Gret Lkes Fruit, Vegetle & Frm Mrket EXPO Michign Greenhouse Growers EXPO Decemer 4-6, 2012 DeVos Plce Convention Center, Grnd Rpids, MI Greenhouse: Controlling Other Greenhouse Plnt Diseses Where: Grnd Gllery (min level) Room D Sponsored y Syngent Flowers. MI Recertifiction credits: 1 (COMM CORE, PRIV CORE) Modertor: Chris Lufkin, Syngent Flowers 3:00 pm Controlling Other Greenhouse Plnt Diseses: Botrytis, Pythium, Powdery Mildew, Rhizoctoni, nd Thielviopsis Blir Hrln, Plnt, Soil nd Microil Sciences Dept., MSU 3:50 pm Session Ends
Controlling Other Greenhouse Plnt Diseses: Botrytis, Pythium, Powdery Mildew, Rhizoctoni, nd Thielviopsis Blir R. Hrln, nd Dr. Mry K. Huseck (517-355-4534) Michign Stte University, Deprtment of Plnt, Soil & Microil Sciences, Est Lnsing, MI Botrytis Blight. The fungus Botrytis cinere cuses disese on greenhouse ornmentl nd vegetle crops including lef spots, lighting, stem cnkers, nd dmping-off. Botrytis produces lrge msses of gry conidi or spores (hence the nme gry mold ) tht re crried on ir currents to helthy plnts where light cn ecome estlished. Infection cn strt s smll lef spot tht cn quickly colesce into lrge necrotic re or infect the cut stem surfce of stock plnts nd progress downwrd, cusing dieck of the entire plnt. On edding nd stock plnts, Botrytis typiclly ecomes estlished nd produces conidi on older lower leves tht re ner the moist soil surfce nd under the plnt cnopy. Botrytis cn lso infect ded plnt tissue in the pot or on the greenhouse ench or floor, which cn e source of future infections. When the wether is moist nd humid, susceptile plnts my need to e protected from Botrytis infection. Plnts my lso e susceptile if they ecome wet from wter dripping from overhed, dew, or condenstion. Wter llows the Botrytis conidi to germinte nd penetrte the plnt. Wtering in the morning so tht the folige cn dry rpidly is one wy to minimize Botrytis. Reducing reltive humidity y spcing plnts further prt nd providing good ir circultion cn e helpful. Reduce the reltive humidity for minimum of 24 hours immeditely following the hrvesting of cuttings to help dry the wounded stems nd therey limit stem light. Finding the eginnings of rown/gry fuzziness on lower leves cn signl the need for disese control mesures. Snittion is n importnt first step to reduce Botrytis in your greenhouse. If you hve ded plnt tissue on your greenhouse ench, it is likely supporting sporulting Botrtyis! The tle elow shows tht even the est tretments do not completely prevent infection, however, they re often necessry prtners in successful mngement progrm tht includes environmentl control nd snittion. This tle shows the results of tril conducted on poinsetti plnts inoculted with Botrytis. Fungicides were pplied nd llowed to dry prior to introducing Botrytis. The fungicides contining chlorothlonil (Dconil is n exmple) nd iprodione consistently provide effective control. The iopesticide Vernd O hs een shown to e effective in severl studies. Newer products Pgent nd Plldium mke excellent rottionl products in spry progrm. Fungicides must e pplied s folir spry to e effective in controlling this disese. Tretment nd rte/100 gl % of leves with sporulting B. cinere Helth rting 1=helthy, 10=ded Untreted control 65.4 e 7.0 e Dconil Wether Stik 6SC 1.4 pt 7.0 2.0 Vernd O 11.3WDG 8 oz 12.3 3.0 d Pgent 38WG 18 oz 5.2 1.8 Plldium 62.5WDG 6 oz 13.0 2.3 c Decree 50DF 1.5 l 19.1 c 3.3 cd Medllion 50WP 4 oz 0.5 1.3 Chipco 50WP 2 l 6.0 1.8 Heritge 50WG 8 oz 35.8 cd 4.0 cd GANTEC Green E 8 fl oz 58.5 e 7.3 e Disrm O SC 4 fl oz 37.7 cd 4.5 d OHP 6672 F 20 fl oz 69.4 e 6.8 e
