J. M. Beuzelin

Monitoring and First Discovery of the Mexican Rice Borer Eoreuma loftini (Lepidoptera: Crambidae) in Louisiana

The Mexican rice borer, Eoreuma loftini (Dyar), is native to Mexico, and has been reported in the Mexican states of Baja California, Colima, Hustecas, Jalisco, Michoacan, Nayarit, Nuevo Leon, Oaxaca, San Luis Potosi, Sinaloa, Sonora, Tamaulipas, Veracruz, and Yucatan (Morill 1925; Van Zwaluwenburg 1926; Riess 1981; Johnson 1984; Rodriguez-del-Bosque et al. 1989; ReayJones et al. 2007). Eoreuma. loftini was originally described by Dyar (1917) as a member of the genus Chilo Zincken from a specimen collected in Arizona, U.S.A. The species was transferred to Eoreuma Ely by Klots (1970). It has been collected from sugarcane (Saccharum officinarum L.), corn (Zea mays L.), rice (Oryza sativa L.), sorghum (Sorghum bicolor (L.) Moench), and lemongrass (Cymbopogon citrates I flexuosus L.) (Johnson 1984). Weedy grasses including johnsongrass (Sorghum halepense (L.) Pers.), vaseygrass (Paspalum urvillei Steud.), Amazon sprangletop (Leptochloa panicoides (J. Presi) Hitchc), and barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.) also have been reported as hosts (Reagan et al. 2007). It was first reported in the Lower Rio Grande Valley (LRGV) of Texas, U.S.A. during 1959 when a single larva was detected in sugarcane shipped from Mexico (Johnson 1984). By 1980, E. loftini had established itself as a serious pest in the LRGV and populations subsequently spread into the rice production region of Texas along the Gulf Coast (Johnson & van Leerdam 1981, Browning et al. 1989). From 2000 to 2002, female sex pheromone traps captured E. loftini moths in seven new southeast Texas counties (Reagan et al. 2005; Reay-Jones et al. 2007). During 2002, moths were captured within 100 km of sugarcane in east Texas and within 200 km of sugarcane in Louisiana. By 2004, E. loftini was present in over 75% of the Texas rice growing area and had spread into sugarcane plantings in Chambers County, Texas (Reagan et al. 2005, Reay-Jones et al. 2007). In an attempt to slow the spread of E. loftini into Louisiana, in 1999, the Louisiana Department of Agriculture and Forestry (LDAF) entered into a compliance agreement with the Texas Department of Agriculture which placed restrictions on the entry oiE. loftini infested Texas sugarcane into Louisiana for processing. This agreement required that east Texas sugarcane fields be monitored for E. loftini using pheromone traps. The agreements conditions also stipulated that a positive E. loftini finding in east Texas sugarcane would automatically trigger the establishment of a one-mile-radius quarantine around that field and sugarcane within that quarantined area could not be shipped into Louisiana. All truckloads of sugarcane destined for Louisiana were required to be tagged and certified as E. loftini free (Reagan et al. 2005). In a proactive effort to monitor the natural spread of E. loftini, LDAF initiated deployment of 12 pheromone traps during fall 1999 at selected sugarcane fields and adjacent to sugarcane processing facilities in Louisiana. The number of traps deployed annually increased from 12 to 40 through 2005. During this timeframe, traps also were placed near rice fields. Beginning in 2005, 35 to 40 traps have been deployed annually. Traps remained in the field from planting of rice (Mar) through harvest of sugarcane (DecJan), and until processing facilities finished milling sugarcane. The detection of E. loftini in 2 east Texas pheromone traps adjacent to sugarcane in 2004 (2-IX2004, 20-IX-2004, 2-X-2004) triggered a one-mileradius quarantine (Reagan et al. 2005). By 2005, E. loftini was widespread in east Texas and all sugarcane from that area was prohibited from entry into Louisiana due to the risk of accidental introduction of E. loftini (Reagan et al. 2007). This prohibition helped to slow the spread of E. loftini movement into Louisiana (Reay-Jones et al. 2008). The pheromone trap monitoring program determined that E. loftini was expanding its range 16.5 km/yr through the Texas rice belt toward Louisiana (Reay-Jones et al. 2007). Based on natural movement, Reay-Jones et al. (2007) predicted that E. loftini would establish in Louisiana during 2008. On 12-XII-2008 one E. loftini adult was detected in each of 2 pheromone traps in Calcasieu Parish (Louisiana, U.S.A.) located approximately 8 km from the Texas border. These traps were adjacent to harvested rice fields approximately 8 km apart. C. Carlton confirmed identifications by examination of male genitalia and com-

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 m2 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 Vaseys grass, Paspalum urvillei Steud., were infested throughout the year. Johnsongrass was the most prevalent host (41–78% relative abundance), but Vaseys 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.

