Agroecological factors impacting stem borer (Lepidoptera: Crambidae) dynamics in Gulf Coast sugarcane and rice

Diatraea saccharalis (F.) and Eoreuma loftini (Dyar) are stem boring pests of sugarcane (Saccharum spp.) and rice (Oryza sativa L.) crops in the Gulf Coast region. Studies were conducted to determine the role of agroecological factors, including predator disruptions, alternate hosts, and crop phenological conditions, on stem borer populations. The year after Hurricane Rita storm surge flooded sugarcane in Louisiana, a 71% reduction in the predaceous Solenopsis invicta Buren was recorded. Even with a 2.4-fold increase in the number of insecticide applications used for D. saccharalis management in flooded fields, growers still incurred higher injury. In two field experiments, October sampling showed that sugarcane planted in early August harbored 4.7 to 19.0-fold greater D. saccharalis infestations than September plantings. Although there is a potential for increased D. saccharalis overwintering populations in early plantings, differences in infestations were not recorded during the spring. Sentinel plant experiments confirmed that a number of non-crop grasses are stem borer hosts. Subsequently, sampling along transects every 6-8 wk compared stem borer infestations in non-crop grasses adjacent to rice fields. While D. saccharalis densities were relatively low, E. loftini average densities were 0.3 to 5.7 immatures/m2 throughout a 2-yr period. A greenhouse study showed that rice is more preferred for E. loftini oviposition than the primary non-crop hosts johnsongrass [Sorghum halepense (L.) Pers.] and Vasey’s grass (Paspalum urvillei Steud.). In addition, E. loftini larval development duration in degree-days above a threshold temperature is 1.7-fold greater on johnsongrass and Vasey’s grass than on rice. A 2-yr rice study showed that a lower than traditional harvest cutting height (20 vs. 40 cm) reduced E. loftini infestations by 70 to 81% whereas D. saccharalis infestations were not changed. Furthermore, rice stubble under favorable conditions represents an overwintering habitat in addition to non-crop hosts. This research showed that predator disruptions, sugarcane planting dates, non-crop hosts, and rice stubble management impact stem borer populations when they are traditionally left unmanaged. Thus, the evaluation of a stem borer management strategy that targets infestations in late season sugarcane and rice, but also in non-crop hosts, is warranted

Activity of chlorantraniliprole and thiamethoxam seed treatments on life stages of the rice water weevil as affected by the distribution of insecticides in rice plants

BACKGROUND: The systemic insecticides chlorantraniliprole (CAP) and thiamethoxam (TMX), applied to rice as seed treatments, may affect multiple life stages of the rice water weevil, Lissorhoptrus oryzophilus. Effects of CAP and TMX on adult survival, egg-laying and first- and late-instar survivals were determined by infesting plants treated as seeds with different rates of insecticides. The biological activity was related to insecticidal concentrations in leaves, shoots and roots. RESULTS: CAP did not affect adult survival but decreased egg numbers and reduced the survival of the first and late instars. The greatest reduction in weevil population occurred in late instars feeding on roots. In contrast, TMX reduced adult survival and egg and larval numbers. The high biological activity of CAP on root-feeding stages was consistent with the accumulation of CAP in roots, whereas in TMX-treated plants the high activity on adults correlated with high concentrations of TMX in leaves and stems. CONCLUSIONS: The differential activity of insecticides on adults suggests poor inherent potency of CAP as an adulticide and/or its limited systemicity in foliage. The distribution of insecticide in specific plant parts can be attributed to the different physicochemical properties of CAP and TMX. The field implications of this research on management of L. oryzophilus are discussed. © 2013 Society of Chemical Industry

Investigating the use of aquatic weeds as biopesticides towards promoting sustainable agriculture.

Aquatic weeds such as muskgrass (Chara spp.), water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), hydrilla (Hydrilla verticillate), filamentous algae (Lyngbya wollei), and duckweed (Lemna minor) thrive in farm canals within the Everglades Agricultural Area of South Florida. Their presence, particularly during the summer months is an environmental concern with regards to water quality, in addition to being a nuisance because of their ability to multiply and spread rapidly in open waters causing restricted drainage/irrigation flow and low dissolved oxygen levels. Chemical control is effective but can have undesirable off-target effects, so reduced herbicide use is desirable. Hence, need exists to discover ways in which these weeds could be best managed or utilized. The objective of this research was to evaluate the allelopathic effect of these weeds to determine their use as potential biopesticides. Six aqueous extracts were tested against 100 bacterial strains isolated from plants and soil to evaluate their antimicrobial activity. These extracts were also used to determine their insecticidal and antifeedant effects on fall armyworm (FAW, Spodoptera frugiperda). Both extracts and powder form of the aquatic weeds were tested for their herbicidal activity towards seed germination and growth of three common terrestrial weed species. At a dilution of 1:100 and 1:1,000, none of the aquatic weeds inhibited in-vitro growth of the bacterial strains, with one exception (filamentous algae extract at 1:100 reduced growth of one bacterial isolate by 54%). Water lettuce reduced the survival rate of FAW by 14% while hydrilla and duckweed caused 11% and 9% reduction of FAW growth, respectively. Powdered duckweed inhibited the growth of nutsedge by 41%, whereas filamentous algae powder and extract reduced germination of amaranth by 20% and 28%, respectively. Harvesting these weeds and converting them into useable compounds could not only eliminate the in situ farm canal and water quality problems but also result in development of new soil amendments or biopesticides

