Insect species complexes challenge entomologists in a variety of ways ranging from quarantine protection to pest management. Billbugs (Coleoptera: Curculionidae: <i>Sphenophorus</i> spp. Schönherr) represent one such species complex that has been problematic from a pest management perspective. These grass-feeding weevils reduce the aesthetic and functional qualities of turfgrass. Sixty-four species of billbugs are native to North America, and at least ten are associated with damage to turfgrass. Billbug species are sympatric in distribution and their species composition and seasonal biology varies regionally. Since their management relies heavily on proper choice of insecticide active ingredients and timing of insecticide applications that target specific life stages, understanding billbug seasonal biology underpins the development of efficient management programs. However, billbug seasonal biology investigations are currently hindered by our inability to identify the damaging larval stage to species level. DNA barcoding, which involves the use of short DNA sequences that are unique for each species, represents one potential tool that can aid these efforts. By combining DNA-based species identification with morphometric measures capable of serving as a proxy of larval development, it may be possible to gain a more holistic understanding of billbug seasonal biology. In this study, we developed a DNA barcoding reference library using cytochrome oxidase subunit 1 (COI) sequences from morphologically identified adult billbugs collected across Indiana, Missouri, Arizona, and Utah. Next, we applied our reference library for comparison and identification of unknown larval specimens collected across the growing season in Utah and Indiana. We then used a combination of DNA barcoding and larval head capsule diameters acquired from samples collected across a short span of the growing season to produce larval phenology maps. Adult billbug COI sequences varied within species, but the variation was not shaped by geography, indicating that this locus itself could resolve larval species identity. Overlaid with head capsule diameter data from specimens collected across the growing season, a better understanding of billbug species composition and seasonal biology emerged. This knowledge will provide researchers with the tools necessary to fill critical gaps in our understanding of billbug biology thereby improving turfgrass pest management. Using this approach researchers will be able to support efforts to provide growers with the information necessary to develop more prescriptive, location-based management programs and reduce the ecological footprint of turfgrass pest management.

<p>  </p> <p>Several plant-parasitic nematode (PPN) species cause decline in the health of creeping bentgrass putting greens. PPNs target and parasitize the root systems of turfgrass which may exacerbate the impact of other biotic and abiotic stress. Turfgrass managers often apply nematicides preventatively or curatively to control PPN populations. However, the inherent chemistries of the nematicides may inhibit their ability to permeate through the thatch layer and soil, resulting in an ineffective application. This research aimed to evaluate the depth of PPN populations through the growing season to maximize the effectiveness of nematicide applications, with a primary focus on lance (<em>Hoplolaimus</em> spp.) and root-knot nematodes (<em>Meloidogyne</em> spp.). To determine the depth of genera across time, soil samples were taken with a 1.9 cm diameter soil probe to a depth of 25 cm during the months of April, June, August, and October at 7 sites across Missouri, three in eastern Kansas and ten sites in Indiana in 2021 and 2022, respectively. Significant interactions occurred between sampling depth and month in both Missouri and Indiana for some PPN genera. Additionally, individual lance and root-knot nematode species obtained from sampling were characterized with molecular methods and in the case with one lance nematode from Indiana, with scanning-electron microscopy. Results suggest an over-representation of <em>H. galeatus</em> in diagnostic literature, and a diverse collection of <em>Meloidogyne</em> spp. present in Indiana on golf course putting greens. </p>

