- Author: Richard Smith
Cilantro was produced on 5,543 acres in Monterey and Ventura Counties in 2011. The production of cilantro has shifted to high density 80-inch wide beds and a large proportion is now mechanically harvested. Hand weeding high density beds is very expensive and reduces the economic viability of this crop. As a result, there is a need for excellent weed control. Two broadleaf herbicides were registered on cilantro: Prefar and Caparol. Prefar was registered for a number of years and provides good control of a number of key weeds in cilantro such as purslane, lambsquarter and pigweed. Caparol was registered in 2012 and provides good weed control of a wider spectrum of weeds including the nightshades, shepherd’s purse, sow thistle, groundsel and others (see tables below).
Here is the situation with Prefar: EPA moved cilantro (also Mexican & Chinese parsley) out of the "Leafy vegetables" crop group 4 and placed it in the "Herbs and Spices" crop group 19. The issue is that crop group 19 Herbs and Spices has no tolerance for Prefar. Without a tolerance, Gowan Corp. can no longer support the 24c for cilantro. It places growers in a tricky situation, because they may have Prefar with the old label in reserve, but any detectable levels of Prefar residues are detected on cilantro, it could result in seizure of the crop. This is a regulatory snafu that may take some time to untangle; work is being done to resolve this situation but it is unclear how long it will take to resolve.
Caparol is also registered for use on cilantro, but there is a plant back restriction of 12 months prior to planting lettuce, broccoli, cauliflower and spinach. This is of course very difficult to work with this restriction in the Salinas and other coastal valleys.
Other weed control options: bed fumigation of cilantro prior to planting can be highly effective, but issues with the cost and working around buffer zones makes this option difficult to fit into a grower’s production budget as well as schedule. Cultural practices such as pregermination followed by shallow cultivation of emerged weeds prior to planting can help reduce weed pressure. Cilantro seed germinates slowly which opens the possibility of burning off a flush of weeds (with an herbicide or propane flamer) following planting but prior to the emergence of the cilantro. This is a tricky, but highly effective technique for reducing weed density.
In summary, we have a number of regulatory issues that need to be addressed in order use the broadleaf herbicides without difficulty. We will need to continue to work with the regulators and registrants to resolve these issues as quick as possible.
(Click on tables and images to Enlarge)
- Author: Steven T. Koike
- Author: Carolee Bull
Since 2002, a severe leaf spot disease on parsley has occurred throughout central coastal California and particularly in Monterey County. Three different bacterial pathogens (Pseudomonas syringae pv. apii, P. syringae pv. coriandricola and an organism very closely related to P. viridiflava) have been associated with these outbreaks on parsley. Of interest to researchers and of potential importance to growers is the fact that two of these bacteria were already causing problems in coastal crops. Pseudomonas syringae pv. apii is the causal agent of northern bacterial blight of celery and P. syringae pv. coriandricola causes bacterial leaf spot of cilantro. Symptoms of all three diseases are similar and consist of small (usually less than ¼ inch in diameter) leaf spots that are noticeably angular in shape, with the edges of the spot restricted by leaf veins. The color of the leaf spots can vary from light tan to brown to dark brown. These bacterial leaf spots penetrate the entire leaf, so that the spot will be visible from both the top and bottom sides of the infected tissue (in contrast to chemical damage or abrasion in which the symptom is usually only seen from the top side of the leaf). See photos below.
Our research team is also investigating a possible new bacterial disease on fennel, as well. Because of these developments on commercially grown plants in the Apiaceae, we are seeking additional samples of foliar problems from any member of the Apiaceae crop group: celery, cilantro, dill, fennel, parsley, and others. Further clarification of the relationship between these various bacterial pathogens, determination of which hosts are susceptible to which pathogen, and other aspects may assist industry in managing these diseases.
The best samples will consist of diseased plants collected from several different locations of a field. Send samples to the UC Cooperative Extension diagnostic laboratory in Salinas: 1432 Abbott Street, Salinas CA, 93901 (phone 831-759-7550), attention Steve Koike.
Bacterial leaf spot of celery.
Bacterial leaf spot of cilantro.
Bacterial leaf spot of parsley.
- Author: Steven T. Koike
For much of spring and early summer 2010, coastal California continued to receive rain. Such rain significantly increased bacterial leaf spot disease problems on cilantro. Presently, bacterial leaf spot is the only foliar disease affecting cilantro in California. Bacterial leaf spot is greatly increased by splashing water from rains and overhead sprinkler irrigation. The disease initially causes water-soaked, vein-delimited spots on leaves. These spots rapidly turn dark brown in color, remain angular in shape, and can be seen from both top and bottom sides of leaves. If disease is severe, the foliage can take on a blighted appearance when leaf spots coalesce. Cilantro crops with significant amounts of this disease will be unmarketable.
The pathogen is Pseudomonas syringae pv. coriandricola. This pathovar is host specific to cilantro and does not infect celery, parsley, or other apiaceae plants. The most critical disease cycle factor is that this pathogen is seedborne in cilantro. Therefore, infested seed is the primary means by which the pathogen gets into the cilantro production system.
Because most cilantro plantings are irrigated with overhead sprinklers, disease control is very difficult. If possible, use seed that has been tested and found to be pathogen-free or that has been treated. Minimize the use of sprinklers or schedule irrigations to enhance drying of the foliage. For both conventional and organic cilantro, the only foliar treatment available is a copper fungicide. Such copper sprays provide some protection but are generally not effective enough to achieve sufficient control.
We encourage growers and pest control advisors to continue to submit cilantro samples to our UC Cooperative Extension diagnostic lab in Salinas for confirmation of this problem. While bacterial leaf spot is the only documented foliar disease of cilantro in California, other parts of the world have reported a fungus leaf spot disease on cilantro; therefore, laboratory testing of California cilantro is advisable.
Bacterial leaf spot of cilantro is recognized by its dark brown, angular leaf spots that are visible from both top and bottom sides of the leaf.