BY PHILIP BUSEY Goosegrass Most Difficult Weed in South ... · university research SolIm FLORIDI"S Top 10 '

university research BY PHILIP BUSEY

Goosegrass Most Difficult Weed in South Florida Four other grasses lead the list of 'Top Ten Weeds,' according to survey

By faf, the most serious weed of

bcrmudagrass turf in south Florida is

goosegrass, followed by four other

grasses: lorpedograss, crabgrasses. tropical

signalgrass (smallOowered Alexandergrass),

and off-type bCl'lnudagrass. As a result of fouf surveys of golf and sports

turf managers in south Florida, the five top weeds accoullted for 74.3% of the overall

seriousness values of bcrmudagrass turf weeds (TrIble 1). O ther weeds that were ranked in the

""lop Ten" in seriousness were crowfootgrass,

fo llowed by green kyll inga, dollarweed. spurge (probably mostly prostrate spurge), and POll

Il/U!II(] in tenth place. Data were obtained in survey question ~

naires administered at four locations, from 1998 to 200 I. Manage rs of bermuda grass turf were asked, "Please assess the relative serious­

ness of thc following weeds on the golf course by ranking them #1, #2, and #3, with #1 the most serious."

Responses camc fTom 236 attendees at

Florida Golf Course Superintendents Association chapter meetings in south Florida, and the SOllth Florida Turfgrass Expo. The

majority of thc participants were golf course superintendents, assistant superintendents, and spray personnel, and there were a few

bermudagrass sports turf managers. "Seriousness" was defined by respondents

in the first questionnaire (data not presented)

as a combination of complaints by members and loss of use, with a smaller emphasis on the

expense of chemical controL In terllls of the relative importance of

weed~conlrol issues, golf course superinten ~

dents emphasized clean sprig source, to avoid problems of bermuda grass off~type contami­nation (u,ble 2). Next in importance, they

expressed conce rn about weeding and weed invasion from nonplay areas, ornamental

grasses, and lake margins. Vi rtuaJly tied for third place in weed

cOlnrol importance were high visibility areas,

24 FLORIDA TURF DIGEST

Goosegrass

Torpedograss

Signalgrass

e.g., clubhouse and areas next to cart paths and spot trea tment of goosegrass. Lowest on the scale of weed control concerns were communi ~

Gltions to membership, tracking of overseeded grasses, and safety of late summer pree lller~

gelKe herbicides to overseeded ryegrass. By way of background. weeds ,Ire the

second-most reported management problem on Plorida golf courses after insects, based on the 1991 / 1992 study of the Florida turfgrass

industry by Hodges (1994). According to the 1996 Golf Course Superintendents Report,

Florida golf course superintendents spend nearly three times as much on herbicides as do

superintendents elsewhere, $16,800 per yea r compared with $6,300 elsewhere in the United States.

A well targeted weed research program

must prioritize problems based partly on their seriousness, as well as other factors such as the likelihood of making significant improve~

men Is, and the amount of progress already

being done on a particular problem elsewhere. Sometimes people ask for help on niche grasses and niche weed problems. These problems need attention. but priority is placed on the

Annual Bluegrass

Prostrate Spurge

problems of great est concern to turf managers. The surveys were done to help focus the turfg rass weed research at the University of

Florida. The southern tip of peninsular Florida is on

the same latitude as no other place in the

United States. therefore there are weed control problems that arc unique to our area, and a greater need to understand those unique problems. For a widespread weed control problem such as goosegrass, we can "borrow"

to some degree the successful research results

from neighboring states such as Georgia, but

for a weed such as tropical signalgrass (smaUflowered Alexandergrass), which is

primarily a south Florida problem, we need to devote considerably more effo rt.

