Suitability of poaceous plants for nymphal growth of the pecky rice bugs Trigonotylus caelestialium and Stenotus rubrovittatus (Hemiptera: Miridae) in Niigata, Japan

Under laboratory conditions, we investigated the host suitability of 24 poaceous plants for Trigonotylus caelestialium (Kirkaldy) and Stenotus rubrovittatus (Matsumura). More than 50 % of the nymphs of both bugs reached the adult stage on Poa annua L., Alopecurus aequalis Sobol. var. amurensis (Komar.), Poa sphondylodes Trin., Hordeum murinum L., Agrostis clavata Trin. ssp. matsumurae (Hack. ex Honda), and Lolium multiflorum Lam. In addition, a similar number of S. rubrovittatus nymphs reached the adult stage on Dactylis glomerata L. and Digitaria violascens Link. However, a high percentage of T. caelestialium adults emerged on both spikelets and leaves of the host plants, whereas a lower percentage of S. rubrovittatus adults emerged on leaves than on spikelets. While the numbers of T. caelestialium adults that emerged on spikelets and leaves were similar, those reared on spikelets had a shorter developmental period and longer forewings than those reared on leaves, indicating that spikelets were more suitable for growth. In addition, more adults of both species emerged on plants with ears that arise during the spring and early summer than on plants with ears that arise during the summer and fall. Therefore, the development of these bugs is dependent on the season of ear emergence.