How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PESTS

Plant parasitic nematodes are microscopic roundworms that live in soil and plant tissues and feed on plants by puncturing and sucking the cell contents with a needlelike mouthpart called a stylet. Root knot nematodes live within the roots; the second stage juveniles are motile, and the other stages are sedentary. Adult females are swollen and produce eggs in an egg-mass, typically on or just under the root surface.

DAMAGE

Root knot nematodes can cause stunting of celery plants. They can also reduce a stand, but this is rare and usually occurs under high nematode population densities when the growing season extends into warm weather.

Reports of nematode problems in California celery crops have increased in recent years. This increase is attributed to the loss of fumigants that were typically used on crops grown in rotation with celery.

SYMPTOMS

The symptoms described below are characteristic of a nematode problem, but are not diagnostic because they could result from other causes as well. Root knot nematode infestations can cause stunting, uneven stand of plants, and characteristic galls on roots. Nematode-infested plants often tend to wilt earlier than healthy plants even when soil moisture is adequate.

FIELD EVALUATION

It is critical to know whether or not nematodes are present to make management decisions. If a previous field or crop had problems caused by root knot nematode, numbers may be high enough to cause damage to seedlings. If nematode species have not previously been identified, take soil samples and send them to a diagnostic laboratory for identification.

Take soil samples from within the root zone (6 to 18 inches deep). Divide the field into sampling blocks of not more than five acres each that represent cropping history, crop injury or soil texture. Take several subsamples randomly from a block, mix them thoroughly and make a composite sample of about 1 quart (1 liter) for each block. Place the samples in separate plastic bags, seal them, and place a label on the outside with your name, address, location, and the current/previous crop and the crop you intend to grow. Plants suspected of having root knot infestation should be placed in a plastic bag and also sent to the lab for analysis. Keep samples cool (do not freeze), and transport as soon as possible to a diagnostic laboratory. Contact your farm advisor for more details about sampling, to help you find a laboratory for extracting and identifying nematodes, and for help in interpreting sample results.

MANAGEMENT

Cultural Practices
Rotating with nonhost crops can reduce nematode population levels but is difficult in fields with root knot nematodes because of their wide host range. Avoid infesting new fields by cleaning machinery and equipment with water and preventing movement of infested soil. Currently there are no nematode resistant cultivars available.

Treatment Decisions
Damage thresholds for root knot nematode on celery have not been developed. If they are present, damage may occur and treatment is warranted.

Common name		Amount to use	R.E.I.+
(trade name)			(hours)
PREPLANT
A.	METAM SODIUM*	50–80 gal/acre	48
	(Vapam, Sectagon 42)
	COMMENTS: Contact your farm advisor for advice on the most effective application method for a particular situation. Fumigants such as metam sodium are a source of volatile organic compounds (VOCs) but are minimally reactive with other air contaminants that form ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available.
B.	1,3-DICHLOROPROPENE*	Label rates	7 days
	(Telone II)
	COMMENTS: Follow label directions for rates and application procedures. Fumigants such as 1,3-dichloropropene are a source of volatile organic compounds (VOCs) but are minimally reactive with other air contaminants that form ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available.
C.	1,3-DICHLOROPROPENE*/CHLOROPICRIN*
	(InLine)	Label rates	7 days
	COMMENTS: Multipurpose liquid fumigant for the preplant treatment of soil to control plant-parasitic nematodes, symphylans, and certain soil-borne pathogens using drip irrigation systems only. Use of a tarp seal is mandatory for all applications of this product. Fumigants such as 1,3-dichloropropene are a source of volatile organic compounds (VOCs) but are minimally reactive with other air contaminants that form ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available.
D.	1,3-DICHLOROPROPENE*
	(TELONE EC)	Label rates	7 days
	COMMENTS: Liquid fumigant for the preplant treatment of soil against plant-parasitic nematodes and certain other soil pests in cropland using drip irrigation systems only. Fumigants such as 1,3-dichloropropene are a source of volatile organic compounds (VOCs) but are minimally reactive with other air contaminants that form ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available.
+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
*	Permit required from county agricultural commissioner for purchase or use.

PUBLICATION

UC IPM Pest Management Guidelines: Celery
UC ANR Publication 3439
Nematodes
B. B. Westerdahl, Nematology, UC Davis
A. T. Ploeg, Nematology, UC Riverside
J. O. Becker, Nematology, UC Riverside
Acknowledgment for contributions to Nematodes:
U. C. Kodira, Plant Pathology, UC Davis

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