W. Akbar

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-

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

Categorizing Sugarcane Cultivar Resistance to the Sugarcane Aphid and Yellow Sugarcane Aphid (Hemiptera: Aphididae)

1.9 and

Feeding by sugarcane aphid, Melanaphis sacchari, on sugarcane cultivars with differential susceptibility and potential mechanism of resistance

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

Sugarcane Planting Date Impact on Fall and Spring Sugarcane Borer (Lepidoptera: Crambidae) Infestations

ABSTRACT Sugarcane (Saccharum spp.) in Louisiana is colonized by two aphid species, the sugarcane aphid, Melanaphis sacchari (Zehntner), and the yellow sugarcane aphid, Sipha flava (Forbes) (Hemiptera: Aphididae). The main problem associated with M. sacchari is transmission of sugarcane yellow leaf virus, a casual agent of yellow leaf disease whose absence has been added to certification standards for micropropagated sugarcane in Louisiana. Greenhouse studies were conducted to categorize dominant commercial sugarcane cultivars for their ability to tolerate aphid injury and to express antixenotic or antibiotic effects on both aphid species. Antixenosis tests showed no preference among cultivars by either aphid species. Loss of chlorophyll content in tolerance tests also did not show differences among cultivars for both aphid species. However, antibiosis tests revealed that life history parameters such as the duration of the reproductive period and fecundity of both aphid species were negatively affected on ‘HoCP 91-555’ compared with ‘L 97-128’, Estimation of demographic statistics indicated that both aphid species exhibited a significantly lower intrinsic rate of increase (1.8–2.8-fold) and longer doubling time (1.7–3.1-fold) on HoCP 91-555 relative to L 97–128. From these tests, cultivars in the current study can be ranked from most to the least susceptible as L 97–128 > ‘LCP 85–384’ > ‘HoCP 96–540’ > ‘Ho 95–988’ > HoCP 91–555 for M. sacchari and L 97–128 > LCP 85–384 > HoCP 91–555 for S. flava. Therefore, antibiosis is an important category of resistance in sugarcane to both aphid species, and HoCP 91–555 might provide useful germplasm for developing aphid resistant cultivars.

Evaluation of Aphid Resistance Among Sugarcane Cultivars in Louisiana

Feeding behavior of Melanaphis sacchari Zehntner (Hemiptera: Aphididae) was studied on sugarcane, Saccharum spp. (Poaceae), cultivars HoCP 91‐555 (resistant), LCP 85‐384 (moderately resistant), and L 97‐128 (susceptible) using the electrical penetration graph (EPG) technique. Constitutive concentrations of total phenolics and available carbohydrates, water potential at the whole‐leaf tissue level, and free amino acids (FAAs) in phloem sap extracts, and in honeydew produced by aphids fed on L 97‐128 and HoCP 91‐555 were determined. Cultivar did not influence time for M. sacchari to access phloem sieve elements. Total time in sieve elements was ca. two‐fold greater on L 97‐128 than on HoCP 91‐555, whereas it did not differ from LCP 85‐384 in either cultivar. The mean duration of individual events associated with phloem sap ingestion was ca. 50% shorter on both HoCP 91‐555 and LCP 85‐384 than on L 97‐128. Although cultivar effects were not detected for levels of total phenolics, available carbohydrates, and water potential, two free essential amino acids, histidine and arginine, were absent from phloem sap in HoCP 91‐555. Two free essential amino acids, leucine and isoleucine, and two free non‐essential amino acids, tyrosine and proline, were absent from honeydew of aphids fed on HoCP 91‐555. These results suggest that despite apparent biosynthesis of some FAAs, the absence of important FAAs in the phloem sap of HoCP 91‐555 and the inability of M. sacchari and its endosymbionts (e.g., Buchnera) to derive specific free essential and non‐essential amino acids from other ingested molecules, possibly along with other unidentified factors, underlie the pests decreased phloem sap ingestion and consequently reduced growth potential on HoCP 91‐555.

Potential impact of Mexican rice borer non-crop hosts on sugarcane IPM.

ABSTRACT In a two-year field study, sugarcane was planted on 4 dates ranging from the first week of Aug to the third week of Nov, reproducing sugarcane phenologies associated with planting and harvesting operations in Louisiana. Sugarcane planted in early Aug offered an extended period of plant availability for sugarcane borer, Diatraea saccharalis (F.), infestations during the fall. Periodic sampling throughout the fall showed that early Aug plantings had higher (P < 0.05) D. saccharalis-caused deadheart densities than later planted sugarcane. Destructive sampling conducted in early Oct showed that Aug plantings harbored greater deadheart densities (P < 0.05 in fall 2007) and D. saccharalis infestations (P < 0.05 in fall 2006 and 2007) than Sep plantings. Data from this study suggest a potential for increased D. saccharalis overwintering populations in early plantings associated with greater infestations during the fall. However, differences in deadhearts and D. saccharalis infestations in deadhearts were not detected (P > 0.05) during the spring. Three commercial sugarcane cultivare (‘L 99-226’, ‘L 97-128’, ‘HoCP 95-988’) were studied. Differences in D. saccharalis injury or infestations as affected by cultivar were detected (P < 0.05) only in early Oct 2007 when ‘HoCP 95-988” harbored 2.3-fold greater infestations than ‘L 99-226’.

CHEMICAL CONTROL OF THE MEXICAN RICE BORER IN THE LOWER RIO GRANDE VALLEY OF TEXAS, 2008

ABSTRACT Sugarcane (Saccharum L.) in Louisiana is colonized by the sugarcane aphid, Melanaphis sacchari (Zehntner), and the yellow sugarcane aphid, Sipha flava (Forbes). Five commercial sugarcane cultivars, ‘LCP 85-384′, ‘HoCP 91-555′, ‘Ho 95-988′, ‘HoCP 96-540′, and ‘L 97-128′, representing >95% of Louisianas sugarcane-growing area, were assessed under southern Louisiana field conditions for numbers of the two aphid species. Biweekly sampling during 2007 and 2008 growing seasons indicated cultivar and time effects on aphid frequency. Aphid population peaks occurred during June and July and then crashed. M. sacchari was more abundant than S. flava on almost all cultivars and on all sampling dates during both years of the study. HoCP 91-555 was found to be the most resistant compared with the susceptible Ho 95-988 and L 97-128 cultivars. HoCP 91-555 might be useful in areas of high aphid pressure, and as a source of resistance in cultivar development programs.