132 CHAPTER SIX ENDOPHYTE STEM INFECTION AS AFFECTED BY VARIOUS FUNGICIDES ON TURF-TYPE TALL FESCUE Abstract Endophytes are known to enhance turfgrass agronomic performance and confer resistance to insect herbivory. Little is known regarding the effect of fungicides to seedlings for Rhizoctonia blight or gray leaf spot will affect endophyte viability. Various fungicides were applied to 'DaVinci' turf-type tall fescue seedlings to determine their effects on endophyte expression. Eight fungicides, both acropetal and localized penetrants, were applied 7 or 21 days after establishment (DAE). Ten tillers were harvested from each plot and cross sections of each tiller were analyzed for endophyte presence using commercial tissue print-immunoblot test kits. In 2005, fungicide application did not significantly affect endophyte infection rates in turf-type tall fescue 7 or 21 DAE. In 2006, however, fungicide application did significantly affect endophyte infection rates 21 DAE. In general, propiconazole applied at 2.0 kg a.i. ha" 1 , seven DAE reduced endophyte infection to 43% as compared to the control (57%). However, myclobutanil and propiconazole (applied at 1.0 and 2.0 kg a.i. ha" 1 ) significantly reduced endophyte infection 21 DAE as compared to the control (90%) to 40, 40 and 7%, respectively. These results show that propiconazole applied 21 DAE had lower endophyte infection rates than when applied seven DAE. Endophyte mortality was reduced by the fungicides myclobutanil and propiconazole but not eliminated. Therefore to maximize endophytic turf, turfgrass managers should minimize certain fungicides like propiconazole or decrease application rates especially during establishment.
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132
CHAPTER SIX
ENDOPHYTE STEM INFECTION AS AFFECTED BY VARIOUS FUNGICIDES ONTURF-TYPE TALL FESCUE
Abstract
Endophytes are known to enhance turfgrass agronomic performance and confer
resistance to insect herbivory. Little is known regarding the effect of fungicides to
seedlings for Rhizoctonia blight or gray leaf spot will affect endophyte viability. Various
fungicides were applied to 'DaVinci' turf-type tall fescue seedlings to determine their
effects on endophyte expression. Eight fungicides, both acropetal and localized
penetrants, were applied 7 or 21 days after establishment (DAE). Ten tillers were
harvested from each plot and cross sections of each tiller were analyzed for endophyte
presence using commercial tissue print-immunoblot test kits. In 2005, fungicide
application did not significantly affect endophyte infection rates in turf-type tall fescue 7
or 21 DAE. In 2006, however, fungicide application did significantly affect endophyte
infection rates 21 DAE. In general, propiconazole applied at 2.0 kg a.i. ha"1, seven DAE
reduced endophyte infection to 43% as compared to the control (57%). However,
myclobutanil and propiconazole (applied at 1.0 and 2.0 kg a.i. ha"1) significantly reduced
endophyte infection 21 DAE as compared to the control (90%) to 40, 40 and 7%,
respectively. These results show that propiconazole applied 21 DAE had lower endophyte
infection rates than when applied seven DAE. Endophyte mortality was reduced by the
fungicides myclobutanil and propiconazole but not eliminated. Therefore to maximize
endophytic turf, turfgrass managers should minimize certain fungicides like
propiconazole or decrease application rates especially during establishment.
133
Introduction
In recent years, tall fescue (Schedonorus phoenix (Scop.) Holub; formally know
as Festuca arundinacea Schreb.) has gained popularity and become widely planted in
lawns, athletic fields, and golf course roughs throughout the cool-humid region due to the
introduction of darker green, more narrow leaved, turf-type tall fescue cultivars. More
importantly, turf-type tall fescue is tolerant of drought because of its deep root system
which may necessitate less irrigation and less fertilizer to sustain ideal turfgrass quality.
