bromoxynil (Broclean, Brox 2EC, or Moxy 2E)
Idaho and east of the Cascades, dry bulb onions only
Rate 0.25 to 0.375 lb ai/A (1 to 1.5 pints/A) for Broclean, Brox 2EC, Moxy 2E.
Time Apply in 50 to 70 gal water for thorough coverage when onions and garlic have two to five true leaves. Apply on sunny days when plants are dry and humidity is low.
Remarks Use not restricted from W OR for garlic
Caution Do not ingest or inhale spray mist. Prevent contact with skin. Wear protective face shields, respirators, and coverall clothing over long-sleeved shirt and long pants. Do not apply west of the Cascades or when protective waxy cuticle on onion leaves may be thin or damaged. Do not add adjuvants. Injury can sometimes occur, even under ideal conditions. Read the label on precautions and restrictions.
Site of action Group 6: photosystem II inhibitor
Chemical family Nitrile
Bicyclopyrone (Optogen)
Dry bulb, garlic, and green onion
Rate 0.034 to 0.0457 lb ai/a (2.6 to 3.5 fl oz/a)
Time Apply pre-emergence, postemergence as either a row middle or post-directed application to weeds < 4-leaf and 2 inches tall.
Remarks Preemergent and postemergent control of pigweed, common lambsquarters, galinsoga, nightshade, henbit, and purslane. Add a nonionic surfactant (NIS) at 1 qt/100 gallons of water (0.25% v/v) or a crop oil concentrate (COC) at the rate of 1 gal/100 gallons of water (1.0% v/v). In addition to NIS or COC, dry spray grade ammonium sulfate (AMS) may be added at a rate of 8.5 to 17 lb/gal of water.
Caution Avoid contacting the dry bulb, garlic, or green onion foliage during application or crop injury will occur. Using a hooded or shielded sprayer will minimize potential crop injury when applying as row middle or post-directed applications.
Site of action Group 27: inhibits 4-hydroxyphenylpyruvatedioxygenase (4-HPPD)
Chemical family Triketone
carfentrazone (Aim)
Rate Up to 0.031 lb ai/A (0.5 to 2 fl oz/A Aim EC) per application in at least 10 gal/A of finished spray
Time Apply (postemergence only) with hooded sprayer between rows of emerged crop.
Remarks See the table of approved uses on vegetable crops under "Selective Postemergence Applications" at the beginning of Section P. Vegetable Crops in this handbook. Hooded sprayers must prevent spray from reaching green stem tissue, foliage, blooms, or fruit of the crop. Do not use for preplant burndown on fields intended for bulb vegetables.
Site of action Group 14: protoporphyrinogen oxidase inhibitor
Chemical family Triazinone
clethodim (Select Max or Select 2EC, Shadow, and various generic names)
Dry bulb onions, garlic, and shallots only
Rate 0.098 to 0.25 lb ai/A (Select 2EC at 6 to 16 fl oz/A) or 0.068 to 0.121 lb ai/A (Select Max at 9 to 16 fl oz/A) Consult labels for information on dry bulb onion and shallots.
Time Apply to actively growing grass weeds, including annual bluegrass, at growth stage on label.
Remarks Carefully read label for adjuvant instructions and about effects of rain within 1 hr, applying other pesticides, or cultivation. Application should be made in a minimum of 20 gal spray solution per acre. May be applied to onions and garlic using sprinkler irrigation systems. Do not apply using chemigation in ID, OR, and WA.
Caution Consult labels for maximum rates per application and season. Preharvest interval is 45 days for dry bulb onions, garlic, and shallots. Applications to dry bulb onions or shallots should be made in a minimum of 20 gal of spray solution per acre.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Cyclohexanedione
fluazifop (Fusilade DX)
Dry bulb onions only
Rate 0.125 to 0.376 lb ai/A (8 to 24 oz/A) depending on target weed species and growth stage.
