Persistence of the systemic activity of metalaxyl and fosetyl-al applied as a soil drench or foliar spray to control Phytophthora crown rot of peach

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1 Phytopthol. Mediterr. (2002) 41, Persistence of the systemic ctivity of metlxyl nd fosetyl-al pplied s soil drench or folir spry to control Phytophthor crown rot of pech THOMAS THOMIDIS Ntionl Agriculture Reserch Foundtion, Pomology Institute, Nouss 59200, Greece Summry. The persistence of the fungicides metlxyl nd fosetyl-al, when pplied y soil drenching or s folir sprys ginst crown rot of pech y Phytophthor cctorum or ws exmined. Metlxyl nd fosetyl- Al pplied y soil drenching inhiited oth Phytophthor species for 40 dys, ut inhiition ws reduced fter 60 dys. Folir ppliction with fosetyl-al inhiited oth pthogens for t lest 20 dys, ut metlxyl ws ineffective s folir spry. The dt suggest tht when pplied s soil drench oth metlxyl nd fosetyl-al provide effective control of Phytophthor crown rot of pech trees. Key words: crown rot, fungicides, Phytophthor, systemic ctivity. Introduction Crown nd root disorders re responsile for considerle nnul losses in commercil pech orchrds in northern Greece (Thomidis, 2000, 2000). Phytophthor spp. re common cusl gents of crown rot in some of these orchrds. A numer of species including P. megsperm,, P. cmivor, P. cinnmomi, P. cryptoge nd P. syringe hve een ssocited with Phytophthor diseses of pech trees, lthough is the most importnt (Mircetich nd Keil, 1970; Flores nd Hindl, 1983; Kim et l., 1985; Wilcox nd Ellis, 1989). As no pech rootstock is resistnt to ll Phy- To correspond with the uthor: Fx: E-mil: tomgr@otenet.gr tophthor species (Thomidis, 2000, 2000), chemicl control strtegy is required. The efficcy of the systemic fungicides fosetyl-al (Aliette, Rhone Poulenc) nd metlxyl (Ridomil, Ci-Geigy) hs een demonstrted (Rn nd Gupt, 1984; Mtheron nd Mtejk, 1991). Fungicide ppliction cn e y folir sprying, trunk injection with fosetyl- Al, trunk pint or soil drenching (Mtheron nd Mtejk, 1988; El-Hmlwi et l., 1995). The ojective of this study ws to evlute the persistence of systemic ctivity of metlxyl nd fosetyl-al in pech tree fter soil drenching or folir spry ppliction of these gents. Mterils nd methods Fungl isoltes nd plnt mteril In ll experiments, one isolte of nd one of ws used. These isoltes hd proved highly pthogenic on pech trees in 28 Phytopthologi Mediterrne

2 Metlxyl nd fosetyl-al ppliction ginst Phytophthor on pech previous works (Thomidis, 2000, 2000). Fresh cultures were prepred y trnsferring gr plugs with mycelium to pltes contining fresh cornmel gr. Pltes were then incuted t 23 C until mycelium covered the gr surfce. Cornmel pltes were utilized when needed for inoculum preprtion. In ll the experiments performed twoyer-old PR204 pech trees were used Lortory experiments Excised twig ssy. Inoculum ws prepred y plcing n gr plug with mycelium from ech Phytophthor isolte in sterile pyrex jrs (9 cm dim., 12 cm high) contining cornmel gr mended with 10 mg pimricin (one isolte per jr). Jrs were then seled with Prfilm nd incuted t 23 C until mycelium growth covered the gr surfce. Pech trees were drenched with metlxyl or fosetyl-al (2 g/tree; s recommended y mnufcturer) 2, 20, 40 nd 60 dys efore inocultion. For inocultion, twigs out 10 mm in dimeter nd 70 mm long were cut from the centrl prt of 2-yrold shoots. They were disinfected in 10% domestic chloride (sodium hypochloride, 4.89%) for 3 min nd then wshed in sterile distilled wter three times. Twigs were dried on soft pper nd the sl end of ech segment ws pred y mking tngentil cuts 10 mm long nd 1-2 mm deep on opposite sides with sterile sclpel to expose the