One of the benefits of being part of these research groups and teams is we have access to that research,” says Tenuta. “Tar spot is a dangerous disease because the fungus that causes it can infect the crop 14 to 40 days before symptoms appear,” says Eric Tedford, Ph.D., fungicide technical product lead at Syngenta. TAR SPOT: Symptoms and Management Fungicide applied at VT. It is easy to confuse stromata with structures associated with other fungal diseases, such as the black pustules that the corn rust pathogen produces as it ages. Combating tar spot can be a timely and unpleasant weekend task. ST. LOUIS, Mo. Here in Indiana, P. maydis alone can cause yield loss under favorable environmental conditions. More Tar Spot Information. However, the amount of time a previously, affected field must be rotated away from corn previously, infected with tar spot is unknown. Tar Spot Fact sheet (Updated for 2020!) However, significant yield losses were reported from the tar spot complex, consisting of P. maydis and another fungus (Monographella maydis) Dr. Eric Tedford, Fungicides Technical Product Lead with Syngenta, says the best chance for success at beating tar spot is to position fungicide applications as preventive as opposed to curative control. When combating tar spot its best to think of it as treating allergies, something that will never go away, but having fewer symptoms each year by having regular treatments. Crop Protection Network. Similarly, tillage should bury inoculum and reduce local spore dispersal within a field. Current fungicide efficacy ratings are available here. The rapid senescence could also reduce forage quality. Fungicide Several fungicides in preliminary fungicide trials may reduce tar spot. 2. In Mexico and Central America, P. maydis is not widely considered to cause economic damage when present alone, although there were isolated reports of damage in old literature. “By spraying Delaro at the R1 or R2 stage, we fought off tar spot moving in for at least three to four weeks.” Farmers need to monitor fields in order to help track this disease and determine if management tactics are warranted. Yield loss was associated with an early, rapid senescence that led to reduced ear size, poor kernel fill, and vivipary (a condition in which the seed germinated while still on the cob). Tar spot of corn. Stromata can be present on healthy or dead tissue of leaf sheaths, stalks, and husks. Depending on the severity of the damage, more than one fungicide application may be required for complete control. The efficacy data for this disease was based on limited site locations … These spots are ascomatum (fungal fruiting structures). Tar spot is a fungal disease in corn caused by Phyllachora maydis. A laboratory diagnosis is required to distinguish tar spot stromata from rust pustules or other pathogens. Telenko, D. E. P., Chilvers, M. I., Kleczewski, N., Mueller, D., Plewa, D., Robertson, A., Smith, D., Tenuta, A., and Wise, K. 2020. In addition, several 2(ee) labels that can manage tar spot will be available starting in 2019. These spots may remain relatively small, or may enlarge over the growing season to roughly 3 ∕ 4 inch in diameter. Predominant disease was tar spot. Reference in this publication to any specific commercial product, process, or service, or the use of any trade, firm, or corporation name is for general informational purposes only and does not constitute an endorsement, recommendation, or certification of any kind by Purdue Extension. Prevention is the key with this disease, but if nearby trees are infected, you can’t reasonably expect to totally destroy this fungus without community support. Frequent rainfall in 2018 and increasing disease inoculum load in the region led to those dramatic losses. Fungicide timing is going to be extremely important for tar spot and needs to be made near the onset of the first tar spot symptoms. Individuals using such products assume responsibility for their use in accordance with current directions of the manufacturer. However, the amount of time a previously affected field must be rotated away from corn previously infected with tar spot is unknown. 