<p>  </p> <p>Annual bluegrass (<em>Poa annua</em> L.) is the most troublesome weed in turfgrass systems and the second most troublesome weed across all grass crops. Controlling annual bluegrass is exceptionally complicated due to its high genetic adaptability to new environments. Additionally, prolific seed production allowed the rapid development of herbicide resistance to 12 herbicide modes of action. Experiments were initiated with the goal to better understand annual bluegrass ecology and resistance to ethofumesate. A dose-response experiment was initiated in 2022 to determine the potential level of ethofumesate resistance in annual bluegrass collected from seed production systems. Seed from 55 annual bluegrass populations was obtained from three sources: seed production fields (31 populations), seed cleaning process (6 populations), and seed testing prior to retail distribution (18 populations). </p> <p>Individual seedlings (2–3 tillers) were treated with ten doses of ethofumesate: 0, 0.6, 1.1, 2.8, 5.6, 8.4, 11.2, 16.8, 22.4, and 44.8 kg ai ha−1; with 1.1 to 2.2 kg ha−1 as the label application rates for perennial ryegrass (<em>Lolium perenne</em> L.). The resistance to susceptible ratio of populations across all sources ranged from 0.48 to 5.48. The most resistant populations from production fields, removed during the seed cleaning process, or found in seed testing lots had ED50 values of 12.1, 13.1, and 9.4 kg ai ha−1, respectively. Further, 68% of the populations found in production fields had ED50 higher than 6 kg ai ha−1, which indicates that annual bluegrass resistance is common in grass seed production. A garden study was initiated in November 2020 to assess the development, reproduction, and survival of ten annual bluegrass populations in Indiana. Annual bluegrass plants were maintained in the absence of turf competition and not subjected to typical turfgrass management practices including irrigation, mowing and fertilization. Data collected in included growth rate, biomass production, ground cover, morphology, flowering time, seed production and morphology, and both winter survival and subsequent summer survival of plants. Principal component analysis indicated that certain populations grouped together based on their development, morphology, stress tolerance, and seed production. Plants from the cooler climates (OR, PA, and IN) were characterized by higher growth rates and biomass compared to southern ecotypes. These three populations survived the longest during the summer, with the PA population averaging the highest ground cover of 276 cm2 on 23 July 2021. Plants from warm climates (AL, FL, NC, SC, TN, TX) had poor summer survival. Additionally, the FL population had the highest winterkill of 68%, followed by TX at 45%. The NJ population was distinct from other populations, and plants had robust aboveground biomass and high seed production. The results indicate that the development, reproduction, and survival of different annual bluegrass biotypes are dependent on the climate of origin. A third experiment was designed to understand patterns of germination and seed longevity in populations from five climates across the U.S. at two depths of burial. Seed was retrieved in 6-month intervals up to 24 months. Seed viability by depth (surface vs. 5-cm deep) of burial differed only 18 months after the initiation of the study. However, seed viability did differ among populations on each date of seed retrieval. Viability was low ranging from 0.21 to 0.91%, and populations originating from cool climates (New Jersey, Pennsylvania, and Oregon) generally had higher viability than populations originating from warmer climates. Annual bluegrass seed tested in this study typically had low levels of survival (<0.5%); however, all populations retained some level of viability 24 months after burial, which would allow future reproduction of this troublesome weed. Overall, this research determined that herbicides alone will likely be ineffective at controlling annual bluegrass and that knowledge of the development, reproduction, and survival of local annual bluegrass populations should be factored into an integrated weed management strategies created for each site. </p> <p>  </p>

