Louisiana Rice 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.

Modeling interactions of planting date and phenology in Louisiana rice under current and future climate conditions

AbstractThe performance of novel genetic combinations under untested environmental scenarios and management practices can be virtually examined using process‐based crop models. Indeed, there has been a long‐standing interest in the crop modeling community to expand the utility of process‐based models to broader germplasm panels (e.g., breeding lines or diversity panels). Yet, there is often a misalignment between data needed to parameterize process‐based crop models and data routinely collected by breeding programs. To address this gap, we leverage a dataset from a long‐term trial on advanced experimental lines and released varieties from the Louisiana rice breeding program to calibrate and evaluate the decision support for agrotechnology transfer (DSSAT) CSM‐CERES‐Rice model. Next, we use data collected by the same program on a large collection of breeding lines to generate numerous in silico genotypes and evaluate their performance across different management practices (different planting dates) and three climatic conditions (current climate and two future scenarios based on CMIP6‐SSP5‐8.5 climate projections). Our simulations indicate that shifting the current planting date (i.e., March) back by 1–2 months (to January) under moderate warming conditions (+1.3°C warmer and 41% higher CO2 level), and 2–3 months (to December) under extreme warming conditions (+4.1°C warmer and 133% higher CO2 level) could potentially offset the negative impacts of the increased future temperature. Given earlier planting, shorter duration varieties (i.e., those with shorter growing degree day requirements during the vegetative and grain filling periods) are found to be more favorable for supporting high yields. Such varieties with a shorter thermal time to anthesis are found to remain just outside of the current pool of variation for this trait. Opportunities and challenges for leveraging breeding data in process‐based modeling to derive insights into adaptation strategies for future climates are further discussed.

Impact of Nonconventional Selection by Insecticides on Susceptibility of the Southern House Mosquito,Culex quinquefasciatus

Mosquitoes are an important target of pest control as they vector pathogens that are associated with many debilitating human diseases. Given that mosquitoes have been selected with insecticides for over 100 years, much is known about the development of insecticide resistance associated with targeted application against populations of these insects. However, off-target selection by applications of insecticides in agricultural and residential sites also impacts development of insecticide resistance and is understudied. Similarly, the impact of selecting one life stage of mosquitoes on the insecticide susceptibility of different life stages is largely unknown. Here, we show that susceptibility to chlorantraniliprole, which is applied in rice (Oryza sativa) and sugarcane (Saccharum officinarum) fields in Louisiana, decreased (5.7- to 12-fold) in populations of Culex quinquefasciatus collected from near these fields compared with a reference field strain. In addition, application of bifenthrin by commercial application on an individual residence increased the resistance frequencies to bifenthrin in 5 nearby residential sites. These increased frequencies of resistance, as measured with diagnostic concentrations of bifenthrin, were highly correlated (R2 = 0.92) between larvae and adults, suggesting that selection of adults also confers resistance to larvae. Finally, esterase activities and bifenthrin susceptibilities were moderately correlated (R2 = 0.4 for larvae and 0.52 for adults), suggesting that multiple mechanisms (including metabolism by esterases) were associated with the observed resistance. Results from this study suggest that nonconventional selection by insecticides is a variable to consider when developing management strategies for populations of Cx. quinquefasciatus.

Regional expansion and chemical control for invasive apple snails (Pomacea maculata) in Louisiana rice and crawfish production systems

Invasive apple snails, Pomacea maculata, have recently emerged as pests in the rice (Oryza sativa L.) and crawfish (Procambarus clarkii) production systems of southwest Louisiana. Their current distribution, expansion rates, and susceptibility to chemical control methods in these systems are not well known. This study examines the expansion of P. maculata in southwest Louisiana and evaluates chemical control via toxicity assays. The effects of chemical control were also assessed on the non-target species, Pr. clarkii. Westward expansion of P. maculata was recorded at ≈2 km per year and a northward expansion at a rate of ≈4 km per year with most new detections recorded south of established populations. P. maculata had a lower probability of being found in aquatic habitats with decreasing levels of dissolved oxygen. All concentrations of both liquid and crystal copper sulfate caused appreciable P. maculata mortality after 72 h, but control was inconsistent across treatments. Treatment with copper sulfate had no significant effect on Pr. clarkii mortality. Treatment of P. maculata egg masses with 5% and 10% crop oil solutions reduced the number of hatchlings by approximately 80% relative to non-treated controls. Future studies should attempt to find new factors associated with P. maculata occurrence in southwest Louisiana. More research should be conducted on the levels of copper sulfate that are ingested by P. maculata after initial exposure as well as new methods for crop oil applications on P. maculata egg masses.

