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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Seasonal fluctuations in Prosapia (Homoptera: Cercopidae) abundance were documented over 4 yr in 3 upland dairy pastures of Costa Rica. P. nr bicincta (Say) completed only 1 relatively long-lived generationeach year between May and September. First instars appeared in May at the start of the wet season, progressed through 5 instars and peaked in abundance in mid-June. Densities as high as 277 spittlebugs per square meter were reached. Adult populations peaked late June to early July and achieved densities up to 260 froghoppers per 50 sweeps of an insect net. Distinct peaks of adult males generally occurred 3-4 wk in advance of the maturation of 5th instars and the principal adultpeaks. Males outnumbered females 5.6:1 in sweep net surveys. Nymph and adult abundance fluctuated widely among paddock-years in no clear pattern with respect to paddock or predominant forage. Phenological analyses based on cumulative insect-days did not detect differences inpopulation initiation or development rate across paddock-years. Teneral and adult males peaked earlier than their respective females (protandry). In 5 of 8 and 4 of 9 paddock-years, adult males and females,respectively, peaked in abundance before same sex tenerals, indicating colonization of local pastures. Additional evidence for immigration was the abrupt appearance of male P. simulans (Walker) at thesame time in all paddocks each year. This species did not complete its life cycle in local pastures because females and nymphs were absent from surveys. Explorations of pastures at varying elevation and distance from survey paddocks demonstrated that within 10 km P. nr bicincta populations matured 2.5 wk earlier. Adults derived from those populations may become available as colonists to local pastures. The nearest breeding populations of P. simulans to sites where males were recovered were 485 m lower in elevation and 3.4 km distant. [ABSTRACT FROM AUTHOR]