HS193

Weed Management in Bulb Crops (Onion, Leek, Garlic, Shallot)1

Peter Dittmar and Nathan S. Boyd2

1. This document is HS193, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date March 1999. Revised July 2016. Visit the EDIS website at http://edis.ifas.ufl.edu.

2. Peter Dittmar, assistant professor; and Nathan S. Boyd, Horticultural Sciences Department, Cooperative Extension Service, UF/IFAS, Gainesville, FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of the product named, and does not signify that they are approved to the exclusion of others of suitable composition.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office. U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.

Bulb crops are a crop grouping that includes all of the Allium species except chives. Bulb crops include onions (dry and green), leeks, garlic, and shallots. Very few shallots or garlic crops are grown in Florida. Dry bulb onions, green and bunching onions, and leeks are the main crops of this group grown in the state. Where herbicides are limited, the culture of these crops must accommodate cultivation. Bulb crops do not shade out weeds that emerge in the rows. Also, many of the crops, such as dry bulb onions and leeks, require a long growing season. Therefore, a plan for weed control must be made before planting.

Avoid fields that are infested with nutsedge, hard-seeded legumes, or other difficult-to-control weeds. Many weed problems can be reduced by preparing the land well ahead of planting and using Roundup in a “cropping systems” approach, and/or using paraquat in a “stale seed bed” ap-proach. Preemergence and early postemergence herbicides may control many weeds for 4–6 weeks.

Onions and leeks are fairly shallow rooted, and care must be taken not to prune these roots with cultivation, especially when onions begin to bulb. Pulling or hoeing occasional large broadleaf weeds, while labor intensive, may be preferable when plants are older and bulbing.

Emerged grass weeds may be controlled either by Select®, Fusilade® or Poast®. Care should be taken not to apply any herbicide beyond the preharvest interval specified on the labels.

Herbicide performance depends on weather, irrigation, soil type, and proper selection for the weed species to be controlled. Obtain consistent results by reading the herbi-cide label and other information about proper application and timing of each herbicide.

Table 1 includes herbicides and directions for application before crop emergence or transplanting. Table 2 lists herbicides for use after crop emergence or transplanting.

2Weed Management in Bulb Crops (Onion, Leek, Garlic, Shallot)

Tabl

e 1.

Pre

plan

t/pr

eem

erge

nce

chem

ical

wee

d co

ntro

l in

onio

n, le

ek, g

arlic

, and

sha

llot

Act

ive

ingr

edie

nt

lb. a

.i./A

(Tra

de n

ame)

am

ount

of p

rodu

ct/A

MO

A c

ode

Crop

sW

eeds

con

trol

led

/ rem

arks

Bens

ulid

e 5–

6(P

refa

r®) 4

E

5–6

qt.

8D

ry b

ulb

vege

tabl

es: o

nion

, ga

rlic,

shal

lot

Annu

al b

road

leaf

and

gra

ss c

ontr

ol. I

ncor

pora

te o

r irr

igat

e 1–

2 in

ches

dee

p w

ithin

36

hrs.

of a

pplic

atio

n. C

onsu

lt la

bel f

or ro

tatio

n re

stric

tions

.

Brom

oxyn

il 0.

25–0

.38

(Buc

tril®

) 2 E

C 1.

0–1.

5 pt

.6

Oni

on (d

ry b

ulb)

Broa

dlea

f wee

ds. P

reem

erge

nce

is re

stric

ted

to m

uck

soils

con

tain

ing

grea

ter

than

10%

org

anic

mat

ter.

Appl

y at

leas

t 3–4

day

s prio

r to

emer

genc

e. W

eeds

sh

ould

not

exc

eed

the

four

-leaf

stag

e, 2

inch

es in

hei

ght,

or 1

inch

in d

iam

eter

.

Carf

entr

azon

e U

p to

0.0

31(A

im®)

2 E

C U

p to

2 fl

. oz.

14O

nion

, gar

lic, l

eek,

chi

ve,

shal

lot

Appl

y as

a p

repl

ant b

urn

dow

n fo

r em

erge

d br

oadl

eaf w

eeds

. Use

cro

p oi

l con

cent

rate

(CO

C), m

ethy

late

d se

ed o

il, o

r non

ioni

c su

rfac

tant

(NIS

) at

reco

mm

ende

d ra

tes.

Max

imum

rate

of 0

.096

lb. a

.i./A

per

seas

on. N

o pr

etra

nspl

ant i

nter

val.

DCP

A 4.

5–6.

0(D

acth

al®)

W75

6–

8 lb

. (D

acth

al®)

6 F

6–

8 pt

.

3O

nion

(dry

bul

b, g

reen

), le

ek,

shal

lot

Annu

al g

rass

es a

nd c

erta

in b

road

leaf

con

trol

. App

ly a

t see

ding

or p

lant

ing.

