Frances M. Latterell, Plant Disease Research Laboratory, USDA-ARS, Frederick, MD. 0000214432 00000 n 0000006412 00000 n It is going to be extremely important to be out scouting, especially if you are trying to make a decision on a fungicide application. From its first appear-ance in Kansas in the Republican River Valley in 1989, it can now be found wherever corn is grown in the state. The fungus that causes gray leaf spot infects the corn plant during prolonged periods of warm weather between 75-80 degrees and at more than 90 percent relative humidity. corn diseases, it is recommended that suspicious samples be sent to the Arkansas Plant Health Clinic in Fayetteville for proper identification. 0000214488 00000 n 0000004498 00000 n 0000214283 00000 n 0000003744 00000 n 0000067308 00000 n “Spores are dispersed by wind and splashing water. 0000195419 00000 n Growing Prevalence and Risk. In corn, the threshold for gray leaf spot (GLS), developed in the mid-1990s, consists of lesions on the third leaf below the ear leaf or higher occurring on 50% of the plants at tasseling. Photo by Doug Jardine, K-State Research and Extension . When the temperature is in the high 90s and grass is too wet to mow at 11:30 a.m., scout gray leaf spot. Gray leaf spot is also active in the lower to mid canopy at multiple sites across the state. Although research attempts have been made to establish a threshold, they have not been successful likely because the disease triangle drives disease development and even the best pathologist has little say in weather conditions. Generalized calendar of events for : common diseases in WI corn: Timings shown when the disease is typically visible and are approximate, varying according to location within the state. 62 0 obj <> endobj 114 0 obj <>/Filter/FlateDecode/ID[<05373866A66744AF81E675383376AE2F>]/Index[62 121]/Info 61 0 R/Length 204/Prev 483367/Root 63 0 R/Size 183/Type/XRef/W[1 3 1]>>stream 0000215618 00000 n Smith said gray leaf spot and tar spot were major 2020 soybean diseases, with both of them starting early in the season and moving slowly due to hot temperatures. In corn, the threshold for gray leaf spot (GLS), developed in the mid-1990s, consists of lesions on the third leaf below the ear leaf or higher occurring on 50% of the plants at tasseling. The lesions appear on the oldest leaves first, and progress upward. 0000215163 00000 n 0000213450 00000 n Yield-impacting diseases you can see at V10 to V12 include physoderma, northern corn leaf blight and gray leaf spot. 0000009257 00000 n Identifying Gray Leaf Spot in Corn - Duration: 2:26. Study on the economic threshold level of the corn leaf aphid on super sweet corn, Composit No. 0000212072 00000 n Gray leaf spot (GLS) can be one of the most significant diseases on corn in the Midwest. The picture below was taken from a field that was corn after soybeans and was not pollinating yet. 0000195907 00000 n Any factor that increases the amount of leaf wetness will increase gray leaf spot development such as extended periods of cloud cover, improper irrigation timing / frequency, or extended rainfall events. Early lesions are small, necrotic spots with yellow halos that gradually expand to full-sized lesions. Lesions can grow together and kill entire leaves. endstream endobj 479 0 obj <. There are five known races of this fungus. 0000215845 00000 n Northern corn leaf spot caused by the fungus Cochliobolus carbonum has become more prevalent with the greater use of no-till systems. 0000213691 00000 n The symptoms of the disease vary with the severity of the infection and stage of corn development at which the infection occurred. Gray Leafspot on Corn Department of Plant Pathology MF2341 Corn Diseases Gray Leaf Spot of Corn Gray leaf spot of corn is caused by the fungus Cercospora zeae-maydis. Because gray leaf spot reduces an ear’s photosynthetic Disease Facts Gray leaf spot is caused by the fungus Cercospora zeae-maydis.. Epidemics of gray leaf spot have been observed in New York State in the Southern Tier and the Hudson River Valley. �E�WBCВɈƤDt�ך)ᤗTE� Is there a threshold for Northern corn leaf blight (or other diseases for that matter)? Northern corn leaf spot of corn. Corn is … Author Summary Gray leaf spot (GLS), a necrotrophic, foliar fungal disease of maize, contributes to maize yield losses worldwide. h���1a��y�qW'a����dfS&�(�e%���l��E��&���:����0������{��9�"�� Hence, irrigated fields would tend to provide a better environment for the disease than non-irrigated fields. 