Eoreuma Loftini Research Articles

Natural incidence of stem borer damage in U.S. rice varieties

Lepidopteran stem borers (Crambidae) are economically important pests of rice in Louisiana and Texas, and diversified management tactics are needed. Rice varieties differ in susceptibility to stem borers, but resistance has not been studied in modern varieties. Analysis of stem borer injury levels (densities of unfilled panicles or “whiteheads”) was conducted on data from 37 separate field experiments in Acadia and Calcasieu Parishes, LA from 2016 to 2021. In all years, stem borer infestations were predominantly comprised of the Mexican rice borer, Eoreuma loftini (Dyar). Whitehead density was least in 2016 (0.1 whiteheads m−2) and greatest in 2019 (4.0). Across all years, whitehead density was strongly affected by rice genotype. Whitehead densities for 16 common commercial varieties are reported herein. Stem borer infestations were greatest in PVL01 having approximately 7-fold greater whitehead density than the least infested varieties, CL152, Jefferson, and Jazzman. Mean whitehead densities were approximately two-fold higher in inbred varieties than in hybrid varieties. In addition, medium grain varieties showed higher whitehead densities than long grain varieties. Whitehead densities did not differ between imidazolinone-resistant “Clearfield” varieties and conventional varieties. Results suggest varietal resistance can be incorporated into integrated management programs of rice stem borers to reduce reliance on chemical controls.

Lignocellulosic Composition Not Associated with Stem Borer Resistance in Select Louisiana Sugarcane Cultivars

The two most economically damaging insect pests of sugarcane in Louisiana are the sugarcane borer (SCB) and the newly invasive Mexican rice borer (MRB), both of which can be managed in part with cultivar resistance. High stalk fiber levels is a well-documented aspect of stem borer resistance but is inversely correlated with recoverable sugar levels. However, lignocellulosic components such as hemicellulose, cellulose, and lignin are associated with resistance to other borer species in poaceous crops, potentially indicating mechanisms that may provide resistance without substantial trade-offs in yield. The goal of this study was to determine whether lignocellulosic composition varied among four cultivars—HoCP 85-845, HoCP 04-838, Ho 07-613, and HoCP 00-950—selected based on known variation in SCB and MRB resistance and total fiber content. We estimated lignocellulosic composition as well as Brix throughout the growing season and the total stalk fiber and recoverable sugar content at harvest for both plant cane and first ratoon crop years. We found that the Brix content throughout the growing season, as well as total fiber and sugar content at harvest, were significantly associated with the cultivar, aligning with previously documented trends in borer resistance (i.e., higher Brix and lower total fiber indicate a more susceptible cultivar). While lignocellulosic composition during the growing season was not associated with cultivar or resistance to either borer species, it was significantly impacted by sampling month and crop year. These data indicate the potential influence of alternative resistance mechanisms and interactions with abiotic conditions.

Registration of ‘L 14‐267’ sugarcane

Abstract‘L 14‐267’ (Reg. no. CV‐213, PI 701487) sugarcane (Saccharum spp. hybrid) was released for commercial production in Louisiana because of its high yield potential and broad‐spectrum disease resistance. The final testing stage resulted in data from 62 trials at 12 representative sandy silt (light‐textured) and clayey (heavy‐textured) soil locations. Cane yield of L 14‐267 was comparable to that of ‘L 01‐299’, the most widely grown cultivar in the Louisiana sugar industry, in the plant and first ratoon crops but significantly lower in the second ratoon crop. Sucrose content was significantly higher in L 14‐267 than in L 01‐299 in the plant and first ratoon crops and was comparable to that of L 01‐299 in the second ratoon crop. Sugar yield was significantly higher in L 14‐267 than in L 01‐299 in the plant crop, comparable in the first ratoon crop but significantly lower in the second ratoon crop. The performance of L 14‐267 did not differ significantly between the two soil types for any of the traits. L 14‐267 is a mid‐ to late‐season maturing cultivar that appears to respond well to plant growth regulators but poorly to sub‐freezing temperatures. L 14‐267 displayed broad‐spectrum disease resistance, being resistant to mosaic, yellow leaf, smut, and ratoon stunt and moderately resistant to brown rust and leaf scald. L 14‐267 is moderately susceptible to the sugarcane borer and the Mexican rice borer.

