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How to Manage Pests

UC Pest Management Guidelines

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Citrus

Twospotted Spider Mite

Scientific Name: Tetranychus urticae

(Reviewed 9/08, updated 9/08)

In this Guideline:

Description of the pest
Damage
Management

Important links
Publication
Glossary

DESCRIPTION OF THE PEST

All stages of the twospotted spider mite overwinter in protected places on the tree, such as the navel of navel oranges, under the button, and where fruit touch. If the weather is mild, mites continue to feed and reproduce during winter. Activity increases in late spring and peaks in summer. Spider mites first appear on the underside of leaves and when heavy populations build up, also on the upperside of leaves and on fruit. They cover leaves and fruit with a conspicuous webbing.

Eggs are spherical and translucent when first laid, becoming opaque before hatching. Immature mites molt three times before becoming adults; under ideal conditions, a generation can be completed in 7 days.

DAMAGE

Light infestations result in yellow or brown spots between leaf veins. Clusters of dried, brown leaves and profuse webbing indicate a heavy infestation, which if compounded by water stress, could result in leaf and fruit drop.

MANAGEMENT

The twospotted spider mite is an occasional pest on citrus, particularly in the San Joaquin Valley. Its damage potential varies from year to year and is related to water stress and heat. Monitor for twospotted spider mite year round and treat with the most selective miticide to preserve populations of natural enemies.

Biological Control
A number of predators provide substantial control of twospotted spider mites. These include the sixspotted thrips, Scolothrips sexmaculatus, the spider mite destroyer, Stethorus picipes, minute pirate bugs, Orius spp., and the beneficial mite, Euseius tularensis.

Cultural Control
Adequate irrigation will reduce the impact of spider mite feeding.

Organically Acceptable Methods
Cultural and biological controls and certain petroleum oil sprays (such as PureSpray Green [NR 440]) are organically acceptable methods.

Selectivity
Miticides available for controlling twospotted spider mite in bearing orchards include abamectin (Agri-Mek, etc.), acequinocyl (Kanemite), dicofol (Kelthane), fenbutatin oxide (Vendex), fenproximate (Fujimite), hexythiazox (Onager), oil, propargite (Omite), pyridaben (Nexter), spirodiclofen (Envidor); in nonbearing orchards, bifenazate (Acramite) and etoxazole (Zeal) can be used.

Of these miticides, some are more selective than others. Acequinocyl, bifenazate, fenbutatin oxide, and oil have the least effect of all on natural enemies, including predatory mites, but they also provide a shorter period of control of pest mites. Dicofol, etoxazole, hexythiazox, propargite, pyridaben, and spirodiclofen are of intermediate selectivity because they impact both pest mites and predatory mites for up to 6 weeks but have minimal impact on beneficial insects such as lacewings, lady beetles, and Aphytis melinus, which help control caterpillars, scale, thrips, and other pests.

Monitoring and Treatment Decisions
In the San Joaquin Valley, check for twospotted mites when you monitor citrus red mite in late winter and early spring. Continue monitoring twospotted mite occasionally during summer and more closely in late summer and fall. Look for yellow-brown spots on foliage, particularly in the last growth flush, indicating feeding by twospotted spider mites. High populations in summer and fall may require treatments, but thresholds have not been established.

Common name		Amount to Use	R.E.I.+	P.H.I.+
(trade name)		(type of coverage)**	(hours)	(days)


The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.

*NONBEARING TREES ONLY*
A.	BIFENAZATE
	(Acramite) 50 WS	0.75–1 lb/acre (OC)	12	1 year
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
	MODE OF ACTION GROUP NUMBER¹: 25
	COMMENTS: For use in nonbearing orchards only. Do not apply more than once per year.

B.	ETOXAZOLE
	(Zeal)	2–3 oz/acre (OC)	12	1 year
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
	MODE OF ACTION GROUP NUMBER¹: 10B
	COMMENTS: For use in nonbearing orchards only. Do not apply more than once per year.

*BEARING TREES*
A.	NARROW RANGE OIL (92% UR)
	(415, 440)	1.2–1.4% (OC)	4	when dry
	. . . or . . .
	NARROW RANGE OIL (99% UR)
	(415, 435, 440, 455)	1.2–1.4% (OC)	4	when dry
	RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects/mites); Natural enemies: most
	PERSISTENCE: Pests: short; Natural enemies: short
	MODE OF ACTION: Contact including smothering and barrier effects.
	COMMENTS: Use highest rate for July or August applications. Narrow range 440 (or higher) spray oil is preferable in the Central Valley during warmer months because of greater persistence, but risk of phytotoxicity increases unless using products with 99% unsulfonated residues (UR). Caution: Serious hazards are associated with oil treatments to green lemons because of phytotoxicity after sweating; check label for preharvest interval.
	. . . or . . .
	NARROW RANGE OIL (92 OR 99% UR)
	(415)	6–20 gal/acre (LV)	4	when dry
	RANGE OF ACTIVITY: Pests: narrow (citrus red mite) Natural enemies: predatory mites.
	PERSISTENCE: Pests: short; Natural enemies: short
	MODE OF ACTION: Contact including smothering and barrier effects.
	COMMENTS: Higher amounts of oil are for larger trees or for warmer times of the year to increase persistence. Caution: Serious hazards are associated with oil treatments to green lemons because of phytotoxicity after sweating; check label for preharvest interval.

B.	ACEQUINOCYL
	(Kanemite) 15SC	21–31 oz/acre (OC or IC)	12	7
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
	MODE OF ACTION GROUP NUMBER¹: 20B
	COMMENTS: For use on oranges, grapefruit, and lemons only. Apply by ground using 100-250 gal water/acre. Do not use less than 100 gal water/acre. Do not apply more than 62 oz/acre/season. Allow a minimum of 21 days between applications.

