Potassium chloride deters Lygus hesperus feeding behavior

A series of bioassays were conducted to determine the response of adult western tarnished plant bugs, Lygus hesperus Knight (Heteroptera: Miridae), to artificial diets containing potassium chloride (KCl). We first examined the feeding behavior of L. hesperus by direct observation in a no-choice diet feeding arena. We observed a total of 22 Lygus feeding events lasting an average of 411 ± 64 s on the control artificial diet and only three feeding events lasting an average of 11 ± 3 s on the KCl-treated diet. We then conducted several multiple diet choice bioassays to determine the feeding response of L. hesperus when exposed simultaneously to five artificial diet treatments containing different amounts of KCl. For the first bioassay, we used standard clear parafilm diet packets and for the second bioassay we used dark green parafilm diet packets to hold the various diet treatments. Regardless of the diet packet color, L. hesperus overwhelmingly selected the 0% KCl diet treatment over diets containing 3, 6, 9, or 12% KCl. The third and fourth multiple diet choice bioassays were identical to the first bioassay, except that concentrations of the KCl-treated diets were reduced. Lygus hesperus consistently selected the control diet over all diets containing more than 0.5% KCl. However, when the concentration of KCl in the diet was reduced to ≤ 0.4%, there were no significant differences in feeding activity exhibited by L. hesperus . Finally, to determine if the addition of KCl to the diet influenced their upwind response, we examined the responses of L. hesperus that were simultaneously exposed to a control artificial diet and a diet containing 12% KCl in a Y-tube olfactometer bioassay. Of the 95 adults tested, 47 selected the arm containing the normal diet and 48 selected the arm containing KCl-treated diet, indicating that dietary constituents did not preferentially attract or repel L. hesperus . The results from these studies strongly suggest that KCl negatively affects L. hesperus feeding behavior by functioning as a strong gustatory deterrent when concentrations exceed 0.5%. Visual and volatile cues appeared to have no role in mediating orientation or feeding behavior under these test conditions.