8 articles tagged "Plant Diseases".

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Author: Darcy Telenko There are a number of fungal soybean diseases that can greatly impact seed quality. In Indiana, the most common are Phomopsis seed decay (Phomopsis spp.), Cercospora purple seed stain (Cercospora kikuchii); Frogeye leaf spot on seed (Cercospora sojina); Anthracnose (Colletotrichum spp.); Downy mildew (Pernospora manshurica); and various other secondary fungal invaders of injured pods including Alternaria, Fusarium, Cladosporium, and Penicillium. The tables below provides several descriptive characteristics to begin the diagnostic process and choose appropriate management recommendations. It is important to note, however, that although Purple Seed Stain is easily identified by the ‘signature’ purple symptom on the seed, accurate diagnosis of most of the fungal diseases on seed requires microscopic assistance offered by the Purdue Plant and Pest Diagnostic Laboratory (PPDL). The diversity of symptoms that can be observed on diseased soybean seed is shown in the example in Figure 1. In this image, all of[Read More…]

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AUTHOR: Darcy Telenko Heavy rains and wind have started to take a toll on corn that has compromised stalks. Many factors can contribute to stalk decline – I am going to focus on the plant pathogenic causes, but note abiotic stresses factors could also play a role such as drought and flooding. Either way as stalk tissue becomes compromises below the main ear; the stalk may become brittle or weak and be prone to lodging. There are a number of pathogens that can cause stalk rot including, Anthracnose, Bacteria, Charcoal, Diplodia, Fusarium, Gibberella, and Pythium. Some of these stalk rots have very characteristic symptoms that can help identify the specific problem, while others may require laboratory diagnosis. What can you do now – check field by using the Push or Pinch Test by evaluating 20 plants in at least five random areas in a field. Pinch Test – grab the stalk[Read More…]

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He is studying the dynamics of plant disease and epidemiology of crop diseases and in particular grey leaf spot and northern corn leaf blight in corn. His lab is looking to establish a collection of isolates of these two diseases from across the state for epidemiological work that could be the basis for developing strategies to manage GLS in the future.

Author: Darcy Telenko We are collecting corn tar spot samples and we need your help! Tar spot of corn is a new corn disease first identified in the United States in 2015 in Illinois and Indiana. It has since been confirmed in Iowa, Michigan, Wisconsin, and Florida. What to look for: Small, black, raised spots (circular or oval) develop on infected plants, and may appear on one or both sides of the leaves, leaf sheaths, and husks. Spots may be found on both healthy (green) and dying (brown) tissue. Often, the black spots are surrounded by a tan or brown halo; this is especially obvious on healthy leaves (see images). The University of Illinois needs samples of corn infected with tar spot from across the United States as part of a new research project investigating the variability of populations of the corn tar spot pathogen. We would also like to[Read More…]

Author: Darcy Telenko Physoderma brown spot is caused by Physoderma maydis, the only class of fungi that produce zoospores, spores that have a tail (flagellum), and swim free in water. P. maydis can survive in soil and crop debris for 2 to 7 years. The pathogen can be dispersed by the wind or splashed into the whorls of the developing corn. Corn is most susceptible to infection between growth stages V5 to V9. Therefore, even though we are seeing symptoms now as corn is into R-stages, infection occurred in standing water in the whorl. Dark purplish to black oval spots along the midrib of the leaf and on the stalk, leaf sheath and husks are distinguishing characteristic symptoms of Physoderma brown spot. In addition, infected leaves have numerous very small round or oval spots that are yellowish to brown and occur in bands across the leaf. Management options for Physoderma[Read More…]

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Author: Darcy Telenko Corn diseases have been on my radar these past few weeks as I am just getting my boots on the ground in Indiana. Many aerial fungicide applications are going out around the region, corresponding to crop maturity and the uptick of grey leaf spot. As a result the biggest question I have received this week is, “Should we spray our corn for grey leaf spot?” Fungicides can be effective at reducing disease and protecting yield, but there are a number of factors that should be considered: the field history/previous crop, the amount of disease present in the field, hybrid susceptibility, weather conditions, and the price of corn and cost of fungicide application. Grey leaf spot is probably the most prevalent disease issue this year to date. It is caused by the fungus Cercospora zea-maydis. Symptoms of grey leaf spot usually first appear in the lower canopy a[Read More…]

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