Rice Root Aphids, Rhopalosiphum rufiabdominale, Preferentially Choose and Multiply Faster on Monocotyledonous Plants

Abstract

Rice root aphids (RRAs), Rhopalosiphum rufiabdominale (Sasaki) (Hemiptera: Aphididae), reportedly feed on a wide range of monocotyledonous plants (“monocots”) and dicotyledonous plants (“dicots”). However, possible preference for either monocots or dicots, as well as the mechanisms underlying host plant selection, have not yet been investigated. In two-choice and no-choice laboratory experiments, we tested whether RRAs (1) select monocots or dicots as host plants, (2) multiply faster on monocots or dicots, and (3) choose preferred host plants based solely on olfactory cues. When RRAs were offered a choice between two potted monocots (rye vs. barley), they showed no preference, but when they were offered a choice between rye and a dicot (cannabis, celery, coriander, lettuce, pepper, squash, tomato, or marigold), they invariably selected and multiplied faster on rye. Similarly, in a no-choice experiment, where RRAs were confined in a mesh bag fitted with a single host plant, they multiplied equally well on monocots (rye and barley), but significantly less on any of the eight dicots. In moving-air two-choice Y-tube olfactometer bioassays, which presented olfactory but not visual cues of monocots and dicots, the first- and final choices of RRAs were mostly indifferent, suggesting that RRAs locate their preferred monocots based not solely on plant odor. As RRAs are emerging pests in commercial cannabis and vegetable production, it is conceivable to use rye as a trap crop to divert RRAs from valuable cannabis and vegetable crops. This concept, however, still requires testing in commercial crop production settings.