FIGURE 79 in Balclutha jafara (Hemiptera: Cicadellidae): integrative identification of a species introduced in the Western Hemisphere, and notes on other Balclutha

FIGURE 79. IQTree Cluster analysis of all 824 unique COI barcode sequences retrieved from a search on "Balclutha" in the BOLD Public Data BIN database (accessed 27-Mar-2023). The analysis includes newly-reported sequences for the following species: Balclutha caldwelli, Balclutha curvata, Balclutha flavescens, Balclutha frontalis, Balclutha incisa, Balclutha jafara, and Balclutha lucida. To simplify presentation, large clades are represented by terminal triangles (not proportional to clade size). Clades or terminal branches shaded orange include specimens that have been morphologically examined for this study. Numbers in parentheses following BIN numbers indicate the number of unique COI barcode sequences included in the BIN. BIN numbers are followed by the range of identifications of taxa included in the BIN, with the number of specimens included in parentheses following each name. Numbers in parentheses following terminal taxon names in the B. jafara clade indicate the number of additional specimens with the same COI haplotype. Branch supports are SH-aLRT/UFBootstraps, with support shown only for clades with at least 95% UFBootstrap support. The complete, uncollapsed tree is available as Supplementary Figure A1.Published as part of <i>Zahniser, James N., Halbert, Susan E., Moore, Matthew R., Mottern, Jason L. & Beuzelin, Julien M., 2023, Balclutha jafara (Hemiptera: Cicadellidae): integrative identification of a species introduced in the Western Hemisphere, and notes on other Balclutha, pp. 526-554 in Zootaxa 5361 (4)</i> on page 548, DOI: 10.11646/zootaxa.5361.4.4, <a href="http://zenodo.org/record/10151778">http://zenodo.org/record/10151778</a&gt

Jasmonic acid-induced resistance to the fall armyworm, Spodoptera frugiperda, in conventional and transgenic cottons expressing Bacillus thuringiensis insecticidal proteins

To assess potential interactions between Bacillus thuringiensis Berliner (Bt) proteins and jasmonic acid (JA)-induced resistance to the fall armyworm, Spodoptera frugiperda Smith & Abbot (Lepidoptera: Noctuidae), three commercial Stoneville cotton cultivars, Gossypium hirsutum L. (Malvaceae) (\u27ST 475\u27, a conventional cultivar; \u27ST 4575 BR\u27, a Bollgard ® cultivar expressing Cry1Ac protein; and \u27ST 4554B2RF\u27, a Bollgard II ® cultivar expressing Cry2Ab2 in addition to Cry1Ac), were treated with JA. Two experiments were conducted with 6-day-old S. frugiperda larvae on three cotton cultivars at two phenological stages. The first experiment was conducted under laboratory conditions and used excised cotton leaves; the second experiment was performed under greenhouse conditions on intact cotton plants. Relative growth rates (RGRs) and leaf area consumed by 6-day-old S. frugiperda larvae were determined for each combination of treatments. Overall, JA treatment and cultivars significantly impacted RGR and leaf area consumption. Significant JA treatment *cultivar interactions were observed for RGR of larvae in the laboratory experiment and for leaf area consumption in the greenhouse experiment. An additional experiment evaluated S. frugiperda neonates on the same JA and cotton cultivar combinations (at a single phenological stage) under laboratory conditions. Neonate survival was determined after 3, 5, and 10days of feeding, and final larval weight after 10days of feeding. Overall, JA treatment and cultivars significantly impacted final weight and survival of S. frugiperda. Significant JA treatment *cultivar interactions were observed for final weight and on overall survival of S. frugiperda. Combination of the cotton tissue expressing pyramided Bt proteins with JA treatment demonstrated the greatest negative impact on larval development. Apparent synergism between Bt proteins and JA-induced resistance emphasizes that traditional host plant resistance has a role to play in combination with Bt technology. © 2011 The Authors. Entomologia Experimentalis et Applicata © 2011 The Netherlands Entomological Society

Host preference of sweetpotato weevil, Cylas formicarius elegantulus (Summers): an example of Hopkins’ host-selection principle

© 2019, Springer Nature B.V. Sweetpotato weevil (SPW), Cylas formicarius elegantulus (Summers), is the most damaging root-feeding insect of sweetpotato, Ipomoea batatas (L.) Poir., worldwide. Larval feeding on storage roots reduces yield and induces terpene production, rendering roots inedible. Selection of sweetpotato cultivars with resistance to insect pests has been carried out for over a century but no high yielding, production acceptable varieties are currently available that are resistant to SPW. A cultivar with resistance to SPW oviposition would be a desirable choice for growers since it will reduce the number of larvae and damage level from SPW. Previous studies have compared cultivar effect on the oviposition of SPW but have not considered the effect of previous rearing experience. Hopkins’ host-selection principle (Hopkin’s HSP) states that phytophagous insects have an oviposition preference for the host that they have been reared on. In this study, we tested cultivar effect on oviposition preference of SPW reared on different cultivars for a minimum of two generations. For adults reared on cvs. Beauregard and Evangeline, adult oviposition preference followed their previous living experience. Thus, our results indicate a strong effect of host fidelity, supporting Hopkin’s HSP. Our results also confirm that cv. Murasaki is a resistant cultivar, resulting in reduced oviposition but not oviposition capacity. It is possible that the reduced oviposition is due to the stress-triggered oosorption from the females feeding on cv. Murasaki