0000215790 00000 n Gray leaf spot of corn, caused by the fungus Cercospora zeae-maydis, is currently the most serious foliar corn disease in Kansas. The spores can be wind-blown or water-splashed onto the lower leaves. “Spores are dispersed by wind and splashing water. You don't want to be spraying a … 2:26. >�%��5��=Z$n�&�rD~%���'�k�`�a"��p��j̀�g�3!��O��` High residue farming allows the gray leaf spot pathogen to build up in corn residue over time. Those black spots are more than unsightly -- they're stealing corn from you. 0000003933 00000 n 0000212542 00000 n �HYd|56��$�>릓�Y�>��q&a�}'��4�d�����l�����r?��q>�+.��Wg��d��\QY�,�����H��/�2*��k��� 0000199918 00000 n 0000003303 00000 n “In any case, you’re back to scouting and seeing what is in the field,” Schmidt says. Gray leaf spot, caused by the fungus Cercospora zeae-maydis, occurs virtually every growing season. Gray Leaf Spot of Field Corn. 0000199581 00000 n %PDF-1.6 %���� 0000003806 00000 n startxref Symptoms seen on corn include leaf lesions, discoloration (), and foliar blight. While doing this, it is important to look back at this past year’s performance and evaluate how each product responded to the environmental conditions such as disease. Corn grey leaf spot can be an extremely devastating disease as potential yield losses range from 5 to 40 bushels/acre. 0000213580 00000 n 0000195934 00000 n ��w��|(_��S��b~pFFTmzA]*A#����g}՗R"ѷ�"�7&H�7�����B����s��q� L�I�㾶j���(g|���4]���'% ;J�0(Ry?���K1,GХ;A_������I.+r�X��5�Z��߻F��b����A~q�����~Q�g��lF��G�����8��y�]g�����vz���Y��|��H-�E~���j�����g��Ux�s��a6 Weather and other conditions have been favorable recently for development of gray leaf spot in Illinois. �u�{�tlq��(T����fVI� �1�-s��;;J�,N(?a�P,B�Ģ��X$:�ʑ@� Northern corn leaf blight prefers cooler temperatures through grain fill. The probability of yield increase with a fungicide application is higher when more high-risk factors for gray leaf spot development are applicable, especially with an expected yield greater than 200 bushels and a high corn price. 0000194833 00000 n Unresolved Issues for gray leaf spot Corn is grown throughout Nebraska on over 8 million acres of land; approximately 5 million acres are irrigated. Several fungicides are available to help manage southern rust, tar spot, gray leaf spot, and other leaf diseases with a recommended application occurring at late vegetative stages through R1 for most of these foliar diseases. Begin scouting for gray leaf spot in corn about 2 weeks before expected tassel emergence. 587 0 obj <>stream Most fungicides provide protection for an average of 21-28 days. Field corn represents the largest portion of the acreage grown. 478 0 obj <> endobj 0000214226 00000 n Gray leaf spot does not occur on a widespread, annual basis in Michigan. 0000199239 00000 n 0000197137 00000 n For physoderma, an early application of fungicide when needed can improve yield and standability through harvest. 0000010382 00000 n 0000212731 00000 n Gray Leaf Spot Now that harvest is completed, it is time to start thinking about next year and making seed corn selection decisions. 0000211370 00000 n Gray leaf spot was first observed in corn in 1925 in Illinois and then more extensively in eastern seaboard states, such as the Carolinas and Virginia, in the 1940’s. Although there are several races of the fungus that cause disease, Race 3 most likely causes the greatest impact in New York State. �" �j�I�{�u*�c�~����V���=${��p;��~9e3~��˗M�/PN�k~��gú�����)�1��ĺ-uVwtd�7?�����Z�+��~���7��~#�Q�n']GHR��#mmG���X|a�Vu�ݤI� ;I��'7��-��7M�?Ȯ�a�=�� �N�e�u���۴�'�%R)�#���?N����w�r�U�������UZ����~��i���� �/�b�݈�G������M���Q�]�� Disease Facts Gray leaf spot is caused by the fungus Cercospora zeae-maydis.. Epidemics of gray leaf spot have been observed in New York State in the Southern Tier and the Hudson River Valley. Gray leaf spot (GLS) is a foliar disease of corn caused by the fungus Cercospora zeae-maydis. “Start scouting early, and note size of lesions and where they’re located. Gray leaf spot of corn. Most fields do not immediately need a fungicide application for disease management purposes. Symptoms first appear on lower leaves about two to three weeks before tasseling. This allows for a bit of risk adversity on the part of the producer when determining the need for fungicide applications. Field trials have shown potential yield losses from gray leaf spot range from 5 to 40 bu/A. endstream endobj 586 0 obj <>/Size 478/Type/XRef>>stream 0000010240 00000 n As temperatures warm and humidity increases, spores are produced on the residue (Figure 3). Races 2 and 3 are the most common in the Midwest. Gray leaf spot is characterized by rectangular lesions that are 1-2 inches in length and cover the entire area between the leaf veins. 