Caught Between the Devil and the Deep Blue Sea, Mobile Planthoppers Elude Natural Enemies and Deteriorating Host Plants

Abstract

Delphacid planthoppers (Hemiptera: Delphacide) are mostly drab-colored, dimimutive (<5mm) denizens of grassland habitats (Denno and Roderick 1990; Fig.1). Their grassfeeding habit has predisposed a fair number of these phloem feeders for becoming severe agricultural pests of rice, corn, cereals, sorghum, and sugarcance throughout the world (wilson and O'Brien 1987). Most of the remaining 2,000 delphacid species however, occur in marshes, old fields, meadows, praories, and pasture lands where they usually go unnoticed (Denno and Roderick 1990, Wilson et al. 1994). As with most taxa of phytophagous insects, delphacid species very in how widely their populations fluctuate. Many planthopper species undergo dramatic fluctuations, reaching outbreak proportions at times and then crashing to barely detectible levels at others (Waloff 1980, Denno and Roderick 1990, Strong et al. 1990, Perfect and Cook 1994). In contrast, populations of other planthopper species exhibit a much more latent dynamic, fluctuating less and remaining at low levels much of the (Waloff 1980, Denno et al.1981).