What’s New in Plant Pathology

Extension Plant Pathology Team Update Plant and Pest Diagnostic Clinic Update Disease Management Products Table 1. Foliar Fungicide Label Updates Table 2. New Product

Landscape and Garden Plants Sample Submission to the Plant and Pest Diagnostic Clinic

Diagnoses are made easier and turnaround time is improved when the quality of plant samples is maintained. This NebGuide discusses the proper guidelines for submitting landscape and garden plants, turf, and tree samples to UNL’s Plant and Pest Diagnostic Clinic. There are several important things to consider when collecting, packaging, and sending plant or insect samples for diagnosis in a plant diagnostic laboratory. Collect an adequate amount of plant material. When feasible, the sample should include the entire plant — roots, stems, leaves, flowers, and fruits. Whole plants are needed to properly evaluate the sample. If the whole plant is not available, photos of the symptomatic plants can improve accuracy of diagnosis

Storage and breakdown of starch aid \u3cem\u3eP. parviflorus\u3c/em\u3e in leaf re-greening after nitrogen deficiency

Plectranthus parviflorus, common Swedish ivy does not lose leaves when it is deprived of nitrogen. Instead this plant retains its yellow leaves and upon reintroduction of nitrogen will re-green and start to grow. In two experiments, rooted cuttings of common Swedish ivy were grown with (150 ppm N) and without nitrogen for 3 weeks. After some plants were sampled the others were either switched or kept at 0 or 150 ppm N and allowed to grow for another 3 weeks. After another sampling, plants were again switched or kept at 0 or 150 ppm N for a final 3 weeks. At each harvest, leaves were tested for starch, sampled for microscopy and then dried and weighed for soluble carbohydrate extraction. Data collected indicates that yellow leaves store and breakdown starch into soluble carbohydrates (specifically reducing sugars) in order to keep leaves from senescing. When nitrogen is re-supplied to these plants, leaves re-green and the plant continues to grow. We propose that common Swedish ivy’s ability to store and breakdown starch aids in the process of leaf re-greening

Impacts of Drought on Disease Development and Management

Drought conditions such as those that occurred in Nebraska in 2012 can impact the development of plant diseases. In general drought slows down or prevents the development of plant diseases caused by pathogens that thrive under moist conditions. However, some diseases are favored by drought. This is because when plants are stressed due to lack of moisture or excessive heat, they become more susceptible to these diseases. This article presents examples of diseases of agronomic crops favored by drought and how to manage them. Data are provided on the effect of dry or wet conditions on the profitability of applying fungicides to control foliar fungal diseases of wheat. Charcoal Rot Diseases of Field Crops Aspergillus Ear Rot and Aflatoxin Contamination Fusarium Diseases Phoma Black Stem of Sunflower Root and Crown Diseases of Wheat Management of Foliar Diseases of Wheat with Fungicides in a Dry versus a Wet Growing Seaso

What’s New in Plant Pathology

Disease Management Products During the past year several new products have become available for disease management. The new products are summarized in Tables 1 and 2, as well as included in the 2014 Guide for Weed Management in Nebraska with Insecticide and Fungicide Information. In addition, fungicides labeled for use on sorghum and sunflower have also been added to the publication. Table 1. New Foliar Fungicides Table 2. New Seed Nematicide Disease Identification and Management Resource

What\u27s New in Plant Pathology

Changes to the Disease Management Section of the 2016 Guide for Weed, Disease, and Insect Management in Nebraska Biological control Products Trivapro Fungicide Priaxor D. Fungicide Table 1. Foliar products for disease control that were updated in the 2016 Guide for Weed, Disease and Insect Management in Nebraska. Table 2. Seed treatment products for disease control that were updated in the 2016 Guide for Weed, Disease and Insect Management in Nebraska. Table 3. Seed treatment nematicide product that was updated in the 2016 Guide for Weed, Disease and Insect Management in Nebraska