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.

Spatial Distribution of Lepidopteran Stem Borers in Louisiana Rice Fields.

Louisiana rice is attacked by a complex of lepidopteran stem borers that injure the vegetative and reproductive stages of rice, reducing tillering and grain output. Currently, insecticidal seed treatments are used in Louisiana as a preemptive means to control stem borers in rice. Our objective was to better understand the spatial distribution of stem borers in Louisiana rice fields. Thirteen nontreated commercial rice fields in Louisiana were mapped using GPS software and surveyed for stem borer damage in 2017 and 2018. Damage was recorded by counting the number of blank panicles (whiteheads) within quadrats located at different areas in each field. An ANOVA, spatial interpolation, hotspot analysis, and negative binomial regression were used to determine where stem borer injury was concentrated and whether the distribution of these pests was influenced by rice stand count, field composition, and site location. The results show that stem borers are typically aggregated along field edges, with population density decreasing toward the center of rice fields. Stem borer damage was 4.2- and 3.9-fold greater along field edges than in field centers in 2017 and 2018, respectively. Hotspot spatial analysis revealed 41.7 and 52.1% of low-density clusters occurred at or near field centers, respectively. Negative binomial regression revealed stem borer injury declines with increasing distance from field edges, with regional differences in infestation levels. This suggests stem borer control efforts could be spatially targeted to improve the efficiency of pest management.

The impact of cultivar development and cultural practices on Louisiana rice yield

AbstractThis analysis investigates the impact of cultivar development and cultural practices on Louisiana rice (Oryza sativa L.) yield growth using the Chow test (Chow, 1960) in combination with regression analysis. The analysis examines the 1895–2019 period, and uses four scenarios in which one, two, three, and four subperiods show varying rates of rice yield growth in Louisiana. There has been a significant increase in Louisiana rice yields over time. However, the growth in yields for some of the subperiods is greater than for others. Our results of significant rice yield increase over time correspond with events such as the establishment of Louisiana's Foundation Seed Program, the release of the Magnolia rice cultivar, and increased mechanization.

Regional Expansion and Chemical Control for Invasive Apple Snails (Pomacea Maculata) in Louisiana Rice and Crawfish Production Systems

Regional Expansion and Chemical Control for Invasive Apple Snails (Pomacea Maculata) in Louisiana Rice and Crawfish Production Systems

Spatial Distribution of Lissorhoptrus oryzophilus (Coleoptera: Curculionidae) in Rice.

Rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is a destructive insect pest of rice in the United States. The pruning of rice roots by L. oryzophilus larvae can cause up to 25% yield loss. Currently, insecticidal seed treatments are used in the Louisiana rice industry as a pre-emptive means of controlling this weevil species. Our objective was to gain a better understanding of the spatial distribution of L. oryzophilus in Louisiana rice fields. Thirteen untreated commercial rice fields in Louisiana were mapped using GPS software, and surveyed for L. oryzophilus larvae over two years (2017 and 2018). An ANOVA, spatial interpolation, hotspot analysis, and multiple linear regression were used to determine where populations of L. oryzophilus were concentrated and whether distributions of the pest were related to edge effects. The results showed that L. oryzophilus larvae are typically aggregated along the edges of rice fields, with populations decreasing toward the center of rice fields. Lissorhoptrus oryzophilus densities were 3.3- and 2.2- fold greater along field edges than in field centers in 2017 and 2018, respectively. Hotspot spatial analysis revealed 59% and 32% of low-density clusters occurred at or near field centers, respectively. Multiple linear regression revealed larval densities decline with increasing distance from overwintering sites and alternative habitats (such as tree lines and levees containing bunch grasses and other alternative noncrop plants). These results suggest potential for insecticidal seed treatments to be applied selectively within rice fields to control this pest.

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.