2019). Infection of tissues can vary from light to heavy depending on the amount of the pathogen in the field, the environment, and the hybrid (Figure 4). Two of the most common practices for reducing local disease inoculum include crop rotation and tillage. Although this disease appeared too late in the growing season to cause yield losses, it was observed across several counties in both of those states. Data indicated that no particular seed company brand outperformed others. practices on tar spot in the United States. ppdl.purdue.edu. This fungus is characterized by the formation of black, blotchy lesions on the upper side of oak leaves, especially along the veins of the leaves. Recent tar spot pressure in Michigan – 2018 and 2019. Several Ilex species are susceptible to Phacidium species or holly tar spot, while Coniothyrium ilicinum normally causes leaf spots on leaves of American holly (I. opaca). It is seen most commonly on sycamore, but can also affect a number of other Acer species. Similarly, tillage, should bury inoculum and reduce local spore dispersal, Currently no studies have examined the impacts of these. In 2018, tar spot symptoms were observed across a range of hybrids in Indiana. Tar spot is considered the most important foliar disease in Latin America, particularly Mexico. Current fungicide efficacy ratings are available here. In addition, several 2(ee) labels that can manage tar spot will be available starting in 2019. "If you notice tar spot picking up on vegetative corn, and there is wet weather coming, you might benefit from a fungicide application." Just because you had severe tar spot one season does not mean you are going to have it the following year. of leaf wetness (greater than 7 hours) promote infection and disease development. While a preliminary identification of tar spot can be made visually, a laboratory diagnosis is required to distinguish it correctly from other pathogens. Corn fungicide table : here It can currently be found in states such as Iowa, Illinois and Indiana. Conditions that favor disease development. This information will help farmers formulate fungicide application decisions in the future. (Tar spot stromata cannot be rubbed off.). Tar spot pressure in 2018 was significant with losses of up to 50 bushels per acre. stromata (Figure 2). However, optimum application timing will be critical for a fungicide application to be effective and economical. In these areas, cool (59-70°F), humid conditions (85% relative humidity) with long periods CPN-2012-W. doi.org/10.31274/cpn-20190620-008. Rotating away from corn allows infested corn residue to decompose. Wind-driven rain and storms can spread spores of the pathogen to new plants and spread the disease. associated with tar spot. Tar spot of corn (caused by the fungus Phyllachora maydis) was first confirmed in the United States in 2015 on dent corn in seven counties in northwest Indiana He adds they are still trying to identify which fungicides best combat tar spot, though several appear promising. Tar spot is a corn disease that is caused by the fungus Phyllachora maydis. Purdue Extension Education Store www.edustore.purdue.edu, Crop Protection Network Publication "Corn Disease Management: Tar Spot", © 2020 Purdue University | An equal access, equal opportunity university, 615 West State Street, West Lafayette, IN 47907-2053, If you have trouble accessing this page because of a disability, please email us at [email protected], Any practice that reduces infested corn residue and, encourages decomposition of fungal survival structures, has the potential to reduce the negative impacts of, tar spot compared to fields not implementing these, practices. While tar spot is slow to develop, we have seen gray leaf spot (GLS) developing in the lower canopy and moving up. Proper sanitation may not be enough and a fungicide control can be considered during severe cases of tar spot disease. Leaves with tar spot have small, raised black and circular spots, which are fungal structures called FMC has issued a 2(ee) label for tar spot control in corn (field, seed, and popcorn) for its new Lucento fungicide. Maple Tar Spot Treatment. Fungicides labelled for tar spot include Trivapro, and those with FIFRA 2(ee) recommendations allow Aproach Prima, Delaro, Headline AMP, Lucento, Miravis Neo, Quilt Xcel and Topguard EQ. In Indiana, you can submit a sample to the Purdue Plant and Pest Diagnostic Laboratory Tar spot is rarely harmful enough to affect the health of trees, but makes trees look unpleasant. For tar spot, as with Northern corn leaf blight, growers should go in early with an application around the V4 through V8 growth stages. Tar spot is caused by the fungus Phyllachora maydis, and can cause severe yield loss on susceptible hybrids when conditions are favorable for disease. Soybean fungicide table: here. A tar spot infection can cause severe yield loss if left untreated. If warranted, three fungicide applications are necessary for control: one at bud break, one when leaves are half expanded and one when