-
Nov 14, 2018Aphid Movement in Desert Vegetables 2018With shorter days, cooler temperatures and winds consistently blowing out of the north and west, PCAs should begin to see an increase in winged aphids and colonies showing up on desert produce crops. We’ve already had reports of green peach aphid colonizing broccoli plants in the Gila and Dome Valleys. Experience tells us that this is an annual occurrence. The key aphid pests found on winter produce do not over-summer here, rather they migrate into our cropping system from mountainous regions of southern California via wind currents during the late fall. Once the aphids reach our desert valleys, they typically move from crop to crop until they find a suitable host to feed and colonize on. No need to panic if you suddenly find a few winged aphids on a lettuce plant. But it is important that you correctly identify the aphid species found on your crops. It is not uncommon to find winged aphids on lettuce or broccoli that do not colonize on the crop. An example of these would be cabbage aphid which will colonize and infest cole crops but not lettuce, spinach or celery. Other examples would include aphids that colonize small grains (i.e., oat bird-cherry aphid) or alfalfa (i.e., blue alfalfa aphid). Because these aphid species will not colonize produce crops, it is important to be able to distinguish them from the aphids that do colonize and require management to prevent problems at harvest (i.e., green peach aphid, foxglove aphid, lettuce aphid, cabbage aphid). Proper aphid ID can also influence your choice of insecticide, but more on that in a later update. Don’t be surprised if you start finding small colonies of cowpea aphids showing up on frame leaves in lettuce. That is a common occurrence every fall. Not to worry, experience has shown us that although small cowpea aphid colonies may be found on lettuce, the populations generally stay low on the plant on the frame leaves and rarely increase to levels causing contamination issues. But you never know. So keep a close watch out for these aphids found in your crops, as our weird weather this year may be more conducive to their development than normal. Bottom Line: proper aphid identification is important; it can save a PCA time and money, and prevent unnecessary insecticide applications. If you find an unusual aphid in your produce, don’t hesitate to drop it by the Ag Center and we’ll get it identified for you. If you want to make fast and accurate IDs, you might use the attached publication Aphid Identification in Desert Produce Crops that can assist you in identifying winged and wingless (apterous) aphids important in leafy vegetables and cole crops.
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
