West Indian Canefly (Hemiptera: Delphacidae): An Emerging Pest of Louisiana Sugarcane.

The West Indian canefly, Saccharosydne saccharivora (Westwood) (Hemiptera: Delphacidae), is a sporadic pest of sugarcane in Louisiana which has recently emerged as a more consistent threat with outbreaks occurring in 2012, 2016, 2017, and 2019. Surveys of commercial fields in 2016 revealed that S. saccharivora infestations were present throughout Louisiana sugarcane and populations peaked in mid-June before declining. High minimum winter temperatures are generally associated with S. saccharivora outbreaks. Six insecticide evaluations demonstrated effective control with several insecticides including λ-cyhalothrin, flupyradifurone, acetamiprid, and imidacloprid. In five of the six insecticide trials, S. saccharivora infestations had substantially declined by 21 d after treatment. Effects of insecticidal control of S. saccharivora on sugar yields were detected in one of four small plot trials in which yield data were collected. Linear regression revealed S. saccharivora cumulative insect days in a grid sampling study were inversely associated with sugar yields. Results from these collective experiments suggest impacts on sugar yields are influenced by pest density and infestation duration. Differences were detected in numbers of S. saccharivora nymphs and adults as well as sooty mold coverage among commercial sugarcane cultivars with more than twofold increases in the most susceptible compared to resistant cultivars. The research presented herein documents the impact of S. saccharivora to Louisiana sugarcane and provides important ground work for developing effective pest management strategies. Future research efforts should aim to identify ecological factors influencing population dynamics, varietal preferences, and economic thresholds.

Effect of Sugarcane Cultivar and Foliar Insecticide Treatment on Infestations of the Invasive Sugarcane Thrips, Fulmekiola serrata (Thysanoptera: Thripidae), in Florida.

Fulmekiola serrata (Kobus) was observed infesting sugarcane, Saccharum spp. hybrids, in the United States for the first time in January 2017 in Florida. Field studies were conducted to determine F. serrata infestation levels on popular sugarcane cultivars and to determine the efficacy of foliar insecticide treatments that could be used for management. Cultivar evaluations comparing six and five commercial cultivars representing >46% of the sugarcane production area in Florida were conducted in 2017 and 2018, respectively. Fulmekiola serrata infestation levels did not differ among cultivars in 2017. However, infestation levels on CP 00-1101 were greater than on CP 96-1252 grown on organic soils, and infestation levels on CP 96-1252 were greater than on CPCL 97-2730 grown on mineral soils in 2018. Three insecticide evaluations, two in 2017 and one in 2018, were conducted. The pyrethroid lambda-cyhalothrin, which is registered for use on sugarcane, was consistently associated with the greatest decreases in F. serrata infestation levels. The neonicotinoids imidacloprid and thiamethoxam, as well as the butenolide flupyradifurone, decreased infestation levels but to a lesser extent than did lambda-cyhalothrin. The spinosyn spinetoram was associated with the lowest decreases in F. serrata infestation levels. Our results supported short-term F. serrata management recommendations: Popular Florida sugarcane cultivars should be considered equally susceptible to F. serrata until additional evaluations are conducted and F. serrata outbreaks can be treated with lambda-cyhalothrin when infestations stress the crop beyond acceptable levels.

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.

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.

Monitoring Mexican Rice Borer (Lepidoptera: Crambidae) Populations in Sugarcane and Rice With Conventional and Electronic Pheromone Traps.