Survey Details A method of analysis was developed that

was robust to the fact that respondents did not

always answer the questions in the same way. Some provided a #1, #2, and #3 ranking for

three and only three weeds. Others ranked as many as 14 weeds. while others merely checked off three weeds, or even one weed, without

SEPTEMBER/OCTOBER 2001

university research SoUTH FLORIDA'S Top 10 W EEDS

ranking. That may have been a reasonable intent ion of the respondents, because if a

person has onl y one serious weed, there is not point ranking nil 14. So the method of 3nal}'sis look these var iations into account, by providing equal total weight to each individual respondent. <lnd always prO\·jded a stepwise imporlance value on the ra nkings.

To develop relative seriousness values, rank scores were in verted to fractions, thlls I was

inverted to I, and 2 was inverted to 0.5, and 3

was inverted to 0.333. Inverted rank scores were converted to relat ive values, based on the sum of inve rted ranks fo r each observer. For

example. if someone ranked two and only two

weeds, I and 2, then the relative ra nk fo r weed

I would be 1/ 1.5 or 0.667, and the relative rank

for weed 2 would be 0.5/1.5 or 0.333. This way,

each individua l's ra nkings had the sam e value,

and the converted sco res gave a d iminishing

cred it to a weed, depending on how low it was

on the list of a person's seriousness ranking.

Ties were treated equally, that is, if a person

checked off th rec weeds, each received a

relative rank of 0.333

The sum of rclative inverted ra nk scores

was found fo r each weed and each weed

cont rol issue, and these were converted to an

overall pcrcentagc of the sum of all aCCU11lu ·

laled units scores for all weeds, fo r each group

of participants. For purposes of presentation

here. lIIl\veighted averages were used , i.e., each

location cOll llted equally even though the

num ber o f responden ts varied by location.

Except, averages were adjusted to prorate for

totals greater than 100%, due to the (<lct that

di ffe rent weeds were am ong the choices in

differen t surveys.

As the survey developed, <l nd was givcn to

di ffe ren t groups, the list of weeds changed

accordi ng to previous responses. Respondents

were asked to add any weeds missi ng from the

Jist of choiccs.

Interpretalions

The varia tion among groups of participants

may reflect diffcrent regional wced control

scriousness, o r it ll1a)' rcflect seasonal factors.

Crowfootgrass cxcecdcd Poa an nua in

seriollsness, in thc questionnaire taken at the

Everglades GCSA, in the coolest month of the

year, when Poa annua would normally be at its

most prolific condition. A show of hands at the

2001 meeting revealed that approxi mately 750/0

of the superi ntendents had not overseeded.

At the same meeting, there were write· in

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FLORIDA TURF DIGEST 25

university research SolIm FLORIDI"S Top 10 ' <\'EI:OS

I vOles fo r pigwecds (i ncluding five for redroot

Table 1 pigweed, almost certainly a m isidentification ),

Relalive seriousness for four participant groups, weighted importance , and rank, of and five for doveweed. O ld Vlo rld 14 weeds (species or genera) in golf and sports lurf in South Florida, 1998·2001. d iamondOower is frequently misidentified as

Occasion South Ftorida Everglades South Treasure dovcweed, so it is possible that th is too was a

EXPO GCSA Ftorida EXPO Coast GCSA misiden tification. When pigweed was added to

Date Mar 12 1998 Jan 29 2001 Mar 22 2001 Jun 19 2001 the questionnaire for the third and fourth

No. ot 98 59 60 23 gro ups of participants, it rated in seriousness

Participants only I % overall.

Weed Relative importance (%) Weighted Rank Sedges were not asked about at the

species: Importance Everglad es GCSA meeting in 2001, but there

Goosegrass 49 20 26 t2 32.2 1 were 20 write-in votes for sedges. mostly

T orpedograss 18 t2 11 10 14.4 2 nonspecific "sedge," although three respon-

Crabgrasses 20 11 13 3 t4.2 3 dcnts indicatcd that kyll inga was serious. Even

Signalgrass 12 14 20 13.9 4 after green k1,Uinga was restored to the --- questionnai res, there were numerous write-in

OHtype 1 18 9 14 8.5 5 votes fo r nutsedges (yellow and purple). Bermudagrass

Crowfoolgrass · 7 4 9 5.9 6 Other write- in votes b), single individuals

Kylling, 3 . 4 14 4.5 7 were for speedwell, spra nglctop, Virginia buttonweed, creeping beggarweed, volunteer

