Gret Lkes Fruit, Vegetle & Frm Mrket EXPO Michign Greenhouse Growers EXPO December 9-11, 214 DeVos Plce Convention Center, Grnd Rpids, MI Crrot Wednesdy fternoon 2: pm Where: Grnd Gllery (min level) Room C MI Recertifiction credits: 2 (1B, COMM CORE, PRIV CORE) OH Recertifiction credits:.5 (presenttions s mrked) CCA Credits: NM(.5) PM(1.5) Modertor: Corey Noyes, Horticulture Dept., MSU 2: pm Updte on Disese Control in Crrots (OH: 2B,.5 hr) Mry Husbeck, Plnt, Soil nd Microbil Sciences Dept., MSU 2:3 pm Testing for Aster Lefhopper Infectivity in Michign Crrot nd Celery Crops Zsofi Szendrei, Entomology Dept., MSU 3: pm Slow-Relese Nitrogen for Crrots: Effects of Rte nd Timing on Qulity nd Yield. Corey Noyes, Horticulture Dept., MSU Dniel Brinrd, Horticulture Dept., MSU 3:3 pm Mnging Plnt-Prsitic Nemtodes with Cover Crops in MI Fred Wrner, Plnt, Soil nd Microbil Sciences Dept. MSU 4: pm Session Ends
Updte on Disese Control in Crrots Dr. Mry K. Husbeck, 517-355-4534 Michign Stte University, Deprtment of Plnt, Soil & Microbil Sciences Cercospor nd Alternri lef nd petiole blights. Becuse high humidity nd frequent rinfll or irrigtion is common during the Michign growing seson, yield-thretening folir blights re recurring problem, reducing photosynthetic re nd wekening leves nd petioles, nd requiring mngement progrm to prevent crop loss. Michign growers hrvest crrots mechniclly nd wekened petioles nd folige (Fig. 1C) cn disrupt hrvest due to crrot tops breking off during lifting. In situtions where folir disese is severe nd not controlled, the tops my be compromised to the extent tht the crop cnnot be hrvested. Cercospor blight (Fig. 1B) is cused by the fungus, Cercospor crote, nd is n importnt folir disese of crrots. The fungus cn ttck young folige, either on the leves or petioles. Cercospor lef spot occurs s smll circulr brown spots tht rpidly enlrge, ccompnied by yellow/red discolortion on younger leves nd cn girdle petioles, resulting in defolition. Alternri blight (Fig. 1A) is cused by the fungus, Alternri duci, nd is usully detected lter in the seson on older folige. Symptoms of Alternri lef spot include drk brown/blck spots with yellow mrgins ppering on older leves. Petioles my lso become blighted. Severe disese results in wek petioles or defolition. Wrm tempertures nd long periods of lef wetness promote disese development. Spores of these fungi re wind-blown to nerby plnts or even djcent fields. Alternri nd Cercospor folir blights my occur together nd re mnged similrly. Methods to reduce disese pressure include plnting disese-free seed, following 2-yer crop rottion, minimizing overhed irrigtion during wrm wether, nd pplying fungicides. Methods to effectively schedule fungicide pplictions ccording to field scouting nd the TOM-CAST disese forecsting system hve been developed nd dopted by mny growers. A B C Fig. 1. A, Alternri lef spot. B, Cercospor lef spot. C, Petiole lesions.