Walker et al. (2007) found that turf-type tall fescue can be fertilized at relatively low
rates of nitrogen (74-123 kg N ha"1 yr"1) and still achieve a high visual appearance with
moderate growth compared to perennial ryegrass (Lolium perenne L.) and Kentucky
bluegrass (Poapratensis L.). In addition, turf-type tall fescue, even though it's a cool-
season turfgrass species, is a popular lawn species in the Southeast (warm-humid region)
due to its' lack of winter dormancy, remaining green throughout the year (Burpee, 1995)
unlike its warm-season counterparts. Seedling turf-type tall fescue, wherever grown, is
extremely susceptible to Rhizoctonia solani Kiihn and Pyricularia grisea which causes
the turfgrass diseases Rhizoctonia blight or brown patch and gray leaf spot, respectively
(Couch 1985).
Rhizoctonia solani causes foliar necrosis of circular or irregularly shaped patches
of necrotic turf that may exceed 1 m in diameter (Burpee and Martin, 1992). Pyricularia
grisea also causes foliar necrosis (blue-gray cast) which readily infects and kills leaf
blades which can progress down to the crown resulting in plant death. Both diseases,
brown patch and gray leaf spot, can be devastating on seedling tall fescue (< 1 yr.) killing
the entire turfgrass stand within weeks of infection. Weather conditions (hot, humid and
raining) favoring pathogen activity for both brown patch and gray leaf spot extend into
the early fall. This presents a major problem because the best time to seed cool-season
turfgrass species such as tall fescue is in the early fall so the plant can become established
before winter. Integrated methods for control against these diseases include avoiding
cultural practices that would extend the dew period to reduce of leaf wetness such as
watering or irrigating in the late afternoon and early evening and excessive nitrogen
134
applications. However, the best control against brown patch and gray leaf spot especially
on seedling tall fescue requires the use of fungicide applications (Smith et al., 1989).
Tall fescue is frequently infected with the endophytic fungus Neotyphodium
coenophialum [Morgan-Jones and Gams] Glenn, Bacon, and Hanlin) formally known as
Acremonium coenophialum. Endophytes and grasses have a mutualistic, symbiotic
association in which the plant provides the fungi with water, nutrients, and structural
refuge from the host in return the endophyte provides several benefits to the plant. These
benefits include: increased tillering and root growth, resistance to drought stress
(Arachavaleta et al., 1989), protection against insect herbivory (Rowman, 1993),
nematodes (Kimmons et al., 1990), mammalian herbivores (Bacon et al., 1977), and
fungal pathogens (Gwinn and Gavin, 1992). These benefits have made the use of
endophytes in turf an attractive alternative to chemical inputs used to enhance overall
turfgrass performance (Funk et al., 1985, 1992; Sun et al., 1990; Clarke et al., 2006).
Previous research by both White and Cole (1986) and Siegel et al. (1991) showed
that Acremonium coenophialum and other endophytes of grasses were able to inhibit the
growth of several fungal pathogens in vitro. However, disease resistance in endophyte-
infected grasses is still somewhat limited. Vincelli and Powell (1991) found that when
endophyte infection levels where high 'Manhattan IF perennial ryegrass (Lolium
perenne) had less red thread {Laetisaria fuciformis (McAlp) Burdsall) than endophyte
infection levels were low. In 1992, Gwinn and Gavin found that the survival of
endophyte-infected tall fescue seedlings was greater than that of non-endophyte-infected
seedlings in soil infested with two isolates of Rhizoctonia zeae Voorhees. Burpee and
Bouton (1993), however, reported that the progress of Rhizoctonia blight was not altered
by N. coenophialum in field grown tall fescue. Bonos et al. (2005) observed that
differences in red thread severity between endophyte-infected and non-endophyte-
infected fine fescue (Festuca spp.) occurred within the same host genotype. In 2006,
Clarke et al. reported endophyte-infected Chewings, hard, blue, and strong creeping red
fescue cultivars, selection, and crosses taken from fine fescue germplasm from the United
States and Europe, exhibited endophyte-mediated suppression of dollar spot (Sclerotinia
homoeocarpa) when compared to closely related non-endophyte-infected entries.
