Description of the Pest
Alfalfa looper and cabbage looper larvae are green caterpillars with three pairs of true legs in the front and two pairs of robust, unjointed prolegs on the abdomen (back portion of the body). A distinguishing characteristic of looper caterpillars is that as they crawl, they move their rear end up toward their heads so their body arches into a circular loop. Adult moths have dark brown, mottled forewings with a characteristic figure-eight marking in the center.
Loopers may occur at any time during the growing season. Infestations early in the season on seedling plants may result in damage to cotyledons, new leaves, and terminal buds. Looper eggs are deposited singly, usually on the underside of younger leaves. The larvae feed on larger, more mature leaves.
Loopers have many natural enemies that frequently keep them below economically damaging levels, unless the natural enemies are killed by insecticide applications applied for other pests. Important parasitoid wasps include the tiny egg parasitoid, Trichogramma pretiosum, and four wasps that attack the caterpillars: Hyposoter exiguae, Copidosoma truncatellum, Microplitis brassicae, and Cotesia medicaginis (alfalfa looper only). In addition to the parasitoid wasps, a tachinid fly, Voria ruralis, also attacks the caterpillar. In some areas, the nuclear polyhedrosis virus, an important biological control agent, occurs naturally in fields and kills loopers. Plant habitat that attracts natural enemies and avoid the use of broad-spectrum pesticides known to harm natural enemies.
Organically Acceptable Methods
Use biological control, Bacillus thuringiensis, and the Entrust formulation of spinosad for an organically certified crop.
Monitoring and Treatment Decisions
Specific treatment thresholds have not been established for loopers. Late-season infestations do not usually cause significant crop loss. If damaging numbers during mid-season results in excessive foliage loss, an insecticide application may be warranted to prevent crop loss.
|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.|
|(Intrepid 2F)||4–16 fl oz||4||7|
|MODE-OF-ACTION GROUP NUMBER1: 18|
|COMMENTS: Early season applications: 4 to 8 fl oz; Mid- to late season applications: 8 to 16 fl oz.|
|(Coragen)||3.5–5 fl oz||4||1|
|MODE-OF-ACTION GROUP NUMBER1: 28|
|(Steward)||6.7–11.3 fl oz||12||7|
|MODE-OF-ACTION GROUP NUMBER1: 22A|
|D.||BACILLUS THURINGIENSIS ssp. AIZAWAI #|
|(XenTari)||0.5–1.5 fl oz||4||0|
|MODE-OF-ACTION GROUP NUMBER1: 11A|
|COMMENTS: To maximize control, ensure thorough coverage and by make applications when larvae are small.|
|MODE-OF-ACTION GROUP NUMBER1: 5|
|COMMENTS: Do not apply more than 12 oz/acre per season of Success or 3.75 oz/acre per season of Entrust. For blackeyes, apply with an oil.|
|**||Mix with sufficient water to obtain full 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.|
|#||Acceptable for use on organically grown produce.|
|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; pesticides with a 1B group number should be alternated with pesticides that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|