How to Manage Pests

UC Pest Management Guidelines

Common name		Amount/Acre	R.E.I.+	P.H.I.+
(trade name)			(hours)	(days)
When choosing a pesticide, consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
PREPLANT
Preemergence (before weeds germinate)
A.	TRIFLURALIN	0.5–1 lb a.i.	12	NA
	(Treflan)
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Broadcast preplant in 5 to 40 gallons of water per acre. Trifluralin must be incorporated immediately after application to avoid loss of activity. Plant tree roots below treated soil. Do not place treated soil near roots during planting. Controls many annuals and is helpful in suppressing perennial weeds. Residual period: 2–12 months.
B.	PENDIMETHALIN	2–3.96 lb a.i.	24	NA
	(Prowl H2O)
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Preemergence, selective herbicide for annual grasses and some broadleaves. Apply to soil in 10 gal/acre or more before planting and incorporate mechanically 2.5 inches deep. Use untreated soil to fill in around tree roots.
Postemergence (after weeds emerge)
A.	GLYPHOSATE
	(Roundup)	1–2.268 lb a.i.	4	17
	. . . or . . .
	(Touchdown)	1–3.75 lb a.i.	12	17
	WSSA MODE OF ACTION GROUP NUMBER1: 9
	COMMENTS: Apply with a controlled applicator or with low-pressure flat fan nozzles. For annual weed control, use 1 lb/acre in 3–10 gal water. Ammonium sulfate can also be added (1 to 2% by weight or 8.5 to 17 lbs per 100 gallon of water) to the spray solution to significantly improve control in areas with hard water. It is important to add the ammonium sulfate to the water before adding the herbicide. Apply to young annuals or vigorously growing perennials in flowering stage. Some perennials require the 4 lb/acre rate for control. May be used on young weeds in the planting row followed by planting into the dead weeds. As a result of the no-till effect, new weeds usually do not establish for a month or more. Do not use more than 6.0465 lb a.i./year for Touchdown and 9.625 lb a.i. for Roundup.
NEWLY PLANTED ORCHARDS (nonbearing trees)
Preemergence
A.	ISOXABEN
	(Gallery T&V)	0.5–0.9975 lb a.i.	12	365
	WSSA MODE OF ACTION GROUP NUMBER1: 21
	COMMENTS: Wait until soil has settled around newly planted trees before applying. Controls broadleaf weeds only before they have germinated; will not control emerged weeds. If weeds are emerged, lightly cultivate or add a postemergence herbicide. Requires incorporation for activation, either by light cultivation (1 to 2 inches) or rainfall (minimum of 0.5 inches) within 21 days after application. Sprinkler or flood irrigation can also be used for incorporation. Apply in at least 10 gal/acre of water.
B.	TRIFLURALIN
	(Treflan, etc.)	see label	12	0
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Preemergence selective herbicide for annual grasses and some broadleaves. Apply prebloom by ground as a directed spray and mechanically incorporate, taking care not to injure the trees with the incorporation. Must be incorporated immediately after application to avoid loss of activity. Used on new plantings or established orchards as a strip treatment. Suppresses bermudagrass, johnsongrass, and dallisgrass rhizomes. Only one application per year. Residual period: 2–12 months, depending on rate.
C.	ORYZALIN
	(Surflan, Oryzalin 4 A.S. etc.)	2–6 lb a.i.	24	0
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Preemergence selective herbicide for annual grasses and some broadleaves. Apply to the soil surface in 20–40 gal water/acre. If rain does not occur within 21 days, sprinkle irrigate with 0.5–2 inches of water. May be combined with a postemergence herbicide if weeds are present. Most effect on annual grasses and numerous broadleaf annuals. Very safe for young or newly planted trees and on sandy or sandy loam soils. Used to maintain control in strips down the row. The higher rates give the longest soil residual. Usually used at 4 lb a.i./acre. Residual period: 4–10 months.
D.	PENDIMETHALIN
	(Prowl H2O)	2–3.96 lb a.i.	24	NA
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: For use on dormant nonbearing trees only. Selective preemergence herbicide for annual grasses and some broadleaves. Apply in 10 or more gal water/acre to soil under trees. Do not apply on newly planted trees unless soil is firm and there are no cracks in soil around base of trees. Best control is achieved when irrigation or rainfall occurs within 7 days. Will not control emerged weeds. Residual period: 4–10 months
E.	THIAZOPHYR
	(Visor 2E)	0.5-1 lb a.i.	12	1 year
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: For use on nonbearing trees only; use allowed under a SLN registration. Apply in 20 or more gal water/acre. Provides nutsedge and horseweed suppression on coarse textured soils with low organic matter. Best control is achieved when irrigation or rainfall occurs within 7 days of application. Will not control emerged weeds. Residual period: 4-10 months.