phloem-cmium region. Ten of these twigs per fungicide were plced verticlly in the gr medium of ech jr t the periphery of the fungl colony. Jrs were seled with Prfilm to void contmintion nd desicction nd incuted t 23 C in the drk for four dys. Sixteen jrs were used for ech fungicide, four jrs for ech tretment; two jrs were inoculted with nd two with. Twigs from untreted trees were used s control. After incution, the rk ws scrped to expose ny necrosis. The results were recorded y mesuring the length of the necrosis. Excised segment ssy Pech trees were drenched with metlxyl (Ridomil 2E, 2 g/tree) or fosetyl-al (Aliette WP, 2 g/tree) 2, 20, 40 nd 60 dys efore inocultion. For inocultion, segments out 10 cm long nd 2 cm in dimeter were collected from ech tree. Segments were wounded y removing 6-mm strip of rk to expose the cmium using shrp knife nd inoculted in the centre y plcing 6-mm-dimeter disk of cornmel gr with or P. citrophthor in the centre of the cmium. Wounds were covered with dhesive tpe to void desicction nd incuted for four dys t 23 C in moist chmers, fter which the length of the necrosis ws mesured. There were 160 segments per fungicide, 40 segments per tretment, hlf of which were inoculted with nd the rest with. Twenty segments from untreted trees were used s control. Glsshouse experiment Pech trees were grown in 1-l plstic pots in the glsshouse. The men trunk dimeter of the trees used in this experiment ws 2 3 cm. Trees were drenched with 500 ml of one of the fungicide solution (Ridomil 2E t 2g/tree; Aliette WP t 2 g/ tree; s recommended y mnufcturer) 2, 20, 40 nd 60 dys efore inocultion. Using flmed shrp knife, 6 mm strip of rk ws removed from the trunk out 10 cm ove the soil surfce. Inocultions were done y trnsferring n gr plug with mycelium of pthogen to the wound. Wounds were then covered with petroleum jelly nd seled with dhesive tpe. Results were expressed s the length of necrosis (cm) produced. There were 80 pots per fungicide, 20 pots per tretment, ten of which were inoculted with P. cctorum nd ten with. Ten untreted trees were used s control. Field experiment Soil drench experiments Pech trees were drenched with metlxyl or fosetyl-al 2, 20, 40 nd 60 dys efore inocultion. Drench solutions were prepred y mixing 2 g fungicide nd 500 ml tp wter for ech tree. Trees were inoculted on the trunk 10 cm ove the soil surfce y removing 6-mm strip of rk to expose the cmium. Agr plug, tken from the periphery of culture, ws plced directly on the cmium. Wounds were covered with petroleum jelly nd seled with dhesive tpe. There were 48 trees per fungicide, six trees per tretment, hlf of which were inoculted with nd hlf with P. Vol. 41, No. 1, April

3 T. Thomidis citrophthor. Six untreted trees were used s control. Results were recorded 15 dys fter inocultion y mesuring the length of the necrosis. Recovery of pthogens ws on the selective medium of Jeffers nd Mrtin (1986). Folir spry experiments Pech trees were spryed with metlxyl (Ridomil 2E t 1g l -1 ) or fosetyl-al (Aliette WP t 1 g l -1 ) 2, 20, 40 nd 60 dys efore inocultion. Inocultions were s in the soil drench experiment, on 48 trees per fungicide, six trees per tretment, hlf of which were inoculted with, nd hlf with. Six untreted trees were used s control. Results were recorded 15 dys fter inocultion y mesuring the length of necrosis. Recovery of fungus ws on the selective medium of Jeffers nd Mrtin (1986). Sttisticl nlysis A completely rndomised experimentl design ws used throughout the experiments. Dt were nlysed y one-wy nlysis of vrince (ANO- VA). To comine experiments, Brtlett s test of homogeneity of vrince ws used nd tretment mens were seprted y Duncn s Multiple Rnge Test (P=0.05). All