Seasonal Infestations of Two Stem Borers (Lepidoptera: Crambidae) in Noncrop Grasses of Gulf Coast Rice Agroecosystems

Abstract

Infestations of two stem borers, Eoreuma loftini (Dyar) and Diatraea saccharalis (F.) (Lepidoptera: Crambidae), were compared in noncrop grasses adjacent to rice (Oryza sativa L.) fields. Three farms in the Texas rice Gulf Coast production area were surveyed every 6-8 wk between 2007 and 2009 using quadrat sampling along transects. Although D. saccharalis densities were relatively low, E. loftini average densities ranged from 0.3 to 5.7 immatures per m(2) throughout the 2-yr period. Early annual grasses including ryegrass, Lolium spp., and brome, Bromus spp., were infested during the spring, whereas the perennial johnsongrass, Sorghum halepense (L.) Pers., and Vasey's grass, Paspalum urvillei Steud., were infested throughout the year. Johnsongrass was the most prevalent host (41-78% relative abundance), but Vasey's grass (13-40% relative abundance) harbored as much as 62% of the recovered E. loftini immatures (during the winter). Young rice in newly planted fields did not host stem borers before June. April sampling in fallow rice fields showed that any available live grass material, volunteer rice or weed, can serve as a host during the spring. Our study suggests that noncrop grasses are year-round sources of E. loftini in Texas rice agroecosystems and may increase pest populations.

Associations between host plant concentrations of selected biochemical nutrients and Mexican rice borer, Eoreuma loftini, infestation

“…Insects absorb nitrogen through the gut mostly in the form of free amino acids and very small peptides, and the initial cost of proteolysis is saved if amino acids are ingested as small molecules (Brodbeck & Strong, ). The relatively low levels of free essential amino acids in broadleaf signalgrass and Vasey's grass found in this study might explain low oviposition on these grasses by Mexican rice borers (Beuzelin et al., ; Showler et al., ). However, of 16 free amino acids detected in our study, only free histidine concentrations occurred in the order of oviposition preference and larval stem entry reported by Showler et al.…”

“…Histidine may have a specific physiological role, for example, to promote larval growth, as in the pink bollworm, Pectinophora gossypiella (Saunders) (Vanderzant, ). However, free histidine was not detected in Vasey's grass, which can host overwintering Mexican rice borer larvae in rice growing areas of the Texas Gulf Coast (Beuzelin et al., ). Free methionine, also essential, was absent from sudangrass, a preferred host among forage and weed species (Showler et al., ).…”

“…The preferred utilization of sudangrass and the sorghum‐sudangrass hybrid in this study, and of maize in previous studies (Showler et al., ), suggests that fructose is important in determining host plant suitability for use by larvae. However, barnyardgrass and Vasey's grass, which did not have detectable accumulations of fructose, harbor appreciable numbers of Mexican rice borer eggs and larvae (Beuzelin et al., ; Showler et al., ). Hence, other biochemical, physical, and ecological factors probably have roles in larval Mexican rice borer host plant utilization (Beuzelin et al., ).…”

Biology and Management of the Mexican Rice Borer (Lepidoptera: Crambidae) in Rice in the United States

“…Feeding on plants in the family Cannaceae ( Canna spp.) and Cyperaceae ( Cyperus spp., Scirpus validus Vahl) has been reported (Osborn and Phillips 1946, Beuzelin et al. 2011a).…”

“…In addition, seasonal activities of the two species differ, with Mexican rice borer populations active and abundant year-round, whereas the majority of sugarcane borer populations overwinter as large larvae (Rodriguez-del-Bosque et al. 1995, Beuzelin et al. 2011a, 2011b).…”