Botrytis A Tem Botrytis B Tem Dconil Wetherstik SC chlorothlonil Compss O WDG trifloxystroin Decree 50DF fenhexmid Dithne DF mncoze Chipco 26019 WDG, 26GT F iprodione Heritge WDG zoxystroin Pgent 38WG pyrclostroin + osclid Insigni WG pyrclostroin Vernd O WDG polyoxin D zinc slt Plldium WDG cyprodinil + fludioxonil Pythium Root Rot. Pythium crown nd root rot is common nd persistent disese in the greenhouse industry. Pythium is wter mold tht cn nile the feeding roots of plnts, resulting in stunted growth. Pythium cn lso cuse severe symptoms, such s crown rot, tht cn result in plnt deth. Pythium fvors wet, sturted soil conditions, such s overwtered medi. The persistence of this pthogen cn e trced to its ility to hiernte on dirty plnt continers, enches, hoses, nd greenhouse wlkwys, redy to ecome ctivted y the right crop nd wether conditions. Although Pythium cn e prolem on lmost ny greenhouse crop, plnts like gernium, poinsetti, nd snpdrgons re often the most ffected. Snittion is especilly importnt in limiting root rot. Conditions tht fvor good plnt growth nd minimize stress mke the plnt less vulnerle to ttck y root rot. Use pressure wsher with sop nd wter when clening wlkwys, enches, etc. You cn follow this with disinfestnt to remove ny remining Pythium. If you ve done everything right nd still find yourself with Pythium prolem, choosing the right fungicide tools cn minimize your losses. Scouting is n importnt first step in controlling Pythium root rot. If Pythium hs significnt hed strt, the root system of some plnts will e too rotted nd the fungicides will not e le to rescue them. If Sudue MAXX hs een the only or primry fungicide used over the yers, nd Pythium continues to e n issue in your greenhouse, it is possile tht the Pythium hs ecome resistnt nd is no longer ffected y this fungicide. To know for sure, the Pythium present in your greenhouse must e tested in dignostic l. To void the development of resistnce, rotte mong the different ctive ingredients ville mong fungicide products. If Pythium hs not een mjor issue in your greenhouse, fungicide such s Bnrot 40WP is mixture of two different ctive ingredients nd trgets ll three common root rots. If Pythium is dignosed s the prolem, choosing fungicide tht is specific for Pythium is importnt nd include Sudue MAXX (lso ville s Mefenoxm 2), Trun, Terrzole, Aliette, nd FenStop. If you hve Pythium resistnt to Sudue MAXX in your greenhouse it is recommended tht Trun or Terrzole e used s they hve een shown to e the most effective products in our greenhouse trils. Since Trun nd Terrzole hve the sme ctive ingredient, rotting etween these two fungicides is not recommended. Aliette nd FenStop re tools for Pythium control tht cn e helpful if used erly nd if the disese is not severe. For the est control, the time etween fungicide pplictions should not e stretched eyond the minimum intervl listed on the lel. Only drench pplictions, not spry pplictions, re effective in controlling Pythium root rot. Pythium A Tem Pythium B/B- Tem Trun WP/Terrzole WP etridizole Adorn SC fluopicolide Sudue MAXX EC mefenoxm Aliette WDG fosetyl-l Cptn WDG cptn Heritge WDG zoxystroin FenStop SC fenmidone Segwy SC cyzofmid
Powdery Mildew. The white tlcum-like colonies of powdery mildew cn strt smll ut cn rpidly light the leves, stems, nd flowers of susceptile crops. Some powdery mildews cn e specific to one type of plnt while other powdery mildews, such s Erysiphe cichorcerum, cn infect mny different nnul nd perennil flowers nd vegetles. The undnt conidi (spores) give white, powdery or fluffy ppernce. There re times when identifying the disese cn e difficult s infection sometimes cn only cuse yellowing nd withering of leves nd stunted plnt growth. High reltive humidity cn prompt epidemics. Some plnt species such s gerer disy, clircho, sters, nd veren re very susceptile nd should e spryed more frequently with the most effective fungicides. Other plnt species my not need frequent pplictions