M

axim

um ra

te o

f 10.

5 lb

. a.i.

/A p

er se

ason

.

Flum

ioxa

zin

Up

to 0

.06

(Cha

teau

®) 5

1 W

DG

U

p to

2 o

z.14

Oni

on (d

ry b

ulb)

Broa

dlea

f con

trol

. App

ly to

tran

spla

nted

oni

ons b

etw

een

the

2- a

nd 6

- lea

f st

age.

App

ly to

dire

ct se

eded

oni

ons b

etw

een

the

3- a

nd 6

- lea

f sta

ge.

Flum

ioxa

zin

Up

to 0

.19

(Cha

teau

®) 5

1 W

DG

U

p 6

oz.

14G

arlic

Broa

dlea

f con

trol

. App

ly w

ithin

3 d

ays o

f pla

ntin

g ga

rlic.

Gly

phos

ate

(Var

ious

form

ulat

ions

) Co

nsul

t lab

el9

Oni

on, g

arlic

, lee

k, c

hive

, sh

allo

tCo

ntro

l of e

mer

ged

broa

dlea

f and

gra

ss w

eeds

. Con

sult

indi

vidu

al la

bels

for

rest

rictio

ns.

Oxy

fluor

fen

2.0

(Goa

l® 2

XL) 2

EC

2.0

pt.

(Goa

lTen

der®

) 4 E

C 1.

0 pt

.

14O

nion

(dry

bul

b), g

arlic

(dry

bu

lb)

Cert

ain

broa

dlea

f wee

ds. T

rans

plan

ted

only

. App

ly w

ithin

2 d

ays o

f tr

ansp

lant

ing.

Nec

rotic

lesi

ons,

twis

ting,

or s

tunt

ing

of p

lant

s can

occ

ur

if ap

plic

atio

ns a

re m

ade

durin

g co

ol, w

et w

eath

er o

r prio

r to

the

full

deve

lopm

ent o

f the

true

leav

es.

Para

quat

0.

5–1.

0(G

ram

oxon

e®) 2

SL

2–4

pt.

22O

nion

(dry

bul

b)Co

ntro

ls e

mer

ged

wee

ds. A

pply

prio

r, du

ring,

or a

fter

pla

ntin

g, b

ut b

efor

e cr

op

emer

genc

e. O

nly

2 ap

plic

atio

ns a

seas

on. U

se a

non

ioni

c su

rfac

tant

.

Para

quat

0.

63–1

.0(G

ram

oxon

e®) 2

SL

2.5–

4.0

pt.

(Fire

stor

m®)

3 S

L 1.

7–2.

7 pt

.

22O

nion

(see

ded)

, gar

licEm

erge

d br

oadl

eaf a

nd g

rass

wee

ds. A

pply

as a

pre

plan

t bur

ndow

n. A

m

axim

um o

f 1 lb

. a.i.

/A p

er se

ason

.

 Pel

argo

nic

acid

(Scy

the®

) 4.2

EC

3–10

% v

/v27

Oni

on, g

arlic

, lee

k, c

hive

, sh

allo

tEm

erge

d br

oadl

eaf a

nd g

rass

wee

ds. A

pply

bef

ore

emer

genc

e of

cro

p. P

rodu

ct

is a

con

tact

, non

sele

ctiv

e, fo

liar a

pplie

d he

rbic

ide.

The

re is

no

resi

dual

act

ivity

.

 Pen

dim

etha

lin

0.5–

0.75

min

eral

1.

0–2.

0 m

uck

(Pro

wl®

) 3.3

EC

1.2–

1.8

pt. m

iner

al

2.4–

4.8

pt. m

uck

(Pro

wl®

H2O

) 3.8

1.

0–1.

5 pt

. min

eral

2.

0–4.

0 pt

. muc

k

3O

nion

(dry

bul

b), s

hallo

t (dr

y bu

lb)

Min

eral

soils

: App

ly w

hen

crop

has

2 to

9 tr

ue le

aves

. Muc

k so

ils: M

ay b

e ap

plie

d as

sequ

entia

l app

licat

ion:

pre

emer

genc

e th

roug

h lo

op st

age,

ear

ly

post

emer

genc

e (2

to 6

true

leaf

stag

e), l

ate

post

emer

genc

e (6

to 9

true

leaf

st

age)

. Do

not e

xcee

d 5.

9 lb

. a.i.

/A in

a g

row

ing

seas

on. P

HI 4

5 da

ys.

 Pyr

afluf

en

0.00

08–0

.003

(ET®

Her

bici

de/D

efol

iant

) 0.

5–2.

0 fl.

oz.

14Bu

lb v

eget

able

sEm

erge

d br

oadl

eaf a

nd g

rass

wee

ds. A

pply

as a

pre

plan

t bur

ndow

n tr

eatm

ent.