experiments were repeted twice. Results nd discussion Results from different experiments were in good greement. They showed tht soil drenches with metlxyl nd fosetyl-al were effective ginst Phytophthor crown rot of pech trees (Tle 1 nd 2). Mny other reserchers hve successfully used metlxyl nd fosetyl-al to control diseses cused y fungi of the genus Phytophthor (Ellis et l., 1982; Mtheron nd Mircetich, 1985; Utkhede, 1987; Mtheron nd Mtejk, 1988; Wicks nd Hll, 1988; Jeffers, 1992; Guest et l., 1994). It hs lso een found tht oth these fungicides reduce sporultion of Phytophthor (Rn nd Gupt, 1984; Coffey nd Joseph, 1985; Hnson nd Shttock, 1998). El-Hmlwi et l. (1995) reported tht fosetyl-al pplied s soil drench or folir spry ws effective in controlling stem cnker diseses. In the field nd glsshouse experiments of this study, oth fosetyl-al nd metlxyl completely inhiited nd for t lest 40 dys when they were pplied s soil drench (Tle 1). These fungicides still reduced development of oth pthogens significntly when pplied 60 dys efore inocultion. Mtheron nd Mircetich (1985), found tht oth metlxyl nd fosetyl-al were ctive in the stems of wlnut for t Tle 1. Inhiition of cnker development on PR204 pech trees inoculted with Phytophthor cctorum or 2, 20, 40 nd 60 dys fter soil drenching with two fungicides in the glsshouse nd in the field. Length of necrosis (cm) Dys etween fungicide ppliction Glsshouse Field nd inocultion Metlxyl Fosetyl-Al Metlxyl Fosetyl-Al Control dys dys 0 c 0 c 0 c 0 c 20 dys 0 c 0 c 0 c 0 c 2 dys 0 c 0 c 0 c 0 c Control dys dys 0 c 0 c 0 c 0 c 20 dys 0 c 0 c 0 c 0 c 2 dys 0 c 0 c 0 c 0 c Vlues re the mens of two experiments with ten replictes for ech tretment. Numers in ech column with the sme letter do not differ (P=0.05) ccording to Duncn s multiple rnge test. 30 Phytopthologi Mediterrne

4 Metlxyl nd fosetyl-al ppliction ginst Phytophthor on pech Tle 2. Inhiition of cnker development on twigs nd segments of PR204 pech trees inoculted with Phytophthor cctorum or 2, 20, 40 nd 60 dys fter soil drenching with two fungicides in the lortory. Length of necrosis (cm) Dys etween fungicide ppliction Twigs Segments nd inocultion Metlxyl Fosetyl-Al Metlxyl Fosetyl-Al Control dys dys dys dys Control dys dys dys c 0 2 dys c 0 Vlues re the mens of two experiments with twenty replictes for ech tretment. Numers in ech column with the sme letter do not differ (P=0.05) ccording to Duncn s multiple rnge test. lest 54 dys fter ppliction. Lter, they reported tht oth fungicides were still ctive even fter 160 dys (Mtheron nd Mtejk, 1988). It hs een reported tht metlxyl nd fosetyl-al re sored through the roots nd re then trnslocted upwrd y the plnt through the xylem (Gupt et l., 1985; El-Hmlwi et l., 1995). Similrly, the results from lortory experiments showed tht oth metlxyl nd fosetyl-al moved sipetlly in the tree. The sorption of metlxyl nd fosetyl-al y pech roots my e essentil for these fungicides to e effective under orchrd conditions. In the lortory experiments, oth fungicides lost their fungicidl ctivity erlier thn in the field nd glsshouse experiments (Tle 2). It is possile tht the ctivity of metlxyl nd fosetyl-al is reduced s they move in sipetl direction. In this study, it ws lso found tht folir ppliction with fosetyl-al inhiited oth pthogens for t lest 20 dys (Tle 3). Erwin nd Rieiro (1996) reported tht the ctive ingredient of fosetyl- Al (phosphonte) ws unique phloem-moile xenoiotic with remrkle ntifungl ctivity ginst some importnt oomycete plnt pthogens. However, its persistence in tissues s lef spry Tle 3. Inhiition of cnker development on PR204 pech trees inoculted with Phytophthor cctorum or 2, 20, 40 nd 60 dys fter folir spry with two fungicides in the field. Dys etween Length of necrosis (cm) fungicide ppliction nd inocultion Metlxyl Fosetyl-Al Control dys dys dys c 2 dys c Control dys dys dys dys Vlues re the mens of two experiments with six replictes for ech tretment. Numers in ech column with the sme letter do not differ (P=0.05) ccording to Duncn s multiple rnge test. Vol. 41, No. 1, April

