The Structure of Rice Stemborer Assemblages: A Review of Species’ Distributions, Host Ranges, and Interspecific Interactions

Abstract

This review describes global rice stemborer assemblages based on published species distributions, apparent host preferences, and reported shifts in assemblage composition in response to environmental factors. At least 56 moth (Lepidoptera: Crambidae, Pyralidae, Noctuidae) and fly (Diptera: Diopsidae, Chloropidae) species have been associated with rice; however, only 21 species are of potential, large-scale economic importance with a further 2 species of localized concern; most of the remaining species’ associations with rice are based on dubious records without economic impacts on rice production. A list of stemborer–host associations indicates that rice stemborers are largely oligophagous on grasses (Poaceae), but a few species are polyphagous (also attacking Cyperaceae, Typhaceae, and some Eudicotyledon plants). Total stemborer abundance is determined by rice cropping patterns and management. Assemblage species richness is determined by geographical location, surrounding habitat (particularly as regards secondary and occasional species), and season. Evidence suggests that stemborer assemblage structure is largely determined through conditional interspecific competition. Regional assemblages typically include a single dominant lepidopteran species (primary species) that is largely restricted to rice and for which the climate is optimal; one or more secondary species that vary based on the age of rice attacked, rice anatomy, and the proximity to other habitats (including other crops); and occasional species that probably spill over from adjacent grasslands. The co-occurrence of lepidopteran with dipteran rice stemborers requires further research attention.

Heterosis for Resistance to Insect Herbivores in a 3-Line Hybrid Rice System

“…In the field, the A lines had profuse tillering and often attained a relatively large size compared to the fertile lines. Recent detailed studies of plant growth and stemborer occurrence in the Philippines has indicated that YSB—the predominant species occurring in our field plots—is associated with high tillering and relatively thick stems; and that much of the variability in stemborer damage to rice varieties can be explained by crop duration [ 40 , 60 ]. Rice varieties that are exposed for longer in the field tend to incur greater damage from stemborers, which is better regarded as crop ‘vulnerability’ and not ‘susceptibility’ [ 60 ].…”

“…This can be reduced by avoiding long-duration varieties, thereby reducing vulnerability [ 60 ]. However, even where varieties are selected to avoid specific stemborer-related susceptibilities, i.e., by reducing tillering to avoid YSB damage or reducing stem thickness to avoid SSB damage, other stemborers from the regional assemblage of species can become prevalent [ 40 ]. For this reason, calls have been made for greater attention to issues of rice tolerance to stemborers.…”

“…We also used YSB in our greenhouse experiments. This species is the main stemborer pest of rice in tropical Asia [ 40 ]. Stemborers attack rice at the seedling or tillering stages when adults deposit egg masses on the rice foliage.…”

“…After emergence, the neonates migrate to the base of the rice plant and tunnel into the tillers where they feed and develop. There can be up to two generations of stemborer per crop [ 40 ]. YSB is difficult to maintain in laboratory colonies; therefore, we collected adults from rice fields in Laguna Province, 3–5 days before they were required for the experiments.…”