135
Latch and Christensen (1982) reported that seed treatments of propiconazole and
prochloraz and drenches of benomyl to potted plants eliminated an unidentified
endophyte from perennial ryegrass. Several studies have shown that triadimenol,
triadimefon, bitertanol, and propiconazole were the most effective fungicides for
eradicating Neotyphodium in tall fescue seed (Williams et al., 1984; Bilotti et al., 1989;
Maddaloni et al., 1989). Leyronas et al. (2006) found that prochloraz eliminated
Neotyphodium endophytes in perennial ryegrass and tall fescue seed. Few studies,
however, have investigated the effects on endophyte infection in plant stems as a result of
fungicide applications used to control turfgrass diseases (Dernoeden et al., 1990; Hill and
Brown, 2000). Dernoeden et al. (1990) found none of the fungicides used in the field
study (benomyl, triadimefon, iprodione, chlorothalonil, and thiram) reduced the percent
of the Acremonium endophyte in 'Regal' and 'Fiesta' perennial ryegrass infected with
endophytes. Hill and Brown's (2000) greenhouse study found that weekly applications of
the systemic fungicide, propiconazole (5%), virtually eliminated the endophyte in
Vincelli, P. and A.J. Powell. 1991. Reaction of perennial ryegrass varieties to red thread,
1990. Biol. Cult. Tests Cont. Plant Path. 6:102.
Walker, K.S., C.A. Bigelow, D.R. Smith, G.E. Van Scoyoc, and Z.J. Reicher. 2007.
Above ground responses of three cool-season lawn species to varying annual
nitrogen rates and application timings. Crop Sci. 47:1225-1236.
White, J.F., Jr., and G.T. Cole. 1986. Endophyte-host associations in forage grasses. IV.
The endophyte of Festuca versuta. Mycologia. 78:102-107.
Willams, M.J., P.A. Backman, E.M. Clark, and J.F. White. 1984. Seed treatments for
control of the tall fescue endophyte. Plant Dis. 68:49-57.
144
Table 6-1. Percent endophyte stem infection of 'Da Vinci' turf-type tall fescue after eightfungicides were applied 7 and 21 days after emergence (DAE) in 2005.
f AP=Acropetal Penetrant, LP=Localized PenetrantJTen tillers from each 2.3 m2 plot were tested for endophyte stem infection on 5 Nov.,2005 using a tissue print-immunoblot assay for Neotyphodium spp.NS refers to non-significantTurf-type tall fescue ('Da Vinci') was provided by Lebanon Seed Co., Lebanon, EN andseeded at rate of 391 kg ha'on 28 Aug., 2005. Emergence as defined as a uniform standof one-leaf seedlings occurred on 5 Sept., 2005.Seven DAE was applied on 12 Sept., 2005 and 21 DAE was applied on 26 Sept., 2005 ata spray volume of 215 gal ha"1.Randomized complete block design with three replications.
145
Table 6-2. Percent endophyte stem infection of 'Da Vinci' turf-type tall fescue after eightfungicides were applied 7 and 21 days after emergence (DAE) in 2006.
t AP=Acropetal Penetrant, LP=Localized Penetrant{Ten tillers from each 2.3 m2 plot were tested for endophyte stem infection on 26 Oct.,2006 using a tissue print-immunoblot assay for Neotyphodium spp.*, *** and NS refer to significant at the 0.05 and 0.001 level and non-significant relative to theuntreated control using pair-wise comparisons with the untreated control according to Dunnett'stest, respectively.Turf-type tall fescue ('Da Vinci') was provided by Lebanon Seed Co., Lebanon, IN andseeded at rate of 391 kg ha^on 18 Aug., 2006. Emergence as defined as a uniform standof one-leaf seedlings occurred on 25 Aug., 2006.Seven DAE was applied on 1 Sept., and 21 DAE was applied on 14 Sept., 2006 at a sprayvolume of 215 gal ha1.Randomized complete block design with three replications.
146
Table 6-3. Analysis of variance (ANOVA) for both 2005 and 2006 study periods.ANOVARepDAEFungicideDAE*Fungicide
2005NSNSNSNS
2006NSNS***
*e, *** and NS refer to significant at the 0.05 and 0.001 level and non-significant, respectively.
147
200
150
1ca:
50
RainfallHighLow
Total = 246 mm
Jk
Total = 275 mm
Aug. Sept. Oct. Nov.
2005
Aug. Sept. Oct. Nov.
2006
40
30
20 Q
10
-10
-20
(D
2CDQ.
Figure 6-1. Daily temperature (high and low) and rainfall during Aug. through Nov. of2005 and 2006 in West Lafayette, IN.