F.	FLUMIOXAZIN
	(Chateau SW)	0.188-0.376 lb a.i.	12	1 year
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: For use on dormant nonbearing trees only. Provides effective control of many annual grasses and broadleaves, including horseweed. Apply in 10 or more gal water/acre to soil under trees when completely dormant. Do not apply on newly planted trees unless soil is firm and there are no cracks in soil around base of trees. Best control is achieved when irrigation or rainfall occurs within 21 days. Can be mixed with other pre- or postemergence herbicides. It will not provide adequate control of emerged weeds, unless mixed with a postemergence herbicide. Use allowed under a supplemental label. Residual period: 3–6 months
Postemergence
A.	CLETHODIM
	(Select Max)	0.095-0.12125 lb a.i.	24	1 year
	WSSA MODE OF ACTION GROUP NUMBER1: 1
	COMMENTS: For use on nonbearing trees only. Do not use in Solano County. Apply to young, nonstressed annual or perennial grasses. Repeat applications will be required for the control of perennial grasses. Apply in 5 to 40 gal water/acre. Add 0.25% volume per volume nonionic surfactant to the spray solution. Spray pressure should be between 30 and 60 PSI, with higher pressures used when weed density is high. Do not apply a broadleaf herbicide within one day following application or reduced grass control may occur. Residual period: less than one month.
B.	SETHOXYDIM
	(Poast)	0.19–0.46 lb a.i.	12	25 days
	WSSA MODE OF ACTION GROUP NUMBER1: 1
	COMMENTS: Apply to young nonstressed annual or perennial grasses. Repeat applications will be required for the control of perennial grasses. Add 2 pt/acre of a nonphytotoxic crop oil concentrate to the spray solution. Residual period: less than one month.
C.	CARFENTRAZONE
	(Shark)	0.008–0.031 lb a.i.	12	3 day
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: A postemergence, contact herbicide used for quick top kill of most broadleaf weed species. Can be applied anytime during the season, but if fruit are present, it should either be avoided or applied with extreme care to avoid drift. It can also be used for sucker control. Apply in a minimum of 20 gal water/acre to weeds less than 6 inches tall. Do not exceed 30 psi. Repeat treatments as new growth occurs, but they must be at least 14 days apart. Do not use more than 0.124 lb a.i./acre/season. Use 0.25% volume per volume nonionic surfactant, 1.0% volume per volume of a crop oil concentrate, or a silicone or MSO surfactant.
ESTABLISHED ORCHARDS
Preemergence
A.	TRIFLURALIN
	(Treflan, etc.)	1–2 lb a.i.	12	0
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Preemergence selective herbicide for annual grasses. Apply prebloom by ground as a directed spray and mechanically incorporate, taking care not to injure the tree. Must be incorporated immediately after application to avoid loss of activity. Frequently used as a strip treatment. Suppresses bermudagrass, johnsongrass, and dallisgrass rhizomes. Only one application per year. Residual period: 2–12 months.
B.	ORYZALIN
	(Surflan, Oryzalin 4 A.S. etc.)	2–6 lb a.i.	24	0
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Apply to the soil surface in 20–40 gal water/acre. If rain does not occur within 21 days, sprinkle irrigate with 0.5–2 inches of water. Most effect on annual grasses and numerous broadleaf annuals. Very safe for sandy or sandy loam soils. Used to maintain control in strips down the row. May be combined with a postemergence herbicide if weeds are present. The higher rates give the longest soil residual. Usually used at 4 lb a.i./acre. Residual period: 4–10 months.
C.	NORFLURAZON
	(Solicam DF)	1.97–3.93 lb a.i.	12	60
	WSSA MODE OF ACTION GROUP NUMBER1: 12
	COMMENTS: Similar to oryzalin but is effective on more annual broadleaf and grass species. Can suppress yellow nutsedge or bermudagrass when used year after year. Apply to soil as a directed spray from fall to early spring under trees established for at least 2 years. If no rainfall occurs within 4 weeks, incorporate with sprinkler or flood irrigation. Remove existing weeds with cultivation or a postemergence herbicide, because it has no postemergence activity. Avoid higher rates on sandy or gravelly soils to prevent injury to trees. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas. Do not use in the Coachella Valley. Apply in 20–100 gal water/acre. Residual period: 6–12 months.
D.	OXYFLUORFEN
	(GoalTender etc.)	0.5–2 lb a.i.	24	see comments
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: For use on dormant trees only. Apply following harvest up to February 15 (February 1 in the Coachella Valley). Apply by ground one time per season in 40–100 gal water/acre on firm soil. Must not be mechanically disturbed or poor weed control will result. Effective as a pre- and postemergence herbicide. Effective on little mallow (cheeseweed). Useful combined with other postemergence herbicides, such as glyphosate, or in combination with preemergence herbicides, such as oryzalin, simazine, or thiazopyr. Check label for use period. Residual period: 4–10 months.
