Probability of return on investment with using soybean seed treatments

With soybean commodity prices at record high prices, the number of questions regarding key management considerations also remains high. One of the question that we often receive regards the use of seed treatments, in particular the use of seed treatment fungicides and/or insecticides. Since 2008, we have conducted trials throughout Wisconsin to examine if seed treatments are economically viable for soybean production. In particular, we are most interested in trying to answer the following question: “what is the probability that if I use a seed treatment, the cost of the application is covered?

Severe risk for Stewart\u27s disease

Stewart\u27s disease of corn, also known as Stewart\u27s wilt, is caused by the bacterium Pantoea stewartii. The 2000 growing season is predicted to be a very severe year for this disease, largely because of six successive winters with above-average monthly temperatures that have favored the survival of the insect vector for this disease, the corn flea beetle (Chaetocnema pulicaria). There are commonly two stages to the disease. Initially, leaf lesions that are off-green to yellow extend along the leaf veins, followed by mild-to-severe early seedling blight symptoms

Meteorological factors and Asian soybean rust epidemics: a systems approach and implications for risk assessment

Favorable meteorological and environmental conditions are critical components that affect Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, the most damaging fungal disease of soybean. In this review, we used available knowledge on the effect of meteorological factors affecting the disease to construct a systems-based approach to understand the risk of ASR epidemics. The systems approach is based on a hierarchical framework where relevant environmental factors that affect the key stages of the ASR disease cycle are identified and this included both aerobiological and epidemiological components. The formal framework we used examined the following epidemic characteristics: spore release, spore dispersal, spore deposition, infection efficiency, latent period and spore production. It provided the ability to identify the most important meteorological-related factors along with relevant knowledge gaps from which the implications for disease forecasting were described. This is new information that can be used as a guide for further epidemiological research and especially to develop and improve upon both local and regional risk models.Condições meteorológicas e ambientais são componentes críticos nas epidemias de ferrugem asiática da soja (FAS), doença causada pelo fungo Phakopsora pachyrhizi e que causa o maior dano na cultura da soja. Nesta revisão, o conhecimento sobre o efeito de fatores meteorológicos que influenciam nas epidemias foi usado para construir uma abordagem sistêmica para compreender o risco de epidemias de FAS. Esta é baseada em uma estrutura hierárquica onde os fatores relevantes que afetam os estágios chave no ciclo da doença foram delineados, incluindo os componentes aerobiológicos e epidemiológicos. As seguintes características epidemiológicas foram avaliadas: liberação de esporos, dispersão de esporos, deposição de esporos, eficiência de infecção, período latente e produção de esporos. O conhecimento sobre os fatores meteorológicos que afetam cada um dos componentes foi revisado, sendo identificados os fatores mais importantes e as falhas de conhecimento, bem como as implicações para a previsão da doença. A informação é importante para orientar a pesquisa epidemiológica futura e especialmente desenvolver e melhorar modelos de risco da doença em níveis locais a regionais

Geographical and Temporal Dynamics of Chaetocnema Pulicaria Populations and Their Role in Stewart's Disease of Corn in Iowa

This thesis is organized into five chapters. Chapter 1 is the introduction and justification, chapters 2 and 3 are journal papers, chapter 4 is a preliminary analysis of winter environmental variables and their use in forecasting for Stewart's disease of corn, and chapter 5 is general conclusions and discussion. References can be found at the end of each chapter, except chapter 5 and are specific to that chapter

Geographical and Temporal Dynamics of Chaetocnema Pulicaria and Their Role in Stewart's Disease of Corn in Iowa

This thesis investigated the biology and importance of the corn flea beetle vector and its role in the Stewart's disease of corn pathosystem. This was accomplished by determining the number of corn flea beetle generations that occur in Iowa and by quantifying the proportions of those populations found to be infested with the causal agent of Stewart's disease, pantoea stewartii. In addition, a preliminary study was conducted to determine how soil temperature was influenced by air temperature and how this may be applied to forecasting for Stewart's disease of corn. Research using yellow sticky cards and sweep netting demonstrated that there are overwintering, first, and second field generations of the corn flea beetle in Iowa. It was also observed that there was a period during June of both 1999 and 2000 when corn flea beetles were not found, which is important new management information. This research has also demonstrated that the incidence of P. stewartii-infested corn flea beetles can be monitored by ELISA testing and that the incidence fluctuates greatly throughout the corn growing season. The initial level of inoculum (P. stewartii-infested corn flea beetles in the adult overwintering generation) does not remain static during the spring as was previously hypothesized. This signals that additional research is needed concerning the mechanisms of fluctuation in the proportion of beetles infested with P. stewartii

Quantifying the Feeding Periods Required by Corn Flea Beetles to Acquire and Transmit Pantoea stewartii

The feeding periods required by corn flea beetles to acquire and transmit Pantoea stewartii were investigated in the Stewart\u27s disease of corn pathosystem. To quantify the effect of acquisition feeding period on percentage of acquisition, field-collected corn beetles were allowed to feed for 6, 12, 24 36, 48, and 72 h on corn seedlings previously inoculated with a rifampicin- and nalidixic acid-restraint strain of P. stewartii. Acquisition of P. stewartii by corn flea beetles was considered positive if the rifampicin- and nalidixic acid-marked strain was recovered on selective media. To quantity the effect of transmission feeding period on percent transmission of P. stewartii by corn flea beetles, P. stewartii- infested corn flea beetles were allowed to feed on healthy corn seedlings for periods of 3, 6, 12, 24, 36, 48, and 72 h. After the appropriate transmission feeding period, leaf tissues surrounding the sites of feeding scars were cultured for the presence of the P. stewartii-marked strain. Transmission of P. stewartii was considered positive if the marked strain was recovered on selective media. Acquisition of P. stewartii occurred within 6 h and the percentage of corn flea beetles that had acquired P. stewartii after 72 h ranged from 68 to 94%. The change in P. stewartiiacquisition by corn flea beetles (Y) with respect to acquisition feeding period (X) was best described by the Gompertz model, with R2 values ranging from 91 to 99%. The mean time for acquisition by 50% of the corn flea beetles was 36.5 ± 11.6 h. The minimum transmission feeding time required for corn flea beetles to transmit P. stewartii following a 48-h acquisition feeding period was less than 3 h. The percent transmission of P. stewartii by corn flea beetles was nearly 100% after a 48-h transmission feeding period and was 100% by 72 h. Among population growth models evaluated, the monomolecular model best described the relationship between percent transmission (Y) and transmission feeding periods (X), with R 2 values of up to 84%. However, a nonlinear form of the monomolecular model better quantified the relationship between percent transmission and transmission feeding period, because pseudo-R2 values ranged between 98.1 and 99.5%. The predicted transmission feeding time required for 50% of P. stewartii-infested corn flea beetles to transmit the pathogen was 7.6 ± 0.87 h. These results suggest that the corn flea beetle is a highly efficient vector that can quickly acquire and transmit P. stewartii, thereby requiring insecticide seed treatments and foliar insecticides that act quickly to prevent corn flea beetles from acquiring and transmitting P. stewartii to corn plants