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 per acre** | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used. | ||||
| A. | IMIDACLOPRID | |||
| (Admire Pro -foliar) | 1.2 fl oz | 12 | 7 | |
| MODE-OF-ACTION GROUP NUMBER1: 4A | ||||
| COMMENTS: Thorough, uniform coverage is important for good control. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | ||||
| B. | THIAMETHOXAM | |||
| (Platinum 75SG) | 1.7–4.01 oz | 12 | NA | |
| MODE-OF-ACTION GROUP NUMBER1: 4A | ||||
| COMMENTS: Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | ||||
| C. | ZETA-CYPERMETHRIN* | |||
| (Mustang) | 3.4–4.3 fl oz | 12 | 1 | |
| MODE-OF-ACTION GROUP NUMBER1: 3A | ||||
| COMMENTS: Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | ||||
| D. | FLONICAMID | |||
| (Beleaf 50SG) | 2–2.8 fl oz | 12 | 3 | |
| MODE-OF-ACTION GROUP NUMBER1: 9C | ||||
| * | Permit required from county agricultural commissioner for purchase or use. |
| ** | See label for dilution rates. |
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) 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 pesticides 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; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. Mode-of-action group numbers for insecticides and miticides (un=unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee). |
| NA | Not applicable |