Mixture interactions of quizalofop and reduced rates of halosulfuron

AbstractA field study was conducted in 2017 and 2018 at the Louisiana State University Agricultural Center H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate the impact of reduced rates of halosulfuron on quizalofop activity in Louisiana rice production. Halosulfuron and a prepackaged mixture of halosulfuron plus thifensulfuron were evaluated at 0, 17, 35, or 53 g ai ha−1 and 34 or 53 g ai ha−1, respectively, in a mixture with quizalofop at 120 g ai ha−1. Control of barnyardgrass, red rice, and two non-acetyl-CoA carboxylase resistant rice lines, CL-111 and CLXL-745, were recorded at 14 and 28 d after treatment (DAT). The red rice, CL-111, and CLXL-745 represented a weedy rice population. Across all species evaluated at 14 DAT, all mixtures containing halosulfuron and halosulfuron plus thifensulfuron resulted in antagonism with an observed control of 79% to 90%, compared with an expected control of 96% to 99%. At 28 DAT, all mixtures containing halosulfuron resulted in neutral interactions for barnyardgrass control. Quizalofop mixed with halosulfuron plus thifensulfuron at the lower rate of 34 g ha−1 was able to overcome the antagonism compared with the higher rate of 53 g ha−1 for barnyardgrass control at 28 DAT. Both the high and the low rate of halosulfuron plus thifensulfuron resulted in antagonistic interaction for red rice, CL-111, and CLXL-745 control at 28 DAT. This research suggests that mixing quizalofop with halosulfuron plus thifensulfuron should be avoided, especially at the higher rate of 53 g ha−1.

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.

Economic Returns on Insecticidal Seed Treatment Combinations in Louisiana Rice

Economic Returns on Insecticidal Seed Treatment Combinations in Louisiana Rice

The taxonomic status of Aphelenchoides besseyi Christie, 1942 (Nematoda: Aphelenchoididae) populations from the southeastern USA, and description of Aphelenchoides pseudobesseyi sp. n.

Summary Populations reviously identified as Aphelenchoides besseyi were studied. Using an integrated approach, the A. besseyi species complex contains several cryptic species: A. besseyi sensu stricto, A. oryzae, A. pseudobesseyi sp. n. and other putative undescribed species. A population from Florida strawberry morphologically fits the A. besseyi of both Christie and Allen and is considered the only representative of this species. A Louisiana rice population fitted the descriptions of A. oryzae of both Yokoo and Fortuner; PUS length was consistently less than one-third of VA. Aphelenchoides oryzae, parasitising rice and other monocots, was re-established based on morphological and molecular datasets. Three populations from Florida ornamental plants (Dryopteris erythrosora, Echinacea sp. and Farfugium japonicum) differed from those of the two above-mentioned species and are described as A. pseudobesseyi sp. n. Populations previously identified as ‘A. besseyi’ from several countries were considered representatives of this new species, which usually had a large and conspicuous PUS, 8-14 μm wide and with a length greater than one-third of VA in 40-70% of studied specimens. Morphological variability made separation of A. pseudobesseyi sp. n. from A. oryzae and A. besseyi unreliable without the examination of numerous specimens and molecular analysis.

Evaluating Behavioral Responses of Selected Stink Bugs (Hemiptera: Pentatomidae) to Spinosad

Southern green stink bug, Nezara viridula (L.) and redbanded stink bug, Piezodorus guildinii (Westwood) are two of the most important seed sucking pests affecting Louisiana soybean production and rice stink bug, Oebalus pugnax (F.) is an important late season pest in Louisiana rice. Exploration of chemicals that exhibit attraction or repellent activities toward major stink bug species would be beneficial in developing push-pull strategies. Spinosad is a commercially available natural insecticide that may have arrestant, attractant, or phagostimulant properties against stink bugs. To test this, a series of laboratory experiments were conducted to investigate the tactile, olfactory, and feeding responses of these stink bugs toward two commercial spinosad products (Entrust and Tracer) and technical grade spinosad. In tactile assays, female and male redbanded stink bug were arrested by Entrust, Tracer, and technical grade spinosad, whereas only rice stink bug and southern green stink bug males were arrested by Entrust. Y-tube assays revealed no attraction to any of the products by either male or female rice stink bug, redbanded stink bug, or southern green stink bug. In paired (treated or untreated soybean seed) feeding preference experiments, southern green stink bug showed no preference for any treatment, whereas redbanded stink bug fed more on Entrust- and Tracer-treated seed. From these results, spinosad appears to have an arrestant and phagostimulant effect on redbanded stink bug in the laboratory.

Methane and Nitrous Oxide Emission from Louisiana Rice Fields under Three Water Management Practices

Louisiana rice production is the third largest producer in the U.S. with approximately 185,000 ha. Various water management practices are used for the production in this area (i.e. continuous flooding, delayed flooding, straighthead, intermittent flooding (or alternate wetting and drying elsewhere), and furrow irrigation). However, only three water management practices were included in this study, delayed flooding, straighthead, and intermittent flooding.

