COMPARISON OF FOLIAR AND SOIL-DRENCH APPLICATIONS OF AQUEOUS RUBIDIUMCHLORIDE SOLUTIONS TO PLANTS FOR MARKING FEEDING APHIDS (HOMOPTERA, APHIDAE)

Aqueous solutions of rubidium chloride, RbCl, (10 g/l, 10,000 ppm) wer e applied to foliage or soil of potted bell pepper and tomato. After 4 8 h, green peach aphid (Myzus persicae Sulzer) and potato aphid (Macro siphum euphorbiae Thomas) were transferred to pepper and tomato, respe ctively. Leaf and aphid samples were collected after 6 d; remaining ap hids were transferred to untreated plants. Aphid samples were collecte d periodically for 5 to 7 d. All samples were analyzed for Rb content. Results were similar for the pepper and tomato experiments. Soil-dren ch treatment produced significantly greater levels of Rb in leaf and i nitial aphid samples relative to foliar treatment. Levels of Rb in aph ids from the two treatments were comparable after aphids fed on untrea ted plants for 24 h. Levels of Rb in aphids declined rapidly after rem oval from the source: undetectable by Day 6 in the potato experiment a nd reduced by nearly 90% by Day 5 in the tomato experiment. Foliar app lication of RbC1 solution should be used in field situations. Applicat ion is more precise, and the length of detection is comparable with so il drench. Additionally, soil drenching with Rb produced an initially high peak of Rb in the aphids, which may have a physiological effect.