Potential vegetative and reproductive increases in yield, as well as the biological efficacy against Fusarium verticillioides and F. proliferatum causing ear and stem rot in maize crops of commercially-formulated micro-organism formulation T-Gro (Trichoderma harzianum isolate DB103 WP) combined with Spartacus (Beauveria bassiana isolate DB 105 WP), T-Gro combined with Armenius (Bacillus subtilis isolate DB 109 WP), T-Gro combined with Maximus (Bacillus subtilis isolate DB 108 WP), T-Gro combined with Shelter (Bacillus subtilis isolate DB 101), T-Gro combined with Bismarck (Microbacterium maritypicum isolate DB 107 WP), as well as individual treatments of T-Gro, Armenius, Bismarck, Maximus and Shelter, were investigated when applied to maize seed and soil under field conditions. All the micro-organism treatments were compared with Thiram 750WP (750g/kg thiram WP) and an untreated control. The micro-organism treatments showed an increase in vegetative as well as reproductive yields when compared to the reference product Thiram 750 WP and the untreated control. There were no observations of adverse effects on the germination of maize seed in all the treatments that were applied. The three isolates B. subtilis, T. harzianum, and M. maritypicum, showed a significant reduction in vascular tissue discolouration of the main and ear stems, indicating a potential to be used in the reduction and control of diseases caused by Fusarium spp. Results also showed poor to very good increases of stem and foliage biomass as well as cob yield per plant produced by the micro-organism treatments when compared to the untreated control. The highest cob yield per plant that differed significantly from the untreated control was produced by T-Gro and Shelter. No phytotoxicity of any kind was observed with the application of the micro-organism formulations and they could therefore be deemed suitable to be used for the treatment of maize seed. The micro-organism formulations containing fungal and bacterial biological control agents have the potential to be used in commercial maize production to increase vegetative and reproductive yields and reduce the severity of ear and stem rot in maize. / Agriculture Animal Health & Human Ecology / M.Sc. (Agriculture)

A aplicação de herbicidas pós-emergentes na cultura de milho é intensa, expondo a cultura às inumeras situações de manejo em coincidência com a utilização destes agroquímicos, podendo resultar em interações prejudiciais a cultura. Sendo assim, desenvolveu-se esta pesquisa, com o objetivo de avaliar a possibilidade de interação entre esses herbicidas com inseticidas e adubos nitrogenados, bem como a eficácia dos herbicidas no controle de plantas daninhas. Foram instalados experimentos a campo e em casa-de-vegetação, nas dependências do Departamento de Produção Vegetal da ESALQ-USP. Foram três modalidades de experimentação, onde foi utilizado o delineamento estatístico de blocos casualizados com quatro repetições. O primeiro experimento avaliou a interação entre os herbicidas pós-emergentes, mesotrione, nicosulfuron e iodosulfuron + foramsulfuron, e as fontes nitrogenadas, sulfato de amônia em cobertura e uréia incorporada. Após a analise dos resultados, foram observados alguns sintomas fitotóxicos causados pelos herbicidas. Tais sintomas evoluíram até o total desaparecimento, tornando-se imperceptíveis ao longo do ciclo da cultura, a qual apresentou altura de pendoamento semelhante a testemunha. Os rendimentos de grãos e o peso de mil grãos não indicam reduções de produtividade. Tanto para a uréia, quanto para o sulfato de amônio, não detectou-se sintomas de interatividade fitotóxica para o híbrido AGN 2012. O segundo, avaliou a interação entre herbicidas pós-emergentes, nicosulfuron e mesotrione em mistura com atrazina, e os inseticidas clorpirifós, lambdacyhalotrina, e thiamethoxan + lambdacyhalotrina, aplicados em mistura de tanque. Ocorreram injúrias fitotóxicas sinérgisticas para os tratamentos envolvendo o inseticida clorpirifós. Não ocorreram reduções de altura, rendimento e peso de 1000 grãos. Isso indica a capacidade do híbrido AGN 2012 em superar as fitotoxicidades, mas não isenta a mistura do risco de perda de rendimento em outras situações. A terceira, testou a eficácia dos herbicidas pós-emergentes mesotrione + atrazina, nicosulfuron + atrazina, nicosulfuron e iodosulfuron + foramsulfuron, no controle de Brachiaria plantaginea, Digitaria horizontalis, Panicum maximum, Eleusine Indica, Ipomoea grandifolia e Bidens pilosa suscetível e resistente aos herbicidas inibidores da ALS. Foi observado que a planta daninha no estádio inicial de crescimento, é melhor controlada pelos herbicidas; as misturas de herbicidas são mais eficazes, permitindo