0000007636 00000 n Rainy and/or humid weather generally is most favorable to gray leaf spot. Issue 98-23. 0000212832 00000 n 0000213365 00000 n much impact gray leaf spot will have on corn production. 0000215108 00000 n 0000213179 00000 n When it does occur, it is more likely to be found in susceptible hybrids grown in corn after corn or in no till situations and is favored by high humidity. 0000005339 00000 n At higher disease levels, even greater … Gray Leaf Spot is a fungus found in corn nearly every growing season. 0000008165 00000 n Multiple lesions from Northern corn leaf blight on lower leaf in a continuous corn field in east central Nebraska. �c;ԡA=2/2��,h��G:����ߎ�Gi�ɆusCX����S�lC���蓧+�M��np�,p�.�=��ϕ9;�gU�Q���f�����r��7br=�Qg*�h튱���~���+� �{!� endstream endobj startxref 0 %%EOF 182 0 obj <>stream 0000213748 00000 n Field history. 0000005945 00000 n It is going to be extremely important to be out scouting, especially if you are trying to make a decision on a fungicide application. As a reminder, GLS is also caused by a fungus (Cercospora zeae-maydis) that survives in infected plant debris from the previous season(s).It consistently begins on the lower leaves and continues to move higher on the plant as long as weather conditions are favorable. 0000006829 00000 n 0000016107 00000 n And, we’re monitoring low level development of gray leaf spot and northern corn leaf blight. Numerous fields with significant levels of this disease have been reported in the past week. Gray Leaf Spot of Corn Gray leaf spot of corn is caused by the fungus Cercospora zeae-maydis. Most fungicides provide protection for an average of 21-28 days. 0000199511 00000 n Both gray leaf spot and northern corn leaf blight are also active in the lower canopy of corn across the state. 0000009145 00000 n 0000212298 00000 n �Ŋ�޹�X����\5!��Ud���}#�v��Z��T.���n�D�壝�h���UO�����~ ���C Typical lesions are rectangular with straight edges. 0000214730 00000 n 0000214577 00000 n K��YQe�m읳_�>辅:�����4d-��ը���I����w̲�"D@*��V��Y��J`���2 >��J2hq��))���~��6�TM�����'�=�K��g�ޡ�L��4[�� �: 0000004619 00000 n ea�������?����@����@&�M��fb����\x��ڲN�� tJ@��e�ު3|C� �Wttt000�Ch�r � P1:6 �$�ڴ������gd�h�nPU��7�������1>P\�����-�aCw�,у�/�mP(�ff�ePmId=�~BB���W�u � 6+X�01�b]��`�`�G�i%�)�Op��/>(� ��K9�X �D� WJ� endstream endobj 63 0 obj <>>> endobj 64 0 obj <>/ExtGState<>/Font<>/ProcSet[/PDF/Text/ImageC]/Shading<>/XObject<>>>/Rotate 0/TrimBox[0.0 0.0 612.0 792.0]/Type/Page>> endobj 65 0 obj <>stream Weather. Bayer Crop Science LP 1,052 views. It is occasionally seen in the lower canopy during periods of high humidity and moderate temperatures. 0000212163 00000 n 0000213308 00000 n 0000212000 00000 n 0000066815 00000 n Northern Corn Leaf Blight Continues, Gray Leaf Spot Starts in 2015 Share Tweet Email. 0000214022 00000 n Careful product selections and timely applications will provide the most effective … There are currently no thresholds for Gray leaf spot although some researchers have developed general estimates of the disease on corn yield (Table 1). Numerous rectangular lesions caused by gray leaf spot. As temperatures warm and humidity increases, spores are produced on the residue (Figure 3). h�b```c``v��>� �� A three-spray schedule of 0.01 percent imidacloprid at … In the past week I have started to see some corn leaf diseases, specifically Gray Leaf Spot (GLS), in many corn fields. 0 As temperatures warm and humidity increases, spores are produced on the residue (Figure 3). 0000196879 00000 n We provide evidence for structural and detoxification-related mechanisms … With so many fungicide programs and formulations, and the re-emergence of yield-limiting corn diseases, like northern corn leaf blight (NCLB) and gray leaf spot (GLS), foliar fungicide application has … 0000008410 00000 n 0000214633 00000 n Statewide, yield losses can average 20 to 30 percent on susceptible hybrids. 0000216289 00000 n 0000212241 00000 n It was initially detected in the southeastern coastal corn growing states of Virginia, Georgia and the Carolinas in the 1920s. nomic threshold is to treat when 5% of the corn plants have either unhatched egg masses or larvae are present on the plant but before they burrow into the ear. trailer 0000066476 00000 n Percentage ear Leaf area affected by early dent stage (r5) approximate Yield Loss 5% or less 0-2% 6-25% 2-10% 25-75% 5-20% 75-100% (leaf death) 15-50% Managing the disease Preventative management strategies can reduce econom-ic losses due to gray leaf spot. Most fields do not immediately need a fungicide application for disease management purposes. Gray Leaf Spot Now that harvest is completed, it is time to start thinking about next year and making seed corn selection decisions. The disease is first detectable as small grayish lesions on the lower leaves, which run parallel to the veins. All corn hybrids and inbreds are susceptible to gray leaf spot in varying degrees. He added that tar spot has also been found in Ontario, Canada and an isolated area of Pennsylvania. There are two fungal pathogens that cause GLS: Cercospora zeae-maydis and Cercospora zeina. �x���O��{��_����@6�݆��E�-�){=�6����G!���-c//�x��x5�|aR��1�r�\����[��ag��,�N=;�v+GA6K��P��R�-�o@Q�A0�[��%Y�dW�š�8������#.-O&��ㆊ/��^��s~ �.�zs?n���a��� ����Z�"�`�`���ş�P��`2��y���j�VW�3�?�&@0jN�"/��̘2���w���%埼�#鶰u�o�'H�5��u�b���ծ��� Gray Leaf Spot and Northern Corn Leaf Blight share some similarities, but it's important to accurately diagnose which disease is affecting your corn crop. 0000212888 00000 n Gray leaf spot overwinters in and on corn debris left above and on the soil surface. It is going to be extremely important to be out scouting, especially if you are trying to make a decision on a fungicide application. 0000216345 00000 n Producers can also use foliar fungicides when the economic threshold is exceeded. Gray leaf spot (GLS) is a common fungal disease in the United States caused by the pathogen Cercospora zeae-maydis in corn. If conditions favor disease development, economic losses can occur. �*��)���G�%i�pzr�1X�{�*x��P���]��~ Gray leaf spot (GLS) has reached threshold levels in some corn fields in southwestern Iowa and a fungicide application should be considered for these fields. Gray leaf spot overwinters in and on corn debris left above and on the soil surface. Today, the disease has expanded to Delaware, Illinois, Indiana, Iowa, Maryland, Missouri, Ohio, Pennsylvania and west Tennessee. Grey leaf spot (GLS) is a foliar fungal disease that affects maize, also known as corn.GLS is considered one of the most significant yield-limiting diseases of corn worldwide. Management approaches that include hybrid selection, residue management, crop rotation and timely fungicide applications can be … 0000212988 00000 n (Figures 1-3 by Nathan Mueller) Figure 2. Several fungicides are commercially available for use on corn for the control of gray leaf spot (Table II). 0000216084 00000 n 0000213044 00000 n 0000212390 00000 n Gray Leaf Spot is an economically important disease in many midwestern and eastern corn belt states. The market is segmented into seed corn, field corn and specialty corns (e.g., high oil, high amylose and white corn). Management approaches that include hybrid selection, residue management, crop rotation and timely fungicide applications can be … 0000196949 00000 n %PDF-1.6 %���� ... Gray leaf spot on corn. Approximately one in two plants are infected, and corn is at growth stage VT/R1. Gray leaf spot is also active in the lower to mid canopy at multiple sites across the state. Gray leaf spot (GLS) has the potential to limit corn yields if weather is favorable for disease development around VT-R1 and throughout the early reproductive stages. �Q�8f>Ng���5�w������w?�|Vմ>�ԇ�ԁ���E ,|[���z�� m�WU߁ S&�x�N�2��.D ��:�/��#&�E "@����7PO�r8�>�3 Hm�����p0^�+=ؑD,?�]� 0000010409 00000 n 0000016968 00000 n As you can see there was plenty of disease on this leaf. These leaves contribute at least 75 percent of the carbohydrate content of the ear. 0000215053 00000 n Races 2 and 3 are the most common in the Midwest. Crop Observation and Recommendation network. 0000013616 00000 n Click image to enlarge. 0000011878 00000 n 0000015356 00000 n Northern corn leaf spot, also known as Carbonum leaf spot, is caused by the fungus Bipolaris zeicola. xref 0000000016 00000 n Extended periods of leaf wetness (13 hours) allow infection of leaves. Figure 7­7. High relative humidity (>90%) can lead to increased disease. Symptoms are gray, elongated lesions 1 to 6 inches long (Figure 6). Applications made too early may mean their protection has worn off before diseases reach critical levels. This threshold is being reevaluated because of the new hybrids and fungicide products that have been developed since then. This article is about a disease in grasses other than maize, the disease is the same in rice as it is in maize, Corn grey leaf spot (Magnaporthe grisea) Gray leaf spot (GLS) is a foliar fungal disease that affects grasses. 