Use of Herbicides in Pecan Orchards in West Cross Timbers Area

Pecan Research

TOM E. DENMAN*

WEED PROBLEMS in native and cultivated upland pecan orchards are somewhat different. Some weeds and grasses that are found in both areas are welcome in one location and are considered a pest in other areas.


Native Pecan Orchards

The owner of a native pecan orchard spends considerable time and money in attempting to establish a uniform turf of bermudagrass over his entire orchard floor. He utilizes the grass for grazing purposes thus realizing an extra return from his land. In addition, the bermudagrass sod creates an ideal condition for the operation of pecan harvesting equipment.

After the foreign timber has been removed from native pecan orchards, numerous weeds, seedling trees and brush become real problems. Excellent control of some plants has been obtained by mowing at frequent intervals. Others can be controlled with light applications of relatively safe herbicides, but there are a number of plants that have been very difficult to eradicate.

A weed and brush control test was initiated in 1967 in a native pecan orchard on the Leon River near Gustine, Texas. The area had not been mowed for 2 years and was heavily infested with a number of species of weeds and woody plants.

Two new formulations of the systemic weed and brush killers, Dacamine 4D

Weed Killer and Dacamine 2D/2T Brush Killer, were used in the test since they are non-volatile and have a low drift hazard.

One gallon of solution was applied to individual tree plots covering an area under the canopy of the tree. Each material was replicated four times. The herbicides were applied on May 13,1967,and final evaluation was completed July 3, 1967.

The kinds and amounts of materials used and results obtained are summarized in Table. 1.


Table 1. Treatments, pounds/acre (active), amount/acre (active) and rating for control of certain weeds and woody plants in test of herbicides, Gustine, Tex., 1967.

Application rate Rating for control¹

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Pecan

Amount/ (small

Treat- Lbs. / A. Acre Hack- Green- Iron- seed-

ment Actual Material berry Elm brier weed lings)

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  1. 4D     0 0 1 1 1 1 1
  2. 4D     1 1 qt. 3.6 2 1.2 4 1.7
  3. 4D     2 2 qts. 4.5 2.5 1.3 5.3 2.1
  4. 4D     4 4 qts. 6.2 3 2.2 8 5.2
  5. 2D/2T     0 0 1 1 1 1 1
  6. 2D/2T     1 1 qt. 3 2 1.3 4 3.6
  7. 2D/2T     2 2 qts. 5.5 2.5 2 5.5 4.5

8.2D/2T     4 4 qts. 8.2 5.5 2.5 7.3 8

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Rating for control---I no control, 10 complete kill of top growth.


Common name Trade name

2, 4-D Dacamine 4D weed killer

2, 4-D plus 2, 4, 5-T Dacamine 2D/2T brush killer

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*Associate horticulturist, West Cross Timber Experiment Station, Stephenville.

58 PROCEEDINGS TEXAS PECAN GROWERS ASSOCIATION


Control of some species was not very effective. This could have been caused by lack of preparation of the site prior to application of the herbicides. The area probably should have been mowed several weeks in advance of the application date and the plants allowed renewing growth. Very effective control of greenbriers and ironweeds was obtained in another test following this means of preparation prior to applying the herbicides.


No damage to trees or foliage was observed. The materials seem useful in native orchards if reasonable precautions in their use are observed.


Cultivated Pecan Orchards

Bermudagrass is highly prized as a floor cover for native pecan orchards, but it is considered the most troublesome problem in cultivated orchards. Johnson-grass, more widespread than bermudagrass, requires constant attention to keep it under control. Other grasses such as crabgrass, nutgrass, coloradograss, grass-burs and several minor pests are also troublesome. Careless weeds, bullnettles, horsenettles and other broad-leaved plants frequently invade orchard sites.


A number of pre-emerge and post-emerge herbicides were evaluated in an

8-year-old cultivated pecan orchard planted on upland sandy soil in Parker County.

The orchard site was badly infested with most of the plants described above with the exception of bermudagrass.


The orchard was cultivated with a tandem disc 3 weeks prior to the application of the herbicide. Johnsongrass was allowed to renew growth and attain a height of 10 inches. Other grasses and weeds were emerging and some had reached a height of about 2 inches.


All of the chemicals were applied at the rate of 80 gallons of solution per acre with pressure maintained at 30 p. s. i. Tractor speed was held to 1-1/2 mph.

The materials were applied May 3, 1967 and final evaluation was made July 3, 1967.

In Table 2, the treatments, amount per acre and results are summarized.


Most of the chemicals killed top growth of the plants quickly but regrowth occurred after a few weeks following the use of the contact herbicides, Daconate and Dow General. The other materials gave some control of a number of weeds for a longer period. Sinbar seemed especially promising and should be investigated further. No damage to the young pecan trees was observed in this test.


Interest in mechanical harvesting of pecans has increased in recent years. This scene, duplicated many times throughout the state, was demonstration time at the 1967 Annual Conference of the Texas Pecan Growers Association, Fort Worth. Growers continue to seek machines that will harvest their crop at the lowest possible cost per pound.





Treatment

Amount 

per acre

Horse-

nettle

Careless

weed

Crab-

grass

Colorado-

grass

Johnson-

grass

Grass

Seedlings

Nutsedge

1. Paraquat

1 quart

0

7

10

8

1

10

0

  Simazine 80w

2 pounds

  Spreader X-77

8 ounces

2. Daconate

½ gallon

0

2

2

2

4

1

0

3. Dow General

3 pints

0

2

5

5

3

5

0

    Diesel

15 gallons

    Water

65 pounds

4. Amizine

7 pounds

8

10

10

10

7

10

5

    Amitrol-T

5. Amitrol-T

1 gallon

8

2

0

0

5

0

5

6. Dowpon

3½ pounds

0

10

10

10

5

10

0

    Simazine

2 pounds

7. Sinbar

2 pounds

6

9

10

10

5

10

9

8. Check

0

1

1

1

1

1

1

1














Rating for control---1 no control, 10 complete kill of top growth.