How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Cotton (melon) aphid is a small to medium-sized aphid. It is highly variable in color, ranging from lemon yellow to blackish green in different individuals, often within the same colony. The aphid is commonly lighter in color during the hotter times of the year and darker during cooler periods, but both color forms may be found throughout the year.

DAMAGE

Cotton aphid is known to transmit more than 50 viruses, some of which affect carrots. It does not generally build up large populations on carrots but may occasionally cause some feeding injury. Injury is typical of aphid feeding with curled and distorted leaves. If populations are large enough, honeydew accompanied by sooty mold may be produced.

MANAGEMENT

Biological Control

Cotton aphid is attacked by the common aphid predators including green lacewing, lady beetles, and syrphid fly larvae. Several parasites of this aphid are present in California and can provide effective control. Parasitized aphids can be identified by their tan color and bloated appearance.

Cultural Control

Carrots planted adjacent to infested cotton or melons are at risk of becoming infested with this aphid, particularly in fall following cotton defoliation or termination of the melon crop. Carrots should be planted a safe distance from both, if possible.

Organically Acceptable Methods

Biological and cultural controls are acceptable for use on organically grown produce.

Monitoring and Treatment Decisions

Monitor fields for aphids weekly during spring and summer by examining the upper and lower surfaces of leaves. Also, look for evidence of predators and parasites and their impact on aphid populations. Treatment not normally required. No thresholds for cotton aphid on carrots have been established. Chemical treatments are not effective in preventing virus transmission and this aphid rarely causes economic damage.

Common name		Amount/Acre**	R.E.I.+	P.H.I.+
(trade name)			(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 the label of the product being used.
A.	IMIDACLOPRID
	(Provado 1.6F)	3.5 fl oz	12	7
	MODE OF ACTION GROUP NUMBER1: 4A
	COMMENTS: Thorough, uniform coverage is important for good control. Use allowed under a supplemental label.
B.	DIAZINON* 50 WP	1 lb	24	14
	MODE OF ACTION GROUP NUMBER1: 1B
	COMMENTS: Avoid drift and tailwater runoff into surface waters.
**	See label for dilution rates.
+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treat ment 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/.
*	Permit required from county agricultural commissioner for purchase or use.

PUBLICATION

UC IPM Pest Management Guidelines: Carrot
UC ANR Publication 3438

Insects

E. T. Natwick, UC Cooperative Extension, Imperial County
D. R. Haviland, UC IPM Program, Kern County
C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
Acknowledgment for contributions to Insects:
W. E. Chaney, UC Cooperative Extension, Monterey County

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