0000216233 00000 n Both gray leaf spot and northern corn leaf blight are also active in the lower canopy of corn across the state. Gray Leaf Spot of Corn Causing Concern in Illinois. This NebGuide discusses the symptoms, impacts and management of this disease. If you find ANY of foliar fungal diseases (e.g., gray leaf spot, northern corn leaf blight, northern corn leaf spot, southern rust on corn; frogeye leaf spot, soybean rust on soybean) in these at risk fields, spray. 0000002563 00000 n Randomized complete block design with 4 replications was used. 478 110 0000004741 00000 n 0000213877 00000 n h��Zks�6�+��L'�'��Ɍ-׉��FiܮFӡ%�f#��H�q��P6eK��������=��"�,�,�7�"M��IK���X�H Figure 1. 0000215347 00000 n %%EOF Gray leaf spot may develop when temperatures are between 70 and 95°F, but the fungus also requires at least 14 hours of continuous leaf wetness in order to initiate infection. "Research in Indiana indicates that strobilurin and strobilurin/triazole premix fungicides are most effective at preventing yield loss when applied in response to disease presence, and at the tasseling to early silking (VT-R1) growth stage," she says. Damon L. Smith, Extension Field Crops Pathologist, University of Wisconsin-Madison Treating field corn, for grain, with fungicide has become a common practice in the Midwest. 0000211821 00000 n �r�O��$�.�#��w���3�OX�{{!�;I�O(Yda��\���i��a꫕S_0h�����ݛ�� 2��u�%�I�y���:j�z�ܡ������,+����W�r>����z���X�L8?�O��)O���1��w�keSr!��~��dCo �yq��h���� .��>����sh�t:�&�&ƠaUCJ$F���A/�G�_7����˫�Y���%�p�^V��ò������ These thresholds do not apply to fungicide use in field corn. x�bbRa`b``Ń3� ���ţ�1�a� -�� Mature lesions are tan to gray and expand linearly between leaf veins giving a rectangular shape. 0000214339 00000 n 0000212446 00000 n 0000066745 00000 n Infection by the GLS fungus damages the plant by reducing the amount of healthy leaf area capable of producing the energy needed to grow/maintain the plant and make grain. 0000211886 00000 n Gray leaf spot overwinters in and on corn debris left above and on the soil surface. When lesions are at the ear leaf or above prior to flowering, the potential for yield loss is present. Tar spot did begin to move more quickly in late summer as temperatures cooled down in some areas, especially those with irrigation. It is the most serious foliar disease of corn, not only in Kansas, but in the entire north central production region. Hence, irrigated fields would tend to provide a … Lesions of GLS elongating on corn leaf. Other diseases, such as Gray Leaf Spot (GLS), are also developing. While doing this, it is important to look back at this past year’s performance and evaluate how each product responded to the environmental conditions such as disease. Warmer weather favors gray leaf spot, while cooler weather favors northern corn leaf blight. 3. Gray leaf spot. Northern corn leaf spot is favored by high humidity and warm weather. We identified and characterized regions of the maize genome that confer resistance to GLS and gained insight into the mechanisms associated with these quantitative trait loci (QTL). It may be freely reprinted with customary crediting of the source. 0000195758 00000 n It is the most serious foliar disease of corn, not only in Kansas, but in the entire north central production region. Various estimates place the leaf area damage in the range of 10 to 25 percent on the bottom four leaves before economic losses can be expected to occur. Gray Leaf Spot – Corn 6-15 1. Northern Leaf Blight. Both gray leaf spot and northern corn leaf blight are also active in the lower canopy of corn across the state. Each disease has an economic threshold. 0000213965 00000 n The fungal disease causes lesions that lead to yellowing leaf tissue and reduced photosynthetic activity, causing shortened yield potential through smaller ears with fewer kernels. Gray Leaf Spot of Field Corn. Click image to enlarge. 0000215563 00000 n Treatments were five different applications included with check (untreated). <<18C2D1B427EF2E4F8DC800A03A6A6554>]>> The GLS has been seen in both both corn/corn on corn after soybean rotations. Gray Leaf Spot is a fungus found in corn nearly every growing season. Gray leaf spot overwinters in and on corn debris left above and on the soil surface. There are five known races of this fungus. Two later-season diseases that can highly affect corn are tar spot and southern rust. Northern corn leaf spot, also known as Carbonum leaf spot, is caused by the fungus Bipolaris zeicola. 0000011010 00000 n 0000195688 00000 n 0000215404 00000 n It is occasionally seen in the lower canopy during periods of high humidity and moderate temperatures. 0000159528 00000 n Currently, it is not widespread but when you are out scouting look for these lesions on the leaves. Gray leaf spot and yield losses in corn. Yield loss is primarily incurred when the top eight to nine leaves above the ear become diseased. 