Spurge · 7 2 3 4.2 8 q 'e, and Muhl), grass in Sparti na (an example

(proslrale) of the problems of maintaining native grass

ooll,oveed 2 3 8 3 4. t 9 beds). There were a few wri te-in votes for Poa Annua 3 5 3 5 3.4 10 problems of bermudagrass contamination in Smulgrass · 2 2 4 2.5 11 --- seashore paspalu lll .

o'~lower · 1 2 2 1.6 12 Goosegrass was considered the most

Diamond/lower · 2 0 2 1.5 13 se rious weed in golftur r, and was ra ted

Pigweed · . 0 2 0.8 14 Il umber one b)' three out or ro ur groups. This is consistent wilh the 1996 Gol r Course Superin tendents Report, in which goosegrass

Table 2 was also listed as the highest problem intensity Relative importance for three participant groups , weighted importance , and weed in the Florida region. Following rank , of seven weed control issues for golf and sports turf managers in south gooscgrass, no weed was consistentl y in second Florida, 1998·2001. pillce.

Occasion Everglades South Florida Treasure GCSA EXPO Coast GCSA Weed resea rch priori ties

Date Jan 29 2001 Mar 22 2001 Jun 19 2001 Goosegrass is easily prevented on south

No. of Participants 58 35 23 Florida gol r courses by several preemergence

Weed Control Problem Relative importance (%) Weighted

Rank herbicides. Unrortunately, the cost or season-

Importance long protection is considered too great fo r

Clean sprig source; bermuda 21 15 25 19.1 1

some golf courses to be on a regular program, ofltype contamination thus they gel into a pattern of spot treatment,

Weeding 01 and invasion Irom which should be the me thod orlast resort. (Ref non-play areas, ornamental 16 15 17 15.8 2 2) Research should focus on improving the grasses, lake margins timing of preemergence application, and the Spol treatment 01 goosegrass 13 17 13 14.8 3 need ror investment in consistent treatments, High visibility areas. e.g ..

17 11 15 14.4 4 to reduce the goosegrass seed bank. clubhouse, cart paths Torpedograss is a potential problem Communications to membership

12 16 9 13.1 5 everywhcre 011 the golf course, including on weed control activities

mit iga ted wetlands and native grass plantings. Cleanup and tracking of

8 12 13 to.7 6 While Drive 75DF lessens torpedograss, based overseeded grasses

on l11y observations, it requires more than two Safety ollale summer preemergence herbicides to 8 14 8 10.4 7 years of treatments to remove it cnti rely. (Ref

overseeded ryegrass 3) A complete program of torpedograss removal must address the problem along lake margins and wetland areas.

26 flORIDA TURF DIGEST SEPTEMBER/OCTOBER 2001

Tropical signa lgrass can be control led in

bcrmuciagrass turf with two to four

postemergence applications o f MSMA, but the

problem is often allowed to get out of hand

because of misidentifica tio n, and failure to

follow through wi th multiple trea tments. (Ref 4).

One hypothesis has been proposed that

the increased reliance on preemergence

herbic ides for gooseg rass cont ro l has left the

go lf course vulnerable to seedling germina­

tion o f tropical signalg rass. Companio n

work o n sad fa rms shows that tropica l

signal grass is dirfi cult to prevent with

existing preemergence her bicides. (Ref 5).

Among o ther se r io us weeds, the crabgrasses

arc closely rela ted to tropica l signalgrass, but

mllch eas ier to control. Areas wi th a

crabgrass problem have probably no t had

MSMA applied on a regular basis.

Among the sedges, large areas of green

kyllinga often in fest the fairways. This is

primar il y a problem in late fall and ea rl y

winter, as the kylli nga seems to fade o ut

between March and Apri l. Onl y Ma nage,

Image. and MSMA+Se l1 co r are highly

effec tive aga inst kyll inga, and Manage is the

least likely to injure the bermudag rass. (/?ef 6)

Poa annua is the ma in weed of perennial

ryegrass overseeded into bermudagrass turf.

