How to Manage Pests

UC Pest Management Guidelines

Common name		Amount/Acre	R.E.I.+	P.H.I.+
(trade name)			(hours)	(days)
When choosing an herbicide, consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
FALL BEDS
Before weeds emerge
A.	METRIBUZIN	0.25–0.5 lb a.i
	(Metribuzin 75)	0.33–0.66 lb	12	—
	WSSA MODE OF ACTION GROUP NUMBER1: 5
	COMMENTS: Used generally for broadleaf weeds. Rate is dependent on soil type: apply low rates when soil organic matter is less than 2% and high rates when organic matter exceeds 2%. Do not plant within 4 months of application to prevent crop injury. Irrigation or rainfall (0.5 inch) is needed to activate metribuzin. It has reduced activity under cool, wet, cloudy conditions. Low amounts of rainfall or irrigation can reduce chemical breakdown of metribuzin leading to crop injury. Do not disturb the soil surface after application as this reduces weed control. Note rotation restrictions before using this herbicide. Do not use in Kern County, the Coachella Valley, Imperial Valley, and Blythe, or in highly alkaline or light sandy soils.
B.	OXYFLUORFEN	0.25–0.5 lb a.i.
	(Goal 2XL)	1–2 pt	24	—
	(GoalTender)	0.5–1 pt	24	—
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: Provides control of annual broadleaves both before and after they emerge. Rate depends on weed size, but the rate used also determines the minimum period between treatment and planting: 60 days for the low rate and 120 days for the high rate. The minimum period between treatment and transplanting is 30 days. Incorporate with 2 inches of irrigation water and do not disturb soil until planting time. Work beds with a rolling cultivator or similar tool to a depth of 2.5 inches before planting to avoid crop injury or stand loss. Once beds have been worked before planting, the herbicide is no longer effective. However, crop injury can result if beds are not thoroughly worked before planting, or if seedling tomatoes are stressed. This herbicide lasts 4 to 8 weeks in the soil and has a 10-month plantback restriction for nonlabeled crops.
After weeds emerge
A.	PARAQUAT*	0.5–1 lb a.i.
	(Gramoxone Inteon)	2–4 pt	24	30
	WSSA MODE OF ACTION GROUP NUMBER1: 22
	COMMENTS: A nonselective, foliar herbicide without residual activity that is applied as a band treatment over the crop row or as a broadcast treatment before, during, or after tomato planting but before crop emergence. Controls only emerged weeds. Controls annual weeds and provides some suppression of perennials. Apply when weeds are succulent and about 1–4 inches high; larger weeds are less affected. Apply in 10 to 60 gal water/acre (5 gal by air) with a nonionic surfactant added at the rate of 8 to 32 oz/100 gal. Use the high surfactant rate with cereals and heavy weed infestations. Do not apply when weather conditions favor drift.
B.	GLYPHOSATE
	(Roundup)	annuals: 0.38–1.406 lb a.i. /perennials: 0.5–4.53 lb a.i.	4	14
	(Touchdown)	perennials: 0.5–3.75 lb a.i.	12	0
	WSSA MODE OF ACTION GROUP NUMBER1: 9
	COMMENTS: A nonselective, foliar herbicide that is used at least 3 days before transplanting or up to the time of crop emergence. For direct-seeded tomatoes, weeds must be emerged and actively growing. Rate depends on weed species and to some extent on size. Annual weeds are best controlled when small (less than 4 inches) and not water-stressed; control is poor when weeds exceed the maximum size indicated on the label. Apply in 3 to 20 gal water. Provides good annual weed control and some suppression of perennial weeds. Control of perennials improves with late summer or fall applications during noncrop periods when perennials are actively growing. Higher application rates are needed for perennial control.
C.	CARFENTRAZONE	0.031 lb a.i.
	(Shark EW)	2 fl oz	12	0
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: Preplant burndown of weeds for transplants only. A nonselective, foliar herbicide without residual activity that is applied as a band treatment over the crop row or as a broadcast treatment at least one day before transplanting. Controls only emerged weeds. Controls annual weeds and provides some suppression of perennials. Apply when weeds are succulent and about 1 to 4 inches high; larger weeds are less affected. Apply in 10 gal water/acre (3 gal by air) with a nonionic surfactant at 0.25% v/v, or methylated seed oil or crop oil concentrate at 1 to 2% v/v. Do not apply when weather conditions favor drift.
PREPLANT
Before weeds emerge
A.	METAM SODIUM*	159.75–319.5 lbs a.i.
	(various trade names, 42%)	37.5–75 gal	see label	—
	. . . or . . .