Tle 1. List of products tested in field trils. Product Active ingredient FRAC Leled Brvo WetherStik SC chlorothnonil M5 yes Fontelis SC penthiopyrd 7 yes Inspire EC difenoconzole 3 no Lun Senstion SC fluopyrm/trifloxystrobin 7/11 no Lun Trnsquility fluopyrm/pyrimethnil 7/9 no Omeg SC fluzinm 29 no Presidio SC fluopicolide 43 yes Prixor SC fluxpyroxd/pyrclostrobin 7/11 no Qudris SC zoxystrobin 11 yes Reson SC fenmidone 11 yes Ridomil Gold SL mefenoxm 4 yes Rovrl SC iprodione 2 yes Serende Optimum WP Bcillus subtilis -- yes Serende Soil FL Bcillus subtilis -- yes Tilt EC propiconzole 3 yes Folir blight field tril. A field tril compred fungicide progrms pplied ccording to the Tom-Cst disese forecster versus clendr-bsed pplictions of fungicides (Tle 1). Five tretments were scheduled ccording to Tom-Cst on 31 July; 13, 22 nd 29 August; nd 8 September. Six clendrscheduled tretments were pplied every 14 dys on 31 July; 13 nd 25 August; 8 nd 23 September; nd 7 October. Plnts were evluted for disese on 21 October. Roots were hrvested from the center 1 feet of tretment row nd yields weighed on 23 October. The percentge of plnts with infected petioles (%) ws reltively high in the untreted control nd nerly 5% of the plnts were infected (Fig. 2). All tretments significntly limited disese compred with the untreted control. The pplictions of Rovrl were not s effective s the other fungicides included in the study. Applying fungicides ccording to the Tom-Cst disese forecster ws especilly effective, limiting plnts with infected petioles to 3.9%, nd disese to.8, when rted on scle of to 12. Brvo WetherStik pplied ccording to Tom-Cst resulted in the gretest yield, significntly higher thn Rovrl nd Lun Trnquility pplied t 14-dy intervls. Adding Fontelis to fungicide rottion in conjunction with the Tom-Cst disese forecster ws effective nd could ese relince on Brvo nd Qudris which hve been stndrds for crrot growers. Root Diebck (Pythium Brown Rot nd Forking). Dmged, disesed or otherwise unmrketle crrots re known s culls. Approximtely 3% of the crrots delivered to pcking plnts re rejected s not suitle (cull) for fresh mrket pcks. Forking nd stubbing of crrot roots (Fig. 3) is complex problem likely resulting from combintion of mechnicl dmge, disese, nd/or nemtodes. Root diebck cused by Pythium spp. cn occur wherever crrots re grown. Root diebck of crrots produces excessively brnched or stubbed roots. The fungus kills young tproots fter seed germintion, reducing root length nd/or stimulting forking. Forking nd stubbing symptoms cn lso be cused by soil compction, nemtodes, nd/or excessive wter. The severity of the disese my be depend on the density of Pythium spores in fields, in ddition to other fctors such s wet soil conditions nd lrge mounts of crop residue. Pythium spp. produce sporngi nd overwintering spores (oospores). Spores nd myceli re responsible for the spred of the fungus in the field, which is fcilitted by wet soil conditions. Disese control cn be chieved by voiding excessive wtering, by providing good field dringe nd by plnting crrots in deep, frile, nd well-drined soils. Post-emergent fungicides contining the ctive ingredient mefenoxm (i.e., Ridomil Gold EC) cn be pplied to control dmpingoff. Rottions with smll grins my reduce soil popultions of some Pythium spp.
