New Plantings, Soil-active Herbicides

isoxaben (Trellis)

Rate 0.495 to 0.998 lb ai/a (0.66 to 1.33 lb/a Trellis)

Time Apply after harvest in fall until 6 months before the next harvest, or immediately after cultivation, to debris-free soil surface.

Remarks Limited to 2 applications per year up to 1.33 lb product per year. Activate with 0.5 inch water or shallow cultivation before weeds begin to emerge. Chemical stability remains adequate when left on soil surface for 21 days. Identify weeds and adjust rates according to charts on label.

Caution Preharvest interval is 165 days. Do not apply to newly transplanted crops until the soil has settled and cracks disappear.

Site of action Group 21: inhibits cell wall synthesis Site B

Chemical family Benzamide

napropamide (Devrinol)

Rate 4 lb ai/a (8 lb/a Devrinol 50-DF)

Time Apply after transplanting to firm soil, before weeds germinate.

Remarks The day of treatment, wet soil 2 to 4 inches deep to reduce degradation by sun and to activate herbicide. If convenient, shallow mechanical incorporation appears to improve activity. Avoid exposure of transplant roots contacting soil. May be applied through irrigation system. Can be tank mixed with broad-spectrum herbicides glyphosate and paraquat. Do not leave on soil surface for more than 3 weeks in winter and 24 to 72 hrs in summer. PHI is 70 days.

Site of action Group 15: inhibits very long chain fatty acid synthesis

Chemical family Acetamide

oryzalin (Surflan)

Rate 2 to 6 lb ai/a (2 to 6 quarts/a Surflan)

Time Apply after transplanting to firm soil, before weeds germinate.

Remarks Requires sprinkler irrigation, rain, or shallow cultivation (1 to 2 inches) to activate. Rate depends on duration of weed control desired. Inhibits mitosis, primarily in roots.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

oxyfluorfen (Goal 2XL)

Rate 1.25 to 1.5 lb ai/a (5 to 6 pints/a Goal 2XL) for preemergence control; as low as 2 pints/a for early postemergence control of susceptible species.

Time Apply only to healthy vines.

Remarks Direct the spray toward the base of vines, avoiding direct plant contact. Acts as contact, either directly on broadleaf weeds or at soil surface as weeds emerge. Controls broadleaf weeds pre- and postemergence depending on application rate and weed species.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Diphenylether

pendimethalin (Prowl H2O, Satellite Hydrocap, Prowl 3.3EC, and other products)

Nonbearing crop for Prowl 3.3

Rate 1.9 to 3.8 lb ai/a (2 to 4 quarts/a Prowl H2O); 1.98 to 3.96 lb ai/a (2.4 to 4.8 quarts/a Prowl 3.3EC)

Time Apply before or after planting or to 1-year dormant vines.

Remarks Spray directly on the ground beneath newly planted and 1-year-old vines. Overhead watering or rain is required (usually 0.5 inch is adequate) within 7 days for herbicide activation. Can also be applied before transplanting vines by incorporating into the top 2 inches of soil, or by applying to soil surface. Minimize contact of treated soil with the vine roots when transplanting.

Caution Do not apply over the tops of vines with leaves or open buds. Do not graze treated areas, or apply more than 6.3 quarts/a per year.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

trifluralin (Treflan and several other products)

Rate 0.5 to 2 lb ai/a (1 to 4 pints Treflan)

Time Before transplanting, or in established bearing and nonbearing vineyards.

Remarks Apply before times of expected weed emergence or immediately after existing weeds are controlled. Apply as a directed spray to the soil and incorporate with methods that do not injure the crop. Use lower rates on sandy soils or soil containing low organic matter levels. Inhibits mitosis in roots and shoots. Preharvest interval is 60 days.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline