Nolte, Scott

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Smutgrass	Management	in	Bermudagrass	and	Bahiagrass	Pastures		Smutgrass	(Sporobolus	indicus)	is	a	tuft	forming	non-native	 perennial	 weed	 that	 affects	 many	improved	 perennial	 grass	 pastures	 in	 Texas,	Florida,	Georgia	and	other	southern	states.		As	a	warm	 season	 perennial,	 smutgrass	 remains	dormant	 in	 the	 winter,	 begins	 growing	 in	 the	spring,	 and	 can	 produce	 seed	 from	 July	 to	September.	 	 In	Florida,	smutgrass	 is	considered	the	 third	 most	 troublesome	 weed	 in	 pastures	(Crawford	2007)	likely	due	to	its	ability	to	adapt	to	 almost	 all	 soil	 types	 and	 to	 its	 competitive	nature	 in	 pastures.	 	 While	 some	 grazing	 of	smaller	 more	 tender	 smutgrass	 may	 occur,	cattle	 will	 not	 preferentially	 consume	 mature	smutgrass	possibly	due	to	a	reduction	in	forage	quality	 as	 the	 grass	 matures	 (McCaleb	 et	 al.	1963;	 Smith	 and	 Cole	 1972;	 Mullahey	 2000).	Therefore,	 if	 left	 untreated,	 smutgrass	populations	 can	 dominate	 grazing	 lands	 to	exclusion	 of	 the	 desirable	 species	 (Simon	 and	Jacobs	1999).		Control	 of	 smutgrass	 through	mowing,	 fertility	management,	 and	 intensive	 rotational	 grazing	has	 traditionally	 been	 difficult	 to	 achieve.	While	it	has	been	shown	that	smutgrass	growth	will	 decline	 with	 intense	 grazing	 management	(Ahmad	1979),	maintaining	the	needed	level	of	grazing	 pressure	 without	 overgrazing	 desirable	species	can	be	very	challenging.		More	consistent	management	of	smutgrass	has	been	 achieved	 through	 use	 of	 herbicides,	 and	from	 the	 1950’s	 through	 the	 1980’s	 the	 only	selective	 herbicide	 available	was	 Dalapon	 (2,2-Dichloropropionic	 acid).	 	 In	 the	 late	 1980’s	 a	new	 product	 called	 Velpar	 (hexazinone)	 was	labeled	 for	 use	 in	 established	 stands	 of	bermudagrass	and	bahiagrass	for	the	control	of	smutgrass.		Currently,	Velpar®	L	VU	is	marketed	and	sold	by	Bayer	and	is	the	primary	chemistry	recommendation	 for	 the	 control	 of	 smutgrass	across	 the	 southern	 US.	 	 Research	 has	 shown	Velpar	to	provide	good	control	when	applied	in	late	 spring/early	 summer	 to	 actively	 growing	smutgrass,	when	rainfall	is	typically	sufficient	to	move	 the	 herbicide	 into	 the	 root	 zone	 for	uptake.	 	 More	 consistent	 long-term	 control	 is	typically	achieved	when	a	sequential	application	is	 made	 in	 the	 following	 year	 (Mislevy	 et	 al.	1999;	 Rana	 et	 al.	 2015).	 	 Current	 pricing	 for	Velpar	 would	 typically	 be	 around	 $40/ac	depending	 on	 the	 rate	 utilized.	 	 Based	 on	research	 conducted	 by	 B.	 J.	 Brecke	 (1981),	SCS-2017-18	Scott	Nolte,	Professor & State	Extension	Weed	Specialist	Texas	A&M	AgriLife	Extension	Service,	Texas	A&M	University	hexazinone	 the	 active	 ingredient	 in	 Velpar,	provided	slightly	better	control	of	 smutgrass	 in	bahiagrass	 pastures	 and	 with	 lower	phytotoxicity.		When	applying	Velpar,	care	must	be	 taken	 to	 maintain	 a	 buffer	 of	 100	 feet	between	 the	 area	 of	 application	 and	 any	desirable	trees	or	death	of	the	tree	may	occur.		Application	 rates	 are	 2¾	 to	 4½	 pints	 per	 acre.		Use	the	lower	rate	on	sandy	soils	and	the	higher	rate	 on	 heavier	 textured	 clay	 soils.	 	 