Movement of Mexican rice borer (Lepidoptera: Crambidae) through the Texas rice belt.
ABSTRACT Pheromone-baited traps were used to monitor the movement of the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), through the Texas rice belt from 2000 to 2005. Based on location of discovery in each county and year, the average rate of spread from 1980 to 2005 was 23 km/yr. From 2000 to 2005, the leading edge of the infestation has moved 16.5 km/yr toward Louisiana. The 1.8-fold increase (99% confidence interval) of the area occupied from 2000 to 2005 in the Texas rice belt indicates an expansion of the distribution of E. loftini. If movement continues to occur at similar rates, E. loftini will reach Louisiana by 2008.
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ABSTRACT: a b s t r a c t a r t i c l e i n f o Cotesia flavipes is an important gregarious larval endoparasitoid of several crambid stem borers, including Diatraea saccharalis. The suitability of two crambid species, Eoreuma loftini and D. saccharalis, pests of sugarcane and rice in Texas, for C. flavipes development was tested. The effect of parasitization by C. flavipes on encapsulation response was assessed in vivo in both D. saccharalis and E. loftini. The results indicated that the parasitoid developed and emerged successfully in D. saccharalis larvae. Although E. loftini larvae were readily parasitized by C. flavipes parasitoids, no wasp larvae hatched from the eggs in this host because eggs were encapsulated by the host's hemocytes. The developmental fate of the E. loftini larvae with encapsulated parasitoids was variable. Most died as abnormal fifth instars or as post-wandering prepupae, while a few developed normally to the pupal stage. In vivo experiments, there was a significant reduction in the percent of beads encapsulated in parasitized larvae in both hosts. However, the percent of beads showing melanization decreased significantly in parasitized D. saccharalis larvae but did not differ significantly in parasitized or unparasitized E. loftini larvae. Our results showed that D. saccharalis is a suitable host for C. flavipes whereas E. loftini is an unsuitable host. This study indicated that lepidopteran stem borers that are taxonomically, behaviorally, and ecologically very similar can differ in their ability to encapsulate a parasitoid species.Journal of Asia-Pacific Entomology 08/2011; 15(1-15):63–68. · 0.88 Impact Factor
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ABSTRACT: A 2-year field study in Texas compared infestations of the stem borers Eoreuma loftini (Dyar) and Diatraea saccharalis (F.) in rice, Oryza sativa L., as affected by main crop harvest cutting height and the production of a ratoon crop. Substantial infestations (>5.6 stem borers/m2) remained in rice culms regardless of cutting height (20 vs. 40 cm). However, the 20-cm cutting height reduced E. loftini infestations by 70–81% whereas D. saccharalis infestations were not affected. Plant dissections showed that compared to D. saccharalis larvae and pupae, relatively more E. loftini immatures are located high in rice plants (>20 cm from the base of the culm). In October, the ratoon crop was more infested with stem borers than the unmanaged main crop stubble during the first year of the study. The opposite was observed during the second year. Differences in unmanaged main crop stubble phenology between the two years likely caused these differences in infestation levels. During the post-growing season, infestations in main and ratoon crop stubble decreased over the winter. After favorable winter conditions, infestations in main and ratoon crop stubble did not differ, attaining 3.3 E. loftini/m2 and 0.4 D. saccharalis/m2 by March 2008. In March 2009, rice stubble harbored 0.3 E. loftini/m2 and 0.2 D. saccharalis/m2 regardless of whether only a main crop or a main and ratoon crop had been produced. This study showed that a lower rice harvest cutting height can suppress late season E. loftini populations. Furthermore, rice stubble under favorable conditions represents a substantial overwintering habitat, thus warranting evaluation of pest management tactics targeting overwintering populations.Crop Protection 04/2012; 34:47–55. · 1.54 Impact Factor