Population Dynamics of the Rice Bugs, <i>Leptocorisa chinensis</i> Dallas (Hemiptera: Alydidae) and <i>Cletus punctiger</i> (Dallas) (Hemiptera: Coreidae), in Grass Fields

Abstract

The population dynamics of two major rice bug species in the fields of Italian ryegrass and gramineous weeds were compared in southern Ibaraki Prefecture, Japan from 2002 to 2004. Overwintered adults of Leptocorisa chinensis appeared in grass fields from late June to early July. Their progeny appeared soon, and the population fluctuation until October was bimodal. In contrast, overwintered adults of Cletus punctiger appeared much earlier, in early May, while the next-generation nymphs were seldom detected until late June. Based on the immigration dates of overwintered adults and the cumulative effective temperature for development and ovarian maturation, it was confirmed that L. chinensis is bivoltine in the study area. The first appearance date of first-generation adults of L. chinensis in grass fields did not coincide with the heading date of mid-season rice cultivated most widely in southern Ibaraki Prefecture. This reveals that current rice cultivation practices in this area are suitable to prevent the massive invasion of L. chinensis.