How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PESTS

The most common aphid on citrus in the coastal and intermediate districts of southern California is the spirea aphid. In the San Joaquin Valley, the cotton or melon aphid is the most commonly found aphid on citrus. The three species can be distinguished by color: spirea aphids are always green whereas the cotton aphid can range in color from yellow, to green, to dull black. A colony of cotton aphids is usually composed of several different color forms. Black citrus aphids are, as their name suggests, black.

DAMAGE

Aphids feed on buds and on the underside of leaves (mainly feather growth), causing leaves to curl toward the stem. Spirea aphid, black aphid and cotton/melon aphid can all transmit citrus tristeza virus. However, because the transmission rate is fairly low and insecticides are not very effective in preventing transmission of the virus, insecticidal control of aphids is not recommended.

MANAGEMENT

Aphids are generally not a problem on citrus except on young trees because their populations decline when the foliage hardens off. Natural enemies normally control aphid populations, and a spray is rarely warranted. Treatment of aphids to prevent transmission of tristeza virus has not been shown to be effective.

Biological Control
A number of coccinellid and syrphid predators, parasites, and fungal diseases usually keep aphid populations below damaging levels. A moderate aphid population (about 40% of growth flushes infested) can be considered beneficial on mature trees because aphids and their honeydew provide a good food source for natural enemies of other pests early in the season when other hosts are not available.

Organically Acceptable Methods
Biological control is acceptable on organically managed citrus.

Resistance
Populations of cotton aphids in the San Joaquin Valley have been shown to have resistance to organophosphate, carbamate, and pyrethroid insecticides.

Treatment Decisions
On newly established trees and on new growth flushes on mature trees, it is not uncommon for aphids to cause curling of leaves and produce honeydew. Treatment is usually not warranted because citrus can tolerate extensive leaf curling without yield effects.

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.
A.	PYRETHRIN/ROTENONE
	(Pyrellin E.C.)	Label rates (OC)	12	12 hours
	RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
	PERSISTENCE: Pests: short; Natural enemies: short
	MODE OF ACTION GROUP NUMBER1: 3A/21B
	COMMENTS: For use on all varieties.
B.	PYRETHRIN/ROTENONE
	(Pyrellin E.C.)	Label rates (OC)	12	12 hours
	RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
	PERSISTENCE: Pests: short; Natural enemies: short
	MODE OF ACTION GROUP NUMBER1: 3A/21B
	. . . PLUS . . .
	NARROW RANGE OIL
	(415)	1.2 qt/100 gal (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: For use on oranges, lemons, and grapefruit. Slurry the pyrethrin/rotenone material with oil before adding to spray tank.
**	OC - Outside coverage uses 100–250 gal water/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.
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/.

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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