controlar plantas em estádios de crescimento mais avançados; o Panicum maximum requer doses maiores dos herbicidas ou a mudança da estratégia de controle; o milho pode ser uma alternativa no controle de Bidens pilosa resistente aos inibidores da ALS, se cultivado como cultura de sucessão em um sistema de produção, com uso de herbicidas com alternativos mecanismos de ação. A pesquisa conclui que herbicidas pós-emergentes aplicados na cultura de milho, podem ter sua seletividade reduzida quando aplicado simultaneamente com inseticidas e adubos nitrogenados, porém as fitotoxicidades causadas por estas interações sinérgicas podem não reduzir a produtividade final como ocorreu neste trabalho, em função de combinações entre fatores climáticos e culturais. A eficácia desses herbicidas, estudada para plantas daninhas da cultura de milho, depende do estádio fenológico destas plantas, sendo que a mistura de mesotrione + atrazina é uma alternativa para o controle de B. pilosa resistente aos inibidores da ALS. / The application of post-emergence herbicides at corn crop is intense, exposing the crop to countless management situations in coincidence with the using of these agrochemicals that can result in damaging interactions to the crop. Therefore, this research was developed, with the objective of evaluating the possibility of interaction between these herbicides with insecticides and nitrogen fertilizers, as well the herbicides efficacy on weeds control. There were installed experiments in field and green-house, at Crop Science Department annexes, ESALQ/USP. There were three experimentation modalities, where it was used the statistical design of randomized blocks with four replicates. The first experiment evaluated de interaction between the post-emergence herbicides, mesotrione, nicosulfuron and iodosulfuron + foramsulfuron, and the nitrogen sources, ammonium sulfate in covering and incorporated urea. After the results analysis, there were observed some phytotoxics symptoms caused by the herbicides. These symptoms evolved until the total disappearing, becoming imperceptible along the crop cycle, witch presented height at flowering similar to the check. The kernel yield and the weight of 1000 kernels did not presented productivity reduction. Each for urea or for ammonium sulfate, it was not detected symptoms of phytotoxic interactivity to the hybrid AGN 2012. The second experiment evaluated the interaction between the post-emergence herbicides, nicosulfuron and mesotrione in mixture with atrazine, and the insecticides clorpirifos, lambdacyhalotrin and thiamethoxan + lambdacyhalotrin, applied in tank mixture. It was observed synergistic phytotoxics injuries to the treatments involving the insecticide clorpirifos. Although, it was not observed height, yield or weight of 1000 kernels reductions. It indicates the capacity of the hybrid AGN 2012 in overcoming the phytotoxity, but it did not exempt the mixture of yield losses risk in other situations. The third experiment, tested the efficacy of the post-emergence herbicides mesotrione + atrazine, nicosulfuron + atrazine, nicosulfuron and iodosulfuron + foramsulfuron, on control of Brachiaria plantaginea, Digitaria horizontalis, Panicum maximum, Eleusine Indica, Ipomoea grandifolia and Bidens pilosa susceptible and resistant to ALS-inhibiting herbicides. It was observed that the weeds are better controlled by herbicides at initial growth stage; the herbicides mixtures are more efficient, permitting to control plants in more developed growth stages; the weed Panicum maximum require upper herbicides rates or changings on control strategies; the corn may be an alternative crop to control Bidens pilosa resistant to ALS-inhibiting herbicides, if conduced as a succession crop in the production system, using herbicides with alternative action mechanisms. This research concluded that post-emergence herbicides applied on corn crop may have its selectivity reduced when simultaneously applied with insecticides or nitrogen fertilizers, although the phytotoxity caused by these synergistic interactions may not reduce the final productivity, as occurred at this work, in function of combinations of climatic and crop factors. The efficacy of these herbicides, studied for weeds at corn crop, depends on weeds phenologic stage, and the mixture of mesotrione + atrazine is an alternative to control B. pilosa resistant to ALS-inhibiting herbicides.

