Feb 10, 2021Lettuce Aphids Showing Up Early Again
Like last winter, lettuce aphids, Nasonovia ribisnigri, (aka., red aphid) have already been found colonizing lettuce fields in several locations throughout the Yuma area. In the desert, we typically associate lettuce aphid with the warm growing conditions in February and March. However, lettuce aphids have been found during January the past two seasons. With the above average temperatures, we’ve experienced this winter, its not surprising they are showing up early. I’ve had reports and identified lettuce aphids appearing from head lettuce and leaf lettuce in Bard and Yuma Valley. We’ve picked them up this week in head lettuce at the Yuma Ag Center. Previous experience has taught us that daytime high temperatures in the 70-80's are ideal for population growth. Given their widespread incidence, they likely came into the desert on one of the multiple flights of winged aphids we’ve reported from sticky traps this winter. Nonetheless, they are here and PCAs should be prepared to battle them, particularly with the above-average temperatures we’re experiencing.
A few things to remember about lettuce aphids relative to the other aphids we commonly see. First, the immature nymphs are small and have a red appearance, whereas the apterous (wing-less) adults are typically a large brown colored aphid with dark bands running across the abdomen (see images below). Second, among the crops we grow locally, lettuce aphids are only found on the lettuce types (Lactuca spp.). Lettuce aphids prefer to colonize the terminal growth, and can often be found in heads or hearts, whereas green peach aphids are often found on the frame leaves in high numbers before moving into the heads. Sampling should be focused in the terminal growth of young plants, and in the heads and hearts of older plants. Third, they can reproduce prolifically, producing many more alates (winged) adults than other species, which can quickly lead to widespread abundance in a field and dispersal throughout a growing area. Finally, as the saying goes "he who hesitates is lost". If lettuce aphids are found on your lettuce, it is recommended that you respond quickly with an insecticide treatment. The product of choice is Movento at 5 oz/ac. Because of its systemic activity, Movento will reach aphids in the protected terminal growth. Be sure to include a penetrating adjuvant for best results at a rate of at least 0.25% v/v. It normally requires 7-10 days of activity before significant reduction in the infestation is observed. Sequoia and Sivanto are good rotational products if coverage of terminal areas can be attained. For more information on lettuce aphid please refer to Lettuce Aphid on Spring Produce-2021.
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu