Onion and Garlic

Agricultural pest management


Field bindweed, Convolvulus arvensis.

Herbicide Treatment Table

(Reviewed 1/07, updated 5/10, pesticides updated 6/16)

In this Guideline: More about weeds in onion and garlic:

Herbicide Amount per acre REI‡ PHI‡
(Example trade name)   (hours) (days)

UPDATED: 6/16
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Bee precaution pesticide ratings
The following are listed alphabetically. When choosing a pesticide, consider information relating to environmental impact, resistance management (PDF), the pesticide's properties, and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
PREPLANT
 
A. GLYPHOSATE 1–4 lb a.i.   
  (Roundup Ultra) 1–4 qt 12 NA
  WSSA MODE-OF-ACTION GROUP NUMBER1: 9
  COMMENTS: A nonselective, foliar herbicide applied before planting to pre-made beds to kill emerged weeds. Can be used before planting or after planting but before the crop emerges. Allow 3 days after spraying before planting. Use the lower rate for annual weeds, the higher rate on perennial weeds. Consult the label for specific recommendations on particular weed species. Do not apply to weeds stressed for moisture or weeds with significant dust. For perennial weeds, allow 7 days after application before cultivating.
 
B. METAM SODIUM* 50–75 gal See label NA
  (various products)
  COMMENTS: Beds must be free of large clods and the soil should be moistened by rainfall or irrigation before application. Soil temperatures should be between 40° to 90°F at the 3-inch depth. Broadcast rate is 50 to 75 gal /acre but if only the planted row is to be fumigated, reduced rates can be used depending on the number of rows to be planted per bed. Applications are made using a spray blade cutting 2 to 3 inches below the soil surface, depending on soil moisture. Disk hillers follow directly behind the spray blade to form a 3- to 5-inch soil cap over the treated area. After 7 to 14 days, depending on the rate applied, the soil caps are removed and allowed to air. The label requires a 14-day interval between application and planting. Avoid moving untreated soil into the banded area. This fumigant is effective against nightshade and many other weeds. Other methods of application include shank and drench application. Fumigants such as metam sodium are a source of volatile organic compounds (VOCs) but are minimally reactive with other air contaminants that form ozone.
 
C. PARAQUAT* 0.625–1 lb a.i.   
  (Gramoxone SL 2.0) 2.5–4 pt 12 200
  WSSA MODE-OF-ACTION GROUP NUMBER1: 22
  COMMENTS: A nonselective foliar herbicide that kills emerged weeds. Can be used before planting or after planting but before the crop emerges. Any crop plants exposed to the spray will be killed, even germinating seed in the crook stage. No soil residual activity. Use the lower rate on small broadleaf weeds, the higher rate on larger weeds. Highly toxic if ingested; wear protective clothing. Faster acting on warm, sunny days. For use on seeded onions and garlic.
 
AT SEEDING OR TRANSPLANTING
 
A. DCPA 4.5–10.5 lb a.i.   
  (Dacthal Flowable) 6–14 pt 12 NA
  WSSA MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: Apply at planting to control annual grasses and some annual broadleaf weeds. DCPA can be sprayed directly over transplants without injury
 
POSTPLANT
Before crop and weeds emerge
 
A. ETHOFUMESATE
  (Ethofumesate 4SC) 16–32 fl oz 12 30 (+/-2)
  WSSA MODE-OF-ACTION GROUP NUMBER1: 8
  COMMENTS: For use on onions. Apply preemergence. Use lower rates on coarse-textured soils and higher rates on fine-textured soils for preemergence applications. Do not exceed 48 floz on coarse-textured soils and 96 floz on fine-textured soils in one season.
 
Crop established
 
A. BENSULIDE 4 lb a.i.   
  (Prefar 4-E) 4 qt 12 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 8
  COMMENTS: Registered for use on bulb onions and garlic, but recommended only for onions in California. Do not incorporate by mechanical methods.
 
B. BROMOXYNIL Onion: 0.25–0.375 lb a.i.
Garlic: 0.375–0.5 lb a.i.
   
  (Buctril 4EC) Onion:0.5–0.75 pt
Garlic: 0.75–1.0 pt
24 Onion: —
Garlic: 112
  WSSA MODE-OF-ACTION GROUP NUMBER1: 6
  COMMENTS: Very good for control of shepherd's purse, mustard species and Russian thistle. Chemigate or apply by ground when onions have 2 to 4 true leaves. Use at least 50 gal water in spray mix (lower than this amount concentrates the spray mixture and can cause crop damage). Foliage needs to be dry at the time of application. Other conditions can lead to crop injury; consult label before application. Can be used in sequence with oxyfluorfen; use lower rates than those listed in tank mixes.
 
C. CLETHODIM 0.091-0.2425 lb a.i.   
  (Select Max) 12–32 fl oz 24 45
  WSSA MODE-OF-ACTION GROUP NUMBER1: 1
  COMMENTS: Labeled for use on onion (dry bulb only), garlic, and shallots. Controls annual bluegrass in the 2- to 3-leaf stage as well as other annual and some perennial grasses. Do not apply through any type of irrigation system. Always apply with a crop oil concentrate. Use higher rate on perennial grasses.
 