Dans les agroécosystèmes, l'utilisation de la biodiversité pour la régulation naturelle des arthropodes nuisibles vise à proposer une protection agroécologique des cultures, en alternative à la protection agrochimique actuelle. Notre étude a porté sur les agroécosystèmes à base de manguiers à La Réunion, avec l'objectif de comprendre les facteurs qui influencent la biodiversité et la régulation des arthropodes nuisibles. Cet agroécosystème est caractérisé par une importante diversité (797 espèces d'arthropodes et 114 espèces de plantes) et nos résultats ont révélé l'existence de contrôles ascendants et descendants positifs de cette biodiversité au sein des communautés. Nous avons également mis en évidence les services et disservices des espèces dominantes de fourmis envahissantes : deux d'entre elles fournissent un service de prédation et l'une d'elles réduit la diversité des ennemis naturels omnivores, ce qui semble expliquer la relation négative entre la diversité des omnivores et le service de prédation. Enfin, nous avons montré l'effet positif de la diversité des parasitoïdes et de la diversité des prédateurs, respectivement sur l'abondance des populations de la Cochenille des Seychelles et sur le service de prédation. Le seul effet significatif du paysage qui a été décelé est l'effet positif de la proportion des vergers de manguiers sur l'abondance du Thrips Sud-Africain des agrumes. L'ensemble de ces résultats nous permet d'identifier deux leviers pour la protection agroécologique des vergers de manguiers : l'implantation d'enherbements diversifiés dans les vergers ; la gestion collective du paysage en y limitant la proportion des vergers de manguiers. / In agroecosystems, the use of biodiversity for natural control of arthropod pests aims to propose an agroecological crop protection, as an alternative to current agrochemical protection. Our study focused on mango agroecosystems in Reunion Island, with the goal of understanding the factors that influence biodiversity and control of arthropod pests. This agroecosystem is characterized by a large diversity (797 arthropod species and 114 plant species) and our results highlight the positive bottom-up and top-down controls of biodiversity in communities. We also highlight the services provided by the dominant species of invasive ants in pest regulation. Two species provide a predation service, and one reduces the diversity of natural enemies of omnivores and appears to explain the negative relationship between omnivore diversity and predation. Finally, we highlight the positive effect of parasitoid diversity and predator diversity on, respectively, the abundance of Seychelles mealybugs and on predation in general. The only significant landscape effect measured in our work is the positive effect of the proportion of mango orchards on the abundance of South African citrus Thrips. These results allow us to identify two factors in the agroecological protection of mango orchards in Reunion: the management of diversified ground cover in orchards; and collective landscape management by limiting the proportion of mango orchards.

Plants regulate responses to their environment through complex hormone signaling; these hormones can be categorized broadly into two categories: growth and defense, though many have roles in both. Much remains to be understood about the complexity of hormone signaling in relation to environmental responses, especially species- and genotype-specific differences. Unraveling this complexity of hormone signaling will lead to the development of resilient crops that are able to respond appropriately to their environment. In this dissertation, I hypothesize novel roles for growth and defense hormones in <i>Solanum </i>spp. responses to 1) biochar, a black carbon soil amendment (Chapter 2), 2) infection with<i> Ralstonia solanacearum</i>, an economically important soilborne pathogen causing bacterial wilt (Chapter 3), and 3) endophytic colonization by the soil bacterial community (Chapter 4). In Chapter 2, I showed that biochar upregulates GA signaling and affects GA-related traits in a species- and cultivar-specific manner. Biochar amendment also downregulates defense signaling. In Chapter 3, I demonstrated a novel role for auxin in resistance against <i>R. solanacearum, </i>including differential expression of auxin signaling genes in resistant genotype H7996 compared to susceptible WV in response to <i>R. solanacearum</i> infection. In addition, I observed stronger and faster upregulation of defense hormone marker genes for SA and ET in H7996 compared to WV. In Chapter 4, I showed that SA and ET are required for normal tomato root microbial community assembly, affecting the colonization of a few key taxa in order to promote alpha diversity. H7996 and WV root communities differ in alpha diversity, and a panel of H7996 x WV RILs showed quantitative variation in alpha diversity that correlated negatively with the abundance of these key taxa. In conclusion, I elucidated novel roles for hormones in responses to the soil environment, pathogen infection, and root community colonization. These findings are important for developing resilient, sustainable crops.

No description available.