Impact of Hurricane Rita Storm Surge on Sugarcane Borer (Lepidoptera: Crambidae) Management in Louisiana

ABSTRACT Twelve thousand to 16,000 ha of Louisiana sugarcane (Saccharum spp.) fields were flooded by saltwater from the Hurricane Rita storm surge in September 2005. A four treatment, 12-replication study comparing storm surge flooded and nonflooded plant and ratoon sugarcane fields was conducted during summer 2006 to assess sugarcane borer, Diatraea saccharalis (F.), pest severity, pest control actions, and soil-associated arthropod abundance and diversity. Even with a significant 2.4-fold increase in the average number of insecticide applications used for D. saccharalis management in flooded fields, growers still incurred higher injury. A significant 2.8-fold reduction in the predaceous red imported fire ant, Solenopsis invicta Buren, was associated with the storm surge, whereas no reduction in abundance of other soil-associated arthropods was recorded. Arthropod diversity measured by the Shannon diversity index significantly increased by a factor of 1.3 in sugarcane fields flooded by the storm surge. Increase in D. saccharalis pest severity associated with the storm surge caused an estimated loss in revenue between

Improved Chemical Control for the Mexican Rice Borer (Lepidoptera: Crambidae) in Sugarcane: Larval Exposure, a Novel Scouting Method, and Efficacy of a Single Aerial Insecticide Application

1.9 and

Effects of Chlorantraniliprole and Thiamethoxam Rice Seed Treatments on Egg Numbers and First Instar Survival of Lissorhoptrus oryzophilus (Coleoptera: Curculionidae)

2.6 million to the Louisiana sugarcane industry for the 2006 production season.

Activity of chlorantraniliprole and thiamethoxam seed treatments on life stages of the rice water weevil as affected by the distribution of insecticides in rice plants

ABSTRACT A three-treatment aerial application insecticide experiment was conducted in five commercial sugarcane, Saccharum spp., fields in south Texas to evaluate the use of pheromone traps for improving chemical control of the Mexican rice borer, Eoreuma loftini (Dyar), in 2009 and 2010. A threshold of 20 moths/trap/wk was used to initiate monitoring for larval infestations. The percentage of stalks with larvae on plant surfaces was directly related to the number of moths trapped. Reductions in borer injury and adult emergence were detected when a threshold of >5% of stalks with larvae present on plant surfaces was used to trigger insecticide applications. Novaluron provided superior control compared with &bgr;-cyfluthrin; novaluron treated plots were associated with a 14% increase in sugar production. A greenhouse experiment investigating establishment and behavior of E. loftini larvae on two phenological stages of stalkborer resistant, HoCP 85–845, and susceptible, HoCP 00–950, sugarcane cultivais determined that more than half of larvae on HoCP 00–950 and >25% on HoCP 85–845 tunneled inside leaf mid-ribs within 1 d of eclosion, protected therein from biological and chemical control tactics. Exposure time of larvae averaged <1 wk for all treatments and was shortest on immature HoCP 00–950 and longest on mature HoCP 85–845. This study shows a short window of vulnerability of E. loftini larvae to insecticide applications, and demonstrates the potential utility of pheromone traps for improving insecticide intervention timing such that a single properly timed application may be all that is required.

A Relative Resistance Ratio for Evaluation of Mexican Rice Borer (Lepidoptera: Crambidae) Susceptibility Among Sugarcane Cultivars

ABSTRACT Effects of treatment of rice seeds with an anthranilic diamide, chlorantraniliprole, and a neonicotinoid, thiamethoxam, on egg laying and first instar survival in rice water weevil, Lissorhoptrus oryzophilus Kuschel, were examined under greenhouse conditions. Exposure of adult weevils to rice (6–7 leaf stage) grown from seeds treated with chlorantraniliprole and thiamethoxam resulted in reduction in numbers of eggs and first instars. The low egg numbers by adults exposed to chlorantraniliprole-treated plants was confirmed as a sublethal effect on adults: adult survival was not impacted after 4 d of feeding on foliage from chlorantraniliprole-treated plants but the number of eggs laid by these weevils was reduced when released on untreated plants. Furthermore, a comparison of first instar emergence from chlorantraniliprole-treated plants and from untreated plants infested with weevils previously exposed to this chemical suggested that chlorantraniliprole was also reducing egg or first instar survival. In contrast, adults that fed on foliage from thiamethoxam-treated plants showed increased mortality. Possible sublethal effects of thiamethoxam on the number of eggs laid by adults were investigated by infesting untreated plants with weevils that survived exposure to thiamethoxam via foliar feeding (7 µg active ingredient / seed). Prior exposure to thiamethoxam through adult feeding reduced egg numbers. However, potential larvicidal or ovicidal effects of thiamethoxam seed treatments could not be detected in this study because of low first instar emergence from both thiamethoxam-treated plants and from untreated plants infested with weevils previously exposed to this chemical. These experiments revealed that the two seed treatments accomplish weevil control in different ways.