Mulched and soil-incorporated sugarcane greenchop residue and compost: effects on selected soil components, sugarcane nutrients, Mexican rice borer injury, and yield

Burning sugarcane, Saccharum spp., fields to remove leaves before harvest is a routine practice in many sugarcane production areas, including the United States. The method is environmentally deleterious and has been discontinued in some parts of the world. Alternatively, excised preharvest leaf residue, or greenchop, is used as mulch. This field study examined the effects of greenchop, applied in several ways to sugarcane soil, on soil fertility, selected sugarcane plant physiochemicals, injury inflicted by the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), and sugarcane yield parameters, compared to plots augmented by soil-incorporated compost and a nontreated control. The compost amended soil had elevated concentrations of many nutrients, and in sugarcane leaves, heightened concentrations of certain sugars and free amino acids. None of the greenchop treatments affected soil and sugarcane leaf nutrients. During the first year of the study, E. loftini injury to sugarcane stalks during the first season, however, was generally greater in the greenchop and compost treatments than in the control. In the second growing season, the compost treatment was the only treatment associated with heightened E. loftini infestations. Relationships between soils augmented with organic amendments and E. loftini injury to sugarcane are discussed in terms of mediation through physiochemical changes induced by the amendments.

Characterization of Resistance to the Mexican Rice Borer (Lepidoptera: Crambidae) among Sugarcane Cultivars.

Simple SummaryThe Mexican rice borer, Eoreuma loftini, is one of the most important insect pests of sugarcane in the US. Management strategies that are environmentally friendly and economically profitable are needed to mitigate the pest’s impact. Cultivar resistance can become a key management strategy for Mexican rice borer control in sugarcane because it is inexpensive and easy for sugarcane growers to implement. Resistance is compatible with almost all other management strategies and minimizes further input costs incurred by the grower. However, the mechanisms of resistance are not completely understood. Elucidating which mechanisms and traits confer resistance can help sugarcane breeding programs increase the resistance level of future cultivar releases. We found that the currently grown commercial cultivars L 01-299 and HoCP 85-845 had the least amount of borer-related injury, while L 12-201 and HoCP 00-950 had the greatest level of injury. These differences appear to be related to the ability of recently hatched larvae to establish feeding rather than female preference to lay eggs on specific cultivars. Further work is needed to determine the influence of environmental factors on resistance expression and identify plant characteristics that are responsible for Mexican rice borer resistance.Cultivar resistance is an essential management strategy for the Mexican rice borer, Eoreuma loftini (Dyar), in sugarcane in the USA, but resistance mechanisms are poorly understood. Resistance was evaluated among Louisiana’s (USA) commercial sugarcane cultivars and experimental clones through field screenings, greenhouse trials, and a diet incorporation assay. Cultivars L 01-299 and HoCP 85-845 had the lowest borer injury levels, while HoCP 00-950 and L 12-201 were among the most heavily injured in field and greenhouse trials. The variability of results between the two field trials suggests that a genotype × environment interaction might affect the expression of resistance. Oviposition did not differ among evaluated cultivars in the greenhouse choice study. Results from the no-choice experiment showed that neonatal establishment differed among cultivars by up to 3-fold. In a diet incorporation assay, all cultivars reduced larval weight up to 86.5% and increased days to pupation by 1.8-fold relative to the diet-only control. Collectively, these results suggest that Louisiana’s sugarcane breeding germplasm contains various resistance levels to E. loftini, emphasizing the importance of screening cultivars before they are released to growers. Future studies should try to determine the influence of environmental factors on resistance expression.