The Mexican rice borer, Eoreuma loftini (Dyar), is a major pest of sugarcane, Saccharum spp., rice, Oryza sativa L., and other graminaceous crops in Texas and Louisiana. The ability of conventional and electronic pheromone traps to monitor E. loftini in sugarcane and rice habitats was evaluated in two separate 2-yr field studies. Bucket traps baited with a synthetic female sex pheromone monitored E. loftini populations in commercial sugarcane fields in Calcasieu and Jefferson Davis Parishes throughout the 2014 and 2015 growing seasons. The number of E. loftini captured differed among months, but not between years or parishes. The percentage of E. loftini-injured stalks was greater in 2015 than in 2014, peaking in September of both years. Daily trap capture was correlated with the percentage of injured stalks. Injury from E. loftini in Louisiana sugarcane remained relatively low (<3% bored internodes) in both 2014 and 2015. In a second experiment, electronic traps were compared with conventional pheromone traps for monitoring E. loftini populations in sugarcane and rice habitats in Texas in 2013 and 2015. Performance of earlier electronic trap prototypes in 2013 was inconsistent and less effective than conventional traps. Improved trap design in 2015 resulted in more than threefold greater moth capture in electronic traps than in conventional pheromone traps. Electronic traps demonstrated potential to improve monitoring strategies for this pest and should be evaluated for lepidopterous pests in a variety of cropping systems.

Biology and Management of the Mexican Rice Borer (Lepidoptera: Crambidae) in Rice in the United States.

The Mexican rice borer, Eoreuma loftini (Dyar), is an invasive pest of rice, Oryza sativa L., in the Gulf Coast region of the United States. This pest also damages sugarcane, Saccharum spp. hybrids; corn, Zea mays L.; and sorghum, Sorghum bicolor (L.) Moench, and feeds on weedy noncrop grasses. Multiple aspects of integrated pest management including use of pheromone traps, manipulation of planting dates, harvest cutting height, stubble management, noncrop host management, soil fertility management, host plant resistance, use of insecticides, and biological control have been studied for Mexican rice borer management. However, the current management strategy in rice primarily relies on the use of chlorantraniliprole insecticide seed treatments. This profile addresses Mexican rice borer biology and management in rice in the United States.

El barrenador mexicano del arroz [Eoreuma loftini (Dyar)] es una plaga invasora de arroz (Oryza sativa L.) en la región de la Costa del Golfo de Estados Unidos. Esta plaga también afecta híbridos de caña de azúcar (Saccharum spp.), maíz (Zea mays L.), sorgo [Sorghum bicolor (L.) Moench), y se alimenta de malezas gramíneas. Múltiples aspectos del manejo integrado de plagas incluyendo el uso de trampas con feromonas, la manipulación de las fechas de siembra, la altura del corte durante la cosecha, el manejo de rastrojos, el manejo de hospederos alternos, el manejo de la fertilidad del suelo, la resistencia de la plantas, el uso de insecticidas y el control biológico han sido estudiados para el manejo del barrenador mexicano del arroz. Sin embargo, la estrategia de actual de manejo en arroz se basa principalmente en el tratamiento químico de la semilla con el uso del insecticida clorantraniliprol. Esta revisión se enfoca en la biología y manejo del barrenador mexicano del arroz en arroz en los Estados Unidos.

Yield Response to Mexican Rice Borer (Lepidoptera: Crambidae) Injury in Bioenergy and Conventional Sugarcane and Sorghum.

The Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae) is an invasive stem borer of sugarcane, Saccharum spp., and sorghum, Sorghum bicolor (L.), and poses a threat against the production of dedicated bioenergy feedstocks in the U.S. Gulf Coast region. A 2-yr field study was conducted in Jefferson County, TX, to evaluate yield losses associated with E. loftini feeding on bioenergy and conventional cultivars of sugarcane and sorghum under natural and artificially established E. loftini infestations. Bioenergy sugarcane (energycane) 'L 79-1002' and 'Ho 02-113' and sweet sorghum 'M81E' exhibited reduced E. loftini injury; however, these cultivars, along with high-biomass sorghum cultivar 'ES 5140', sustained greater losses in fresh stalk weight. Negative impacts to sucrose concentration from E. loftini injury were greatest in energycane, high-biomass sorghum, and sweet sorghum cultivars. Even under heavy E. loftini infestations, L 79-1002, Ho 02-113, and 'ES 5200' were estimated to produce more ethanol than all other cultivars under suppressed infestations. ES 5200, Ho 02-113, and L 79-1002 hold the greatest potential as dedicated bioenergy crops for production of ethanol in the Gulf Coast region; however, E. loftini management practices will need to be continued to mitigate yield losses.

Expansion of the Mexican Rice Borer (Lepidoptera: Crambidae) into Rice and Sugarcane in Louisiana.

The Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), is an invasive pest of sugarcane, Saccharum spp., rice, Oryza sativa L., and other graminaceous crops in the Gulf Coast region of the United States. Traps baited with E. loftini female sex pheromones were used to document establishment and distribution of E. loftini near sugarcane, rice, and noncrop hosts in seven southwest Louisiana parishes from 2009 to 2013. Additional field surveys documented larval infestations in commercial sugarcane and rice. After its initial detection in 2008, no E. loftini were detected in Louisiana in 2009 and only two adults were captured in 2010. Trapping documented range expansion into Cameron, Beauregard, and Jefferson Davis parishes in 2011 and Allen, Acadia, and Vermilion parishes in 2013. During the course of this study, E. loftini expanded its range eastward into Louisiana 120 km from the Texas border (≈22 km/yr). Surveys of larval infestations provided the first record of E. loftini attacking rice and sugarcane in Louisiana. Infestations of E. loftini in rice planted without insecticidal seed treatments in Calcasieu Parish reached damaging levels.

Effects of chlorantraniliprole and thiamethoxam rice seed treatments on egg numbers and first instar survival of Lissorhoptrus oryzophilus (Coleoptera: Curculionidae).

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 microg 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.

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.

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 beta-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 cultivars 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.

Seasonal infestations of two stem borers (Lepidoptera: Crambidae) in noncrop grasses of Gulf Coast rice agroecosystems.

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 m(2) 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 Vasey's grass, Paspalum urvillei Steud., were infested throughout the year. Johnsongrass was the most prevalent host (41-78% relative abundance), but Vasey's 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.

Rice tillering and yield as affected by artificial and sugarcane borer (Lepidoptera: Crambidae) culm injury.

A 2-yr study was conducted to evaluate the tillering and yield response of rice, Oryza sativa L., whose culms were injured artificially or by larval sugarcane borers, Diatraea saccharalis (F.). Artificially injured plants produced approximately 0.49 more tillers than uninjured plants, similar to what has previously been reported for larval injured plants. In contrast, artificial injury did not affect yield per tiller, whereas larval injury did. The proximity of larval injury to the panicle had a negative impact on tiller yield, whereas artificial injury did not. Artificial injury apparently resulted in less injury to vascular tissue than did sugarcane borer larval injury. Until an artificial method of injury is developed that mimics the effects of larval feeding, further injury studies will continue to require sugarcane borer larvae.

Impact of Hurricane Rita storm surge on sugarcane borer (Lepidoptera: Crambidae) management in Louisiana.

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 $1.9 and $2.6 million to the Louisiana sugarcane industry for the 2006 production season.

Selection and life history traits of tebufenozide-resistant sugarcane borer (Lepidoptera: Crambidae).

Varying susceptibility to tebufenozide was recorded in the sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), collected from Louisiana sugarcane locations with different selection pressures. Results from diet incorporation bioassays with tebufenozide indicated significant increases in LC50 (3.78-fold) and LC90 (7-fold) values for a colony from Duson (DU), an area with higher selection pressure, compared with a colony from Alexandria (ALEX), an area with no selection pressure. Differences were not detected in LC50 values among colonies from areas where use of tebufenozide was discontinued or rotated with other chemistries. Selections with tebufenozide of DU larvae over 12 generations resulted in a highly resistant colony (DU-R) with 27.1- and 83.3-fold increases in LC50 and LC90 values, respectively. Comparison of pupal weight, days to pupation, and emergence after exposure to an equitoxic (LC20) concentration of tebufenozide revealed a decrease in pupal weight (34 and 33% for males and females, respectively), and an increase in days to pupation (47 and 40% for males and females, respectively), and emergence (43 and 33% for males and females, respectively) for the DU-R colony compared with the parent DU colony. Fecundity of DU-R females decreased to 72 eggs per female compared with 180 (DU) and 261 (ALEX). Egg viability of the ALEX and DU colonies was 61 and 56%, respectively, whereas only 27% of eggs laid by females from the DU-R colony hatched. These results are discussed in terms of their practical implications for control of D. saccharalis in Louisiana sugarcane.