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Insect Activity Picking-up in Desert Produce (February 5, 2014)
Foxglove Aphid: Foxglove aphid have been found colonizing lettuce here at the Yuma Ag Center. This is not unusual considering this aphid species tends to be more biologically active under warmer temperatures. However, foxglove aphid is important because it has a tendency to colonize on younger leaves. This often translates into contamination of the heads or hearts of iceberg lettuce, romaine and celery. The key to effective foxglove aphid (and other aphids as well) management with foliar insecticide is to initiate sprays at the time apterous (wingless) aphids begin to colonize. Of course, this requires diligent scouting and sampling. On older lettuce, make sure you thoroughly examine developing heads/hearts. Fortunately, PCAs have alternatives for foliar aphid control. For more information on insecticide alternatives please visit the Foxglove Aphid on Desert Lettuce Crops.

Corn Earworm: We’re beginning to catch corn earworm moths in pheromone traps throughout the area. This is significant since we had not previously caught any earworm since early November. Trap catches have been high in the Gila Valley over the past 2 weeks (see Areawide Trapping Network). This could be an early indication of egg deposition in fields which is important because once head formation begins, larvae will typically bore into the head 1-2 days upon hatching. They are much more likely to bore into lettuce heads than other Lepidoptera larvae. Larvae may enter the head from any point, although recently we’ve observed them burrowing in from the base of the plant near the core. If fields are not watched closely, infestations may not be noticed until the head is harvested. Once inside the head, it is almost impossible to control the larvae with insecticides.

Mystery Lepidopterous Larvae: An unidentified lepidopterous larvae has been found burrowing into the roots of young romaine plants in the Yuma Valley. Several PCAs have reported this larvae and damage over the past 2 weeks when finding romaine plants wilting in the field. When plants were removed and examined, the damage and larvae could be found near the base of the plant. Images of the damage and larvae can be found in the attached document Mystery Larvae. We have reared one of the larvae and waiting to have the adult moth identified to species. If anyone has seen this larvae in the field please contact us, as we would like to collect more larvae for further identification.

Remember: "When in Doubt...Scout"

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For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.

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