and is not liable orthe use or misuse o the inormation provided.

7/27/2019 Soy Nemas


www.UnitedSoybean.org

www.ext.vt.edu

for more infoplease visit

2011 Virginia Polytechnic Institute and State University AREC-9

Virginia Cooperative Extension programs and employment are open to all, regardless of race, color,national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or familystatus. An equal opportunity/afrmative action employer. Issued in furtherance of Cooperative

Extension work Virginia Polytechnic Institute and State University Virginia State University and the

soy nemas

Documents