Time Apply to actively growing grasses with 0.5 to 1% crop oil, or 0.25 to 0.50% nonionic surfactant. Results often are erratic on grasses stressed from lack of vigor, drought, high temperature, or low fertility. Do not apply more than 48 fl oz/A in total per season. Maintain a minimum of 14 days between applications. Use sufficient spray volume (20 to 40 gal/A) to ensure complete coverage of target grasses. When grass foliage is dense, use a minimum of 20 gal/A.
Remarks Identify grasses; adjust rates depending on susceptibility and stage of weed growth as label instructs. 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 45 days. Do not exceed 3 pints/A per year. Grazing is prohibited.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Aryloxyphenoxy propionate
fluroxypyr (Starane Ultra)
Dry bulb onions only
Rate 0.122 to 0.244 lb ae/A (0.35 to 0.7 pints/A product)
Time Apply broadcast postemergence from the two true-leaf stage though the six-leaf stage. Weeds should be 4 to 8 inches tall.
Remarks SLN labels OR-210010, ID-080007, and WA-080008 (Starane Ultra) for control of kochia, volunteer potatoes, common purslane, and other susceptible broadleaf weeds. Adjuvants are not recommended. Heavy flushes of weeds can be controlled with two sequential applications at 10- to 14-day intervals. Do not exceed 0.7 pint/A, or two applications, per year.
Caution Crop injury may occur with some onion varieties. Do not broadcast after the six-leaf stage. Applications after the six-leaf stage should be made as a directed spray with drop nozzles (consult the label for the warning). Do not apply through any type of irrigation system. Preharvest interval is 42 days.
Site of action Group 4: synthetic auxin
Chemical family Pyridine
paraquat (Gramoxone SL 2.0 and 3.0)
Rate 0.63 to 1 lb cation/A (2.5 to 4 pints/A Gramoxone SL 2.0)
Time Apply before, during, or after planting but before crop emerges, to control emerged weed seedlings only.
Remarks Add a nonionic surfactant or crop oil concentrate according to label specifications, taking care to avoid anionic formulations that react in the tank to form insoluble precipitates. Acts as contact; absorbs energy from photosynthesis, forming peroxides that disrupt living cells.
Caution Restricted use pesticide due to acute toxicity. For retail sale to and use only by certified applicators -not to be used by uncertified persons working under the supervision of a certified applicator. Do not ingest or inhale spray mist. Wear protective equipment as indicated on the label. Do not exceed 4 pints/A per season (Gramoxone 3 SL). Preharvest interval is 60 days.
Site of action Group 22: photosystem 1 electron diversion
Chemical family Bipyridilium
pendimethalin (Prowl H2O or Prowl 3.3EC, Framework 3.3EC, Satellite HydroCap and other trade names)
Dry bulb onion and shallots, direct-seeded and transplanted
Rate 0.6 to 1.24 lb ai/A (1.5 to 3.0 pints/A Prowl H2O) or 0.74 to 1.49 lb ai/A (1.8 to 3.6 pints/A Prowl 3.3EC) depending on soil texture. May be applied at 1.42 to 1.9 lb ai/A (3 to 4 pints/A Prowl H2O) or 1.48 to 1.98 lb ai/A (3.6 to 4.8 pints/A Prowl 3.3EC) for dodder control on medium- and fine-textured soils in Oregon, Idaho, and Washington. The indicated rate is for all uses, regardless of application timing (delayed preemergence [Prowl H2O only SLNs] or postemergence).
Time Apply Prowl 3.3EC between the flag leaf to ninth true-leaf stage. DO NOT apply Prowl 3.3EC using chemigation at the dodder control rate. Do not irrigate in excess of 0.5 inch of water.
Remarks Prowl H2O and Prowl 3.3EC may be applied by ground, air, or chemigation (only to direct-seeded, transplanted dry bulb onions and shallots). May be applied through sprinkler irrigation systems (only to direct-seeded, transplanted onions and shallots). Follow all directions, special instructions, and precautions about chemigation in the spraying instructions section of the main labels. Adjust rates according to soil texture. Rain or overhead irrigation is needed within 10 days of application. Inhibits mitosis in shoots and in roots.