3Weed Management in Bulb Crops (Onion, Leek, Garlic, Shallot)

Tabl

e 2.

Pos

tem

erge

nce

chem

ical

wee

d co

ntro

l in

onio

n, le

ek, g

arlic

, and

sha

llot

Act

ive

ingr

edie

nt

lb. a

.i./A

(Tra

de n

ame)

am

ount

of p

rodu

ct/A

MO

A C

ode

Crop

sW

eeds

con

trol

led

/ rem

arks

Brom

oxyn

il 0.

25–0

.38

(Buc

tril®

) 2 E

C 1.

0–1.

5 pt

.6

Oni

on (d

ry b

ulb)

Broa

dlea

f wee

ds. S

oil a

nd o

nion

leav

es sh

ould

be

dry

befo

re a

pplic

atio

n.

Wax

y co

atin

g on

leav

es re

duce

s cha

nces

for i

njur

y. V

arie

ties v

ary

in

sens

itivi

ty, a

nd u

se o

n a

tria

l bas

is.

Brom

oxyn

il 0.

38–0

.5(B

uctr

il®) 2

EC

1.5–

2 pt

.6

Gar

licBr

oadl

eaf w

eeds

. App

ly a

fter

em

erge

nce

but b

efor

e 12

inch

es in

hei

ght.

Wee

ds a

re m

ost s

usce

ptib

le u

p to

the

four

-leaf

stag

e or

2 in

ches

in h

eigh

t or

1 in

ch w

ide.

PH

I 112

day

s.

Carf

entr

azon

e U

p to

0.0

31(A

im®)

2 E

C, 1

.9 E

W

Up

to 2

fl. o

z.14

Oni

on (d

ry b

ulb)

, gar

lic, l

eek,

ch

ive,

shal

lot

Emer

ged

broa

dlea

f con

trol

. Pos

t-di

rect

hoo

ded

appl

icat

ion

to ro

w

mid

dles

for b

urnd

own

of e

mer

ged

wee

ds. U

se c

rop

oil c

once

ntra

te o

r no

nion

ic su

rfac

tant

at r

ecom

men

ded

rate

s. PH

I 0 d

ays.

Clet

hodi

m

0.09

4–0.

25

0.07

–0.2

5

(Arr

ow®,

Inte

nsity

® O

ne,

Sele

ct®)

2 E

C 6–

16 fl

. oz.

(S

elec

t Max

®) 1

EC

9–32

fl. o

z.

1O

nion

(dry

bul

b), g

arlic

, sha

llot

(dry

bul

b)An

nual

and

per

enni

al g

rass

con

trol

. Som

e la

bels

incl

ude

gree

n on

ion.

Co

nsul

t lab

el fo

r use

of a

cro

p oi

l con

cent

rate

or n

onio

nic

surf

acta

nt. P

HI

45 d

ays.

Clet

hodi

m

0.09

4–0.

125

(Arr

ow®,

Inte

nsity

® O

ne)

2 EC

6–

8 fl.

oz.

(S

elec

t Max

®) 1

EC

12–1

6 fl.

oz.

1Ch

ive,

leek

Emer

ged

annu

al a

nd p

eren

nial

gra

sses

. Con

sult

labe

ls ra

te o

f CO

C or

N

IS. D

o no

t app

ly m

ore

than

0.5

lb. a

.i./A

per

seas

on. S

elec

t Max

is n

ot

regi

ster

ed in

leek

. PH

I 14

days

.

DCP

A 4.

5–6.

0(D

acth

al®)

W75

6–

8 lb

. (D

acth

al®)

6 F

6–

8 pt

.

3O

nion

(dry

bul

b, g

reen

), le

ek,

shal

lot

Annu

al g

rass

es a

nd c

erta

in b

road

leaf

con

trol

. App

ly a

t lay

by u

p to

14

wee

ks a

fter

pla

ntin

g. If

wee

ds h

ave

emer

ged,

cul

tivat

e or

wee

d fie

ld.

Max

imum

rate

of 1

0.5

lb. a

.i./A

per

seas

on.

Dim

etha

nam

id-p

U

p to

1.0

(Out

look

®) 6

EC

Up

to 2

1 fl.

oz.

15O

nion

(dry

bul

b, g

reen

), ga

rlic,

le

ek, s

hallo

t (dr

y bu

lb, g

reen

)Br

oadl

eaf a

nd g

rass

wee

ds. A

pply

aft

er th

e tw

o tr

ue le

af st

age.

App

ly

as a

sing

le a

pplic

atio

n or

split

app

licat

ion.

Spl

it ap

plic

atio

ns o

f 10–

14 fl

. oz

. fol

low

ed b

y 7–

10 fl

. oz.