II is hard to con trol because of the risk of

inj uring both the perennial ryegrass and the

unde rl ying berl11 udagrass turf. While this is

a ni che problem in sou th Flo rida. for the

m inor ity of super in tendents who overseed , it

deserves more ca reful resea rch.

For the broad leaf weeds, which arc

ge nera lly no t ser ious in golf and sports turf,

there a rc man)' excellent phenoxy broadleaf

m ixtures, although there is some unce rtai n ty

about which to use 0 11 d irfi cult tap-roo ted

spec ies such as pigweed. r ... lanor herbicide

and poss ibly Lonlrei arc the best backups for

very diffi cult broad leaf weeds. O ther

mixtures for the fu ture ma r incl ude

carfen trazo ne.

Philip Busey, PII.!J., is (l ssocitlle professor

of lurfgrnss science (II the Ullil'erit)' of Florida/ IFA S Research alld £dllWlioll Cell ler ill Fori LflIu/erdale. He ilia), be reached (/I 954-577-

6337; fax 954-577-6337; e-mail [email protected]

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university research SOUTH F I.ORIDA'S Top 10 'W EEDS

References

1. Anonymous. 1996. "1996 Gall Course Superin­tendents Report,· Golf Course Superintendents Association of America, Lawrence, Kansas.

2. Busey. ~ 1999. "Goosegrass and gall don't mix: Golf Course Managemenl67(9): September 1999, pages 63-66.

3. Busey. P. 2001. "Can Drive 75DF Eradicale TorpedograssT Florida Green: Summer 2001, pp. 56,5B.

4. Busey, P. "Tropical signatgrass spreads easily and is lough to eradicate: Florida Turf Digest 17(3):May/June 2000, pages 14, 16-1B.

5. Busey, P. 2001. "Ask the Expert: Regarding Tropi­cal Signalgrass: Turf News 25(4): July/August 2001, pages 70·72.

6. Busey, P. 2001. ·Optimum herbicide slralegy for managing mixao weed populations in the south· ern U.S." International Turlgrass Society Research Journal 7:1001-1004.

7. Hodges, A. W .. J. J. Haydu, ~ J. van Blokland, and A. P. Bell. 1994: Contribution ollheturtgrass induslry to Floridas economy, 1991/92: A value added approach: University 01 Florida IFAS Eco­nomics Report ER 94-1.

FLORIDA TURF DIGEST 27

1".""" -Ilr 1J1fjeI6'

Official Journal of the Florida Tulfgrass Association

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EDITOR Sieve Pearson

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contents vol. t8/No.5 Seplember/ Oclober 2001

ON THE ISSUES

The new system for governing Ftorida·s state university system may have a serious negative impact on scientific research inctuding turt. A statewide program to controt mote crickets with nematodes is under way.

COVER STORY: MIAMI-DADE PARKS & RECREATION

It's a challenge to run a recreation program for a county that covers an area targe enough to be the 49th-targest state and contains more peopte than 11 states!

UNIVERSITY RESEARCH

Most herbicides are safe for seaside paspatum; goosegrass was chosen by South Ftorida turtgrass managers as their most probtematic weed; 5-year summary of overseed triat s.

PRACTICALLY SPEAKING

Not all safety equipment is safe; use sod to patch damaged turt; hetping a tawn survive a drought; Ftorida's pest-controt ticense requirements; tawn maintenance business advice.

AROUNDTHE INDUSTRY

Annuat conference addresses serious issues facing the industry; FTGA wrestles with dectining revenues, staff upheavat; Gtenn Obertander and Dr. Wayne Mixson honored with Wreath of Grass.

DEPARTMENTS

President's Message FTGA Viewpoint ... Turtgrass Catendar .. FGCSA Turt Links

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Cover: Scenes of Miami-Dade County's Parks & Recreation Department Region Five.

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