Herbicide Drift Influence on \u3ci\u3eAmaranthus\u3c/i\u3e spp. Herbicide Resistance Evolution

The adverse consequences of herbicide drift towards sensitive crops have been extensively reported in the literature. However, no information is available on the consequences of herbicide drift onto weed species inhabiting boundaries of agricultural fields. Exposure to herbicide drift could be detrimental to long-term weed management as several weed species have evolved herbicide resistance after recurrent selection with low herbicide rates. Despite the herbicide drift exposure and its potential implications on resistance evolution and weed management, resistance prone weed species such as Palmer amaranth (Amaranthus palmeri) and waterhemp (Amaranthus tuberculatus) are often neglected and not properly managed in agricultural field margins. The first study of this research investigated the frequency and distribution of glyphosate-resistant Amaranthus spp. in Nebraska. The study also investigated how agronomic practices influenced the occurrence of glyphosate resistance in Amaranthus spp. in Nebraska. While glyphosate resistance was widespread in waterhemp, few glyphosate-resistant Palmer amaranth populations were reported in Nebraska. Weed species, geographic region within the state, and current crop were the most important factors predicting the occurrence of glyphosate resistance in fields infested with Amaranthus spp. in Nebraska. Moreover, glyphosate resistance was widespread in waterhemp populations collected on field borders and ditches. The second study investigated the near-field deposition of glyphosate, 2,4-D, and dicamba spray drift from applications with two different nozzles in a low-speed wind tunnel, and their impact on Palmer amaranth and waterhemp growth and development. Herbicide drift was influenced by nozzle design and resulted in Amaranthus spp. biomass reduction or complete plant mortality. Herbicide drift can expose weeds inhabiting field margins to herbicide rates previously reported to select for herbicide-resistant biotypes. The third study investigated if recurrent selection with glyphosate, 2,4-D, and dicamba spray drift could select for Amaranthus spp. biotypes with reduced herbicide-susceptibility over two generations. The study results confirmed that herbicide drift towards field margins can rapidly select for weed biotypes with reduced herbicide sensitivity. Preventing the establishment of resistance prone weeds on field margins is an important management strategy to delay herbicide resistance. Weed management programs should consider strategies to mitigate near-field spray drift, and suppress weed populations on field borders. Advisor: Greg R. Kruge

Water Quality, Carrier Volume and Droplet Size Effects on Herbicide Efficacy and Drift Potential

Herbicide performance is directly related to the amount of active ingredient that has been deposited on the plant. Hence, spray solution characteristics and application parameters are crucial in determining the efficacy of an herbicide application. To maximize the effectiveness of chemical control, methods to deliver full chemical dose must be utilized: allowing the active ingredient to be readily absorbed once added to the carrier and mitigating off-target movement and low herbicide doses. Water is the most frequently used carrier in herbicide applications. Chemical parameters, such as water hardness and pH, can have a critical role in herbicide performance. It is generally believed that weak acid herbicides, such as glyphosate and 2,4-D, have higher dissociation in higher carrier pH, which leads to decreased uptake into plants. Moreover, increased concentration of hard water cations may have antagonistic effect on weak acid herbicide applications. To overcome the negative effect of water quality on weak acid applications, addition of water conditioning adjuvants is recommended. Carrier volume and droplet size are crucial parameters in application technology that can also impact herbicide performance. Nozzles and their spray characteristics have gone under significant development in past decades to enhance spray potential under a wide range of conditions. Introduction of air inclusion nozzles provided the ability to create larger droplets at the same pressure and flow rate as conventional nozzles, resulting in less drift. Controlling off target movement essentialy decreases the potential for herbicide resistance selection on weeds, as well as injury on sensitive crops. Hence, the objectives of this research were to investigate water quality, carrier volume and droplet size effects on herbicide efficacy and drift potential. Advisors: Christopher Proctor and Greg Kruge

Characterization of pyrethroid resistance in the western corn rootworm Diabrotica \u3ci\u3evirgifera virgifera\u3c/i\u3e LeConte

The western corn rootworm (WCR), Diabrotica virgifera virgifera Le Conte (Coleoptera: Chrysomelidae), is a major pest of maize (Zea mays L.) in the United States and has continuously challenged our ability to develop sustainable pest management solutions. Resistance to chemical insecticides, crop rotation, and most recently transgenic plants that express toxins derived from Bacillus thuringiensis Berliner (Bt) have been well documented among WCR populations. Furthermore, US regulatory insecticide prohibitions and the lack of new active ingredients have reduced the options for WCR control. Pyrethroid insecticides are one of the few remaining chemical options. Therefore, the recent confirmation of WCR field-evolved resistance to pyrethroids in the US western Corn Belt is a major concern. The present research aimed to characterize WCR pyrethroid resistance. The initial objective was to evaluate the field performance of formulated pyrethroids on pyrethroid-resistant WCR populations. An aerial application simulation method was developed to evaluate the performance of foliar adulticides whereas soil insecticides targeting WCR larvae were tested in field plots with representative WCR populations. Laboratory bioassays estimated the susceptibility of tested WCR populations against the active ingredients of formulated insecticides. Results indicated that relatively low levels of WCR pyrethroid resistance are enough to significantly impact the performance of pyrethroid products commonly used for either adult or larval control. A second objective was to artificially select a pyrethroid-resistant WCR population to be used along with field populations for pyrethroid resistance characterization. A population was selected in the laboratory with a diagnostic bifenthrin concentration for several generations reaching levels of pyrethroid resistance observed in field-collected WCR populations. A pilot heritability investigation suggested that a major portion of WCR bifenthrin resistance phenotypic variance may be due to genetic variation, and that a substantial increase in resistance could be expected afterexposure. Finally, the third objective was to identify WCR pyrethroid resistance mechanisms. Biochemical assays and High-Throughput RNA Sequencing results revealed that insecticide-related metabolism in pyrethroid-resistant WCR populations was significantly enhanced compared to pyrethroid-susceptible populations. The relevance of results is discussed within the context of WCR pyrethroid resistance monitoring and management. Advisor: Lance J. Meink