Assessing the Potential Infection of Tagosodes orizicolus (Hemiptera: Delphacidae) by Rice Hoja Blanca Virus in Texas.

Tagosodes orizicolus (Muir) is the most important pest of rice in Latin America. Besides causing direct damage called hopperburn from feeding on and ovipositing in rice leaves, this insect pest also transmits rice hoja blanca virus (RHBV, Family Phenuiviridae, Genus Tenuivirus) in a persistent-propagative manner. This pathosystem can cause up to 100% yield loss in Latin American rice fields. T. orizicolus and RHBV symptoms were detected in Louisiana, Mississippi, and Florida rice fields in the 1950s, 1960s, and 1980s. However, neither has been detected in the United States since. Two outbreaks of T. orizicolus on ratoon rice occurred in the fall of 2015 and 2018 in counties southwest and south of Houston, TX. Insects were collected from ratoon rice fields by sweep net methods. Insects from the 2015 and 2018 outbreaks were tested individually and in pools of 10, respectively, for RHBV infection and the cytochrome oxidase 1 (CO1) gene from Delphacidae. No insects were positive for RHBV, however, all samples yielded amplicons for the CO1 gene. Furthermore, the CO1 gene from five 2015 individuals was sequenced and found to have a 100% identity to the Fer26_Argentina and 99.81% identity to the DEL074 Venezuela isolates of T. orizicolus. Five new sequences from 2015 individuals have now been deposited in GenBank. It is imperative to stay up to date on the potential invasion and establishment of this exotic pest of rice in Texas and other rice-growing regions of the United States through continued monitoring and research.

Florpyrauxifen-benzyl activity on perennial grass weeds found in Louisiana rice production – ERRATUM

Florpyrauxifen-benzyl activity on perennial grass weeds found in Louisiana rice production – ERRATUM

Florpyrauxifen-benzyl activity on perennial grass weeds found in Louisiana rice production

AbstractA glasshouse study was conducted on the Louisiana State University campus in Baton Rouge, LA, to evaluate the control of brook crowngrass, rice cutgrass, southern watergrass, and water paspalum. Florpyrauxifen-benzyl was applied at 30 g ai ha−1 to each grass species at the 3- to 4-leaf or 1- to 2-stolon stage of growth. Brook crowngrass treated with florpyrauxifen was controlled 71% at 21 d after treatment. Southern watergrass and water paspalum control did not exceed 56% and 36%, respectively, across all evaluations. Rice cutgrass treated with florpyrauxifen did not reach 15% control. Plants treated with florpyrauxifen, except rice cutgrass, displayed reduction in leaf number, stolon number, plant height, and plant fresh weight. These results indicate florpyrauxifen-benzyl can help manage a brook crowngrass infestation and suppress southern watergrass. However, florpyrauxifen-benzyl has little to no activity on water paspalum and rice cutgrass, and other management options should be employed if these weeds are present.

Benzobicyclon Activity on Common Louisiana Rice Weeds

AbstractA study was conducted at three locations in Louisiana to evaluate the response of common Louisiana rice weed species to different rates of application of benzobicyclon herbicide. Benzobicyclon was applied at 31, 62, 123, 185, 246, 493, 739, 986, and 1,232 g ai ha–1into flooded field conditions when ducksalad was at the first elongated-leaf stage. Barnyardgrass, false pimpernel, and yellow nutsedge control never exceeded 50% from any rate of benzobicyclon applied, averaged across evaluation timing. Ducksalad control, averaged across evaluation timing, was 83% when treated with 493 g ha−1and did not increase when treated with higher rates of benzobicyclon. At 42 d after treatment (DAT), purple ammannia and Indian toothcup treated with 185 and 246 g ha–1of benzobicyclon were controlled 58% and 81%, respectively, and did not differ in control compared with higher rates of benzobicyclon. All weeds were hand-harvested from each plot and separated by species at the conclusion of the study. No differences in fresh-weight biomass were observed for barnyardgrass, false pimpernel, purple ammannia, or yellow nutsedge. Treatment with benzobicyclon at ≥62 g ha–1resulted in reduced ducksalad fresh weight 42 DAT compared with the nontreated sample. Indian toothcup fresh weight was reduced 77% to 96% compared with the nontreated sample when treated with benzobicyclon at 246 to 1,232 g ha–1.