Successful Cogongrass Suppression

using Loblolly Pine Reforestation

James Miller, US Forest Service R&D

Stephen Enloe, Auburn University Erwin Chambliss, US Forest Service R&D

AU Cogongrass Research Team: Dr. Stephen Enloe (Agron), Dr. Nancy Loewenstein (Forestry), Dr. Luke Marzan (Remote Sensing), and Dr. Jim Miller (Emeritus USFS R&D)

Cogongrass Rhizomes must be killed or removed for eradication

Integrated Vegetation Restoration for Cogongrass Management

Mechanical Herbicides

Cultural – Plant Something

The Study Site in the southern most county in Alabama, Mobile Co. Uniform infestation 10 years after farming ceased

Test Treatments for Establishing Loblolly

All Combinations of the 3 Main Treatments plus 2 extras

1. Mechanical Site Preparation “Scalping” treatment using fireplow behind a dozer Laid back a 6 to 10 inch deep layer of soil and rhizomes, creating a

planting trench but a double deep rhizome mat between rows

2. Herbicide Site Preparation – at 26 gallons total volume per acre Arsenal AC imazapyr 12 oz /A (1 % solution) Accord Conc glyphosate 0.8 gal /A (3 % solution)+

surfactant 0.5 % v/v

3. Pine release May or Oct - banded sprays over rows Arsenal AC 4 or 6 oz /A (0.3 % or 0.5 %) alone and mixtures with Oust 2 oz /A and/or Escort 1 oz /A

– Double Rate Herbicide SP and release with Arsenal + Escort+Oust Arsenal AC 24 oz/A (2% solution) + Accord 1.6 gal/A (6% solution) – Check Non-treated Plots

Experimental units: • Treatment Plot 100 trees ( 8 x 8 ft spacing = 650 trees/acre) • Measurement Plot 36 measurement trees • Cover 5 subplots

• 2 ½ gen ‘Super’ seedlings • Culled to > 0.25 in root collar diameter

25m (82 ft)

25m (82 ft)

36 Measurement Trees

100 Trees Treatment

Plot

Plot (82 x 82 ft) 8.2 x 8.2 ft spacing

650 trees/acre

1

3 4

5

2

5 Subplots for Cover

Study Site during Study Establishment

Each Planting Spot Kicked Down to Permit Optimum Planting without Grass Wicks

Second Generation seedlings were re-graded onsite To have over a 3/8th inch groundline diameter

Seedling after 1st growing season

A Farmer eradicated cogongrass on half of the Area By multiple plowings and then planting Roundup Ready

Crops that could withstand multiple Roundup Treatments

Mechanical Site Preparation (Scalping)

Cogongrass infestation reforestation by planting loblolly pine Seedling after herbicide SP + scalp and scalp alone

January 2001

2 x 2 meter spacing 8.2 x 8.2 ft, 650 trees /ac

In 1st growing season

Mechanical SP only Herbicide + Scalping

April of the 2nd growing season on Check

April or the 2nd Year on Herbicide Site Prep

April of 2nd Year Herbicide SP and Scalp

September after 3rd growing season Max Site Prep with early succession initiated which later was reinvaded by

cogongrass

August of the 6th Growing Season

After 8 Growing Seasons

Herbicide Site Prep 2X Rate + Fall Arsenal Release

Herb + Scalping Site Prep

After 8 Growing Seasons Significant Suppression has occurred

Plant Pines Only with yaupon, privet, and

waxmyrtle volunteer establishment and Pine cover with needle Litter layer

Herb Site Prep & Missing Tree permits light to

sustain cogongrass

Age 8 Cogongrass Cover (%)

Check 2x Herb SP + Release

Release Herb SP

Herb SP + Release

0

2

4

6

8

10

12

14

16 18

Spring Release with Arsenal AC 0.5 % alone best

Age 8 Loblolly Volume (ft3 / acre)

Check Release Herb SP

2x Herb SP + Release

Herb SP + Release

0

100

200

300

400

500

600

8% Inc

13% Inc

22% Inc

25% Inc

What We Learned

• Initial cogongrass control increased with the intensity of treatment and positively increased pine growth.

• Cogongrass re-invaded all plots by year 3 due to absence of eradication even after multiple treatments.

• Scalping site preparation that laid the rhizome mats back as a mound between pine rows sustained the cogongrass longer than other treatments, which is not advised as a useful treatment.

• Dense pine canopies with pine litter layers or pine canopies with woody shrub midstories suppressed cogongrass by an average of 84 to 99 percent after 8 years

• 8-yr pine volumes averaged 25 % greater with multiple treatments compared to the check. This should maintain where woody competition does not occur.

We Can Establish Loblolly Pine Plantations in Cogongrass Infestations for Suppression