Plnts with Cercospor -infected petioles (%) Petiole disese severity (=helthy, 1=1 lesion on 1 petiole, 12=1% disesed) Yield (lb/1' row) 5 4 3 2 1 5 4 3 2 1 4 3 2 1 c e Brs with letter in common re not significntly different Untreted control Tom-Cst Clendr sprys -c -c -c -c -c -c Plnts with infected petiole (%) -c -c -c bc cd Petiole disese severity b-d b d Yield c Untreted control Apps 1,2 BWS App 3 Qudris 15.5 fl oz Apps 4,5 Fontelis 24 fl oz Tom-Cst: 5 sprys BWS BWS -lt- Qudris 15.5 fl oz -lt- Fontelis 24 fl oz BWS -lt- Qudris 15.5 fl oz Inspire 7 fl oz Lun Senstion 7.6 fl oz Clendr: 6 sprys t 14-dy intervls Qudris Tilt Fontelis 15.5 fl oz 4 fl oz 24 fl oz Lun Trnquility 15.5 fl oz Prixor 8 fl oz Omeg 1 pt Fig. 2. Evlution of fungicides pplied ccording to the Tom-Cst disese forecster or in clendrbsed progrm. BWS=Brvo WetherStik. Petiole disese severity rted on modified Horsfll-Brrtt scle of to 12, where =% plnt re disesed, 1=1 lesion on 1 petiole/plnt, 2=>1 lesion to 3% of plnt re disesed, 3=>3 to 6% plnt re disesed, 4=>6 to 12%, 5=>12 to 25%, 6=>25 to 5%, 7=>5 to 75%, 8=>75 to 87%, 9=>87 to 94%, 1=>94 to 97%, 11=>97 to <1%, 12=1% plnt re disesed. Rovrl Root forking/stubbing field tril. A field tril evluted fungicide progrms for control of Pythium forking nd stubbing of crrots. The first ppliction ws pplied s bnd over the seedbed on 8 My. Folir tretments were pplied on 31 July; 8, 15, 22 nd 29 August; 4 nd 18 September. Roots were hrvested from the center 1 feet of the tretment row nd totl yields nd forked/stubbed yields were weighed on 18 September. There were no significnt differences mong tretments for totl yield (Fig. 4). Forking/stubbing reched 34.1% in the untreted control. Progrms tht included Ridomil Gold or Presidio pplied both t plnting nd s 7-dy folir spry significntly limited forking/stubbing compred to the untreted control, s did Serende Soil t plnting/serende Optimum s 7-dy folir spry. Fig. 3. Root forking nd stubbing.
Totl yield (lb/1') Forked, stubbed yield (%) 3 25 2 15 1 5 3 2 1 b Untreted control Brs with letter in common re not significntly different BrvoWS + Qudris 15 fl oz folir 7-dy Ridomil Gold 1 pt t plnting Ridomil Gold 1 pt folir 7-dy Serende Soil 4 qt t plnting Serende Optimum 16 oz folir 7-dy Totl yield Forked, stubbed yield (%) Presidio 4 fl oz t plnting Presidio 4 fl oz folir 7-dy Serende Soil 4 qt t plnting Reson 8.2 fl oz folir 7-dy Serende Soil 4 qt t plnting Reson 8.2 fl oz -lt- Serende Optimum 16 oz folir 7-dy Fig. 4. Evlution of fungicides pplied in bnd t plnting nd s 7-dy folir sprys for control of Pythium forking nd stubbing of crrots. Acknowledgements. This reserch ws supported by funding from the Michign Crrot Committee, nd by Stte Block Grnt dministered by the Michign Crrot Committee.
Mnging Plnt-Prsitic Nemtodes with Cover Crops in Michign INTRODUCTION Fred Wrner, Dignostic Services 578 Wilson Rd., 117 CIPS Michign Stte University Est Lnsing, MI 48824-6469 517-432-1333 -- fwnemlb@msu.edu Plnt-prsitic nemtodes re microscopic roundworms tht feed on plnts. The longest plntprsitic nemtode in Michign is the corn needle nemtode tht mesures lmost 6 mm in length (c. ¼ inch). Every described plnt species hs t lest one nemtode prsite. Most plnts re fed upon by multiple species of nemtodes. Feeding by plnt-prsitic nemtodes typiclly results in the production of symptoms. Most of these symptoms re not chrcteristic therefore, plnt-prsitic nemtode problems often go undignosed. This cn be costly s feeding by nemtodes on mny host crops cn result in significnt yield losses of 5% or more. Since this presenttion is in the crrot session, the plnt-prsitic nemtode of emphsis is the northern root-knot nemtode (NRKN). Root-knot nemtodes re serious pthogens of crrot becuse they ffect qulity nd quntity. Infected crrots re often stubby or forked, reducing mrketility. Glls, which re smll swellings on feeder roots cused by northern root-knot nemtodes, re chrcteristic symptoms cused by these prsites. There re other importnt nemtode prsites