Economic returns on seed treatment combinations in Louisiana rice

The use of multiple insecticidal seed treatments in combination to control a greater spectrum of pests has been increasing in rice production in the U.S. Mid-South. The economic benefits of individual seed treatments in rice are well documented, but returns on investment (ROI) on combinations are unknown. Efficacy and economic returns of insecticidal seed treatments alone and in combination were evaluated through a series of five field trials conducted in Louisiana from 2018 to 2020. In all trials, treatments containing chlorantraniliprole or cyantraniliprole provided the best control of rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), and control was not significantly improved by the addition of a second insecticide. Insecticidal control of L. oryzophilus by all seed treatments was reduced in late-planted rice fields relative to rice planted within the recommended planting window. Control of the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), did not improve rice yields. Fungicidal seed treatments generally protected rice yields over treatments without fungicides despite having no effect on early-season plant populations. All seed treatments provided returns on investment which ranged from $94.30 (fungicide only 2018) to $519.75/ha (chlorantraniliprole + thiamethoxam + fungicides in 2019–2020). Increased yields resulting from the use of multiple insecticides in combination appears to justify the added expense. Collectively, results demonstrate the immense value of insecticidal seed treatments to rice production in Louisiana and throughout the U.S. Mid-South. Future research efforts should aim to assess returns on seed treatments across a range of rice production conditions and to quantify the impacts of sporadic pests on rice yields.

A New Detection of the Invasive Mexican Rice Borer (Lepidoptera: Crambidae) From Georgia in the United States Based on Morphological and Molecular Data

Abstract The Mexican rice borer, Eoreuma loftini (Dyar), is an invasive herbivore that attacks many gramineous host plants. The species is an economic pest of several grass crops in North America including sugarcane (Saccharum spp.), rice (Oryza sativa), corn (Zea mays), and sorghum (Sorghum bicolor). The species was first detected in the United States in 1980 and has since expanded its range eastward along the Gulf Coast reaching Louisiana in 2008. A disjointed introduction was detected in Florida in 2012, though range expansion of this population within the state has been limited. Most recently, a separate introduction was detected along the Atlantic coast of Georgia near the South Carolina border (32.19884° N, 81.35894° W). Larvae were collected from sugarcane in 2020 and 2021 and identified as E. loftini. The identification was confirmed with genetic analysis showing >99% similarity with most mitochondrial cytochrome c oxidase subunit 1 (COI) sequences of known E. loftini. This is the furthest north and east of any established population in North America. Potential routes of introduction and impacts to crop production along the U.S. Atlantic Coast are discussed.

Management of Stemborers (Lepidoptera: Crambidae) Using Foliar-Applied Chlorantraniliprole in Rice

Rice is one of the most important crops in Louisiana and Texas, USA. It is subjected to various insect pests throughout the growing season. Lepidopteran stem-boring pests including the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), are increasing in economic importance as insect pests in rice production, particularly in southwest Louisiana, USA. Field trials were conducted in Louisiana and Texas to examine the efficacy of foliar-applied insecticides (chlorantraniliprole and the pyrethroids ζ-cypermethrin and λ-cyhalothrin) and chlorantraniliprole seed treatment for control of rice stemborers during 2018 and 2019. Furthermore, a diet incorporation assay assessed the toxicity of chlorantraniliprole to laboratory-reared E. loftini. Results of field experiments in Louisiana showed foliar applications of chlorantraniliprole, at 22 to 35 d after permanent flood was established, reduced stemborer injury to rice by 57.9 to 96.5% in 2018 and 73.9 to 87.5% in 2019 compared to nontreated or pyrethroid-treated field plots. However, rice yields in 2019 did not vary among insecticide-treated and nontreated plots. In the Texas field experiments, chlorantraniliprole applied as seed treatment reduced stemborer injury, but was not effective in reducing injury when sprayed directly to soil after planting or when applied at permanent flood. The LC50 and LC90 (lethal concentration that produced 50% and 90% mortality, respectively) of chlorantraniliprole on third-instar E. loftini were 0.09 ± 0.03 and 0.53 ± 0.17 µg a.i. mL-1, respectively, at 6 d after exposure. At 10 d after exposure, LC50 and LC90 were 0.04 ± 0.02 and 0.16 ± 0.04 µg a.i. mL-1, respectively. In addition to chlorantraniliprole seed treatment, foliar application of chlorantraniliprole in rice could provide a new tool for management of damaging stemborer infestations.

