Blueberries, Gooseberries, Currants, and Elderberries

Ed Peachey
Revised March 2014

BLUEBERRIES, GOOSEBERRIES, CURRANTS, AND ELDERBERRIES—Weed and Vegetation Management

Mulches contribute significantly to weed control if constructed and maintained properly. Even without the benefit of weed control, blueberries grow well under mulch because they are shallow rooted and lacking root hairs. A layer of mulch over the soil conserves soil moisture for blueberries. Gooseberries, currants and elderberry are less likely to benefit directly from mulches compared to blueberries, but given the dearth of herbicides labeled for use in these crops, mulches may be essential to achieve weed control goals.

Mulches are usually constructed from sawdust, bark, wood chips, wood shavings, compost, and woven fabrics. Mulches made from these plant materials or compost are usually applied in a 2 to 4 (sometimes 6) inch layer after planting and will suppress emergence of most annual weeds. As the mulch matures, it may eventually become a haven for annual weeds. Perennial weeds will soon dominate if only using plant material mulches; therefore, it is imperative that perennial weeds be controlled before the crop is planted. An alternative is fabric weed barriers. These are costly, but if amortized over 10 to 12 years, may prove cost effective when considering accrued benefits, particularly in organic systems. Polyethylene mulches are less expensive but are not recommended because they restrict water movement to the roots and may promote surface rooting, making blueberry plants more susceptible to drought stress.

Flailing or mowing Frequently mowing improved turf grasses or perennial sods improves water infiltration and drainage in blueberry aisles. Vegetation between rows of other berries is mowed or flailed.

Herbicides Choose combinations of practices including herbicides that act together to achieve your desired level of vegetation management within berry plantings. Herbicides must be applied as directed on the label (time and rate), otherwise excessive herbicide residues may be present on fruit and jeopardize marketability, or crop injury may occur. DO NOT increase delivery rates of herbicides by slowing tractors or walking speed when there is a large patch of weeds. Slowing or stopping to wet-down the foliage of weeds (for example, Stinger herbicide applied to thistles) may cause excessive herbicide rates that may damage the crop.

BLUEBERRIES, GOOSEBERRIES, CURRANTS, AND ELDERBERRIES—Site Preparation

glyphosate (numerous products)

Rate Consult labels

Time Apply to weeds at least 10 days before planting crop.

Remarks Use highest rate on field bindweed. Inhibits production of three amino acids and protein synthesis.

Caution Do not apply to weeds stressed by drought, weather, or maturity. Rain within 6 hours after applying may reduce effectiveness.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

BLUEBERRIES, GOOSEBERRIES, CURRANTS, AND ELDERBERRIES—New Plantings

clethodim (Select Max, Arrow, and others for bearing crops, Envoy Plus, and others for nonbearing crops)

Rate 0.07 to 0.12 lb ai/A (9 to 16 fl oz/A Select Max for annual grasses; 12 to 16 oz/A Select Max for perennial grasses). Consult label for rate for other products.

Time Apply to actively growing grass weeds, including annual bluegrass, at labeled growth stage.

Remarks Read label carefully for adjuvant instructions, and for information about effects of rain within 1 hour, applications of other pesticides, or cultivation.

Caution Do not broadcast spray. Direct spray at base of the plant where grassy weeds are growing. Do not exceed 68 fl oz/A per season. Do not apply to non-bearing crops grown for rootstock.

Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor

Chemical family Cyclohexanedione

fluazifop (Fusilade DX)

Non-bearing only

Rate 0.25 to 0.38 lb ai/A (16 to 24 oz/A) depending on target weed species

Time Apply to actively growing grasses, or within 7 days after irrigation, as a directed spray with 1% crop oil or 0.25% nonionic surfactant.

Remarks Identify grasses and adjust rates depending on susceptibility and stage of weed growth as label instructs. Results often are erratic on grasses stressed from lack of vigor, drought, high temperature, or low fertility. More mature grasses and quackgrass can be controlled but may require two applications. Annual bluegrass and all fine fescues resist treatment. Inhibits fatty acid production, cell membranes, and new growth.

Caution Preharvest interval is 1 year. Grazing is prohibited.

Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor

Chemical family Aryloxyphenoxy propionate

glyphosate (numerous products)

Rate Consult label

Time Apply to actively growing weeds.