ut should e scouted regulrly for signs of the disese. It should e noted tht certin vrieties of plnt species re more susceptile thn others. Growing susceptile crops cn e chllenge, nd fungicides hve typiclly plyed key role. Powdery mildews re tricky nd hve een known to geneticlly dpt to overcome some of the most effective fungicides. You my wnt to strt out with the most effective products, such s Egle nd Terrgurd if you re growing n especilly susceptile crop. Currently there re severl excellent products ville (Insigni, Pgent, Tourney, etc.) to rotte with your est fungicides in comprehensive spry progrm. Helth (1=helthy, 10=ded) 10 8 6 4 2 0 c Untreted Powdery Mildew on Aster 'Henry I' Terrgurd SC 8 fl oz 7-dy Pgent 8WG 12 oz 7-dy Plldium WDG 6 oz 7-dy Tourney 50WDG 4 oz 14-dy Gntec GREEN EC 8 fl oz 5-dy Powdery Mildew A Tem Powdery Mildew A-/B Tem Egle EW/WP mycloutnil Compss O WDG trifloxystroin Terrgurd SC triflumizole Heritge WDG zoxystroin Insigni WG pyrclostroin Pgent WG pyrclostroin + osclid Strike WDG tridimefon Tourney WDG metconzole Zyn WSP t-methyl + mncoze Brs with letter in common re not significntly different Phytophthor Root Rot. Phytophthor is wter mold (like Pythium) nd cn e prticulrly devstting nd difficult-to-control prolem. It cn spred quickly in greenhouse, especilly in flood floor nd hydroponic systems. Two types of Phytophthor (Phytophthor nicotine nd Phytophthor drechsleri) re usully found in floriculture crops nd cn cuse root, crown, nd folir lights. Phytophthor nicotine cn infect snpdrgon, fuchsi, veren, cop, vinc, Africn violet, nd dusty miller to nme few. Phytophthor drechsleri my infect poinsettis. Losses cn e especilly severe where mple wter nd wrm tempertures fvor disese epidemics. Symptoms include rown-lck cnkers t the soil line nd disesed roots. Infected folige will hve wter-soked, drk necrotic re. In some cses, the crowns will e the first plnt prt to ecome infected, fter which the infection will move up the stem into the folige ner the petiole. This type of symptom is especilly noticele on English ivy nd Africn violets. Controlling the spred of Phytophthor spp. cn e difficult. First, Phytophthor must e kept out of the production site. This is prticulrly difficult with floriculture crops ecuse of the widespred distriution of prefinished plnts. Also, plnts my not exhiit ovious symptoms until the infection is
well estlished or the plnt ecomes stressed (e.g., over- or underwtering). Infected plnts treted with fungicides my pper helthy until the fungicides wer off nd Phytophthor increses. The second chllenge is erdicting Phytophthor once it hs een introduced. Snittion cn limit disese nd includes removing plnt deris nd disinfesting production surfces. Power wshing enches nd replcing floor mts re importnt steps to tke to reduce inoculum for future crops. The grph on this pge shows the wide rnge of susceptiility mong osteospermum cultivrs to Phytophthor drechsleri. Sunrell Turus nd Sunny Olivi showed resistnce to infection from Phytophthor while the remining cutivrs in the study hd >80% plnt deth. If fungicides, such s the stndrd Sudue MAXX, re used to control Phytophthor, rotte it with other effective products. The newly registered fungicide Micor SC (mndipropmid) hs een effective in greenhouse studies. Also, Adorn hs controlled disese on pnsy, poinsetti nd snpdrgon. The phosphorous cid products, Deth (%) Disese severity (1=helthy, 10=ded) Phytophthor drechsleri on Osteospermum Cultivrs such s Alude nd Vitl, my lso limit disese. Other fungicides such s FenStop, Insigni, Heritge, Terrzole/Trun, Stture, Segwy, nd Aliette, my offer help if the disese pressure is not too severe. Some products hve performed well on one crop ut filed on nother, so cre must e tken to use fungicide progrm tht