Aphid ID in Leafy Vegetables 2014 (January 8, 2014)

The famous lawman, Wyatt Earp was once quoted as saying “fast is fine, but accuracy is everything”. Of course, he was referring to his Buntline Special .45 caliber revolver with a 12 inch barrel that was presumably difficult to quickly draw from a holster. The same could be said about aphid management in desert produce crops. There are certainly “fast acting” insecticides available to control aphids, but “accuracy” in aphid identification is extremely important for cost-effective management. With the windy weather we’ve been experiencing lately, it’s no surprise that we’re seeing an increase in winged (alate) aphids showing up on desert produce crops. A quick glance at the recent Areawide Insect Trapping Network data shows that winged aphid counts found on sticky traps have increased dramatically in some locations in the Yuma and Gila Valleys. Not all of the aphids found on the traps could be identified but several were common species such as green peach and cabbage aphids. This is where the accuracy part comes in; just because you’re quick to find a few winged aphids on produce crops does not mean the these species are important to leafy vegetable and cole crops. As we discussed in a previous update most of the important aphid species you find on local produce crops do not over-summer here, but rather migrate into our cropping system 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. 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 alates which colonize on cole crops but not lettuce, spinach or celery. Other examples would include aphids that colonize small grains (i.e., corn leaf aphid) or alfalfa (i.e., pea 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 the next update. Also, we have had reports of small colonies of cowpea aphids showing up on frame leaves in lettuce. Not to worry, experience has shown us that although small cowpea aphid colonies may be found on lettuce, the populations rarely increase in lettuce crops. So, proper aphid identification 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. But if you want to be fast and accurate you might use the attached publication Aphid Identification in Desert Produce Crops that may assist you in identifying winged and wingless (apterous) aphids important in leafy vegetables and cole crops.