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/melon 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/melon 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/melon 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**	P.H.I.+
(trade name)			(days)
When choosing a pesticide, consider information relating to water quality and impact on natural enemies and bees.
A.	IMIDACLOPRID
	(Provado) 1.6F	3.5 fl oz	7
	MODE OF ACTION: A neonicotinoid (Group 4A)1 insecticide.
	COMMENTS: Thorough, uniform coverage is important for good control. Use allowed under a supplemental label.
B.	DIAZINON* 50 WP	1 lb	14
	MODE OF ACTION: An organophosphate (Group 1B)1 insecticide.
	COMMENTS: Avoid drift and tailwater runoff into surface waters.
** See label for dilution rates.   + Preharvest interval. Do not apply within this many days of harvest.   1 Modes of action are important in preventing the development of resistance to pesticides. 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. 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 is 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
C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
W. E. Chaney, UC Cooperative Extension, Monterey Co.
E. T. Natwick, UC Cooperative Extension, Imperial Co.
D. R. Haviland, UC IPM Program, Kern Co.

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