	METAM POTASSIUM*
	(K-PAM HL)	30–62 gal	see label	—
	COMMENTS: A liquid soil fumigant that controls many weeds, but is used mainly for nightshade control and nutsedge suppression. Also suppresses nematodes and disease. 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 a 3-inch depth. Broadcast rate is 50 to 75 gal/acre, but typically a 6-inch band is treated using 5 to 7.5 gal/crop acre (single row planting of tomatoes). Applications are made using a spray blade cutting 2 to 3 inches below the soil surface, depending on soil moisture. Disc 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 preplant interval between application and planting. Avoid moving untreated soil into the banded area. This treatment is effective against nightshade and many other weeds. 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.	METOLACHLOR	0.95–1.59 lb a.i.
	(Dual Magnum)	1–1.67 pt	24	60
	WSSA MODE OF ACTION GROUP NUMBER1: 15
	COMMENTS: Suppresses nutsedge and nightshades. Apply preplant for transplants only. Incorporate or apply as a surface application before transplanting. If incorporated, make certain to place transplant roots below the treated soil or injury may occur. Does not control emerged weeds. Rate depends on soil texture. Metolachlor plus trifluralin or pendimethalin tank mixes are particularly effective.
C.	NAPROPAMIDE	1–2 lb a.i.
	(Devrinol 50DF)	2–4 lb	24	—
	(Devrinol 2EC)	2–4 qt	24	—
	WSSA MODE OF ACTION GROUP NUMBER1: 15
	COMMENTS: Controls most annual grasses and broadleaves. Rate is dependent on soil type. Incorporation to a depth of 2 to 3 inches is needed soon after application to prevent loss. Band applications are frequently used to reduce costs. If napropamide is used on fall beds, do not treat a second time with this material.
D.	TRIFLURALIN	0.5–1 lb a.i.
	(Treflan HFP, 4EC)	1–2 pt	12	—
	(Trilin 10G)	5–10 lb	12	—
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Can be applied preplant for transplants only. Rate is dependent on soil type. Trifluralin is volatile and must be immediately incorporated to avoid loss. Keep treated soil above the roots. Apply in 5 to 40 gal water/acre and incorporate into the top 2 to 3 inches of the bed before transplanting. It provides good season-long control of many annual grasses and broadleaves as well as partial control of seedling field bindweed.
E.	PENDIMETHALIN	0.475–1.42 lb a.i.
	(Prowl H20)	1–3 pt	24	21
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Provides good, season-long control of many annual grasses and broadleaves as well as partial control of dodder. Can be applied preplant for transplants only. Rate is dependent on soil type. Apply in a minimum of 10 gal water/acre by ground or 5 gal water/acre by aircraft. Rainfall, sprinkler irrigation, or shallow mechanical incorporation after application is required to move the herbicide into the upper soil layers where weeds germinate. Do not apply more than 3 pt/acre. Use allowed under a supplemental label.
F.	1,3-DICHLOROPROPENE*
	(Telone EC)	label rates	120	—
	. . . or . . .
	1,3-DICHLOROPROPENE/CHLOROPICRIN*
	(Telone C35)	label rates	120	—
	COMMENTS: Efficacy affected by soil texture, moisture, temperature, and percent organic matter. 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.
POSTPLANT
Before weeds emerge
A.	RIMSULFURON	0.5–1 oz a.i.
	(Matrix 25DF)	2–4 oz	4	45
	WSSA MODE OF ACTION GROUP NUMBER1: 2
	COMMENTS: Provides good control of many weeds including most nightshade species, pigweeds, lambsquarters among others. Length of control may be reduced under cool, wet conditions. Apply treatment after tomato seeding or transplanting. Apply using a ground application in 10 to 40 gal water/acre. If weeds have already emerged, add a nonionic surfactant at a rate of 0.25% v/v. Rainfall or sprinkler irrigation (0.5–1 inch) is needed for activation within 5 days of treatment.
B.	METOLACHLOR	0.95–1.59 lb a.i.
	(Dual Magnum)	1–1.67 pt	24	90
	WSSA MODE OF ACTION GROUP NUMBER1: 15
	COMMENTS: Will provide control of yellow nutsedge during crop establishment. May be applied to postdirected transplants after the first settling rain or irrigation in a minimum of 20 gal water/acre. Minimize contact with tomato plants. May be applied to direct-seeded tomatoes that are at least 4 inches tall. Apply in a minimum of 20 gal water/acre and minimize contact with plants. Rate depends on soil texture.
C.	HALOSULFURON	0.37–0.75 oz a.i.
	(Sandea)	0.5–1 oz	12	30
	WSSA MODE OF ACTION GROUP NUMBER1: 2
	COMMENTS: Can be used preemergence in transplanted tomatoes to control nutsedge. Tomatoes may be transplanted 7 days after treatment unless conditions demonstrate safety at an earlier interval. Take care to prevent movement of treated soil during the transplant process.
