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The U.S. Gulf Coast has ideal conditions, including abundant rainfall and a long growing season, for production of dedicated bioenergy crops. Interest in producing bioethanol from high-biomass graminaceous crops including energycanes (Saccharum spp.) and energy sorghums (Sorghum spp. hybrids) in the region has increased. However, insect pests including the sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), will likely adversely affect bioenergy crops. The impact of D. saccharalis infestations on yields of conventional and bioenergy sugarcanes and sorghums was investigated in three separate field studies conducted from 2012 to 2013. These studies compared D. saccharalis injury and crop yield parameters among insecticide-protected and unprotected plots of sugarcanes, energycanes, high biomass sorghums, and sweet sorghum. In unprotected plots, D. saccharalis injury ranged from 2.9 (resistant sugarcane) to 13.6% bored internodes (susceptible sugarcane). A resistant energycane cultivar was among the least injured (3.5% bored internodes) and demonstrated the greatest potential for bioethanol production with an average of >17,000 L/ha. Linear regressions revealed negative relationships between percentage of bored internodes and ethanol yield in all cultivars. At one location, D. saccharalis injury resulted in a 13% reduction in bioethanol production across all years and cultivars. These studies indicate D. saccharalis has potential to substantially reduce yields in bioenergy crops and pest management programs will be needed to maximize ethanol production.

Melanaphis sacchari (Zehntner) is a major pest of sorghum, Sorghum bicolor (L.) Moench, in the United States and neighboring Caribbean countries including Haiti. Laboratory, greenhouse, and field experiments were conducted to determine the effects of biological insecticides on M. sacchari infesting sorghum. Azadirachtin, pyrethrins, Beauveria bassiana strain GHA, Isaria fumosorosea Apopka strain 97, Chromobacterium subtsugae strain PRAA4-1T, Burkholderia spp. strain A396, and vetiver oil were compared to a conventional insecticide, flupyradifurone. In the laboratory, sorghum leaf discs were sprayed with treatment solutions and subsequently infested with M. sacchari nymphs. In the greenhouse, potted sorghum plants were sprayed with treatment solutions before or after infestation with M. sacchari nymphs. In the field, plots exposed to natural M. sacchari infestations were sprayed with treatment solutions. All insecticide treatments except I. fumosorosea and Burkholderia spp. were associated with 58–100% aphid mortality after 72 h in the laboratory, which was greater than the 20% mortality observed in the non-treated control. In the greenhouse, azadirachtin and pyrethrins were the biological insecticides associated with the lowest aphid infestation levels 7 days after treatment. Flupyradifurone was associated with the greatest mortality in the laboratory and the lowest infestation levels in the greenhouse. In the field, decreases in aphid infestation levels relative to the non-treated control were not observed although flupyradifurone was consistently associated with the lowest infestations. Our results suggest that biological insecticides including azadirachtin, pyrethrins, and B. bassiana could potentially control M. sacchari infestations in sorghum if applied under favorable environmental conditions.

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most injurious insect pest in US rice production. Yield losses in excess of 25% can occur from severe infestations. Management demonstrations were conducted in the 2008, 2009, 2010, and 2011 growing seasons to evaluate the use of commercially available insecticides to control L. oryzophilus in commercial rice fields. The demonstration tests, conducted on farms throughout Louisiana, compared the efficacies of recently registered seed treatment insecticides to untreated controls and to foliar applications of pyrethroids. Efficacy was assessed by collecting root/soil core samples three to four weeks after application of permanent flood and counting numbers of larvae and pupae in core samples. Tests were replicated across locations in multiple rice-producing Louisiana parishes. Densities of larvae and pupae in core samples exceeded the larval threshold (three larvae or pupae per core sample) in over 80% of untreated plots/cuts, confirming the ubiquity and severity of this insect as a pest of rice. Use of chlorantraniliprole (Dermacor® X-100, DuPont™ Crop Protection, Wilmington, DE), thiamethoxam (CruiserMaxx® Rice, Syngenta® Crop Protection, Greensboro, NC), and clothianidin (NipsIt Inside®, Valent® USA Corporation, Walnut Creek, CA) seed treatments significantly reduced L. oryzophilus infestation compared to untreated checks. Fewer larvae and pupae were observed in rice treated with chlorantraniliprole than in rice treated with other insecticides.