IN1341] Stem Borers (Lepidoptera: Crambidae) in Florida Rice

Three stem borers, the sugarcane borer, Diatraea saccharalis (F.), rice stalk borer, Chilo plejadellus Zincken, and Mexican rice borer, Eoreuma loftini (Dyar), infest rice in the southern United States. They occur in Florida, with the Mexican rice borer being an invasive species recently introduced into the state. This publication briefly describes stem borers and sampling methods and reports results of the first extensive survey conducted to measure their occurrence in Florida rice.

Integration of Host Plant Resistance and Cultural Tactics for Management of Root- and Stem-Feeding Insect Pests in Rice

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most important early-season pest of rice in the U.S. Additionally, lepidopteran stem-boring pests particularly the invasive Mexican rice borer, Eoreuma loftini (Dyar), are increasingly becoming problematic in Louisiana rice. Although insecticidal seed treatments have been widely adopted and have proven highly effective against weevils and stemborers, alternative management tactics are needed. This study was conducted to evaluate the effects of flood timing and rice cultivar on rice water weevil and stemborer infestations. Field experiments were conducted in Crowley, Louisiana, from 2019–2020. In each year, early- and late-planted trials were established according to a split-split-plot randomized block design. Four commonly grown rice cultivars were selected and were either treated or not treated with a chlorantraniliprole seed treatment. Permanent flood was established at normal timing (approximately the five-leaf stage) or delayed by 2 weeks. Seed treatment reduced weevil densities and stemborer injury by 70–84% and 87–94%, respectively, across planting dates, years, cultivars, and flood timings. The rice cultivar ‘Jupiter' consistently supported the highest numbers of immature weevils, whereas low levels of stemborer injury were observed in ‘Jazzman-2'. Weevil densities were 72 and 20% lower in plots subjected to delayed flood compared to normal flood timing in the 2019 and 2020 late-planted trials, respectively. Reductions of 79 and 93% in stemborer injury in the 2019 early- and late-planted trials, respectively, were observed in delayed flooded plots. Weevil and stemborer infestations negatively affected rice yields, with losses among cultivars ranging from 14 to 49%. Yield losses were generally lower in plots subjected to delayed flood compared to normal flood timing but the difference was only significant in the 2020 late-planted trial. Our data suggest that the combination of cultivar resistance and delayed flooding can serve as a valuable component of an integrated pest management program for both rice water weevil and stemborers.

Assessment of tolerance and resistance of inbred rice cultivars to combined infestations of rice water weevil and stemborers

AbstractPlants possess defense‐related traits that both reduce injury from herbivores (resistance) and the amount of yield loss per unit injury (tolerance). Plant resistance and tolerance can be utilized in pest management programs. The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most destructive early‐season pest of rice (Oryza sativa L., Poaceae) in the USA. Additionally, lepidopteran stemborers, particularly the invasive Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), are increasing in economic importance as pests of rice in Louisiana, USA. This study was conducted to evaluate both the resistance and tolerance of commonly grown inbred rice cultivars in Louisiana to combined infestations of rice water weevils and stemborers. Field experiments were established at the Rice Research Station in Crowley, LA, USA from 2017 to 2019. Eight commonly grown inbred cultivars were selected and pest infestation levels were manipulated using insecticidal seed treatments. The rice cultivar ‘Jupiter’ supported the highest numbers of immature rice water weevils, whereas weevil densities on other cultivars were intermediate. Low levels of stemborer injury were observed in ‘Cheniere’ and ‘Jazzman‐2’, which suggests that these cultivars express some resistance to stemborers, whereas high stemborer injury was observed in ‘Cocodrie, ‘CL151’, and ‘Mermentau’. Together, rice water weevil and stemborer infestations negatively affected rice yields, with losses up to 18%. However, differences among cultivars in overall yield losses were minimal. Comparisons of slopes of yield × weevil density relationships among cultivars revealed a greater decline, that is, yield loss per weevil, for Cheniere relative to Cocodrie. Our data suggest that plant resistance can serve as a valuable component of an integrated pest management program, particularly for stemborers.

