With the cold weather conditions we experienced last week, one might conclude that aphid pressure will subside. However, aphid populations being monitored in untreated lettuce plots at the Yuma Agricultural Center (YAC) suggest differently. To date, we have observed a steady increase in both green peach aphids and Acyrthosiphon lactucae, which is an aphid species specific to lettuce with no common name that occurs sporadically in desert produce. The highest abundance we've recorded is about 18 aphids / plant, and on average we're finding about 4-5 aphids / plant in untreated lettuce. This is up from less than 2 aphids per plant early last week prior to the light freeze we experienced. We've also observed an increase in winged (alate) aphids, which is likely due to the gusting north winds we've experienced recently. With warmer temperatures forecast in the next week or so, we anticipate these numbers to increase. So you might want to pay particular attention for aphid colonization when visiting fields.

Additional notes: (1) Imidacloprid soil applications at 0.25 lb AI/ac (i.e., Alias 2F at 16 oz) are holding aphids to low numbers in lettuce trials at YAC, (2) preliminary efficacy trial have shown that Movento, Beleaf and Assail are maintaining green peach aphids at low levels for 14 days following sprays. (3) Anecdotal reports have been coming in from area PCAs that Foxglove aphid has been found in celery, and Lettuce "red" aphid in romaine. For more information on the identification, biology, ecology and management of aphid species important on desert produce please read: Insect Management on Desert Produce Crops: Aphids also you can check out the Aphid Control Chart.

Acyrthosiphon lactucae

To contact John Palumbo go to: jpalumbo@ag.arizona.edu

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.