effectively rottes products to mintin disese control nd minimizes the chnce of fungicide resistnce developing in Phytophthor. Phytophthor A Tem Phytophthor B Tem Adorn SC fluopicolide Aliette WDG fosetyl-l Alude L phosphorous cid slts Cptn WDG cptn FenStop SC fenmidone Insigni WG pyrclostroin Micor SC mndipropmid Segwy SC cyzofmid Stture DM WP dimethomorph Sudue MAXX EC mefenoxm Terrzole WP etridizole 100 80 60 40 20 0 5 4 3 2 1 Brs with letter in common re not significntly different Sunrell Turus Sunny Olivi Trdewinds Deep Purple c c c c Mrgrit Sunset Ornge Symphony Soprno Rhizoctoni Root Rot. The Rhizoctoni solni fungus typiclly cuses dull rown to drk rown rot on lower plnt stems. In severe cses it cn lso destroy the root system of n infected plnt. This pthogen cn thrive in wet/dry or wrm/cool conditions. Snittion is n importnt method of limiting the pthogen s it is most likely to spred with contminted soil, flts, or pots. Terrclor, Terrgurd, Clery s 3336/OHP 6672, nd Medllion pplied s drench hve een importnt tools in preventing Rhizoctoni nd hlting its spred. Repeted studies with the iopesticide Vernd O hve shown it to e very effective product ginst Rhizoctoni. Biocontrol gents re ecoming more widely ville for use in controlling dmping-off fungi such s Rhizoctoni. Growing mixes tht re nturlly suppressive to dmping-off soilorne fungi re lso ville to growers. A suppressive medium is one tht represses, restrins, or checks the growth of dmping-off fungi. Intitilly, interested growers my wnt to test the usefulness of suppressive medi in their growing system y plnting smll portion of their crop in suppressive medi. Communiction with sles representtives nd extension personnel my e helpful to evlute nd perhps modify growing systems using suppressive medium to chieve the est results.
Rhizoctoni A Tem Rhizoctoni B+ Tem Medllion WG fludioxonil Clery s 3336 WP/OHP 6672 FL t-methyl Terrclor WP PCNB Cptn WDG cptn Terrgurd SC triflumizole Heritge WDG zoxystroin Vernd O WDG polyoxin D zinc slt Blck Root Rot. Blck root rot, cused y the fungus Thielviopsis sicol, is serious thret to pnsies, petunis, nd vinc. It my lso infect cyclmen, clircho, poinsetti, primul, imptiens, snpdrgon, veren, phlox, egoni, nd nicotin. Symptoms of lck root rot re often mistken for nutrient deficiencies. Leves my turn yellow nd the youngest leves ecome stunted nd tinged with red. In mild infections, older leves re yellow-green with the veins retining their green color. Snittion is the est preventive mesure ginst lck root rot. This pthogen produces spore tht cn persist on floor mts, greenhouse enches, or flts/pots. It is not recommend to reuse plug trys for crops tht re susceptile to Thielviopsis. University studies hve shown tht fungus gnts nd shore flies cn move this pthogen round greenhouse y eting the spores nd excreting them into nery pots. If you hve Thielviopsis prolem nd fungus gnt prolem then you will hve quickly spreding epidemic! Bsed on MSU studies, fungicides tht hve thiophnte-methyl s the primry ctive ingredient (Clery s 3336 F is n exmple) should e used frequently. Good rottionl products include Terrgurd nd Medllion since they hve different mode of ction nd were shown to e effective in MSU studies ginst lck root rot. Choosing n effective fungicide to control lck root rot is criticl ecuse misstep erly in the disese epidemic my result in n unslle crop. It is recommended to use the highest leled rte of ech tretment with close reppliction intervls. Thielviopsis A Tem Clery s 3336 WP/OHP 6672 FL t-methyl Medllion WG fludioxonil Terrgurd SC triflumizole Acknowledgments. This mteril is sed upon work supported y Specific Coopertive Agreement 58-1907-0-096 with USDA ARS under the Floriculture nd Nursery Reserch Inititive nd y the Americn Florl Endowment.