Relative Yield Loss From Stem Borers (Lepidoptera: Crambidae) and Rice Water Weevil (Coleoptera: Curculionidae) in Rice.

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most important economic pest of rice in the United States with the ability to substantially reduce rice yields. Stem borers, including the Mexican rice borer, Eoreuma loftini (Dyar), are emerging as more consistent pests in Louisiana and Texas, but the relationship between blanked panicles (whiteheads) caused by stem borer feeding and yield loss is not well understood. A series of field trials was conducted in Louisiana from 2019 to 2020 to determine the relative yield loss by manipulating infestations of both pests with selective insecticides. Results indicate losses from L. oryzophilus infestations are greater than those for E. loftini in early planted rice. In contrast, relative yield losses were approximately equal in later planted rice in 2019, in which E. loftini infestations were high. Additive impacts of the root-feeding L. oryzophilus and the stem-feeding E. loftini were not observed in our study. Linear regression revealed that each increase of one whitehead per square meter is associated with a 1.7% loss in yield. Results from ratoon rice suggest that protection from L. oryzophilus in the main crop also improves yield in the second crop. Collectively, results demonstrate the continued need for effective L. oryzophilus management programs to prevent economic losses. Conversely, findings suggest that benefits of E. loftini control may be minimal in many instances. Control of E. loftini is most likely to be economical under conditions where high populations are anticipated such as in late-planted fields or regions that previously had high infestations.

Cyantraniliprole: A new insecticidal seed treatment for U.S. rice

Current pest management practices for the rice water weevil (Lissorhoptrus oryzophilus Kuschel) and the Mexican rice borer (Eoreuma loftini Dyar) in U.S. rice rely heavily on a small number of insecticides. Thus, additional products are needed to delay resistance development and replace products no longer available to farmers. Evaluation of novel and widely used insecticidal seed treatments was conducted in eight small plot field trials from 2015 to 2019 in Louisiana and Texas. Treatments evaluated included the insecticides cyantraniliprole, chlorantraniliprole, thiamethoxam, and clothianidin. Seed treated with chlorantraniliprole and seed treated with both cyantraniliprole and thiamethoxam together provided the best control of L. oryzophilus across trials. Thiamethoxam and clothianidin seed treatments did not provide satisfactory control of L. oryzophilus. Only chlorantraniliprole seed treatment controlled E. loftini. Improved yield was recorded from plots treated with chlorantraniliprole or cyantraniliprole + thiamethoxam across trials from 2017 to 2019 over fungicide only controls. Yield differences among treatments were not detected in 2015–2016 trials. Registration of cyantraniliprole seed treatment for use in U.S. rice provides a new tool for diversification of pest management practices and insecticide resistance management.

A New Species of Eoreuma Ely (Pyraloidea: Crambidae: Crambinae) Feeding on Sugarcane from Colombia

A new crambid, Eoreuma insuastii Solis and Osorio-Mejia, new species, is described from Colombia. The larvae were discovered feeding on young stalks of sugarcane (Saccharum officinarum L.) grown for brown sugar loaf, or “panela.” We provide images of larvae and pupae, as well as damage to sugarcane young stalks for field identification, and describe and illustrate the adults and their genitalia. Only three species of Eoreuma have been previously described from South America; we provide images of the type specimens, their labels, and genitalia. The new species described herein is most like E. donzella Schaus, which was described from Brazil. The other two species are E. paranella Schaus and E. morbidellus Dyar; we designate the male syntype of E. morbidellus as the lectotype. The new species is compared to Eoreuma loftini (Dyar), a common pest species of graminaceous crops such as sugarcane and rice (Oryza sativa L.) in Mexico and the United States.