Sensors Application in Agriculture

Novel technologies are playing an important role in the development of crop and livestock farming and have the potential to be the key drivers of sustainable intensification of agricultural systems. In particular, new sensors are now available with reduced dimensions, reduced costs, and increased performances, which can be implemented and integrated in production systems, providing more data and eventually an increase in information. It is of great importance to support the digital transformation, precision agriculture, and smart farming, and to eventually allow a revolution in the way food is produced. In order to exploit these results, authoritative studies from the research world are still needed to support the development and implementation of new solutions and best practices. This Special Issue is aimed at bringing together recent developments related to novel sensors and their proved or potential applications in agriculture

Development of soft computing and applications in agricultural and biological engineering

Soft computing is a set of “inexact” computing techniques, which are able to model and analyze very complex problems. For these complex problems, more conventional methods have not been able to produce cost-effective, analytical, or complete solutions. Soft computing has been extensively studied and applied in the last three decades for scientific research and engineering computing. In agricultural and biological engineering, researchers and engineers have developed methods of fuzzy logic, artificial neural networks, genetic algorithms, decision trees, and support vector machines to study soil and water regimes related to crop growth, analyze the operation of food processing, and support decision-making in precision farming. This paper reviews the development of soft computing techniques. With the concepts and methods, applications of soft computing in the field of agricultural and biological engineering are presented, especially in the soil and water context for crop management and decision support in precision agriculture. The future of development and application of soft computing in agricultural and biological engineering is discussed

Fleets of robots for environmentally-safe pest control in agriculture

Feeding the growing global population requires an annual increase in food production. This requirement suggests an increase in the use of pesticides, which represents an unsustainable chemical load for the environment. To reduce pesticide input and preserve the environment while maintaining the necessary level of food production, the efficiency of relevant processes must be drastically improved. Within this context, this research strived to design, develop, test and assess a new generation of automatic and robotic systems for effective weed and pest control aimed at diminishing the use of agricultural chemical inputs, increasing crop quality and improving the health and safety of production operators. To achieve this overall objective, a fleet of heterogeneous ground and aerial robots was developed and equipped with innovative sensors, enhanced end-effectors and improved decision control algorithms to cover a large variety of agricultural situations. This article describes the scientific and technical objectives, challenges and outcomes achieved in three common crops

2023 SDSU Data Science Symposium Presentation Abstracts

This document contains abstracts for presentations and posters 2023 SDSU Data Science Symposium

2023 SDSU Data Science Symposium Presentation Abstracts

This document contains abstracts for presentations and posters 2023 SDSU Data Science Symposium

Developing Methods to Survey, Collect, Process, and Screen Endemic Entomopathogenic Fungi Against the Asian Citrus Psyllid in the Lower Rio Grande Valley

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), vectors “Candidatus Liberibacter spp.”, the causative agent of Citrus Greening Disease. Managing ACP is imperative given the continuous increase in HLB positive trees. An aspect of integrated pest management (IPM) is the use of entomopathogenic fungi for the biological control of D. citri. In order to identify endemic entomopathogenic fungi actively infecting D. citri, ACP were collected from local residential areas, surface sterilized, and plated on a semi-selective agar medium. Collection of over 9,300 samples from 278 sites throughout the LRGV led to the positive identification of nine entomopathogenic fungi across several genera via phylogenetic analysis. Primary and secondary acquisition bioassays revealed that both field isolated strains performed atcomparable rates to Cordyceps (Isaria) fumosorosea Apopka97. In addition, thermal profiles for vegetative growth were determined. The findings revealed that the new isolates were capable of inducing mortality at rates greater than the standard, indicating that they may prove to be good candidates for the management of D. citri populations in the LRGV. Alternate abstract: El psílido asiático de los cítricos (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), vector de “Candidatus Liberibacter spp.”, el agente causante de la enfermedad del enverdecimiento de los cítricos. El manejo de el ACP es imperativo dado el aumento continuo de árboles positivos con HLB. Un aspecto del manejo integrado de plagas (MIP) es el uso de hongos entomopatógenos para el control biológico de D. citri. Para identificar hongos entomopatógenos endémicos que infectan activamente a D. citri, se recolectaron muestras de áreas residenciales locales, esterilizados en superficie y colocados en un medio semi-selectivo. La recolección de más de 9,300 muestras de 278 sitios en todo el LRGV condujo a resultados de identificación positivos de nueve hongos entomopatógenos en varios géneros mediante análisis filogenético. Los bioensayos de adquisición primaria y secundaria revelaron que ambas cepas aisladas de campo se realizaron en tasas comparables a Cordyceps (Isaria) fumosorosea Apopka97. Además, perfiles térmicos para el crecimiento vegetativo fueron determinados. Los hallazgos revelaron que los nuevos aislamientos eran capaces de inducir mortalidad a tasas mayores que el estándar, lo que indica que pueden ser buenos candidatos para el manejo de poblaciones de D. citri en el LRGV