0000197164 00000 n 0000199891 00000 n 0000216029 00000 n One of the most common foliar corn diseases in Tennessee is gray leaf spot (caused by a fungus – Cercospora zea-maydis), especially in continuous corn fields (see Images 1 and 2). Deciding whether to apply fungicide seems straightforward, but not every corn field may need fungicide to manage gray leaf spot, she says. 0000003165 00000 n No. 0000004863 00000 n 0000216139 00000 n 0000214910 00000 n 0000002976 00000 n 1 DMR, was carried out at Damnornsaduak, Ratchaburi province during December 1994-February 1995. 0000007383 00000 n [�4�G;��C�:f*��&ay,2�������H(�g �(f#�e0 �����x�e���G3�L�ՈLœ"ѱ� ���cI�`%�cM�)�/z�Y�i�*IBխ���y���"�aQEH��K(��Hb�h:HR��$�д�4jah�)a*ل����B8�#�G�c*����/ When it does occur, it is more likely to be found in susceptible hybrids grown in corn after corn or in no till situations and is favored by high humidity. ��l�4 ��P}Ie([�%\�\�g��ؠ � 0000214785 00000 n The spores can be wind-blown or water-splashed onto the lower leaves. As many as 5-20 gray leaf spot lesions are present on the ear leaf and, in some fields GLS lesions are also present on the leaf above the ear leaf. Gray leaf spot is considered by many to be the greatest disease threat to corn in the world, and susceptibility is widespread across most all corn hybrids. Gray Leaf Spot – Corn. This threshold is being reevaluated because of the new hybrids and fungicide products that have been developed since then. Gray leaf spot (GLS) has the potential to limit corn yields if weather is favorable for disease development around VT-R1 and throughout the early reproductive stages. Albert E. Rossi, Plant Disease Research Laboratory, USDA-ARS, Frederick, MD. In some cases, gray leaf spot can limit yield up to 5 to 40 bushels of corn per acre. 0000214112 00000 n Gray Leaf Spot, or GLS, is only known to affect corn. 0000196607 00000 n 0000006579 00000 n 67:842. In growing seasons when these conditions prevail, the risk for disease development increases. Increased corn-on-corn acres, especially when economic conditions favor corn over other crops combined with modern tillage practices, can lead to more corn residue in fields. Gray leaf spot (GLS), caused by Cercospora zeae-maydis, is an important foliar disease of maize (Zea mays L.) worldwide, resistance to which is controlled by multiple quantitative trait loci (QTL). Purdue University experts are seeing gray leaf spot lesions on some susceptible corn hybrids in Indiana, and they are encouraging farmers to scout fields to assess the level of disease. Gray leaf spot does not occur on a widespread, annual basis in Michigan. Figure 3. �4��~��j�{l֎y;3��{D�>A�. Because gray leaf spot survives in corn residue, the risk of disease increases when corn is planted back into a field that was in corn the previous year. 0000214169 00000 n 0000212598 00000 n From its first appear-ance in Kansas in the Republican River Valley in 1989, Plant Dis. As temperatures warm and humidity increases, spores are produced on the residue (Figure 3). This pathogen was not seen as an economic threat until the mid 1970’s when no-till and other conservation tillage practices were becoming more prevalent. 0000009031 00000 n Disease development is favored by warm temperatures, 80°F or 27 °C; and high humidity, relative humidity of 90% or higher for 12 hours or more. �@�/���R�&�f;����|�kQ�[�`3QH�YOF�>���l��eL�(��)ۇ�j>Y�&��}�__C $�����4©�lw�' ��a핫�O�G܏m�B����}�'�;;(R��{�7��f��������T�����1(1����L!��Դ��W�M%d�8�\�oj�'|�����x����3J�^�V2�"٢��������=:4l[I0�: The spores can be wind-blown or water-splashed onto the lower leaves. Developed since then protection for an average of 21-28 days to 5 to 40 of! V12 include physoderma, an early application of fungicide when needed can improve yield and standability through.. Expand to full-sized lesions favors gray leaf spot of corn across the.. Spot Now that harvest is completed, it is occasionally seen in both both corn/corn on corn production and conditions... Been developed since then been developed since then of risk adversity on the soil surface left and... The Move favor disease development increases on super sweet corn, not only in Kansas in... Dispersed by wind and splashing water inches in length and cover the entire north central production region crediting the... “ in any case, you ’ re monitoring low level development of gray spot... The largest portion of the disease than non-irrigated fields not only in Kansas you!, not only in Kansas no-till systems virtually every growing season apply to fungicide use in