The Sugarcane Borer (Lepidoptera: Crambidae) Infests Rice at Low Population Levels in Florida.

The sugarcane borer, Diatraea saccharalis (F.), rice stalk borer, Chilo plejadellus Zincken, and Mexican rice borer, Eoreuma loftini (Dyar), are stem borers (Lepidoptera: Crambidae) that infest rice (Oryza sativa L.) in the southern United States. A 2-yr study was conducted to determine stem borer injury, infestation, and parasitism levels in Florida. Thirty commercial rice fields were selected during the 2017 and 2018 growing seasons throughout the rice production region in southern Florida. Sampling for stem borer injury and infestations was conducted in each field between the milk and early maturation stages by observing plants at 10 locations, with three 1-m2 quadrats per location. In addition, monitoring for E. loftini adults was conducted using one pheromone trap adjacent to each field. In 2017, the number of rice tillers exhibiting stem borer injury averaged 0.024 tillers/m2 and infestation levels averaged 0.008 stem borers/m2, with only D. saccharalis being observed. In 2018, injury and infestation levels averaged 0.062 injured tillers/m2 and 0.023 D. saccharalis larvae or pupae/m2, respectively. The solitary parasitoid Alabagrus stigma Brullé (Hymenoptera: Braconidae) parasitized 33 and 40% of the collected D. saccharalis in 2017 and 2018, respectively. In addition, pheromone traps did not capture E. loftini adults. This study shows that D. saccharalis infests rice in Florida but at relatively low levels not threatening production and that rice fields are habitats for D. saccharalis parasitoids. This study also suggests that C. plejadellus and E. loftini do not occur in southern Florida.

Interaction of Cultural, Biological, and Varietal Controls for Management of Stalk Borers in Louisiana Sugarcane.

Diatraea saccharalis F is considered the most important pest of sugarcane in the United States. This article focuses on the history of pest management as it relates to the control of this stem borer in Louisiana sugarcane, and how control practices have become more in tune with integrated pest management paradigms. Various pest management strategies are employed against D. saccharalis and the interactions between each of these provide farmers with the tools needed to curb damaging infestations. However, the invasion of the Mexican rice borer, Eoreuma loftini (Dyar), and other confounding environmental factors have presented farmers, consultants, and researchers with new pest management challenges. We address these challenges and provide an overview of ongoing developments, particularly in the Louisiana sugarcane pest management program.

Mexican Rice Borer Control Tactics in United States Sugarcane

The invasive Mexican rice borer, Eoreuma loftini (Dyar), expanded its range from Mexico to South Texas in the early 1980s. By 2008 the pest had moved into sugarcane- and rice-growing areas of East Texas and Louisiana, and by 2012 it was reported on noncrop host plants in Florida. Efforts to suppress E. loftini in United States sugarcane with chemicals and biological control agents were unsuccessful, so both tactics were discontinued, and E. loftini infestation of sugarcane has continued unchecked. During the last 15 years, however, research has focused on the pest’s ecology, improved insecticides and scouting methods, the identification of sugarcane resistance mechanisms, and new cultural tactics. A surveillance technique was developed that indicates when larvae are most vulnerable to insecticide sprays. Currently, registered insecticides for E. loftini control are not widely applied, although some show promise, including an insect growth regulator. A number of potentially useful cultural practices are available, including plowing under fallow stubble, judicious use of fertilizer, adequate irrigation, avoiding proximity to E. loftini-susceptible maize cultivars, and enhancement of natural enemy populations. Demonstrated and potentially useful sugarcane resistance mechanisms involve physiochemical attributes, physical characteristics, and transgenic cultivars.

Oviposition Preference and Survival of the Mexican Rice Borer (Lepidoptera: Crambidae) in Bioenergy and Conventional Sugarcane and Sorghum.