Phorid flies, Pseudacteon spp. (Diptera: Phoridae), have been released in the United States since 1996 as biological control agents for imported fire ants, Solenopsis invicta Buren, Solenopsis richteri Forel, and their hybrid (Hymenoptera: Formicidae). A statewide survey was conducted in Louisiana during 2009 and 2010 to determine the distribution of Pseudacteon tricuspis Borgmeier and Pseudacteon curvatus Borgmeier, and to quantify the potential spatial association between the two species. Additionally, collected phorid flies were tested for the microsporidium Kneallhazia ( =Thelohania ) solenopsae (Knell, Allen, and Hazard), another natural enemy of fire ants, to establish an account of the pathogen’s distribution and prevalence in phorid fly populations. P. tricuspis and P. curvatus have expanded their range from four and three separate release sites, respectively, in Louisiana. By 2010, P. tricuspis and P. curvatus occupied approximately 86,600 and 111,900 km 2 , respectively. Overall, P. curvatus was more abundant than P. tricuspis , with 41.9 ± 7.3 (SE) and 9.8 ± 1.5 (SE) females, respectively, collected on average per sampling site in 2009. Spatial Analysis by Distance IndicEs (SADIE) suggested aggregation for the two phorid fly species. P. tricuspis collections were positively associated with P. curvatus collections, indicating that gaps and clusters of both species generally overlapped. K. solenopsae was detected in 22 of 64 parishes, and among 124 collection sites tested, 19% yielded positive responses for K. solenopsae . P. tricuspis males and females and P. curvatus females were found to harbor K. solenopsae . This study is the first to detect K. solenopsae in P. tricuspis .

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.

The Mexican rice borer, Eoreuma loftini (Dyar), is the key pest of sugarcane, Saccharum hybrids, in south Texas, having largely displaced the sugarcane borer, Diatraea saccharalis (F.), and it is moving into rice- and sugarcane-growing areas of east Texas and Louisiana. While a number of alternative weed and crop hosts have been reported, the extent to which they might support Mexican rice borer populations is unknown. This study involved choice assays that compared oviposition preference for and larval infestations of five mature graminaceous weed species. Levels of infestation between sugarcane and corn, Zea mays L., crop hosts and between corn and sorghum, Sorghum bicolor (L.) Moench, were also assessed. We determined that the average number of larval entry holes in sudangrass stems was ≥2.5-fold more than for any of the other four weed host plants, that corn had ≥5.9-fold more larval entry holes than sorghum and ≥8.2-fold more than sugarcane. Greater oviposition and infestation of one non-crop host over another was not related to numbers of stems per plant, but was associated with the greater stem diameter and abundance of dry leaf tissue found in Sudangrass, Sorghum bicolor (L.) Moench ssp. drummondi (Nees ex Steud.) de Wet & Harlan, johnsongrass, S . halepense (L.) and barnyardgrass, Echinochloa crus-galli (L.) P. Beauv.; relative to the other weed species in this study. In terms of the crop plants, stalk diameter and quantity of dry leaf tissue were not associated with numbers of eggs or larval entry holes in the choice assays between corn and sorghum, and between sugarcane and corn. While corn has been known as a host of the Mexican rice borer for at least 84 yr, its role in area-wide population dynamics and control efforts has likely been greatly underestimated.

A 2-year field cage experiment was conducted in Beaumont, Texas to estimate parasitism of sugarcane borer, Diatraea saccharalis (F.), by Cotesia flavipes (Cameron) on rice. A lab experiment showed that the number of hosts parasitized per female per day reached a maximum (0.961) at 28 °C. Parasitized larvae recovered from the field experiment produced an average of 27.9 ± 19.1 ( x ¯ ± s.d.) parasitoids, with a 2.57:1 (female/male) sex ratio. A cohort-based age-structured model was developed to simulate the population dynamics and economic impact of sugarcane borer and C. flavipes in rice, as affected by overwintering larval density, timing and rate of parasitoid aerial release, and year-to-year climate (temperature and rainfall). The results suggest the cumulative seasonal damaging larval density (3rd or later instars) is negatively correlated with winter temperature, while maximum parasitoid density and maximum proportion parasitized are positively correlated with the cumulative seasonal damaging larval density. C. flavipes was most effective when released 40 or 50 days after rice planting, with simulated yield loss reduced by up to 50.9% when the release rate was 10 females and 4 males m−2. The maximum simulated economic benefit ($59.48 ha−1) is ca. 6.7% of that provided by insecticide-based control, which occurred when the release rate was 1 female and 0.4 males m−2. The inability of C. flavipes to provide economic control in temperate-subtropical areas is due to its high rearing cost, a low effective search rate, a low maximum number of hosts parasitized per female, and failure of the spring emerging parasitoids to find hosts.

On-farm field experiments were conducted in 2004 and 2007 to assess the suitability of novaluron, a chitin synthesis inhibitor, for sugarcane borer, Diatraea saccharalis (F.), management in Louisiana sugarcane (Saccharum spp. hybrids). Aerial insecticide applications reproducing commercial production practices were made when D. saccharalis infestation levels exceeded a recommended action threshold. In addition to decreased D. saccharalis infestations, 6.3 – 14.5-fold reductions in end of season injury, expressed as the percentage of bored sugarcane internodes, were observed in plots treated with novaluron. D. saccharalis control in novaluron plots was equivalent to (P > 0.05) or better (P 0.05) decreases in predaceous and non-predaceous soil-dwelling non-target arthropods were associated with insecticides. However, numerical trends for decreases in immature crickets associated with novaluron and gamma-cyhalothrin were recorded in 2007. Our data suggest that novaluron will fit well in Louisiana sugarcane integrated pest management.