Asparagus growers have choice of many herbicides for asparagus weed control

New herbicides give asparagus growers additional tools for crop management.

Asparagus is a perennial vegetable crop which is maintained in plantings for 12 to 15 years. Major weed problems in perennial crops tend to change from annual weeds to perennial weeds over time. In many cases, the perennial weeds are tolerant of the herbicides used for the same reason that the crops are tolerant of the herbicides. Perennial crops usually are deeply rooted, and herbicides applied on the soil surface do not reach the crop roots. Annual weeds germinate in the upper inch of soil and come into contact with the preemergence herbicides applied early in the growing season. Some residual herbicides have activity against perennial weeds, and they also may suppress asparagus if used repeatedly.

Annual weeds also are a problem in asparagus production. Weeds resistant to photosynthesis inhibitor herbicides have become common problems in Michigan asparagus fields. Weeds that are not controlled by the herbicides proliferate when other weeds are controlled. Since photosystem II (PSII) inhibitors (Karmex, Lorox, Princep, Sencor, Sinbar) have been the primary herbicides used in asparagus for many years, resistance to PSII herbicides has developed in several amaranth species, including Powell amaranth and redroot pigweed.

Annual weeds that are serious problems in established asparagus fields are field sandbur,large crabgrass, fall panicum, common lambsquarters, Russian thistle, horseweed and common groundsel. Common perennial weeds in asparagus include quackgrass, Canada thistle,dandelion, field bindweed, common milkweed, rush skeletonweed and spotted knapweed. Wild carrot is a common biennial weed in asparagus.

Yield of asparagus hybrids peaks in years four through eight after establishment. Most fields of asparagus hybrids maintain productivity for 12 to 15 years. In the past, fields of open pollinated varieties, e.g., Mary Washington and Viking, often were maintained over 20 years, but annual yields were lower than with hybrids. The decline in vigor and yield appears to be a natural characteristic of the hybrid plants. However, repeated use of PSII inhibitors and other herbicides may contribute to the decline. Inadequate weed control also may contribute to the decline in yield.

An effective and safe herbicide program for asparagus includes several residual herbicides applied in combination and rotations over several years. Herbicides labeled for preemergence use in asparagus are listed in Table 1. With the number of herbicides registered for asparagus, growers should not have to use herbicides with the same mode of action twice in the same year. In addition to the long-residual herbicides labeled for preemergence use, several herbicides are labeled for postemergence application in asparagus (Table 2.) Their use will help control difficult and persistent annual and perennial weeds.

Table 1. Preemergence herbicides for asparagus

Herbicide

Trade Name

Common Name

Mode of Action

PHI

Weeds Controlled

Callisto

mesotrione

HPPD inhibitor

None

Annual broadleaves and grasses

Chateau

flumioxazin

PPO inhibitor

14 day

Annual grasses and broadleaves

Dual Magnum

s-metolachlor

Cell division inhibitor

16 day

Annual grasses and broadleaves, nutsedge

Karmex

diuron

PSII inhibitor

None

Annual broadleaves, crabgrass

Prowl H2O

pendimethalin

Mitosis inhibitor

14 day

Annual grasses and broadleaves

Sencor

metribuzin

PSII inhibitor

14 day

Annual broadleaves and grasses

Solicam

norflurazon

Pigment synth. inhib.

14 day

Annual grasses

Spartan

sulfentrazone

PPO inhibitor

14 day

Annual broadleaves, pigweeds

Sinbar

terbacil

PSII inhibitor

5 day

Annual grasses and broadleaves, quackgrass

Table 2. Postemergence herbicides for asparagus

Herbicide

Trade Name

Common Name

Mode of Action

PHI

Weeds Controlled

Banvel

dicamba

Auxin disruption

1 day

Annual and perennial broadleaves

Clarity

dicamba

Auxin disruption

1 day

Annual and perennial broadleaves

Formula 40

2, 4 – D

Auxin disruption

3 day

Annual broadleaves, dandelion

Lorox

linuron

PSII inhibitor

1 day

Annual broadleaves

Sandea

halosulfuron

ALS inhibitor

1 day

Annual broadleaves, horseweed, pigweed, nutsedge

Roundup

glyphosate

EPSP synth. inhib.

5 day

Most annual and perennial weeds

Gramoxone

paraquat

PSI inhibitor

6 day

Most green plants; burn-down only

Poast

sethoxydim

ACCase inhibitor

1 day

Annual and perennial grasses

Fusilade

fluazifop -p

ACCase inhibitor

1 day

Annual and perennial grasses

Select Max

clethodim

ACCase inhibitor

1 day

Annual and perennial grasses

Growers should apply a tank-mix of two herbicides with different modes of action preemergence, and a tank-mix of two other herbicides after harvest. During harvest and immediately after final harvest, growers may apply postemergence foliar-active herbicides to kill emerged weeds. Postemergence herbicides should be chosen based on the weeds they control and the time of application. Some of the postemergence herbicides may injure asparagus if they contact the fern, so follow label directions concerning application timing and placement carefully.

Complete herbicide recommendations for asparagus and other vegetable crops may be found in MSU Extension Bulletin E-433, “2012 Weed control guide for vegetable crops.”

 

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