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

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

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

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

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

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

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

What’s New in Plant Pathology

Extension Plant Pathology Team Update Changes to the Plant Disease Management Section of the 2015 Weed Guide During the past year, several new products have become available for disease management. These products and additional products have been added to the Plant Disease Management Section of the 2015 Weed Guide. Products added to the Weed Guide have been summarized in Tables 1-3. Table 1. Foliar Products Table 2. Seed Treatment Products Table 3. Seed Treatment Nematicide