Search Results (6)

The Mexican rice borer, Eoreuma loftini (Lepidoptera: Crambidae) is an economically important pest of sugarcane, rice, and corn in Louisiana, Texas, and Mexico. This pest is considered invasive in the US and is expanding its range northward. Due to its subtropical origin, E. loftini’s northern distribution might be limited by cold tolerance. A series of assays determined the influence of temperature and photoperiod on E. loftini life table parameters. Adult oviposition was reduced at temperatures > 30 °C. Egg viability was reduced at 20 and 36 °C relative to intermediate temperatures. Egg development time was greatest at 18 °C. Larvae did not develop to the pupal stage at temperatures ≤ 20 °C. Larval duration decreased with increasing temperature from 22 to 36 °C. Adult longevity decreased with increasing temperature from 18 °C (15 d) to 34 °C (7 d). Exposure to a short-day photoperiod decreased larval mortality at −5 °C. Larval survival of >80% up to 5 days at −5 °C suggests E. loftini cold tolerance is sufficient to minimize the influence of hard freezes on overwintering populations. Larval survival for 5 d at 40 °C was 75%. Exposure to 45 °C for periods > 1 d caused 100% mortality. These results suggest that E. loftini exhibits considerable thermal plasticity and cold tolerance, which may facilitate its range expansion in the United States. Full article

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. Full article

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. Full article

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. Full article

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. Full article

Sugarcane, Saccharum spp., in the United States is attacked by a number of different arthropod pests. The most serious among those pests are two stalk boring moths in the Family Crambidae: the sugarcane borer, Diatraea saccharalis (F.), and the Mexican rice borer, Eoreuma loftini (Dyar). The two species are affected by abiotic and biotic environmental stress factors. Water deficit and excessive soil nitrogen alter physical and physiochemical aspects of the sugarcane plant that make the crop increasingly vulnerable to E. loftini. Weed growth can be competitive with sugarcane but it also supports enhanced abundances and diversity of natural enemies that can suppress infestations of D. saccharalis. In an instance where the stalk borer is considered a stress factor, proximity of vulnerable crops to sugarcane can influence levels of E. loftini infestation of sugarcane. The adverse effects of each stress factor, in terms of stalk borer attack, can be reduced by adopting appropriate cultural practices, such as adequate irrigation, judicious use of nitrogen fertilizer, using noncompetitive weed growth, and not planting vulnerable crops near sugarcane fields. Understanding the relationships between stress factors and crop pests can provide valuable insights for plant breeders and tools for incorporation into integrated pest management strategies. Full article