Description of the Pest
The potato aphid and the green peach aphid are commonly found on many crops including spinach; of the two, green peach aphid is more important. Green peach aphids are dark green to yellow and have no waxy covering. The tubercles (base of the antennae) are slanted toward each other. Populations start on the lower leaves, move up the plant, and are spread over the plant.
Potato aphids have both pink and green forms. This aphid is much bigger than the green peach aphid, and the adult has much longer cornicles (projections at the posterior end of the abdomen) and cauda (posterior tip of the abdomen). Potato aphid colonies are composed of adults with offspring closely clustered around them, usually on the youngest leaves. The potato aphid may occur alone, or in colonies with green peach aphid.
High numbers of aphids can stunt seedlings and will contaminate product bound for market. Green peach aphids vector several viruses that may affect spinach.
Important aphid predators include the convergent lady beetle, Coccinella lady beetles, syrphid flies and lacewings. Epidemics of a disease caused by the fungus Entomophthora aphidis may also kill portions of the green peach aphid population under some conditions. Parasites, including Lysiphlebus testaceipes, Aphidius matricariae, and Aphelinus semiflavus, attack these pests. However, natural enemies rarely provide adequate control of high field populations of the aphid in spring or fall crops.
Some row covers (plastic tunnels or Remay-type enclosures) have reduced aphid populations to below economic levels, but the costs are substantial and the economic viability for large- or even small-scale plantings has not been established. Controlling dust is important to facilitate parasite and predator activity. Aphids tend to be especially high in plants that receive an excess of nitrogen fertilizer.
Organically Acceptable Methods
Biological control and sprays of insecticidal soaps are acceptable for use on organically grown produce.
Monitoring and Treatment Decisions
Check all areas of the field twice a week, but especially the edges, which are usually the first area to become infested. Because infestations are clumped, be sure to sample several plants in many areas of the field.
If high populations develop on seedlings, treat as soon as plants appear stressed. If a significant percentage of plants are infested just before harvest, treat to keep aphids from becoming a contamination problem. Continue monitoring to see whether another treatment is needed. Some populations of green peach aphid may be resistant to certain insecticides in your area; check with your farm advisor for more information.
|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 product being used.|
|MODE OF ACTION GROUP NUMBER1: 1B|
|COMMENTS: Do not make more than 5 applications per season. Avoid drift and tailwater runoff into surface waters.|
|(Movento)||4–5 fl oz||24||3|
|MODE OF ACTION GROUP NUMBER1: 23|
|(Assail 70WP)||0.8–1.2 fl oz||12||7|
|MODE OF ACTION GROUP NUMBER1: 4A|
|MODE OF ACTION GROUP NUMBER1: 9B|
|COMMENTS: Works primarily by ingestion but has some contact activity and some residual control. Thorough spray coverage is essential for optimum control.|
|(Admire Pro)||4.4–10.5 fl oz||12||21|
|(Provado 1.6F)||3.75 fl oz||12||7|
|MODE OF ACTION GROUP NUMBER1: 4A|
|MODE OF ACTION: A contact insecticide with smothering and barrier effects.|
|COMMENTS: If aphid populations are heavy and natural enemies are not present in significant numbers, this material can help reduce populations in organically grown crops. If natural enemies are abundant, they should be able to control aphid populations as effectively as this material. Good spray coverage is essential for control and several applications may be necessary.|
|**||Mix with enough water to provide complete coverage.|
|‡||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.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|#||Acceptable for use on organically grown produce.|
|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).|