Livestock	may	 be	 grazed	 immediately	 following	 a	broadcast	application	of	Velpar®	L	VU	Herbicide	at	rates	of	4.5	pints	per	acre	or	less,	and	treated	vegetation	may	be	 cut,	 dried,	 and	 fed	 after	 38	days.			A	non-selective	herbicide	option	would	be	using	glyphosate	 (Roundup)	 in	 a	 rope-wick,	 rotary	wiper	or	spot	treatment	method.		For	rope-wick	or	rotary	wiper	applications,	the	recommended	mixture	 is	a	1:2	 (1	gal	of	glyphosate	 in	2	gal	of	water)	 rate	during	active	weed	growth	and	 for	perennials,	 at	 seedhead	 formation.	 	 Livestock	must	be	removed	after	application	and	a	14	day	wait	 before	 grazing	 and	 harvesting.	 	 No	 more	than	one-tenth	of	any	acre	should	be	treated	at	a	 time.	 	 For	 spot	 treatments,	 a	 1.5	 to	 2.0%	solution	of	a	4.5	lb/gallon	glyphosate	product	is	recommended	 (2.0	 to	 2.5	 fl	 oz	 per	 gallon	 of	water).	 	 Livestock	or	hay	harvest	 can	 return	 to	spot-treated	pastures	7	days	after	application.		References		Ahmad,	I.	B.	1979.	Effects	of	nitrogen	and	grazing	on	a	smutgrass	–	bahiagrass	–	white	clover	pasture.	Master’s	thesis.	Gainesville,	FL:	University	of	Florida.	93	p.		Brecke,	B.	J.	1981.	Smutgrass	(Sporobolus	poiretii)	control	in	bahiagrass	(Paspalum	notatum)	pastures.	Weed	Sci.	29:553–555.		Crawford,	S.	C.	and	L.	F.	Wiggins.	2007.	Beef	Forage	Range	Practices	in	South	Florida.	University	of	Florida	Institute	of	Food	and	Agricultural	Sciences	Cooperative	Extension	Service.	6	P.		McCaleb,	J.	E.,	E.	M.	Hodges,	and	W.	G.	Kirk.	1963.	Smutgrass	control.	Florida	Agricultural	Experiment	Station,	Ona.	Circular	S-149.	10	p.		Mislevy,	P.,	D.	G.	Shilling,	F.	G.	Martin,	and	S.	L.	Hatch.	1999.	Smutgrass	(Sporobolus	indicus)	control	in	bahiagrass	(Paspalum	notatum)	pastures.	Weed	Technology.	13:571–575.	Mullahey,	J.	J.	2000.	Evaluating	grazing	management	systems	to	control	giant	smutgrass	(Sporobolus	indicus	var.	pyramidalis).	Pages	59–60	in	Proceedings	of	the	53rd	Southern	Weed	Science	Society,	Tulsa,	OK:	Southern	Weed	Science	Society.		Rana,	N.,	B.	A.	Sellers,	J.	A.	Ferrell,	G.	E.	MacDonald,	M.	L.	Silveira,	and	J.	M.	Verdramini.	2015.	Integrated	management	techniques	for	long-term	control	of	giant	smutgrass	(Sporobolus	indicus	var.	pyramidalis)	in	bahiagrass	pasture	in	Florida.	Weed	Technology.	29:570-577.				Simon,	B.	K.	and	S.	W.L.	Jacobs.	1999.	Revision	of	the	genus	Sporobolus	(Poaceae,	Chloridoideae)	in	Australia.	Aust.	Syst.	Bot.	12:375–448.		Smith,	J.	E.	and	A.	W.	Cole.	1972.	Selective	control	of	smutgrass	in	permanent	pastures.	Page	194	in	proceedings	of	the	25th	Southern	Weed	Science	Society:	Southern	Weed	Science	Society.						Produced	by	the	Department	of	Soil	and	Crop	Sciences		soilcrop.tamu.edu			The	information	given	herein	is	for	educational	purposes	only.	Reference	to	commercial	products	or	trade	names	is	made	with	the	understanding	that	no	discrimination	is	intended	and	no	endorsement	by	the	Texas	A&M	AgriLife	Extension	Service	is	implied.		Texas	A&M	AgriLife	Extension	is	an	Equal	opportunity	employer	and	program	provider.		The	Texas	A&M	University	System,	U.S.	Department	of	Agriculture,	and	the	County	Commissioners	Courts	of	Texas	Cooperating.	

Smutgrass Management in Bermudagrass and Bahiagrass Pastures

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Smutgrass Management in Bermudagrass and Bahiagrass Pastures

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