Weed Control in Non-Bearing Grape – UKREC - 2005
Joseph Masabni, Department of Horticulture

Herbicides are an important component of a comprehensive weed control regimen, especially in newly established or non-bearing grapes.

Growers are often busy with canopy, disease, and insect management that they neglect the importance of weed control. In order to assist new growers, who just started or considering a new vineyard, with their decision making options, an experiment was conducted in 2005 to compare 6 herbicides regimen .

The experiment was initiated in spring of 2005 to determine the residual control and benefits of various herbicides applied in the spring on weed pressure in spring of 2006.

Herbicides were applied using a CO2-pressurized backpack sprayer with a 2-nozzle shielded boom calibrated to spray a 3 ft band at 30 psi and 3 mph walking speed. The 11002-nozzles were set at 7" above ground level to obtain good spray overlap and complete weed coverage. The spray boom was moved in and out in the tree row to avoid spraying the vine trunks. Therefore, weeds on the base of vine trunks were taller throughout the season and did not reflect the effectiveness of the applied herbicide.

Plots were 6 ft x 54 ft long. The experimental design consisted of a randomized complete block with 3 reps.

The preemergence (PRE) treatments were applied on 15 April 2005 when spring weeds were 3-4" tall, to grapes 0.5-2" green tip stage. Since weeds have already germinated and have been growing since early March, Roundup WeatherMax 16 oz/A (0.68 lb ai/A) was included with all treatments. The postemergence (POST) treatments were applied on 15 June 2005. Roundup was also included with the POST treatment at same rate. All treatments were applied early in the morning with average wind speed of 2.5 mph.

No yield data was collected from this experiment as this was not the original intent. Only visual weed control ratings were collected at various dates. The scale used in these ratings were on a 1-10 scale, with 1 = no control and 10 = complete kill or no weeds present. A rating of 7 (70-75% control) or more is considered a commercially acceptable value.

The following is the full name of the weed codes used in the tables:

DAND = dandelion; PEWE = pepperweed, LACG = large crabgrass; SHPU = shepherdspurse; RRPW = redroot pigweed; HONE = horsenettle.

Treatments 1-3 and 6 significantly reduced the regrowth of clover, whereas Snapshot and Kerb had no significant control on clover or the other weeds present at the time. Treatments 2 and 6 had the best overall weed control on both dates of evaluation.

Chateau at the high label rate of 12 oz still had excellent control of clover 2 months after application. In general, all herbicide currently labeled for non-bearing grape provide acceptable weed control on most annual broadleaves and grasses. Kerb and Snapshot provided a little weaker control on SHPU and LACG.