Remarks Avoid contact with green foliage or suckers of crop. Preharvest interval is 14 days.

Caution Do not exceed 12.8 pints/A product per year. Follow all precautions on label.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

isoxaben + trifluralin (Snapshot)

Non-bearing only

Rate 100 to 200 lb/A, depending on target weed

Time Apply during dormant season to crops that will not bear fruit for at least 1 year.

Remarks Apply evenly with drop or rotary-type spreader to avoid crop injury. Apply to weed-free soil. Controls many weeds that grow from seeds but will not control weeds that emerge from existing stolons, rhizomes, or root pieces. Control existing weeds with cultivation or postemergence herbicides. Activate within 3 days using 0.5 inch of water before weeds begin to emerge. See label for repeat treatments.

Caution Do not make repeat applications at 150 lb/A or greater within 60 days of a previous application. Do not apply when wind favors drift of granule from the target area.

Site of action (isoxaben) Group 21: inhibits cell wall biosynthesis Site B; (trifluralin) Group 3: microtubule assembly inhibitor

Chemical family (isoxaben) benzamide; (trifluralin) dinitroaniline

napropamide (Devrinol 50DF)

Blueberries and currants only

Rate 4 lb ai/A (8 lb/A Devrinol 50DF)

Time Apply after transplanting to firm soil, before weeds germinate or sawdust is spread.

Remarks On day of treatment, wet soil 2 to 4 inches deep to reduce degradation by sun and to activate herbicide. Where convenient, shallow mechanical incorporation appears to improve activation (inhibits root growth).

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

Chemical family Acetamide

norflurazon (Solicam)

Blueberries only

Rate 1.97 to 3.93 lb ai/A (2.5 to 5 lb/A) depending on soil type

Time West of the Cascades, immediately after planting. East of the Cascades, wait 6 months after planting before applying.

Remarks Soil surface must be weed free and relatively free of plant residues or debris. 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)

Rate 2 to 6 lb ai/A (2 to 6 quarts/A)

Time Apply after transplanting to firm soil, before weeds germinate or sawdust is spread.

Remarks Requires sprinkler irrigation, rain, or shallow cultivation (1 to 2 inches) for activation. Avoid exposure of transplant roots contacting treated soil. Inhibits mitosis, primarily in roots.

Caution Do not apply to lowbush blueberries.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

sethoxydim (Poast)

Blueberries only

Rate 0.19 to 0.47 lb ai/A (1 to 2.5 pints/A) depending on target weed species

Time Identify susceptible grasses and apply at optimum growth stage listed on the label.

Remarks Add 2 pints/A of a nonphytotoxic crop oil concentrate to improve leaf absorption. Control often is erratic if grasses are stunted or stressed from drought, high temperatures, or low fertility. Resistant grasses include annual bluegrass and all fine fescues; quackgrass can be suppressed. Inhibits fatty acid production, cell membranes, and new growth.

Caution Do not exceed 5 pints/A per season. Preharvest interval is 30 days.

Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor

Chemical family Cyclohexanedione

simazine (Princep)

Blueberries only

Rate 2 lb ai/A (2 quarts/A)

Time Apply in spring within 2 weeks after transplanting to firm soil before weeds are established.

Remarks Use lowest rate possible. Mix with low rates of other herbicides that have other types of action.

Caution Do not use on light-texture soils. Requires surface moisture to activate. Do not apply if berries are present.

Site of action Group 5: photosystem II inhibitor

Chemical family Triazine

BLUEBERRIES, GOOSEBERRIES, CURRANTS, AND ELDERBERRIES—Established Plantings—Winter or Dormant Applications that Persist in Soil

dichlobenil (Casoron)

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)

Blueberries only

Rate 1.96 to 3.92 lb ai/A (1.4 to 2.8 gal/A)

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)

Blueberries, gooseberries, and elderberries

Rate 1.6 to 2.4 lb ai/A (3.2 to 4.8 pints/A 4L)

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.