E.	PRONAMIDE*
	(Kerb)	1–4 lb a.i.	24	NA
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	COMMENTS: Do not apply to trees less than 1 year old. Selective herbicide for control of winter annual and perennial grasses. Apply in fall after fruit harvest. Apply in 40-50 gal water/acre to the soil at the base of the trees. Must be applied before weed emergence because it will not control emerged weeds. Rainfall or irrigation is essential after application for effective weed control. Residual period: 4-8 months.
F.	DIURON	1.6–3 lb a.i.	12	8 months
	WSSA MODE OF ACTION GROUP NUMBER1: 7
	COMMENTS: Apply to the soil under trees at least 3 years of age. A single application may be made in winter or split between fall and spring. Diuron is sometimes combined with other preemergence herbicides to broaden spectrum of weeds controlled. These combination treatments frequently use lower rates of diuron. Adjust rates according to soil texture. Do not use on soils with less than 1% organic matter. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas. Residual period: 8-12 months.
G.	SIMAZINE
	(Princep Caliber 90)	1–1.98 lb a.i.	12	0
	WSSA MODE OF ACTION GROUP NUMBER1: 5
	COMMENTS: Apply to the soil under trees older than 3 years. Make only one application per year. Use the high rate for heavy soils. Simazine is frequently used in combination with other preemergence herbicides. On light soils, simazine often is used at rates of 0.5-1.0 lb a.i./acre. Do not use on gravel, sand, or loamy sand soils. If an irrigation is applied immediately after application, limit water to 0.5 inch. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas. Residual period: 8-12 months.
Postemergence
A.	GLYPHOSATE
	(Roundup)	1–4 lb a.i.	4	17
	. . . or . . .
	(Touchdown)	1–3.75 lb a.i.	12	17
	WSSA MODE OF ACTION GROUP NUMBER1: 9
	COMMENTS: Apply with controlled droplet application or with low-pressure, flat-fan nozzles. For annual weed control, use 1 lb a.i./acre in 3–10 gal water. Ammonium sulfate can also be added (1 to 2% by weight or 8.5 to 17 lbs per 100 gallon of water) to the spray solution to improve control in areas with hard water. It is important to add the ammonium sulfate to the water before adding the herbicide. For chemical mowing, consult label for exact timing and rates, depending on weed size and species. Apply to young annuals or vigorously growing perennials. Bermudagrass and field bindweed require up to 4 lb a.i./acre rate for control. Persistence is the key for effective control of perennial weeds (i.e. treating every 21 days). Eradication of field bindweed is difficult where roots are deep or tapped into perched water tables. Not effective on some broadleaf weeds at older stages of growth (little mallow and filaree). Avoid drift onto green bark or foliage of tree or injury will result. It is important to monitor treated areas for escaped weeds, as glyphosate resistant weeds have been observed in orchards where glyphosate has been used repeatedly for several years.
B.	PARAQUAT*
	(Gramoxone Inteon)	0.625–1 lb a.i.	24	28
	WSSA MODE OF ACTION GROUP NUMBER1: 22
	COMMENTS: Nonselective postemergence, contact herbicide used for quick top kill of most weed species. Provides temporary burndown only. Less effective against perennials that will regrow (bermudagrass, dallisgrass, johnsongrass and field bindweed). Most effective when used in late winter or early spring on small annual grass species in combination with preemergence herbicides. Apply in 10–60 gal water/acre to young weeds. Use 0.25% volume per volume nonionic surfactant or 1.0% volume per volume of a crop oil concentrate. Repeat treatment as new growth occurs. Do not exceed 3 applications/season.
C.	OXYFLUORFEN
	(GoalTender etc.)	0.5–2 lb a.i.	24	see comments
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: Dormant application to young (4-leaf-stage) weeds. Effective on little mallow (cheeseweed) and filaree. Useful combined with glyphosate or oryzalin. May be combined with other postemergence herbicides for specific weeds. Apply following harvest up to February 15 (February 1 in the Coachella Valley). Apply by ground one time per season in 40–100 gal water/acre on firm soil. Must not be mechanically disturbed or poor weed control will result. Effective as a pre-and postemergence herbicide. Residual period: 4–10 months.
D.	2,4–D*
	(Orchard Master etc.)	0.95–1.425 lb a.i.	48	40
	WSSA MODE OF ACTION GROUP NUMBER1: 4
	COMMENTS: For use on established trees one year or older. Effective on most broadleaf annual weeds. Provides partial control of field bindweed. Apply as a directed spray to weeds, using low-pressure, flooding nozzles between the tree rows. Best results are obtained when applied a few days after an irrigation. Do not allow drift onto the trees or injury may result. No more than two applications allowed during the growing season. Residual period: 4–6 weeks.