Caution Be aware of crop rotation restrictions, including those for sugar beet, winter wheat, and winter barley. Do not apply within 45 days before harvest. Do not exceed the maximum rate per season regardless of application timing (delayed preemergence or postemergence).
Site of action Group 3: microtubule assembly inhibitor
Chemical family Dinitroaniline
pyroxasulfone (Zidua SC)
Dry bulb onion (direct-seeded and transplanted) and leeks (transplanted only)
Rate 0.065 to 0.09 lb ai/A (2 to 2.75 fl oz/A Zidua SC) depending on soil texture. Only to be used on medium to fine textured mineral soils and muck soils (greater than 20% organic matter) to control annual grassy weeds, sedges, and annual broadleaf weeds. The indicated rate is only for postemergence application to dry bulb onions (direct-seeded and transplanted) and leek (transplanted only).
Time Apply Zidua SC postemergence only at the two leaf to sixth true-leaf stage. Zidua SC does not control emerged weeds.
Remarks Use of Zidua SC may result in temporary growth suppression, leaf burn, and/or other injury or stand reduction to dry bulb onions or leek under stressful conditions including inadequate or excessive moisture, extended periods of water saturated soil conditions occurring during early transplant growth and development, cold and hot temperatures, compacted soils, injury from other pesticides, disease or other pest damage, mechanical injury, nutrient imbalances, or other conditions known to cause plant stress. Zidua SC may be tank mixed or applied sequentially with other postemergence herbicides registered for use in dry bulb onions or leek for a broader spectrum of control and/or control of emerged weeds. Follow the adjuvant directions for the tank mix partner of Zidua SC. Adjust rates according to soil texture, but do not use on coarse textured soils. User must possess the supplemental label and the main Zidua SC herbicide container label at the time of application.
Caution Do not apply within 60 days before harvest of dry bulb onion or leek. Do not apply Zidua SC to direct-seeded leek. Do not exceed the maximum rate of 2.75 fl oz/A per season. Do not use on coarse textured soils.
Site of action Group 15: very long chain fatty acid synthesis
Chemical family Chloroacetamide
sethoxydim (Poast)
For dry bulb onion and green onions, garlic, leek, and shallots
Rate 0.19 to 0.28 lb ai/A (1 to 1.5 pints/A) depending on target grass species and growth stage
Time Apply at optimum growth stage as on label.
Remarks Identify susceptible grasses, and add 2 pints/A nonphytotoxic crop oil concentrate to improve leaf absorption. Results often are erratic if grasses are stressed from lack of vigor, drought, high temperature, or low fertility. Resistant grasses include annual bluegrass and all fine fescues, but quackgrass can be suppressed. Inhibits fatty acid production, cell membranes, and new growth. Do not exceed 4.5 pints/A per season.
Caution Preharvest interval is 30 days. Do not exceed 4.5 pints/A per season.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Cyclohexanedione
trifluralin (Treflan TR-10 and other trade names)
Dry bulb onions only
Rate 0.38 to 0.63 lb ai/A (3.75 to 6.26 lb/A broadcast rate)
Time Apply at layby as a directed spray to the soil between rows, and incorporate immediately with sweeps or rolling cultivators. Avoid applying directly to the tops or exposed bulbs of onion plants.
Remarks Use proportionately less when treating area between rows only. Inhibits mitosis in shoots and roots.
Caution Do not apply to soils with more than 3.5% organic matter, because effectiveness will be reduced. Do not apply preplant or preemergence. Preharvest interval is 60 days. Remove emerged weeds before applying. See label for planting sensitive crops within 12 months.
Site of action Group 3: microtubule assembly inhibitor
Chemical family Dinitroaniline