/A w

ith 1

4 da

ys b

etw

een

appl

icat

ions

. Do

not

exce

ed 2

1 fl.

oz.

/A p

er g

row

ing

seas

on. P

HI 3

0 da

ys.

Flua

zifo

p 0.

188

(Fus

ilade

® D

X)

12 fl

. oz.

1O

nion

(dry

bul

b), g

arlic

Annu

al a

nd p

eren

nial

gra

ss w

eeds

. Do

not a

pply

mor

e th

an 4

8 fl.

oz.

/A

per s

easo

n. In

clud

e a

COC

or N

IS in

the

spra

y so

lutio

n. P

HI 4

5 da

ys.

Oxy

fluor

fen

0.5

(Goa

l® 2

XL) 2

EC

0.5

pt. d

irect

seed

ed

(Goa

lTen

der®

) 4 E

C 0.

25 p

t. di

rect

seed

ed

Oni

on (d

ry b

ulb)

, gar

lic (d

ry b

ulb

Cert

ain

broa

dlea

f wee

ds. D

irect

seed

ed o

nly.

App

ly a

fter

the

crop

has

2

true

leav

es. M

ultip

le tr

eatm

ents

can

be

appl

ied

and

do n

ot e

xcee

d 0.

5 lb

. a.i.

/A. N

ecro

tic le

sion

s, tw

istin

g, o

r stu

ntin

g of

pla

nts c

an o

ccur

if

appl

icat

ions

are

mad

e du

ring

cool

, wet

wea

ther

or p

rior t

o de

velo

pmen

t of

true

leav

es. P

HI 6

0 da

ys.

Para

quat

0.

5(G

ram

oxon

e®) 2

SL

2 pt

.O

nion

(dry

bul

b)Em

erge

d w

eeds

. Row

mid

dles

onl

y. O

nly

two

appl

icat

ions

per

seas

on.

Lim

it of

thre

e ap

plic

atio

ns p

er y

ear.

PHI 6

0 da

ys

Pela

rgon

ic a

cid

(Scy

the®

) 4.2

EC

3–10

% v

/vO

nion

, gar

lic, l

eek,

chi

ve, s

hallo

tEm

erge

d w

eeds

. Row

mid

dles

onl

y. U

se a

shie

lded

spra

yer d

irect

ed to

the

row

mid

dles

to re

duce

drif

t to

the

crop

.

4Weed Management in Bulb Crops (Onion, Leek, Garlic, Shallot)

Act

ive

ingr

edie

nt

lb. a

.i./A

(Tra

de n

ame)

am

ount

of p

rodu

ct/A

MO

A C

ode

Crop

sW

eeds

con

trol

led

/ rem

arks

Pend

imet

halin

0.

5–0.

75 m

iner

al

1.0–

2.0

muc

k

(Pro

wl®

) 3.3

EC

1.2–

1.8

pt. m

iner

al

2.4–

4.8

pt. m

uck

(Pro

wl®

H2O

) 3.8

1.

0–1.

5 pt

. min

eral

2.

0–4.

0 pt

. muc

k

Oni

on (d

ry b

ulb)

, sha

llot (

dry

bulb

)M

iner

al so

ils: A

pply

whe

n cr

op h

as tw

o to

nin

e tr

ue le

aves

. Muc

k so

ils:

May

be

appl

ied

as se

quen

tial a

pplic

atio

n: p

reem

erge

nce

thro

ugh

loop

stag

e, e

arly

pos

tem

erge

nce

(tw

o to

six

true

leaf

stag

e), l

ate

post

emer

genc

e (s

ix to

nin

e tr

ue le

af st

age.

Do

not e

xcee

d 5.

9 lb

. a.i.

/A

per g

row

ing

seas

on. A

ll so

ils: D

o no

t irr

igat

e in

exc

ess o

f 0.5

inch

es a

fter

ap

plic

atio

n. D

o no

t app

ly p

reem

erge

nce

thro

ugh

loop

stag

e if

rain

s are

ex

pect

ed. P

HI 4

5 da

ys.

Seth

oxyd

im

0.19

–0.2

8(P

oast

®) 1

.5 E

C 1.

0–1.

5 pt

.O

nion

, gar

lic, l

eek,

shal

lot

Gro

win

g gr

ass w

eeds

. Dec

reas

ed e

ffica

cy if

wee

ds a

re u

nder

stre

ss. D

o no

t exc

eed

4.5

pt./A

per

seas

on. I

nclu

de a

CO

C. P

HI 3

0 da

ys.

Trefl

an

0.35

–0.5

(Tre

flan)

4 E

C 0.

75–1

.0 p

t. (T

refla

n TR

-10)

3.

75–5

.0 lb

.

3O

nion

(dry

bul

b)Br

oadl

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