Weather Variability and Disease Management Strategies

This year’s title of “weather variability and disease management strategies” was chosen because we need to remember how weather conditions this year have impacted crop productivity and disease development. This will enable us to look forward and develop better management decisions for future growing seasons. Agricultural production is dependent on many climatic factors such as rain, humidity, temperature, and sunlight. These climate conditions have direct effects on yield as well as other indirect effects. One specific indirect effect of extreme weather events is increased pressure from pathogens and pests. Plant pathogens are commonly favored by very specific, and sometimes extreme, weather conditions. Pathogens take advantage of these conditions to infect, reproduce, and cause disease in crops that can lead to economic losses, ultimately in the loss of yield quality or quantity. Scientific projections indicate that climate change will continue to have major impacts on crops across the country and the world. It is therefore not surprising that this year the United Nations Summit in New York on September 23 focused on climate change in agriculture with discussions on Global Alliance for Climate-Smart Agriculture. Nebraska is known for its leadership in agricultural production and one germane concern is how we will be able to utilize the available climate data in a timely fashion to our advantage in protecting our crops from the negative impacts of climate change and pathogens. We need to act in a way that can leverage climate change to our advantage, where possible. It is important to monitor soil moisture and irrigation. Late planting and dryer than normal conditions in 2014 resulted in irrigation late into the season in some locations, which will unfortunately result in reduced profits for such farms. Temperature is also an important factor. When conditions are warmer, crops tend to grow faster and the time for seed maturity reduces. However, warmer conditions have the potential to reduce yield and, in addition, can promote certain diseases. The dry and hot weather conditions of 2014, for example, supported charcoal rot infections that were seen in both corn and soybean in many locations this year. Weed control and timely applications of herbicide will be crucial preparation steps in mitigating the impacts of climate change in 2015. Weeds not only act as alternate hosts for many pathogens but also deplete soil moisture. Below we present information on the influence of weather variability on development of diseases in Nebraska field crops. In 2015, crop production practices should be well planned to be climate-ready and climate-compliant

Sunflower Disease Profiles II: Head and Stalk Rots and Wilts

Extension Circular 1902 (EC1902). Photographs and disease descriptions of Phoma/Phomopsis Stalk Rots, Bacterial Stalk Rot, Verticillium Wilt, Rhizopus Head Rot, and White Mold/Sclerotina Diseases

Differentiating Chemical and Disease Symptoms in the Field

In years with conditions favorable for seedling disease and other disease there are typically concerns and inquiries about the cause(s) of symptoms in agronomic plants. Many of the questions focus on differentiating between plant injuries potentially caused by recent herbicide applications versus symptoms caused by plant pathogens. Chemical injury in row crops is caused by chemicals such as herbicides, fertilizers, fungicides, insecticides, growth regulators, and crop oils when they are applied individually, as a mixture, or together with adjuvants. If chemicals are applied incorrectly, plants may be damaged at any point during the growing season. Chemical injury can result from carryover in the soil, contamination of the spray tank, spray drift, or misapplication. Damage may even be realized with chemical applications when recommended application guidelines are followed if other environmental conditions are adverse, including low soil temperatures, high soil moisture levels, or if young plants are exposed to high levels of various fertilizers. Factors such as the mode of action of the chemical, application rate, growing conditions, and growth stage of the crop determine the extent of injury and symptom expression. Symptoms of chemical damage are diverse and include leaf lesions with burned, necrotic patches, wilting, damping off, and sometimes death of mature plants. These symptoms could easily be confused with those caused by various plant pathogens found throughout the state. In most instances management actions cannot be taken during the year of the injury once you are past the replant timing. Therefore, you will want to correctly identify what is causing any stand problems to aid with future management actions

Sunflower Disease Profiles I: Foliar Diseases

Extension Circular 1900 (EC1900). Photographs and disease descriptions of Viruses, Apical Chlorosis, Downy Mildew, Rust, Alternia Leaf Spot, and Bacterial Leaf Spot