POSTPLANT
After weeds emerge
A.	CLETHODIM	0.068–0.2425 lb a.i.
	(Select 2E)	6–16 fl oz	24	20
	(Select Max)	9–32 fl oz	24	20
	WSSA MODE OF ACTION GROUP NUMBER1: 1
	COMMENTS: Controls actively growing small grasses except for bromes and fescues. Use a nonionic surfactant at a rate of 0.25% v/v in Select Max or a crop oil concentrate at a rate of 1% v/v in Select 2E. Apply to annual bluegrass at 4-leaf stage. Repeat treatments necessary for perennial grasses. Apply in at least 30 gal water/acre.
B.	HALOSULFURON	0.37–0.75 oz a.i.
	(Sandea)	0.5–1 oz	12	30
	WSSA MODE OF ACTION GROUP NUMBER1: 2
	COMMENTS: For use on seed and transplant tomatoes for the control of nutsedge. Apply over the top of direct-seeded tomatoes from the 4-true leaf stage through first bloom. Make applications to transplanted tomatoes at least 14 days after transplanting but before first bloom. Following bloom, applications must be made either as a directed spray or with shields to minimize contact with the crop. Injury may result if the spray contacts the foliage. Minimum (0.37 oz a.i.) and maximum (0.50 oz a.i.) rates are lower for direct-seeded tomatoes grown in Riverside and Imperial counties than those grown in other areas of California where the minimum rate is 0.5 oz a.i. and the maximum rate is 0.75 oz a.i. Use of 0.25 to 0.5% v/v of nonionic surfactant is recommended. Use of crop oil concentrate or silicone surfactants is not recommended because of increased risk of injury. Do not apply halosulfuron if a soil application of an organophosphate insecticide has been made. Do not apply a foliar organophosphate insecticide within 21 days before or 7 days after any halosulfuron treatment.
C.	METRIBUZIN
	(Metri 4F)	0.5–1 lb a.i. or 1–2 pt	12	7
	(Metribuzin 75 DF)	0.2475–0.9975 lb a.i. or 0.33–1.33 lb	12	7
	WSSA MODE OF ACTION GROUP NUMBER1: 5
	COMMENTS: Used primarily for black nightshade control on loam or clay loam soils. Has both pre- and postemergence activity. Can be applied as a broadcast spray at rates up to 0.5 lb a.i./acre or as a directed spray at rates up to 1 lb a.i./acre. Rate is dependent on the weed species and soil type and can be applied as a single treatment or split into 2 treatments. If split, the treatments must be at least 14 days apart, with the total applied in a year not exceeding 1 lb a.i./acre for the 4F formulation and 0.9975 lb a.i. for the DF formulation. Apply in 20 to 75 gal water/acre as a directed spray to avoid contact with terminals of the tomato plant. Do not use with a surfactant, with other pesticides as a tank mix, or within 24 hours of other pesticide applications. Tomatoes should be 6 to 10 inches tall or the 6-true-leaf stage. Avoid spraying when tomatoes are stressed by cool, cloudy, wet weather or by drought as injury could occur. Do not use in Kern County. Observe restrictions on rotational crops.
D.	RIMSULFURON	0.25–0.5 oz a.i.
	(Matrix 25DF)	1–2 oz	4	45
	WSSA MODE OF ACTION GROUP NUMBER1: 2
	COMMENTS: Provides good control of many weeds including most nightshades but only partial control of black nightshade. Single or multiple applications may be made per season, but the total applied must not exceed 4 oz product/acre/year. The maximum rate for preemergence use is 2 oz/acre, but up to 4 oz/acre can be used if both preemergence (2 oz) and postemergence (2 oz) treatments are made or if two postemergence treatments are made (2 oz + 2 oz). Tomatoes can be treated as early as the cotyledon stage. Use a nonionic surfactant at a rate of 0.25% v/v, and apply in 10 to 40 gal water/acre. Temporary yellowing of tomatoes may result following treatment but generally disappears after 1 to 2 weeks.
E.	SETHOXYDIM	0.28 lb a.i.
	(Poast 1.5EC)	1.5 pt	12	20
	WSSA MODE OF ACTION GROUP NUMBER1: 1
	COMMENTS: Selective herbicide for control of grassy weeds. Has postemergence activity only. Annual and perennial grasses must be at the proper size, well watered, and actively growing for good control. This treatment can be repeated up to 3 times/season; be sure to observe the preharvest interval. Apply in 10 to 20 gal water plus a crop oil concentrate at the rate of 1 qt/acre. Do not treat transplanted tomatoes within 14 days of transplanting. Labels recommend not cultivating within 5 days before application or within 7 days following application. Do not apply with any other pesticide or fertilizer.
