Established Plantings-Winter or Dormant Applications that Persist in Soil

dichlobenil (Casoron 4G)

Rate 4 to 6 lb ai/a (100 to 150 lb/a granular product)

Time Apply midwinter immediately before a cold rain to reduce volatility and enhance weed suppression.

Remarks Weigh and distribute exact quantities over precisely measured areas. Adjust rates on light, sandy soils and treat at least 4 weeks after transplanting or preferably the next winter. Use 150-lb rate for perennial weeds. Precision application of the higher rate over 3 consecutive years suggests adequate crop tolerance under the following conditions. Oregon results over 9 years suggest perennial weeds can be suppressed with 4-, 3-, and 2-lb ai/a rates applied in 3 consecutive years. Inhibits cellulose and cell wall formation.

Caution Grazing livestock is prohibited.

Site of action Group 20: inhibits cell wall synthesis Site A

Chemical family Nitrile

dichlobenil (Casoron CS)

Blueberry only

Rate 1.96 to 3.92 lb ai/a (1.4 to 2.8 gal/a Casoron CS)

Time Apply midwinter immediately before a cold rain to reduce volatility and enhance weed suppression.

Remarks Liquid formulation of encapsulated crystals of dichlobenil improves potential to apply evenly. Controls most germinating seeds and seedlings of annual and perennial grasses, and broadleaf weeds. Controls Canada thistle but will only suppress growth of field bindweed. Do not use on light sandy soils. Do not apply with high or gusty wind, high temperatures, low humidity, or temperature inversions. Inhibits cellulose and cell wall formation.

Caution Use only around well-established plants; typically wait until 1 year after transplanting. Grazing livestock is prohibited.

Site of action Group 20: inhibits cell wall synthesis Site A

Chemical family Nitrile

diuron (Direx 4L, Diuron 80DF and several other products; check labels for specific crops)

Blueberry and gooseberry only

Rate 1.6 to 2.4 lb ai/a (1.6 to 2.4 quarts/a 4L) Maximum seasonal use: 3.2 lb ai/a (3.2 quarts of product/a)

Time Apply in winter as single application, or apply 3.2 pints/a in October and again in March.

Remarks Reduce rate or rotate to other herbicides after achieving weed control. Sprinkler irrigate if applied before fall rains begin. Spray soil around base of plant, avoiding crop foliage.

Caution Do not use within 1 year after planting or on plants being tip layered. Do not apply on very sandy or gravelly soils. Can be rotated with simazine or other herbicides to reduce weed shifts. For use in western Oregon and western Washington.

Site of action Group 7: photosystem II inhibitor

Chemical family Substituted urea

flumioxazin (Chateau, Warfox)

Rate 0.19 to 0.38 lb ai/a (6 to 12 oz/a product)

Time Preferred timing is fall, to maximize potential of rain to activate the herbicide. In spring, apply no later than 7 days before harvest.

Remarks Supplemental label allows use west of the Cascades in Oregon and Washington, in specified counties, only. Apply to a weed-free surface. Flumioxazin has limited postemergence activity that can be enhanced by adding surfactants. Add 0.25% v/v nonionic surfactant or 1% crop oil concentrate to enhance postemergence burndown activity. Tank mix with herbicides such as glyphosate, glufosinate, or paraquat to kill large weeds. Residual weed control will be reduced if vegetation prevents the spray from reaching the soil. Moisture is necessary to activate the herbicide for residual weed control. Dry weather after application may reduce effectiveness. Do not exceed 12 oz/a per application and 12 oz/a per year. Use the 6 oz/a rate if soil has significant amount of sand or gravel.

Caution Do not apply to blueberries established less than 2 years. Avoid direct or indirect spray contact with foliage or green bark, particularly if using the 12 oz rate with surfactants. Do not apply to soils that are susceptible to dispersal by wind. This herbicide can move to susceptible crops on soil particles and cause damage. Do not apply within 300 yards of nondormant pears. Do not mow treated areas between budbreak and final harvest; dust created by mowing may injure susceptible plants.

Site of action Group 14: inhibits protoporphyrinogen oxidase (PPO)

Chemical family N-phenylphthalimide

hexazinone (Velpar DF)

Blueberry only

Rate 0.975 to 1.95 lb ai/a (1.3 to 2.6 lb/a Velpar DF) depending on blueberry type and soil type

Time Plants should be established for 3 years. Apply to pruned blueberry plants before leaves emerge in spring.

Remarks This herbicide can injure other crops in western Oregon. Consult label for all precautions including blueberries established at least 3 years or more. Preharvest interval is 90 days.

Site of action Group 5: photosystem II inhibitor

Chemical family Triazinone

indaziflam (Alion)

Rate 0.045 to 0.13 lb ai/a (3.5 to 5 fl oz/a Alion)

Time Apply late fall or early spring prior to bud swell. Apply as a directed application to the soil beneath the bushes.

Remarks For control of broadleaf and grass weeds. Do not allow spray to contact green stems or foliage, or unacceptable injury may occur.

Caution Do not apply more than 10 fl oz per year. Apply only to plants that have been in the ground one year or more. Rate is based on soil texture. Indaziflam is a persistent herbicide that may impact follow-crops if blueberries are taken out of production.

Site of action Group 29: disrupts cellulose biosynthesis

Chemical family Alkylazine

napropamide (Devrinol DF-XT, Devrinol 2-XT)

Rate 4 lb ai/a (8 lb/a Devrinol DF-XT, 8 quarts/a Devrinol 2-XT)

Time Apply fall through spring before weeds germinate, or apply foliar-active herbicide to control existing vegetation.