of crrot such s: crrot cysts; lesion nd pin nemtodes. Controlling these nemtodes my require different strtegies nd tctics thn those recommended for mnging NRKN. NORTHERN ROOT-KNOT NEMATODES Northern root-knot nemtodes re importnt pthogens of fruit, lndscpe/nursery nd vegetle crops in Michign. They lso prsitize mny row crops but losses on these plnts due to NRKN re usully minor. Mny vegetles re extremely susceptible s just the detection of NRKN in soil smple is concern for crrot growers where qulittive losses cn exceed 5% in infested fields. Nurseries often suffer significnt losses s reports of 75-1% culled dylily roots hve occurred due to NRKN infesttions. On world-wide bsis, root-knot nemtodes including NRKN, cuse greter economic losses thn ny other types of plnt-prsitic nemtodes. Grsses re non-hosts for the NRKN. Mny grsses (Pocee) re utilized s cover crops nd they re the best choices if mjor objective is to mnge NRKN. They work s pest strvers. All dicotyledonous plnts should be considered hosts unless they hve been screened ginst these nemtodes nd reported s non-hosts. Africn nd French mrigolds re lso effective pest strvers even though they re dicots. As mentioned previously, if mngement of NRKN is impertive, most dicots should be voided. It should be noted tht dicotyledonous plnts differ gretly in their susceptibilities/tolernces to NRKN nd in the numbers of these nemtodes they will support. The ltter becomes cler fter exmining the dt provided in the tle below. Plnt species tht re most often employed s pest gssers re good to excellent hosts for the NRKN. They relly should be voided. Edible rdish cn be used s pest trpper for NRKN but very creful monitoring of the nemtodes within root tissue is impertive if this tctic is to be used effectively. Rdish cn go from seed to hrvest prior to NRKN going from egg to egg. However, if the rdishes re left in the ground too long, NRKN femles will produce eggs nd the trpping is indequte. The roots must be removed from the soil prior to ny egg production for this type of trpping to be efficient. The trpping works only if the rdishes re hrvested prior to egg production becuse the nemtodes re trpped within the roots nd re then physiclly removed from fields. While some cultivrs of oilseed rdishes re very effective pest trppers for sugrbeet cyst nemtodes, they do not function in this mnner ginst NRKN.
The question is often sked, How long should I grow cover or rottionl crop to control nemtodes? This could be expnded to include the length of time required to drive nemtode numbers below dmging levels. The nswer to this question genertes two new questions. 1) How quickly do the nemtode species present decline under non-host or poor host? 2) How susceptible is the min crop(s) to the nemtode species? Root-knot nemtodes do not possess extended survivl stges like cyst nemtodes so typiclly yer or two of non-host should be dequte to reduce their popultion densities below dmging levels. The initil popultion density plys role in this decision. The more nemtodes present, the more time out required. The susceptibility of the min crop is criticl to ddress. Crrots re very susceptible to NKRN, so idelly they re below detectle levels prior to growing this crop without the use of nemticide(s). Soybens, for instnce, will tolerte some feeding by NRKN so it is not necessry to drive their numbers so low. Of course, to ssess NRKN (s well s ll plnt-prsitic nemtodes) popultion densities, it is necessry to collect soil nd root smples nd hve the smples processed in Nemtode Dignostic L such s the one t MSU. As rule of thumb, the more susceptible the min crop is to prticulr species of plnt-prsitic nemtode, the longer the time recommended in non-host crop including cover crops nd the more importnt it is to smple for nemtodes in n ttempt to void significnt yield losses. Men numbers of northern root-knot nemtode second-stge juveniles nd eggs recovered per grm of root tissue from greenhouse study fter 9 weeks. Averge dry root weights lso included. northern root-knot nemtodes/g root tissue second-stge juveniles eggs dry root weights (g) species vriety/type/line X SE X SE X SE lflf Foregrzer 867.5 361.47 68.75 31.92.8.54 lflf L447 HD 361.25 128.86 156.25 74.2.65.6 lflf L449 APH2 53. 