Dans un objectif de réduction de l'utilisation des pesticides, des méthodes alternatives doivent assurer la protection des cultures. Les dégâts causés par les insectes ravageurs sont les manifestations de dynamiques de population dont certains déterminants paysagers sont des éléments structuraux potentiellement relocalisables. Nous explorons ici, par la simulation numérique, la modification du paysage comme stratégie de protection des cultures.Les éléments paysagers peuvent impacter les populations d'insectes par leur influence sur les comportements individuels. Nous avons développé un modèle de population tenant compte de l'approvisionnement individuel. Ce processus résulte (1) de la perception des ressources distantes par l'individu, (2) de la localisation de la population sur une dimension additionnelle quantifiant les réserves énergétiques, et (3) d'une procédure d'optimisation qui définit des mouvements dirigés adaptés.Une heuristique évolutionnaire de modification de paysages a été développée. Elle produit des réarrangements sous contraintes de composition et de structure. Les modèles de paysages et de dynamique de population ont été appliqués à un problème théorique d'aménagement du paysage. La description mécaniste de l'approvisionnement optimal offre des leviers d'action efficaces, basés sur la perturbation des comportements d'approvisionnement. Nos travaux montrent la réactivité de la population aux modifications du paysage, ainsi que la capacité des algorithmes évolutionnaires à proposer des paysages résistants, sous contraintes agronomiques. / Environmental and health issues call for a switch in crop protection towards less chemically driven strategies. Pest damages on crops result of population dynamics that are influenced by landscape features. Those features may be relocated or dismissed to improve landscapes resistance to pest damages. Here we explore numerically the landscape modification as a crop protection strategy.Landscape features can influence population dynamics through their impact on individuals. Therefore, we developed a multiscale population dynamics model accounting for individual foraging. The foraging process results of (1) the perception of distant features used as resources by the individuals, (2) the localisation of the population along an additional dimension quantifying individual energy supply, (3) an optimisation procedure defining adapted directed motionsWe developed an evolutionary heuristic for landscape modification. It is able to rearrange landscapes with respect to compositional and structural constraints. Population and landscape models were applied to a theoretical landscape planning problem. The mechanistic description of the optimal foraging process enables new and efficient levers for crop protection, building on the disruption of the foraging behaviours. This application enlightens the responsiveness of the simulated population to landscape modifications, as well as the ability of evolutionary algorithms to produce resilient landscapes under agronomic productive constraints.

Potential vegetative and reproductive increases in yield, as well as the biological efficacy against Fusarium verticillioides and F. proliferatum causing ear and stem rot in maize crops of commercially-formulated micro-organism formulation T-Gro (Trichoderma harzianum isolate DB103 WP) combined with Spartacus (Beauveria bassiana isolate DB 105 WP), T-Gro combined with Armenius (Bacillus subtilis isolate DB 109 WP), T-Gro combined with Maximus (Bacillus subtilis isolate DB 108 WP), T-Gro combined with Shelter (Bacillus subtilis isolate DB 101), T-Gro combined with Bismarck (Microbacterium maritypicum isolate DB 107 WP), as well as individual treatments of T-Gro, Armenius, Bismarck, Maximus and Shelter, were investigated when applied to maize seed and soil under field conditions. All the micro-organism treatments were compared with Thiram 750WP (750g/kg thiram WP) and an untreated control. The micro-organism treatments showed an increase in vegetative as well as reproductive yields when compared to the reference product Thiram 750 WP and the untreated control. There were no observations of adverse effects on the germination of maize seed in all the treatments that were applied. The three isolates B. subtilis, T. harzianum, and M. maritypicum, showed a significant reduction in vascular tissue discolouration of the main and ear stems, indicating a potential to be used in the reduction and control of diseases caused by Fusarium spp. Results also showed poor to very good increases of stem and foliage biomass as well as cob yield per plant produced by the micro-organism treatments when compared to the untreated control. The highest cob yield per plant that differed significantly from the untreated control was produced by T-Gro and Shelter. No phytotoxicity of any kind was observed with the application of the micro-organism formulations and they could therefore be deemed suitable to be used for the treatment of maize seed. The micro-organism formulations containing fungal and bacterial biological control agents have the potential to be used in commercial maize production to increase vegetative and reproductive yields and reduce the severity of ear and stem rot in maize. / Agriculture Animal Health and Human Ecology / M.Sc. (Agriculture)