E.	FLUAZIFOP-P-BUTYL
	(Fusilade DX)	0.125–0.375 lb a.i.	12	14
	WSSA MODE OF ACTION GROUP NUMBER1: 1
	COMMENTS: For control of annual and perennial grass weeds. A crop oil concentrate at 0.5 to 1% volume per volume or a nonionic surfactant at 0.25 to 0.5% volume per volume must be added to the spray solution. Diammonium phosphate (10-34-0) can also be added to the spray solution to improve control in areas with hard water. Add the diammonium phosphate to the water before adding the herbicide and surfactant. Avoid contact of spray with foliage of trees. Apply in 5-40 gal water, with spray pressures of 30 to 60 psi. Do not apply to grass that is moisture stressed or poor control may result. Apply to johnsongrass when it is between 8 to 18 inches in height. Repeat applications are required for johnsongrass and bermudagrass. Residual period: less than 1 month.
F.	CARFENTRAZONE
	(Shark)	0.008–0.031 lb a.i.	12	3 day
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: A postemergence, contact herbicide used for quick top kill of most broadleaf weed species. Can be applied anytime during the season, but if fruit are present, it should either be avoided or applied with extreme care to avoid drift. It can also be used for sucker control. Apply in a minimum of 20 gal water/acre to weeds less than 6 inches tall. Repeat treatments as new growth occurs, but they must be at least 14 days apart. Do not use more than 0.124 lb a.i./acre/season. Use 0.25% volume per volume nonionic surfactant, 1.0% volume per volume of a crop oil concentrate, or a silicone or MSO surfactant.
HERBICIDE COMBINATIONS
Note: Combinations are most often used to broaden the weed control spectrum. At the rates recommended below, perennial weeds will not be controlled. Other combinations can be used depending upon the weed spectrum present in the orchard. For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i.
A.	GLYPHOSATE	0.5–1 lb a.i.	Roundup: 4	17
	(Roundup, Touchdown, etc.)		Touchdown: 12	17
	WSSA MODE OF ACTION GROUP NUMBER1: 9
	. . . PLUS . . .
	OXYFLUORFEN
	(GoalTender, etc.)	0.1–1 lb a.i.	24	see comments
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: For broad-spectrum control of emerged weeds. Apply in a minimum of 10 gal water/acre in dormant trees. Helps increase control of cheeseweed, filaree, chickweed, and grasses. Glyphosate effectiveness is increased with low-water volume and oxyfluorfen is more effective at the higher volume. Avoid drift and follow directions for application period of oxyfluorfen.
B.	GLYPHOSATE	0.5–1 lb a.i.	Roundup: 4	17
	(Roundup, Touchdown, etc.)		Touchdown: 12	17
	WSSA MODE OF ACTION GROUP NUMBER1: 9
	. . . PLUS . . .
	ORYZALIN
	(Surflan, etc.)	4 lb a.i.	24	0
	WSSA MODE OF ACTION GROUP NUMBER1: 3
C.	ORYZALIN
	(Surflan, etc.)	4 lb a.i.	24	0
	WSSA MODE OF ACTION GROUP NUMBER1: 3
	. . . PLUS . . .
	OXYFLUORFEN
	(GoalTender, etc.)	2 lb a.i.	24	see label
	WSSA MODE OF ACTION GROUP NUMBER1: 14
	COMMENTS: Combined to give broad-spectrum control. Apply preemergence or combined with paraquat or glyphosate if weeds have emerged. Irrigate within 21 days if rain has not occurred.
D.	GLYPHOSATE	0.5 lb a.i.	Roundup: 4	17
	(Roundup, Touchdown, etc.)		Touchdown: 12	17
	WSSA MODE OF ACTION GROUP NUMBER1: 9
	. . . PLUS . . .
	2,4–D*
	(Orchard Master CA, etc.)	0.5 lb a.i.	48	40
	WSSA MODE OF ACTION GROUP NUMBER1: 4
	. . . PLUS . . .
	SURFACTANT	0.5–1%	NA	NA
	COMMENTS: Combined to give broad-spectrum control. Apply postemergence to young, growing weeds. Avoid drift or contact with leaves.

PUBLICATION

UC IPM Pest Management Guidelines: Nectarine
UC ANR Publication 3451
Weeds
J. A. Roncoroni, UC Cooperative Extension, Napa County
S. D. Wright, UC Cooperative Extension Tulare County
Acknowledgment for contributions to Weeds:
A. Shrestha, UC IPM Program, Kearney Agricultural Center, Parlier
W. T. Lanini, Weed Science/Plant Sciences, UC Davis
K. Hembree, UC Cooperative Extension, Fresno County

Top of page