An integrated weed management program is essential for cilantro and leaf parsley production because both crops suffer severe yield loss due to weed competition. There are many challenges to weed management in cilantro and parsley including:
- Slow germination and, therefore, poor early season crop competition with a diversity of weeds
- Thin, feathery leaves and short plant height do not make cilantro and parsley very competitive with weeds
- High-density plantings limit the use of mechanical cultivation and make hand removal expensive
- Mechanical harvest requires a weed-free crop
- Current choices of herbicides for use in cilantro do not provide adequate control of all weeds in the crop
As a consequence, weed management costs can be very high in cilantro and parsley unless weed control programs are carefully planned and implemented. Preplant preemergence herbicides are most commonly used. The choice of herbicide depends upon the weed species that are expected to occur, which necessitates careful monitoring and record keeping. Plantback restrictions need to be considered when selecting herbicides because soil residues of some products can limit the growth of sensitive rotational crops. Herbicide labels are the best source of information regarding plantback restrictions (i.e. rotational intervals). Nonchemical options include solarization and flaming. Cilantro and parsley have a relatively long germination period that allows for the use of flaming during a short window prior to emergence of the crop, but after weeds have emerged.
Only the furrows and bed shoulders are cultivated because the bed top (usually 40 or 80 inches wide) is completely planted. Additionally, because of the high-density planting, handweeding can be expensive and can seriously damage the crop by removing it along with the weeds.
Monitor fields and keep records of the weed species that occur in each field during the period of the year when the crop will be grown. Records of weeds occurring prior to planting time are especially important. Not only are these records valuable in planning which fields should be used to grow cilantro or parsley, they also help track the occurrence of hard-to-control weeds. Avoid fields with high numbers of weeds such as sowthistle, shepherd's-purse, nightshades, and nutsedge.
WEED MANAGEMENT BEFORE PLANTING
Avoid planting cilantro and parsley in fields with known infestations of perennial weeds as available herbicides do not effectively control them. To prevent the buildup of weed seed in the soil, prevent weed seed production in prior rotational crops. After harvest of the rotational crop, maintain the field weed free to prevent weed seed set during the fallow period. In a typical farm mix of crops, cilantro and parsley should be planted in the most weed-freefields.
About 2 weeks before planting cilantro or parsley, preirrigate the field to germinate weed seedlings and cultivate to destroy them. Carry out this operation as close to planting time as possible to maximize the number of weeds germinated and controlled. Cultivate as shallow as possible to avoid bringing up ungerminated weed seed from deeper soil layers.
Metam sodium is used for control of soilborne fungal pathogens and nematodes. It will also kill emerged weeds, ungerminated weed seeds that have absorbed water, and nutsedge shoots. Pre-plant applications are made about 2 weeks after a pre-irrigation event. Typical application is made with spray blades or through solid-set sprinklers. The minimum time allowed between application and planting the crop is 14 days and can be up to 60 days depending upon environmental conditions. Buffer zones are required for this material, so planning ahead is important.
Glyphosate (Roundup) can be used to control emerged weeds just before planting or before the crop emerges. Be sure the crop has not emerged, however, because emerged plants will be killed if contacted by this herbicide. Glyphosate has been particularly helpful in controlling perennial weeds when used as a preplant treatment.
Wind dispersed species such as horseweed and fleabane can aerially deposit seed and germinate in cilantro and parsley fields at any time during the production cycle. Control these weeds in areas surrounding the field, paying particular attention to efficacy since these weeds can be resistant to glyphosate.
WEED MANAGEMENT AFTER PLANTING
Weeds must be controlled in a cilantro and parsley fields throughout the growing season, thereby requiring some post-plant control measures. An herbicide is generally applied before or after the crop emerges, depending on the weed species to be controlled. Generally, handweeding or other cultural practices are needed before harvest for weeds not controlled by herbicides or cultural practices during the crop season.
Linuron (Lorox DF) and prometryn (Caparol 4L) are used for preemergence applications; be careful not to exceed label recommendations on rate. These herbicides will control annual broadleaf weeds such as nightshade, mustards, and sowthistle.
Bensulide (Prefar) can also be used as a preemergence application. Lower rates must be used on coarse-textured soils. This herbicide will provide good control of common purslane, lambsquarter and redroot pigweed.
Following crop emergence, clethodim (Select Max) and sethoxydim (Poast) can be applied for grass control, and linuron(Lorox DF) for annual broadleaf weeds and suppression of yellow nutsedge. Grass herbicides are effective in controlling small seedlings of annual grasses and some perennial grasses. Their effectiveness is reduced when grasses are under moisture stress. Later growth stages of annual grasses are more difficult to control. Only clethodim will control annual bluegrass.
Linuron and prometryn can also be used as postemergence herbicides in cilantro and parsley. Linuron is applied over the top when the crop is 3 inches tall, whereas prometryn can be used until the end of the six-true-leaves-stage. Both control emerged weeds and also have soil residual activity against later emerging weeds. Linuron will suppress yellow nutsedge, but has little to no effect on purple nutsedge. Consult the herbicide label regarding the plant back interval for these materials.