Oviposition preference and host suitability of the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), on bioenergy and conventional cultivars of sugarcane, Saccharum spp., and sorghum, Sorghum spp., were examined in a series of greenhouse experiments. Two energycane cultivars, two sugarcane cultivars, two high-biomass sorghum cultivars, and one sweet sorghum cultivar were assessed at two phenological stages (immature and mature). Mature plants possessed greater availability of dry leaf material compared with immature plants, and all E. loftini eggs were observed exclusively on dry leaves. Oviposition did not vary among host combinations (cultivar by phenological stage); however, eggs per plant and eggs per oviposition event were numerically greater on mature plants than immature plants. In a no-choice experiment, survival from egg to adult did not vary among host combinations, with <2.0% of E. loftini larvae surviving to adulthood. Failed establishment by neonates on plants was 13.4- to 53.9-fold greater than successful establishment across all host combinations. Results from this study suggest that plant physical characteristics continue to play an important role in host selection, but further evaluations will be needed to quantify other characteristics which influence host suitability.

Population Distribution and Range Expansion of the Invasive Mexican Rice Borer (Lepidoptera: Crambidae) in Louisiana.

The Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), is an invasive pest that was first introduced into southern Texas in 1980 and has been expanding its range eastward along the United States Gulf Coast. The pest attacks rice (Oryza sativa L.), sugarcane (Saccharum spp.), corn (Zea mays L.), and other graminaceous crops, and its establishment in Louisiana is expected to have severe economic impacts on crop production. Range expansion and population distribution of E. loftini were monitored with a network of 77 pheromone traps throughout southwestern Louisiana from 2013 to 2015. Eoreuma loftini was ubiquitous throughout the study region, with male moths captured in every habitat sampled. Spatial analysis revealed the population is characterized by high and low density clusters, with the greatest trap captures occurring in southeastern Calcasieu Parish and southern Jefferson Davis Parish. Trap captures in more northern regions of the study were lower than in southern parishes. Trap captures in areas where the pest has been established for >3 yr were greatest in rice habitats. The weighted mean population center moved eastward at a rate of ∼11 km per year. Human-aided movement of E. loftini was probably not involved in the eastward expansion documented during this study. Seasonal population peaks were detected in March-April, July-August, and October-November. This study indicates this species is continuing its spread eastward along the United States Gulf Coast and will likely become established throughout Louisiana within the next 20 yr.

Efficacy of Insect Growth Regulators and Diamide Insecticides for Control of Stem Borers (Lepidoptera: Crambidae) in Sugarcane.

Field experiments assessed control of the stem borers, Diatraea saccharalis (F.) and Eoreuma loftini (Dyar), in sugarcane (Saccharum spp.) with selected insect growth regulators and diamide insecticides. Tebufenozide, novaluron, chlorantraniliprole, and flubendiamide were evaluated for D. saccharalis control in four field experiments in Louisiana between 2009 and 2014. Aerial application of the same insecticides was evaluated for control of E. loftini in commercial sugarcane fields in southern Texas in 2012 and 2015. Stalk injury from D. saccharalis in nontreated plots ranged from 7.4-28.1% bored internodes across the four experiments. All insecticides reduced D. saccharalis injury compared with nontreated plots (39.1-99.4% reduction). Better control was achieved with novaluron, flubendiamide, and chlorantraniliprole than with tebufenozide. Pheromone trap-assisted scouting for E. loftini in Texas sugarcane helped to time insecticide applications. Reduced E. loftini injury was observed in diamide-treated plots (3.6-4.7% bored internodes) compared with nontreated controls (13.1%), but not in novaluron- (6.0%) or tebufenozide-treated (8.3%) plots in the 2012 experiment. Significant E. loftini injury was present prior to the aerial insecticide application in 2015, and differences in overall injury were not detected among treatments. However, chlorantraniliprole reduced injury to the top portion of sugarcane stalks. None of the insecticides improved sugar yields in 2012 or 2015. Results suggest insect growth regulators and diamide insecticides fit well in D. saccharalis management programs in Louisiana sugarcane. These chemistries also have potential to improve control of E. loftini, but more research into application strategies is needed to achieve consistent efficacy.