Site of action Group 7: photosystem II inhibitor

Chemical family Substituted urea

flumioxazin (Chateau)

Blueberries only

Rate 0.19 to 0.38 lb ai/A (6 to 12 oz/A Chateau WDG 51%)

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, West of the Cascades in Oregon and Washington in specified counties. Apply to a weed-free surface. Chateau has limited postemergence activity that is 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 or 24 oz/A per year. Use the 6 oz/A rate if soil has significant 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 non-dormant pears. Do not mow treated areas between budbreak and final harvest. Dust created by mowing may injure susceptible plants.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family N-phenylphthalimide

hexazinone (Velpar DF)

Blueberries only

Rate 0.975 to 1.95 lbs ai/A (1.3 to 2.6 lbs/A) 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

napropamide (Devrinol)

Rate 4 lb ai/A (8 lb/A)

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)

Blueberries only

Rate 1.97 to 3.93 lb ai/A (2.5 to 5 lb/A) 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)

Rate 2 to 6 lb ai/A (2 to 6 quarts/A)

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. Allow 24 months before planting vegetables after berries. 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)

Blueberries 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)

Blueberries only

Rate 2 to 4 lb ai/A (2 to 4 quarts/A 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)

Blueberries only; Oregon and Washington

Rate 0.64 to 1.26 lbs ai/A (0.67 to 1.33 pints/A)

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)

Time Apply to bare soil in fall through spring, before weeds emerge.

Remarks Only apply to plants that have been in the ground at least three years. Requires 0.5 to 1.0 inch of water to activate; if adequate rainfall or irrigation is not received within 7 to 10 days after application, a shallow incorporation may be needed to obtain desired weed control. Do not apply more than 12 fl oz product per acre (0.375 lb ai/A) per season. If weeds are present, tank mix with another burndown herbicide.

Caution Avoid direct or indirect contact with foliage or green bark, particularly new emerging shoots from the crown. Do not tank mix with Chateau.

Site of action protoporphyrinogen oxidase (PPO) inhibitor

Chemical family Triazolinone

terbacil (Sinbar)

Blueberries 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

BLUEBERRIES, GOOSEBERRIES, CURRANTS, AND ELDERBERRIES—Established Plantings—Directed Applications in or between Berry Rows with Soil Residual

halosulfuron-methyl (Sandea)

Blueberries only

Rate For plants 1 to 4 years old: 0.023 to 0.031 lb ai/A (0.5 to 0.67 oz/A); for plants 4 years or older: 0.023 to 0.047 lb ai/A (0.5 to 1 oz/A)

Time Preemergence or postemergence (nutsedge control)

Remarks For nutsedge control, make a single postemergence application of 0.75 oz/A minimum to nutsedge that has 3 to 5 leaves. Two applications are permissible if additional nutsedge plants emerge, but allow 45 days between applications. Do not irrigate for 3 to 4 days after application to maximize efficacy. Add a non-ionic surfactant to improve activity. Preharvest interval is 14 days. Sandea also can be applied preemergence to control annual weeds including marestail and common groundsel. Preemergence control of nutsedge is poor.

Caution Do not let spray contact blueberry bushes. Do not apply more than 2 oz/A per year. Do not apply to plants less than 1 year old, or concentrate the spray in the crop row.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Sulfonylurea

mesotrione (Callisto)

blueberries only

Rate 0.094 to 0.188 ai/A (3 to 6 fl oz/A)

Time Prebloom, post-directed spray.

Remarks Supplemental label. May be applied as a split application, but no more than 6 oz/A per year. Use crop oil concentrate at 1% v/v to enhance weed control. Separate applications by 14 days. Has both burndown and soil-residual activity. Controls many broadleaf weeds, but controls few grasses and no perennial weeds.

Caution Applying after the onset of bloom may result in illegal residues.

Site of action Group 28: inhibits 4-hydroxyphenylpyruvatedioxygenase (4-HPPD)

Chemical family Triketone

rimsulfuron (Matrix SG)

Blueberry only in OR and WA

Rate 0.0625 lb ai/A (4 oz/A Matrix SG)

Time Apply in spring or fall, preemergence or early postemergence, to actively growing weeds.

Remarks Use a directed spray application and minimize spray contact with blueberry plants. Use only in berries that have gone through one growing season, and are in good health. Preharvest interval is 21 days.

Caution Do not exceed one application per year. When applied as a banded treatment (50% band or less), Matrix SG may be applied twice per year.