125.22 1. 5. 1.13.13 white clover Kopu II 3241.25 69.98 146.25 44.74.25.16 red clover mmmoth red 6225. 931.48 761.25 215.26.15.35 red clover medium red 4866.25 1929.92 9. 69.28.25.35 white clover Dutch white 63. 259.32 67.5 32.1.17.19 yellow sweetclover yellow blossom sweet 1767.5 655.4 445. 219.18.73.43 mustrd Cliente 199 blend 822. 1199.1 129. 332.7 1.2.58 brown mustrd Kodic 135. 291.8 351. 684.95.6.35 yellow mustrd Pcific Gold 1824. 1858.67 268. 249.53.53.31 oilseed rdish FumRd 795. 1723.11 287. 774.83.88.83 oilseed rdish Cnnvro 134. 174.31 252. 354.96.4.54 oilseed rdish Crwoodi 1475. 41.84 585. 26.29 2.48.152 oilseed rdish Defender (certified) 86.25 19.8 5. 1.77 3.88.5 oilseed rdish Ground Hog 45. 61.93 5. 11.73 1.35.116 oilseed rdish Pile Driver 491.25 42.41 12.5 16.63 1.25.242 oilseed rdish Respect 71. 2.69 4. 11.55 4.43.189 oilseed rdish Tjun 96.25 221.48 113.75 34.78 3.78.239 oilseed rdish Toro 63. 111.84 35. 1.31 3.13.333 rpeseed Dwrf Essex 26.25 12.31.. 5.83.373 Itlin ryegrss Fest II.... 9.78.715 soyben Pioneer 92Y91 435. 8.43...98.19 soyben Peking 611.25 161.35 35. 1.31 1.85.151 soyben PI 88788 339. 5165.5 457. 166.8.53.55
BENEFICIAL NEMATODES It is estimted tht shovel full of grden soil my contin up to 1,, or more nemtodes. Usully, lmost ll of these nemtodes re beneficil s they feed on bcteri, fungi or other microorgnisms. Prcticlly ll soil inhiting nemtodes re microscopic but, regrdless of their sizes, nemtodes ply huge roles in soil ecosystems. The rhizosphere of roots is typiclly dominted by bcteri or fungi (lso protozons). In nnul cropping systems, bcteri re dominnt in the rhizosphere nd colonize the surfces of roots. In perennil systems, especilly those where trees re dominnt, fungi cn dominte lthough bcteri re common in these hitts lso. Therefore, the types of beneficil nemtodes found in these hitts will differ. Plnts grow better in the presence of beneficil nemtodes prticulrly species tht feed on bcteri. Bcteri often hve higher concentrtions of nitrogen within their cells thn needed by nemtodes, so nemtodes need to excrete this extr nitrogen. Bcteril-feeding nemtodes excrete the excess nitrogen from their bodies often s mmoni. Since nemtodes feed on bcteri colonizing the surfces of roots, mmoni is relesed right in these res mking it redily ville to plnts. This constitutes more effective wy to feed plnts insted of dumping nutrients into the soil t one or two times during growing seson. It s similr to the wy minerliztion occurs fter growing legume nd why these plnts provide nitrogen credits; nutrients re pulsed into the soil over n extended period of time. Feeding plnts stedily is more optiml thn giving them lrge mounts of nutrients infrequently. This is probly true for most living orgnisms. Most beneficil nemtodes re found in the O horizon of the soil where the mjority of the microorgnisms re found. As generl rule of thumb, the undnce of microorgnisms decreses s soil depth increses. Cover crops re often used to increse numbers of beneficil orgnisms becuse the evidence is quite conclusive tht s soil orgnic mtter increses, biologicl undnce nd diversity follows suit. Think of growing cover crops s providing food for your friends. CONCLUSION It is very importnt to recognize tht not ll plnt-prsitic nemtodes re the sme. There is no one mgicl cover crop tht will control ll types of these importnt plnt pthogens. Before choosing cover crop, if nemtode control is n importnt objective, it is criticl the types of nemtodes present in ny given loction re properly identified. Proper cultivr selection is lso importnt. If mnging plntprsitic nemtodes is not n objective, most cover crops will provide food for your friends unless you re trying to tke them out using pest gssers. Respirtory poisons relly don t discriminte.