C.	HEXYTHIAZOX
	(Onager)	12–24 oz/acre (OC or IC)	12	28
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: intermediate; Natural enemies: short to intermediate
	MODE OF ACTION GROUP NUMBER¹: 10B
	COMMENTS: Do not apply more than once per year.

D.	PYRIDABEN
	(Nexter) WSB	Label rates (OC or IC)	12	7
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
	MODE OF ACTION GROUP NUMBER¹: 21
	COMMENTS: When this material was used during April and May in the San Joaquin Valley and thrips were abundant, there was an increase in scarring damage caused by thrips. Do not apply more than twice/year.

E.	FENPROXIMATE
	(Fujimite) 5EC	1–4 pt (OC or IC)	12	14
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
	MODE OF ACTION GROUP NUMBER¹: 21
	COMMENTS: Do not make more than 2 applications/season and allow 14 days between applications. Use allowed under a Supplemental Label.

F.	SPIRODICLOFEN
	(Envidor) 2SC	see comments	12	7
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
	MODE OF ACTION GROUP NUMBER¹: 23
	COMMENTS: Make no more than 1 application/crop season. Application rate is 12-20 fl oz/acre (OC or IC) when horticultural spray oil is not used, and 18-20 fl oz/acre (OC or IC) when it is.

G.	ABAMECTIN*
	(Agri-Mek, etc.)	10 oz/acre (OC or IC)	12	7
	RANGE OF ACTIVITY: Pests: intermediate (citrus thrips, mites, leafminers); Natural enemies: predatory mites & thrips
	PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
	MODE OF ACTION GROUP NUMBER¹: 6
	. . . PLUS . . .
	NARROW RANGE OIL
	(415)	0.25–1%	4	when dry
	RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects/mites); Natural enemies: most
	PERSISTENCE: Pests: short; Natural enemies: short
	MODE OF ACTION: Improves translaminar movement and persistence of insecticide.
	COMMENTS: For use on all varieties. Most effective in the spring when the trees are flushing.

H.	FENBUTATIN OXIDE*
	(Vendex) 50WP	0.25–0.5 lb/100 gal (OC or IC)	48	7
		...or...
		3 lb/acre (LV)
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: short; Natural enemies: short
	MODE OF ACTION GROUP NUMBER¹: 12B
	COMMENTS: For use on all varieties. Use higher rates during cool weather periods. Do not apply more than 1600 gal dilute spray/acre or use more than 6 lb/acre/season.

I.	PROPARGITE
	(Omite) CR	10 lb/acre (OC or IC)	42 days	28
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
	RESISTANCE: In some twospotted spider mite populations.
	MODE OF ACTION GROUP NUMBER¹: 12C
	COMMENTS: For use on oranges, grapefruit, lemons. Do not apply within 40 days of an oil application, but oil may be applied 30 days or more after propargite. Do not apply to resistant mites.
	. . . or . . .
	(Omite)* 30W	7.5–10 lb/acre (OC or IC)	42 days	28
	COMMENTS: For oranges and grapefruit. Check with county ag. commissioner to determine if there is a Special Local Needs permit for southern California areas. Apply from Oct. 1 to petal fall. Ground application only. Be sure temperatures are below 95°F. No more than 2 applications/fruit year at least 21 days apart. Do not apply within 40 days of an oil application, but oil may be applied 30 days or more after propargite. Do not apply to resistant mites.

J.	DICOFOL
	(Kelthane MF) 4E	0.8 pt/100 gal (OC or IC)	12	7
	RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
	PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
	RESISTANCE: In some twospotted spider mite populations.
	MODE OF ACTION: UNC
	COMMENTS: For use on all varieties. Use on nonresistant mites only; resistance has been reported in the San Joaquin Valley. Closed application system required with this material. Can cause secondary outbreaks of citrus red mites. Do not exceed 6 pt/acre.

**	LV - Low-volume uses 20–100 gal water/acre.
	OC - Outside coverage uses 100–250 gal water/acre.
	IC - Intermediate coverage uses 250–600 gal/acre.
+	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 to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
*	Permit required from county agricultural commissioner for purchase or use.
¹	Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

IMPORTANT LINKS

Photos of twospotted spider mite

PUBLICATION

UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441
Insects, Mites, and Snails
E. E. Grafton-Cardwell, Kearney Agricultural Center, Parlier
J. G. Morse, Entomology, UC Riverside
N. V. O‘Connell, UC Cooperative Extension, Tulare County
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura County
C. E. Kallsen, UC Cooperative Extension, Kern County
D. R. Haviland, UC Cooperative Extension, Kern County
Acknowledgments for contributions to Insect, Mites, and Snails:
J. Barcinas, E. S. I., Corona, CA
R. Dunn, Badger Farming County, Exeter, CA
J. Gorden, Pest Management Associates, Exeter, CA
H. Griffiths, E. S. I., Corona, CA
D. Machlitt, Consulting Entomology Services, Moorpark, CA
C. Musgrove, retired entomologist, Riverside, CA
K. Olsen, S & J Ranch, Pinedale, CA
T. Roberts, E. S. I., Corona, CA
J. Stewart, Pest Management Associates, Exeter, CA
P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA
K. Godfrey, USDA Biological Control, Sacramento
D. Headrick, California Polytechnic State University, San Luis Obispo
B. Faber, UC Cooperative Extension, Ventura County
J. Kabashima, UC Cooperative Extension, South Coast Research and Extension Center

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