Remarks Irrigation or shallow incorporation is recommended for treatments made November through February if no rain falls within 2 weeks after application. Irrigate within 24 hours to wet soil 2 to 4 inches deep when applied March through October. Excessive plant residues on soil surface reduce performance (inhibits root growth).

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

Chemical family Acetamide

norflurazon (Solicam DF)

Blueberry only

Rate 1.95 to 3.93 lb ai/a (2.5 to 5 lb/a Solicam DF) depending on soil type

Time Apply as a directed spray from fall to early winter before weeds emerge.

Remarks Soil surface must be weed-free and relatively free of plant residues or debris. Multiple or sequential applications can be made, but total amount applied in any 12 months must not exceed the maximum rate listed on the label for that crop and soil texture. Inhibits yellow pigment formation, bleaching green chlorophyll. Preharvest interval is 60 days.

Caution Do not use on nursery stock.

Site of action Group 12: bleaching; inhibits carotenoid synthesis

Chemical family Pyridazinone

oryzalin (Surflan AS and Fugitive)

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

Time Apply late fall or early spring to bare soil or after existing vegetation has been destroyed by tillage or by a foliar-active herbicide.

Remarks Use higher rates, or apply split treatments in fall and spring for longer residual control. Irrigate with at least 0.5 inch of water or rain to activate herbicide. Shallow cultivation can control newly germinated weeds without reducing herbicide activity. Inhibits mitosis, primarily in roots.

Caution Do not apply to lowbush blueberries.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

pronamide (Kerb 50W, Kerb SC)

Blueberry only

Rate 1 to 2 lb ai/a (2 to 4 lb/a Kerb 50W; 2.5 to 5 pints Kerb SC) depending on target weed species

Time Apply once in fall or winter, preferably October to December when ground is not frozen.

Remarks Use lower rates on annual grasses, higher rates on perennial grasses such as quackgrass. Requires moisture from rain or irrigation to activate. Use only in berries established at least 3 months. Degraded by microorganisms at higher temperatures. Inhibits root growth.

Caution A restricted-use herbicide.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Benzamide

simazine (Princep)

Blueberry only

Rate 2 to 4 lb ai/a (2 to 4 quarts/a Princep 4L)

Time Apply in winter as single application, or split application with 2 quarts/a in spring and 2 quarts/a in the fall.

Remarks Reduce rate or rotate with other herbicides after achieving weed control. Requires surface moisture to activate. Can be rotated with diuron or other herbicides (except terbacil) to reduce weed shifts. Inhibits photosynthesis.

Caution Do not use on light-textured soils. Requires surface moisture to activate. Do not apply when berries are present because illegal residues may result.

Site of action Group 5: photosystem II inhibitor

Chemical family Triazine

S-metolachlor (Dual Magnum)

Highbush Blueberry only; Oregon and Washington

Rate 0.64 to 1.26 lb ai/a (0.67 to 1.33 pints/a Dual Magnum)

Time Prior to weed emergence, up to 28 days before harvest.

Remarks Special Local Needs labels OR-110005 and WA-120002. For control of grasses, small seeded annuals, and nutsedge. Applications should be directed to the soil surface in a 3 foot band on each side of the blueberry row. Avoid direct contact with the crop foliage or crop injury may occur. Use the lower end of the Dual Magnum rate range for soils that are relatively coarse textured and higher rates on fine textured soils. Dual Magnum will not control emerged weeds.

Caution Not all blueberry cultivars have been tested so injury may occur on some types of blueberry. Growers are encouraged to treat a few plants as a test and evaluate crop injury. Blueberry plants that have been established for less than one year may be more sensitive to applications of Dual Magnum than those plants established for more than one year.

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

Chemical family Acetamide

sulfentrazone (Zeus XC)

Rate 0.25 to 0.375 lb ai/a (8 to 12 fl oz/a Zeus XC)

Time Apply as a dormant application to bare soil in fall through spring, before weeds emerge.

Remarks Apply only to plants that have been in the ground at least 3 years. Requires 0.5 to 1.0 inch of water to activate within 14 days after application If weeds are present, tank mix with a burndown herbicide.

Caution Do not apply to frozen ground. Avoid direct or indirect contact with stems or foliage, particularly new emerging shoots from the crown. Do not apply more than 12 fl oz/a product (0.375 lb ai/a) per season. Do not tank mix with flumioxazin or other products containing sulfentrazone.

Site of action Group 14: inhibits protoporphyrinogen oxidase (PPO)

Chemical family Triazinone

terbacil (Sinbar)

Blueberry only

Rate 1.6 to 2.4 lb ai/a (2 to 3 lb/a Sinbar) depending on soil texture and organic matter content

Time Apply in fall after harvest or in spring to blueberries established at least 1 year and to seedling or emerging weeds.

Remarks Some growers have reported injury. Use product on small areas until you are satisfied with the results. Sprinkler irrigate if rain does not fall within 2 weeks. Reduce rates by as much as half, or rotate with other herbicides after achieving effective weed control. Calibrate sprayer and apply with tractor-mounted, fixed-boom sprayer using a constant speed and rate of delivery.

Caution Do not apply on gravelly soils, soils with less than 1% organic matter, or on weak plants or eroded areas with exposed roots. Avoid use for 2 years if replanting is anticipated. Can rotate with diuron or other herbicides (except simazine) to reduce weed shifts.

Site of action Group 5: photosystem II inhibitor

Chemical family Uracil