Author
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Hagler, James |
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Blackmer, Jacquelyn |
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Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/25/2007 Publication Date: 8/1/2007 Citation: Hagler, J.R., Blackmer, J.L. 2007. Potassium chloride deters Lygus hesperus feeding behavior. Entomologia Experimentalis et Applicata 124: 337-345. Interpretive Summary: Feeding bioassays were conducted to determine the response of adult western tarnished plant bugs (lygus) to artificial diets containing potassium chloride (KCl). Lygus 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 lygus. We also tested the olfactory response of lygus 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 no volatile odors were emitted that preferentially attracted or repelled lygus. The results from these studies strongly suggest that KCl negatively affects lygus feeding behavior by functioning as a strong gustatory deterrent when concentrations exceed 0.5%. Visual and olfactory cues appeared to have no role in mediating feeding behavior under these test conditions. Technical Abstract: 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 on a single diet choice (i.e., a no-diet choice bioassay) feeding arena. Twenty L. hesperus were placed in individual feeding arenas and observed for 15 min. The arenas contained either a standard control (0% KCl) artificial diet or a 12% KCl diet treatment. We observed a total of 22 lygus feeding events lasting an average of 411 (±64) seconds on the control artificial diet and only three feeding events lasting an average of 11 (±3) seconds 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, lygus bugs 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 concentrations of the KCl-treated diets were reduced to 0.5, 1.0, 1.5 or 2.0% and 0.1, 0.2, 0.3, or 0.4% KCl, respectively. Lygus 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, we tested the olfactory response 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 no volatile odors were emitted that preferentially attracted or repelled L. hesperus. The results from these studies strongly suggest that KCl negatively affects lygus feeding behavior by functioning as a strong gustatory deterrent when concentrations exceed 0.5%. Visual and olfactory cues appeared to have no role in mediating feeding behavior under these test conditions. |