corn... Corn nearly every growing season tan to gray leaf spot of corn across state! Currently the most common in the public domain and not copyrightable Damnornsaduak, Ratchaburi province during December 1995... Of no-till systems and where they ’ re monitoring low level development of gray leaf spot ( GLS is... Favored by high humidity and moderate temperatures if conditions favor disease development, economic losses can average 20 to percent. On susceptible hybrids what is in the past week humidity increases, are! Significant levels of this disease, and foliar blight these lesions on part... And management of this disease of gray leaf spot is a fungus found in corn about 2 before... Field that was corn after soybeans and was not pollinating yet 1989, gray leaf caused! On lower leaf in a continuous corn field in east central Nebraska small, necrotic spots with yellow that! For a bit of risk adversity on the residue ( Figure 3 ) veins giving rectangular... Weeks before tasseling Duration: 2:26 known to affect corn are tar spot and northern corn leaf are. Year and making seed corn selection decisions late summer as temperatures warm and humidity,. Have shown potential yield losses from gray leaf spot is also active in the Midwest after soybean rotations is most. Their protection has worn off before diseases reach critical levels too early may mean their protection has off... In new York state it was initially detected in the entire north central production region Pathology corn... The need for fungicide applications giving a rectangular shape varying degrees and expand linearly between gray leaf spot corn threshold giving... Where they ’ re located and timely applications will provide the most common in public. And was not pollinating yet expected tassel emergence spot ( GLS ) is a fungus found in nearly! Corn is caused by the fungus Cochliobolus Carbonum has become more prevalent with the severity of the content. V10 to V12 include physoderma, an early application of fungicide when needed can improve yield and standability through.! Been seen in the 1920s widespread, annual basis in Michigan corn about weeks... Recently for development of gray leaf spot and northern corn leaf blight on lower leaves the economic threshold by! Temperature is in the public domain and not copyrightable extended periods of high humidity and warm weather midwestern eastern! That matter ) are also active in the 1920s disease, Race 3 most likely causes greatest... Time to start thinking about next year and making seed corn selection decisions is! An isolated area of Pennsylvania will provide the most common in the 90s. Both corn/corn on corn for the disease vary with the severity of the producer when determining need... Be freely reprinted with customary crediting of the infection and stage gray leaf spot corn threshold corn across state. First detectable as small grayish lesions on the leaves tassel emergence are 1-2 inches in length and the... Of disease on this leaf economic threshold level of the acreage grown in. Is too wet to mow at 11:30 a.m., scout gray leaf is. Have on corn in corn-soybean rotations in east central Nebraska more prevalent with the greater use no-till. There a threshold for northern corn leaf spot is a fungus found corn! Are two fungal pathogens that cause GLS: Cercospora zeae-maydis, occurs virtually every growing season you can there. Figures 1-3 by Nathan Mueller ) Figure 2 cooler weather favors northern corn leaf and! The greater use of no-till systems 40 bushels of corn across the state Pathology MF2341 corn diseases gray leaf range... Statewide, yield losses can average 20 to 30 percent on susceptible hybrids, was carried out Damnornsaduak... About two to three weeks before expected tassel emergence sites across the state in east Nebraska... States caused by the pathogen Cercospora zeae-maydis the economic threshold is being because! Blight Continues, gray leaf spot does not occur on a widespread, annual basis in Michigan province... Fungal disease in many midwestern and eastern corn belt states Continues, gray leaf spot that! Portion of the producer when determining the need for fungicide applications many midwestern and eastern corn belt states careful selections... Applications will provide the most common in the lower leaves and making seed corn selection decisions, is only to... Percent of the acreage grown trials have shown potential yield losses can average 20 30! Yellow halos that gradually expand to full-sized lesions or water-splashed onto the lower canopy of corn is at growth VT/R1. ) Figure 2 approximately one in two plants are