Site of action Group 2: Acetolactate synthase (ALS) inhibitor

Chemical family Sulfonylurea

BLUEBERRIES, GOOSEBERRIES, CURRANTS, AND ELDERBERRIES—Established Plantings—Burndown and Directed Applications in or between Berry Rows without Soil Residual

2,4-D (Saber)

Highbush blueberries only

Rate 1.4 lb ae/A (3 pints/A Saber)

Time Apply labeled rate in 50 gal/A water, as a directed spray to the weed or grass strip between rows. Avoid contact with blueberry foliage.

Remarks Special local needs labels OR-050016 and WA-010009. Apply in spring and fall, depending on broadleaf weeds present. Preharvest interval is 30 days.

Caution Do not apply if temperature is expected to exceed 65ºF. Avoid drift within the field and to adjacent crops.

Site of action Group 4: synthetic auxin

Chemical family Phenoxy acetic acid

acetic acid (Weed Pharm)

Rate 15 to 30 gal product/A

Remarks 20% acetic acid. Apply as a directed application to actively growing small weeds. Application equipment must be hooded or shielded. Any contact with the crop will cause crop injury. Weed Pharm can be applied up to and including the day of harvest. Approved for organic production.

Caution This product is a contact, nonselective, herbicide. Avoid contact with desirable foliage, green bark, or fruit. Causes irreversible eye damage. Wear goggles or face shield.

carfentrazone (Aim)

Hooded spray between rows

Rate 0.016 to 0.031 lb ai/A (1 to 2 fl oz/A in at least 10 gal/A of water)

Time Apply to weeds less than 4 inches tall for best results.

Remarks Apply with hooded sprayers between rows at speeds less than 5 mph. Use nonionic surfactants, crop oil concentrates, or methylated seed oils combined with liquid nitrogen fertilizer to improve efficacy. Aim can be applied up to and including the day of harvest.

Caution Must prevent spray from contacting green stem tissue, foliage, blooms, or fruit. Hooded sprayers must totally enclose the spray pattern.

Site of action Group 14: inhibits protoporphyrinogen oxidase

Chemical family Triazinone

clethodim (Select Max, Arrow, and others)

Rate 0.07 to 0.12 lb ai/A (9 to 16 fl oz/A Select Max for annual grasses; 12 to 16 oz/A Select Max for perennial grasses)

Time Apply to actively growing grass weeds, including annual bluegrass, at labeled growth stage.

Remarks Preharvest interval is 14 days. Read label carefully for adjuvant instructions, and for information about effects of rain within 1 hour, applications of other pesticides, or cultivation. Minimum of 14 days between applications.

Caution Do not broadcast spray. Direct spray at base of the plant where grassy weeds are growing. Do not exceed 64 fl oz/A per season.

Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor

Chemical family Cyclohexanedione

clopyralid (Stinger)

Blueberries only; OR and WA

Rate 2.66 to 5.33 fl oz/A (0.063 to 0.125 lb ae clopyralid/A) depending on weed species present. Make a maximum of two applications with total usage not to exceed 10.6 fl oz/A or 2/3 pint/A per season.

Time Up to 30 days before harvest, or after last harvest.

Remarks Blueberry plants are most sensitive to Stinger when applied in the spring, during the crop’s annual flush of growth and prior to bloom. Blueberries are less sensitive after bloom has ended. Canada thistle, clover, and weeds of the Asteraceae family (dandelion, sowthistle) are controlled. Directed Spray Treatment: Apply Stinger uniformly as a spray at 2.67 to 5.3 fl oz/A directed to the soil, and away from the blueberry plants to the row middle without contacting the foliage or woody portions of blueberry plants. Apply with ground broadcast equipment, backpack sprayer, or wipe applicator in a total spray volume of a minimum of 10 gal/A. Spot Treatment: Hand-held sprayers may be used for spot applications, but care should be taken to apply Stinger at the proper rate per unit area. Do not concentrate the herbicide on the soil. Wipe Treatments: For wipe treatments, apply 2% solution of Stinger in water (2.5 fl oz or 75 mL/gal).