Oviposition and larval development of a stem borer, Eoreuma loftini, on rice and non-crop grass hosts

BACKGROUND The systemic insecticides chlorantraniliprole (CAP) and thiamethoxam (TMX), applied to rice as seed treatments, may affect multiple life stages of the rice water weevil, Lissorhoptrus oryzophilus. Effects of CAP and TMX on adult survival, egg-laying and first- and late-instar survivals were determined by infesting plants treated as seeds with different rates of insecticides. The biological activity was related to insecticidal concentrations in leaves, shoots and roots. RESULTS CAP did not affect adult survival but decreased egg numbers and reduced the survival of the first and late instars. The greatest reduction in weevil population occurred in late instars feeding on roots. In contrast, TMX reduced adult survival and egg and larval numbers. The high biological activity of CAP on root-feeding stages was consistent with the accumulation of CAP in roots, whereas in TMX-treated plants the high activity on adults correlated with high concentrations of TMX in leaves and stems. CONCLUSIONS The differential activity of insecticides on adults suggests poor inherent potency of CAP as an adulticide and/or its limited systemicity in foliage. The distribution of insecticide in specific plant parts can be attributed to the different physicochemical properties of CAP and TMX. The field implications of this research on management of L. oryzophilus are discussed.

Jasmonic acid-induced resistance to the fall armyworm, Spodoptera frugiperda, in conventional and transgenic cottons expressing Bacillus thuringiensis insecticidal proteins

ABSTRACT The Mexican rice borer, Eoreuma loftini (Dyar), is a major pest of sugarcane (hybrids of Saccharum spp.) in Louisiana and Texas. Resistance to E. loftini was evaluated in 51 commercial and experimental cultivars of sugarcane, energycane (hybrids of Saccharum spp.), and sorghum [Sorghum bicolor (L.) Moench and hybrids of Sorghum spp.] in four replicated small plot field experiments from 2009 to 2012. A relative resistance ratio was developed to compare levels of susceptibility among cultivars based on the percentage of bored internodes and survival to adulthood. This index was able to separate cultivars into five resistance categories and provides a new method for comparing levels of resistance among cultivars. E. loftini pest pressure in 2009 was among the highest recorded with injury ranging from 55 to 88% bored internodes. Commercial sugarcane cultivar HoCP 85–845 was identified as resistant in three of four experiments, whereas HoCP 04-838 was identified as susceptible in all experiments. Of the five sugarcane cultivars in commercial production in the Rio Grande Valley of Texas, only TCP 87-3388 was categorized as resistant. Of the cultivars with potential for bioenergy production, all of the energycane cultivars demonstrated higher levels of resistance than high-biomass and sweet sorghum cultivars. Continued evaluation of cultivar resistance to E. loftini is important to development of effective integrated pest management strategies for this pest.

Selection and Life History Traits of Tebufenozide-Resistant Sugarcane Borer (Lepidoptera: Crambidae)

A greenhouse study compared oviposition preference and larval development duration of a stem borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), on rice, Oryza sativa L. cv Cocodrie (Poaceae), and four primary non‐crop hosts of Texas Gulf Coast rice agroecosystems. Rice and two perennials, johnsongrass, Sorghum halepense (L.) Pers., and vaseygrass, Paspalum urvillei Steud. (both Poaceae), were assessed at three phenological stages. Two spring annuals, brome, Bromus spec., and ryegrass, Lolium spec. (both Poaceae), were assessed at two phenological stages. Phenological stages represented the diversity of plant development stages E. loftini may encounter. Plant fresh biomass, dry biomass, and sum of tiller heights were used as measures of plant availability. Accounting for plant availability, rice was preferred over non‐crop hosts, and intermediate and older plants were preferred over young plants. Johnsongrass and vaseygrass were 32–60% as preferred as rice when considering the most preferred phenological stages of each host. Brome and ryegrass received few or no eggs, respectively. Eoreuma loftini larval development (in degree days above developmental threshold temperatures) was fastest on rice and slowest on johnsongrass and vaseygrass. Development duration was only retarded by plant stage on young rice plants. Foliar and stem free amino acid concentrations were determined to help provide insights on the mechanisms of E. loftini oviposition preference and developmental performance.