Potato Grower

May 2019

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direction. More traps are necessary for larger fields. Traps should be placed within fields, about 10 feet from the edge of the field, oriented perpendicular to the stake with one face of the trap facing toward the edge of the field. This should facilitate capturing psyllids as they fly into the field from the field edge. Both sides of the trap have a piece of wax paper that is removed to expose the sticky part of the trap. These sheets of wax paper need to be saved for later retrieval of the traps. The sticky trap should be positioned on the stake just above the potato canopy. Too low, and the foliage will cover the trap; too high, and you may miss psyllids that are attempting to land on the foliage. Traps often need to be positioned slightly above the canopy to compensate for vigorous growth during some parts of the season. Of course, when plants are senescing at the end of the season, the traps need to be moved to a lower position on the stake to stay just above the crop canopy. You remembered to save the wax paper that you peeled off the new sticky traps, right? Good. We use this wax paper to cover both sides of each trap as we retrieve them from the field. The insects and debris collected on the trap typically allow the paper to stick well enough that it remains in place, allowing you to stack a set of traps together without them sticking to each other (or to you). It is very important to remember that this wax paper has a waxy side and a not- so-waxy side. If you stick the less waxy side to the sticky trap, you generally can forget about ever removing it again. Make sure you place the wax paper with the waxy face on the sticky trap so that the paper can be removed later to reveal the insects on the trap. Each sticky trap should be swapped out for a new one every week. Changing out sticky traps on the same day every week is ideal. Traps from the same field can be bundled together with rubber bands or in a zipper closure bag, and they should be stored in a freezer when possible. The date that each group of traps was retrieved should be clearly written on each set of traps from each field. Now that you have succeeded in sending your sticky traps out into the world and returning them home safely, the next step is to inspect them for potato psyllids. Unfortunately, this is no easy task. You will need magnification—ideally a dissecting microscope, but a 15× or 20× hand lens can work. There are several key characteristics to look for, and Andy Jensen, manager of the Northwest Potato Research Consortium, produced a helpful guide to identifying potato psyllids on yellow sticky traps that can be found at www.nwpotatoresearch.com/resources/ insect-trapping-guides. Alternatively, the entomology program at University of Idaho in Kimberly is offering psyllid identification as a fee-for- service arrangement for Idaho growers. For a per-trap fee, we can supply the yellow sticky trap system that growers then deploy, retrieve and return to the research station in Kimberly each week. We will identify and count any potato psyllids and send them to the University of Idaho diagnostics lab in Parma to test for the presence of the zebra chip bacterium (This testing requires a separate fee.). We can then provide you with a weekly report of our findings. Erik J. Wenninger is an entomologist at the University of Idaho's Kimberly Research & Extension Center. Idaho growers interested in the services detailed in this article can contact Wenninger at (208) 423-6677 or erikw@uidaho.edu. WWW.POTATOGROWER.COM 37 A zebra chip symptomatic tuber (above) compared with a healthy tuber (below) A stack of retrieved traps, ready to be read for psyllids. The components of a yellow sticky trap system Adult potato psyllid

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