F.	CARFENTRAZONE	0.031 lb a.i.
	(Shark EW)	2 fl oz	12	0
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: COMMENTS: Controls annual weeds and provides some suppression of perennials. Controls only emerged weeds. Only hooded applications are permitted, as contact with tomatoes will cause injury. A nonselective, foliar herbicide without residual activity. Apply when weeds are succulent and about 1 to 4 inches high; larger weeds are less affected. Apply in 10 gal water with a nonionic surfactant at 0.25% v/v, or methylated seed oil or crop oil concentrate at 1 to 2% v/v.
LAYBY
Before Weeds Emerge
A.	TRIFLURALIN	0.5–1 lb a.i.
	(Treflan HFP)	1–2 pt	12	0
	(Trilin 10G)	5–10 lb	12	0
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Provides good season-long control of annual grasses and many broadleaves as well as partial control of seedling field bindweed. Rate is dependent on soil type. Apply as a directed spray to the soil between rows and beneath tomato plants or as a shielded spray, but not over the top of plants as yields may be reduced. Trifluralin is volatile and must be immediately incorporated to avoid loss. Apply in 5 to 40 gal water/acre and incorporate into the top 2 to 3 inches of the bed.
B.	EPTC	3.0625 lb a.i.
	(Eptam 7EC)	3.5 pt	12	21
	WSSA MODE OF ACTION GROUP NUMBER1: 8
	COMMENTS: EPTC provides good control of hairy nightshade, johnsongrass seedlings, yellow nutsedge and many annuals. Apply as a directed spray at layby and immediately incorporate. Do not apply within 2 inches of the crop row. Tomatoes should be at least 3 to 4 inches tall at the time of this application. Do not irrigate for at least 5 days after application to avoid crop injury. Do not use this herbicide on sandy soils. This herbicide is registered for Northern California only (Fresno County and north). Allow 90 days between application and a grain rotation.
C.	DCPA	4.5–10.5 lb a.i.
	(Dacthal)	6–14 lb	12	0
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Gives partial control of dodder when applied before dodder emerges. Apply as a banded treatment when seeded tomatoes are 4 to 6 inches tall or 4 to 6 weeks after transplanting. Cultivate soil before treatment if weeds have emerged. Apply during warm, dry weather.
D.	METOLACHLOR	0.95–1.59 lb a.i.
	(Dual Magnum)	1–1.67 pt	24	90
	WSSA MODE OF ACTION GROUP NUMBER1: 15
	COMMENTS: Provides control of yellow nutsedge during crop establishment. May be applied to postdirected transplants after the first settling rain or irrigation in a minimum of 20 gal water/acre. May be applied to direct-seeded tomatoes that are at least 4 inches tall. Apply in a minimum of 20 gal water/acre and minimize contact with plants. Rate depends on soil texture.
E.	PENDIMETHALIN	0.475–1.42 lb a.i.
	(Prowl H20)	1–3 pt	24	21
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Provides good, season-long control of many annual grasses and broadleaves as well as partial control of dodder. Can be applied as a post-directed spray for established direct-seeded tomatoes and transplanted tomatoes. Avoid contact with the foliage or stems. Rate is dependent on soil type. Apply in a minimum of 10 gal water/acre by ground. Rainfall, sprinkler irrigation, or shallow mechanical incorporation after application is required to move the herbicide into the upper soil layers where weeds germinate. Do not apply more than 3 pt/acre. Use allowed under a supplemental label.
+	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. Preharvest interval (P.H.I.) is the number of days from treatment until harvest can take place. In some cases the R.E.I. exceeds the P.H.I. The longer of these two intervals is the minimum time that must elapse before harvest may take place.
—	Not applicable or unknown.
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. For more information, see http://www.plantprotection.org/HRAC/.
*	Permit required from county agricultural commissioner for purchase or use.

PUBLICATION

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470
Weeds
W. T. Lanini, Weed Science/Plant Sciences, UC Davis
K. J. Hembree, UC Cooperative Extension, Fresno County
G. Miyao, UC Cooperative Extension, Solano/Yolo counties
C. S. Stoddard, UC Cooperative Extension, Merced/Madera counties
Acknowledgments for contributions to the weed section:
B. J. Mullen,UC Cooperative Extension, San Joaquin County
J. P. Orr, UC Cooperative Extension, Sacramento County
W. E. Bendixen, UC Cooperative Extension, Santa Barbara County

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