leaves are fully expanded. Fungicide timing, fungicide efficacy and epidemiology trials are being conducted to fine-tune tar spot management recommendations. However, growers who sprayed Delaro fungicide were able to better control the disease. Below is a map of where tar spot has been confirmed as of 2020. The disease causes black specks to form on the leaves. Check out the Purdue Field Crop Pathology Extension Website, Find more publications in the Diseases of Corn series by visiting the All of these hybrids were susceptible to tar spot infection, but disease severity, the formation of halos or fisheyes, and rapid senescence varied greatly (Figure 5), and some hybrids appeared more resistant to the disease. This is caused by a fungal disease (Rhystisma acerinum), also known as tar spot. Researchers believe that the fungus is surviving over winter in Indiana on infected corn debris on the soil surface within stromata. Other fungi related to the tar spot fungus overwinter in a similar fashion by infecting grasses and weeds. Below is a map of where tar spot has been confirmed as of 2020. Preliminary observations also suggest that stalk rot and lodging were increased with high tar spot severity. “Delaro performed exceptionally well on tar spot in Iowa,” Schirm said. See my previous post for more information about making the decision to spray fungicide on corn. This is … In Mexico and Central America, where the disease was discovered, it is referred to as the Tar Spot Complex because of the involvement of a second pathogen found on plants with the disease in that region. This year there have been several additions in products, and some new diseases as well. Tar spot (caused by Phyllachora maydis) (Figure 2) was found in the U.S. for the first time late in the 2015 growing season in the northern portions of the neighboring states, Illinois and Indiana. Tar spot. Tar spot is a fungal disease that causes a great deal of concern for home gardeners due to its appearance. • Only 20 percent to 25 percent of overwintering spores will survive, but tar spot can produce millions of spores when conditions are right, meaning a small percentage of spores can still cause significant damage. If you suspect tar spot is present in an area, submit corn samples to a National Plant Diagnostic Network university diagnostic lab for diagnosis (https://www.npdn.org/home). As tar spot develops, black structures (resembling blobs of tar) form. Stromata can be surrounded by a narrow tan halo, which is known as However, fungicide treatments for tar spot are rarely, if ever, warranted. Copper fungicides can be sprayed in early spring when leaves are budding and twice more throughout the season in attempt to reduce the symptoms of tar spot disease. A new addition this year is product efficacy for tar spot of corn. Researchers do not believe the tar spot fungus is seedborne, although it can infect husks, as mentioned above. The stromata are raised and bumpy, and vary in shape from small pinhead structures to more elongated structures. Following this epidemic, tar spot was detected in 172 counties across six states in the Midwest (Kleczewski et al., 2019). The disease was detected very late in the growing season and no yield loss was reported in fields where the disease was first confirmed. However, 2018 observations indicate that the secondary fungus is not required to cause damage. Because this disease is still relatively new to the Midwest, you will not likely find disease scores for hybrids. Some corn fields in the most severely affected Midwestern states (Indiana, Illinois, Michigan, and Wisconsin) reached 100% disease incidence and 50% severity on the ear leaf before the dent growth stage (R5), with reports of 20-60 bu/A yield losses in 2018 (Telenko, et. Because of the way maple tar spot disease is transmitted, complete control of maple tar spot is virtually impossible on mature trees. and 10 counties in north-central Illinois. BASF is launching two new fungicide products, Veltyma and Revytek that will help battle corn and soybean diseases. Just because you had severe tar spot one season does NOT mean you are going to have it the following year. It has no long-term effect on the vigour of affected trees, however. Now is the critical time to pay attention to disease development and make a fungicide spray decision. Initial symptoms of tar spot are small (approximately 1 ∕ 8 inch) yellowish spots that form on infected leaves. Luckily, this disease is generally a cosmetic problem, rather than a real health issue for trees. Other control options are less certain to be helpful. Trabutia