Caution Consult SLN labels OR-100011 and WA-100005 before applying to become familiar with situations that will increase the chance of injury to blueberries. Do not permit Stinger to contact desirable foliage because crop injury will result. Apply spray uniformly over the area to be treated, rather than concentrating the spray onto targeted weeds. Do not apply Stinger during the time from one week prior to bloom until one week after bloom. After bloom, apply Stinger up until 30 days prior to harvest. Do not apply within 30 days of harvest.

Site of action Group 4: synthetic auxin

Chemical family Pyridine

clove or clove leaf oil (Matran EC, Matratec)

Rate 5 to 8% dilution in 25 to 100 gal of water, depending on weed size, temperature, and sunlight intensity.

Time Before weeds are 6 inches tall.

Remarks OMRI listed and WSDA approved herbicide for in-crop use. Apply before crop emerges, or between rows after emergence; avoid contact with desirable foliage. Directed sprays or hooded sprayers are recommended to protect desirable foliage. Works best on annual weeds less than 6 inches. Performance may be erratic depending on environmental conditions. Bright sunlight improves efficacy. No preharvest or re-entry interval.

glufosinate (Rely 280)

Rate 0.88 to 1.5 lb ai/A (1.5 to 2.5 quarts/A) depending on target weed species and size

Time Apply to small, actively growing weeds

Remarks Apply as a directed spray to weeds, avoiding contact with blueberry foliage. Avoid direct spray or drift to desirable vegetation.

Caution Do not apply to green bark on young bushes, or injury will occur. Do not allow glufosinate to contact new emerging shoots. Do not exceed 5.1 quarts/A of Rely 280 (3 lb ai/A) to berry bushes in a 12-month period. Preharvest interval is 14 days.

Site of action Group 10: inhibits glutamine synthase

Chemical family Phosphinic acid

glyphosate (several products)

Rate Broadcast or directed spray: Consult labels

Remarks Select application equipment to prevent crop injury by directing spray or by using selective applicators. Adjust concentration depending on equipment. Consult label about rate and time of application, especially for perennial weeds. Additional surfactant, or mixing ammonium sulfate as label instructs, may improve control of slightly stressed weeds. Inhibits production of three amino acids and protein synthesis. Preharvest interval is 14 days.

Caution Do not allow drift or mist to contact green foliage or bark, suckers, or vines and renewals less than 3 years old. When repeat applications are necessary, do not exceed 10.6 lb ai/A per year. Repeated glyphosate applications have created resistant biotypes of annual ryegrass in Oregon orchards. To avoid weed resistance, rotate and mix weed control practices.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

glyphosate (several products)

Rate Wiper: 33% solution

Time Apply 1 gal product with 2 gal water and wipe weeds; avoid contact with desirable vegetation.

Remarks In severe infestations, reduce equipment ground speed or apply in two directions to ensure contact with wiper. (See remarks above.) Preharvest interval is 14 days.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

limonene (lemongrass oil) (Green Match)

Rate 14% dilution rate, 20% for spot treatment of difficult to control weeds.

Time Up to first fruit set, when weeds are less than 6 inches tall.

Remarks Broadspectrum, non-selective contact herbicide that does not translocate. Spot treatments allowed in bearing crops up to one week before harvest. Do not exceed 8.5 gal/A per application in bearing crops. Most effective on annual weeds. OMRI listed, NOP compliant, and WSDA approved organic burndown herbicide for use in crop and non-crop sites. Foliage contacted by Green Match will be damaged. Directed sprays or hooded sprayers are recommended to protect desirable foliage. Coverage is very important. Leaf damage is visible within hours. Cool weather may slow activity. No re-entry interval. Fast wilting or necrosis of the leaves due to removal of waxy cuticle.

sethoxydim (Poast)

Blueberries only

Rate 0.19 to 0.47 lb ai/A (1 to 2.5 pints/A) depending on target weed species

Time Identify susceptible grasses and apply at optimum growth stage listed on label.

Remarks Add 2 pints/A of a nonphytotoxic crop oil concentrate to improve leaf absorption. Control often is erratic on grasses stunted or stressed from drought, high temperatures, or low fertility. Resistant grasses include annual bluegrass and all fine fescues; quackgrass can be suppressed. Inhibits fatty acid production, cell membranes, and new growth. Preharvest interval is 30 days.

Caution Do not exceed 5 pints/A per season.

Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor

Chemical family Cyclohexanedione