D. DIMETHENAMID 0.5625–0.9843 lb a.i.   
  (Outlook) 12–21 fl oz 12 30
  WSSA MODE-OF-ACTION GROUP NUMBER1: 15
  COMMENTS: Provides yellow nutsedge and broadleaf weed control. Apply at or after the second true leaf stage of onions but before nutsedge emerges. Do not exceed a total maximum of 21 fl oz/acre in a single growing season. Use lower rates on coarse-textured soils and higher rates on fine-textured soils.
 
E. ETHOFUMESATE 0.5 lb a.i.   
  (Ethofumesate 4SC) 16 fl oz 12 30 (+/-2)
  WSSA MODE-OF-ACTION GROUP NUMBER1: 8
  COMMENTS: Up to four foliar applications after crop emergence at evenly spaced intervals can be made; do not apply more than 0.75 gal per season.
 
F. FLUAZIFOP-P-BUTYL
  (Fusilade DX) Label rates 12 45
  WSSA MODE-OF-ACTION GROUP NUMBER1: 1
  COMMENTS: For use on dry bulb onions and garlic. A selective, foliar herbicide for control of grasses. A surfactant (crop oil concentrate or nonionic surfactant) is recommended. Safe to the crop. Not effective on drought-stressed grasses or on certain species (e.g., annual bluegrass, foxtail, sprangletop).
 
G. OXYFLUORFEN 0.12–0.25 lb a.i.   
  (Goal 2XL) See label 48 Onions: 45; Garlic: 60
  (GoalTender 4F) See label 48 Onions: 45; Garlic: 60
  WSSA MODE-OF-ACTION GROUP NUMBER1: 14
  COMMENTS: In onion, chemigate or apply Goal 2XL by ground when onions have 2 to 4 true leaves; GoalTender can be applied at the first true leaf stage. GoalTender is less active as a burndown herbicide and is most effective on young weeds; it causes less damage to crop foliage than the 2XL formulation. Will control some small annual grasses postemergence. Goal has some residual soil activity after application. Very good for control of little mallow (cheeseweed). In garlic, apply as a directed spray before the last irrigation. Controls nightshade. Will damage foliage if it gets on the garlic crop. Garlic must be at least 12 inches in height and weeds should be in the seedling stage and actively growing.
 
H. PENDIMETHALIN 0.5–1.5 lb a.i.   
  (Prowl 3.3 EC) 1.2–3.6 pt 24 60
  (Prowl H20) 1–3 pt 24 60
  WSSA MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: For use on garlic, shallots, and bulb onions. Apply after planting garlic, chemigate or incorporate with sprinklers or a heavy furrow irrigation. Will control many broadleaf weeds and annual grasses. The two formulations of pendimethalin have different application timings: Apply Prowl 3.3 EC between 2 to 6 true leaf stage (shallots/onions) and 1 to 5 true leaf stage (garlic). Prowl H20 has a Special Local Needs registration and can be applied at the loop stage in direct-seeded dry bulb onions. Application rates depend on soil type with lower rates for coarse-textured soils and higher rates for fine-textured soils; do not use on muck soils.
 
I. SETHOXYDIM 0.09–0.28 lb a.i.   
  (Poast) 0.5–1.5 pt 12 30
  WSSA MODE-OF-ACTION GROUP NUMBER1: 1
  COMMENTS: A selective, foliar herbicide for control of grasses. A surfactant (crop oil concentrate or nonionic surfactant) is recommended. Safe to the crop. Not effective on drought-stressed grasses or on certain species (e.g., annual bluegrass, sprangletop).
 
Layby
A. DCPA 4.5–10.5 lb a.i.   
  (Dacthal Flowable) 6–14 pt 12 NA
  WSSA MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: Labeled for layby applications in onion. Cultivate before application to remove emerged weeds. Do not apply over the top of crop. Good control of annual grasses and some annual broadleaf weeds. Do not incorporate mechanically.
 
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
1 Group numbers are assigned by the Weed Science Society of America (WSSA) according to different modes of action. Although weeds may exhibit multiple resistance across many groups, mode-of-action numbers are useful in planning mixtures or rotations of herbicides with different modes of action.
No information
NA Not applicable.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Onion and Garlic
UC ANR Publication 3453

Weeds

R. Smith, UC Cooperative Extension, Monterey County
S. A. Fennimore, Vegetable Crop and Weed Science, UC Davis and Salinas
S. Orloff, UC Cooperative Extension, Siskiyou County

Acknowledgment for contributions to Weeds:
C. E. Bell, UC Cooperative Extension, San Diego County
D. W. Cudney, Botany and Plant Sciences, UC Riverside
G. J. Poole, UC Cooperative Extension, Los Angeles County

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