5 T. Thomidis ws shorter thn when pplied s soil drench. Metlxyl did not ffect the development of nd on PR204 pech trees when it ws pplied s folir spry. This is proly ecuse metlxyl does not hve the ility to move downwrds. Generlly, soil drenching with metlxyl or fosetyl-al is n effective mens to protect pech trees ginst Phytophthor if these fungicides re pplied in this wy month efore pek coloniztion. Literture cited Coffey M.D. nd M.C. Joseph, Effects of phosphorous cid nd fosetyl-al on the life cycle of Phytophthor cinnmomi nd P. citricol. Phytopthology 75, El-Hmlwi Z.A., J.A. Menge nd C.J. Adms, Methods of fosetyl-al ppliction nd phosponte levels in vocdo tissue needed to control stem cnker cused y Phytophthor citricol. Plnt Disese 79, Ellis M.A., G.G. Grove nd D.C. Ferree, Effects of metlxyl on Phytophthor cctorum nd collr rot of pple. Phytopthology 72, Erwin D. nd O. Rieiro, Phytophthor Diseses Worldwide. APS, St. Pul, MN, USA, pp 231. Flores E.S. nd D.F. Hindl, In vitro twig ssy with Phytophthor species on pech. Phytopthology 79, 965 (strct). Guest D.I., R.D. Anderson, H.J. Ford, D. Phillips, S. Woroysnd nd R.M. Middleton, Long-term control of Phytophthor diseses of coco using trunk-injected phosphte. Plnt Pthology 43, Gupt J.P., D.C. Erwin, J.W. Eckert nd A.I. Zki, Trnsloction of metlxyl in soyen plnts nd control of stem rot cused y Phytophthor megsperm f.sp. glycine. Phytopthology 75, Hnson K. nd R.C. Shttock, Effect of metlxyl on formtion nd germintion of oospores of Phytophthor infestns. Plnt Pthology 47, Jeffers S.N., Preplnt root tretment to reduce the incidence of Phytophthor species on dormnt pple rootstocks. Plnt Disese 76, Jeffers S.N. nd S.B. Mrtin, Comprison of two medi selective for Phytophthor nd Pythium species. Plnt Disese 70, Kim S.H., J.F. D Amico nd B.A. Jffe, Assocition of Phytophthor cryptoge with pech collr rot in Pennsylvni. Phytopthology 74, 626 (strct). Mtheron M.E. nd J.C. Mtejk, Persistence of systemic ctivity for fungicides pplied to citrus trunk to control Phytophthor gummosis. Plnt Disese 72, Mtheron M.E. nd J.C. Mtejk, Effect of sodium tetrthiocronte, metlxyl, nd fosetyl-al on development nd control of Phytophthor root rot of citrus. Plnt Disese 75, Mtheron M.E. nd S.M. Mircetich, Control of Phytophthor root nd crown rot nd trunk cnker in wlnut with metlxyl nd fosetyl-al. Plnt Disese 69, Mircetich S.M. nd H.L. Keil, Phytophthor cinnmomi root rot nd stem cnker of pech trees. Phytopthology 60, Rn K.S. nd V.K. Gupt, Effect of fungicides on the viility of Phytophthor cctorum propgules in the soil. Journl of Phytopthology 110, Thomidis T., Sesonl vrition in crown rot of GF677 nd KID I pech rootstocks y Phytophthor cctorum, nd P. syringe. Phytopthologi Mediterrne 39, Thomidis T., Field susceptiility of four pech rootstocks to Phytophthor citrophthor nd P. syringe. Phytopthologi Mediterrne 39, Utkhede S.R., Control of crown rot (Phytophthor cctorum) of pple trees with the systemic fungicides metlxyl nd fosetyl-luminium. Pesticide Science 19, Wicks T.J. nd B. Hll, Preliminry evlution of phosphorous cid, fosetyl-al nd metlxyl for controlling Phytophthor cmivor on lmond nd cherry. Crop Protection 7, Wilcox W.F. nd M.A. Ellis, Phytophthor root nd crown rots of pech trees in the estern Gret Lkes region. Plnt Disese 73, Accepted for puliction: Jnury 18, Phytopthologi Mediterrne