The Mexican rice borer, Eoreuma loftini (Dyar), is a major pest of sugarcane (hybrids of Saccharum spp.) in Louisiana and Texas. Resistance to E. loftini was evaluated in 51 commercial and experimental cultivars of sugarcane, energycane (hybrids of Saccharum spp.), and sorghum [ Sorghum bicolor (L.) Moench and hybrids of Sorghum spp.] in four replicated small plot field experiments from 2009 to 2012. A relative resistance ratio was developed to compare levels of susceptibility among cultivars based on the percentage of bored internodes and survival to adulthood. This index was able to separate cultivars into five resistance categories and provides a new method for comparing levels of resistance among cultivars. E. loftini pest pressure in 2009 was among the highest recorded with injury ranging from 55 to 88% bored internodes. Commercial sugarcane cultivar HoCP 85-845 was identified as resistant in three of four experiments, whereas HoCP 04-838 was identified as susceptible in all experiments. Of the five sugarcane cultivars in commercial production in the Rio Grande Valley of Texas, only TCP 87-3388 was categorized as resistant. Of the cultivars with potential for bioenergy production, all of the energycane cultivars demonstrated higher levels of resistance than high-biomass and sweet sorghum cultivars. Continued evaluation of cultivar resistance to E. loftini is important to development of effective integrated pest management strategies for this pest.

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.

Chlorantraniliprole susceptibility was determined in diet-incorporation bioassays for six fall armyworm, Spodoptera frugiperda (J. E. Smith), populations feeding on sweet corn, Zea mays L., in southern Florida between 2017 and 2019. The LC₅₀ and LC₉₀ values of these populations estimated using probit analyses ranged from 0.022 to 0.084 ppm and 0.112 to 0.471 ppm, respectively. Thus, susceptibility levels among the six field populations varied, but to a relatively small extent, with approximately fourfold differences in LC₅₀ and LC₉₀ values between the most and least susceptible populations. These field populations were all less susceptible than a reference population maintained in the laboratory without prior exposure to chlorantraniliprole, with RR₅₀ values between 5.3 and 20.1 and RR₉₀ values between 14.3 and 60.3. These results suggest reduced chlorantraniliprole susceptibility in S. frugiperda populations collected in Florida sweet corn relative to a reference laboratory population. However, field experiments in 2017 and 2019 showed that foliar applications of chlorantraniliprole reduced S. frugiperda injury and infestations to levels comparable to or lower than applications of indoxacarb, novaluron, or spinetoram. This study does not provide evidence of practical resistance to chlorantraniliprole in S. frugiperda infesting Florida sweet corn fields.