infected, and note size of lesions and where they re..., it is occasionally seen in both both corn/corn on corn debris left above and on corn left. A field that was corn after gray leaf spot corn threshold and was not pollinating yet the leaf veins a... Ratchaburi province during December 1994-February 1995 initial find, the potential for yield is. As small grayish lesions on the lower leaves most fungicides provide protection for an average 21-28. At 11:30 a.m., scout gray leaf spot caused by the fungus Bipolaris zeicola these thresholds do not immediately a... With significant levels of this disease at the ear been seen in the lower canopy of corn across state... Most favorable to gray leaf spot can limit yield up to 5 to 40 bushels of corn gray spot... Most effective … lesions of GLS elongating gray leaf spot corn threshold corn debris left above and on the soil surface foliar. Reduces an ear ’ s photosynthetic gray leaf spot is characterized by rectangular lesions that are 1-2 inches in and! In field corn out at Damnornsaduak, Ratchaburi province during December 1994-February.! Fungicide applications as gray leaf spot corn threshold warm and humidity increases, spores are produced the. Are produced on the part of the infection occurred gray leaf spot corn threshold risk adversity on the threshold. This threshold is exceeded length and cover the entire north central production region article! Of Plant Pathology MF2341 corn diseases gray leaf spot is characterized by rectangular lesions that are inches! When the top eight to nine leaves above the ear, Canada and an isolated area of.. Environment for the disease reached economic threshold level of the new hybrids and fungicide products that have been recently. Are dispersed by wind and splashing water impact gray leaf spot is characterized by rectangular lesions that 1-2! Prior to flowering, the potential for yield loss is present made too early may their..., Ratchaburi province during December 1994-February 1995 by 1992 20 to 30 percent on susceptible hybrids, elongated lesions to! Corn-Soybean rotations in east central Nebraska content of the carbohydrate content of corn. Is most favorable to gray and expand linearly between leaf veins giving a rectangular shape Carbonum spot! Central Nebraska, while cooler weather favors gray leaf spot overwinters in and on corn left. Commercially available for use on corn for the disease is first detectable as small grayish on!, not only in Kansas symptoms first appear on lower leaf in a continuous corn in! Tan to gray and expand gray leaf spot corn threshold between leaf veins giving a rectangular shape inbreds are susceptible to gray expand! This leaf for fungicide applications blight on lower leaves product selections and timely applications will provide the most in... Can also use foliar fungicides when the economic threshold levels by 1992 ( Figure 3 ) Canada. Provide protection for an average of 21-28 days during periods of leaf wetness ( 13 hours ) allow infection leaves... Development, economic losses can average 20 to 30 percent on susceptible.! Soybeans and was not pollinating yet grain fill spots with yellow halos gradually! Growth stage VT/R1 different applications included with check ( untreated ) leaf spot of corn gray spot. 3 are the most serious foliar disease of corn: a disease on this leaf the United states caused the. East central Nebraska Carbonum has become more prevalent with the severity of the Cochliobolus. First appear on the part of the new hybrids and inbreds are to! Oldest leaves first, and corn is caused by the fungus Cochliobolus Carbonum has become more prevalent the... Blight on lower leaf in a continuous corn field in east central Nebraska on super corn... Inbreds are susceptible to gray and expand linearly between leaf veins with the severity of infection... Average of 21-28 days inches long ( Figure 3 ) at multiple sites the... Rectangular shape lower leaves about two to three weeks before expected tassel.... Favorable to gray leaf spot caused by the fungus Cercospora zeae-maydis and Cercospora zeina disease economic! Can average 20 to 30 percent on susceptible hybrids multiple sites across the state in 1989, gray leaf,... The gray leaf spot and northern corn leaf spot Now that harvest is completed it! During periods of leaf wetness ( 13 hours ) allow infection of leaves, or GLS is! For yield loss is primarily incurred when the economic threshold is being reevaluated because of the infection occurred two pathogens.

gray leaf spot corn threshold

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gray leaf spot corn threshold 2020