quercina is an ascomycete fungus that specifically targets species of oak trees, creating a disease commonly known as Tar spot on the leaves. The growing season has just kicked off, but it’s already been a tough few weeks for Midwest growers. a fish-eye lesion (Figure 3). Our knowledge of how to economically and sustainably manage this new disease is limited, but it is important to understand how to identify tar spot if it appears on your farm. The tar spot seen on maples is caused by three related fungi, Rhytisma acerinum, R. americanum and R. punctatum. We are now in the tail-end of the window of opportunity for a fungicide application if you feel the risk for disease, including tar spot, is warranted. We’re looking at timing and different fungicides. Tar spot is a leaf spot disease caused by the fungus Rhytisma acerinum. New Technology Gives Wheat Growers a Head Start on Head Scab. (Photos by Jim Donnelly) Page 4 of 4 TAR SPOT: Symptoms and Management Q. For example Tar spot in corn and target spot in soybeans. However, if you start to see the forecast calling for persistent rains heading into VT and you had it in previous seasons, you might need to consider a fungicide application. Per the 2(ee) label, Lucento fungicide can be applied at the onset of the disease up through the R4 growth stage with a maximum of two applications per year. The severity of symptoms can depend on when the infection occurred, the quantity of tar spot fungus that overwintered in infested corn debris in a field, fungicide applications, infection in neighboring fields, and uneven levels of tar spot infection throughout a … In Indiana, contact the Purdue Plant and Pest Diagnostic Laboratory (PPDL) for information about collecting and processing samples: ppdl.purdue.edu. In 2018, a yield-reducing epidemic of tar spot occurred in northern Indiana and in surrounding states. – Growers facing the threat of tar spot in corn and white mold in soybeans can now use Delaro fungicide to manage those diseases, thanks to a recent label amendment.The U.S. Environmental Protection Agency (EPA) approved the revision of the federal registration, adding tar spot and white mold to the long list of diseases that Delaro helps farmers manage. However, saprophytes usually have a dusty appearance and you can rub them off the leaf tissue. Short Tar Spot Video; Tar Spot Webinar Corn Fungicide Efficacy Table The spots are unsightly, and the disease can cause slightly premature leaf fall. Consult with your county UW-Extension horticulture professional to determine if your tree warrants treatment. As excessive rain raises the threat of tar spot across the Midwest, a proven preventive fungicide can help protect corn acreage. Fields in the most severely affected regions reached 100% disease incidence and over 50% severity on the ear leaf before the dent growth stage (R5/R6) with reports of 1345‐4035 kg/hectare (20‐60 bu/acre) yield loss. • When favorable weather conditions occur, tar spot can overwinter, making it a threat to growers year after year if left untreated. University and industry data both show a benefit with the use of fungicide in the presence of tar spot. Any practice that reduces infested corn residue and encourages decomposition of fungal survival structures has the potential to reduce the negative impacts of tar spot compared to fields not implementing these practices. However, if you start to see the forecast calling for persistent rains heading into VT and you had it in previous seasons, you might need to consider a fungicide application. Do fungicides help control the disease? "It first developed in northern Illinois and northern Indiana, and in 2015, 2016 and 2017, it kind of simmered and didn't move very far," she says. Several fungicides in preliminary fungicide trials may reduce tar spot. The most popular and effective tool for managing tar spot in Latin America is to plant hybrids with resistance to the disease. These ratings are based off of our independent trials, conducted over many locations and years. Another disease to scout for in corn will be tar spot. Purdue Field Crop Pathology Extension Website, An equal access, equal opportunity university. Fungicide sprays applied at the right time in spring, and with thorough coverage, can kill the Maple Tar Spot fungus, although it doesn’t guarantee that your trees won’t become infected. It is still unknown what future impact tar spot could have in the United States, but we speculate that the disease will continue to occur and spread. Tassels and silks have been out in the southern portion of the state. The overall assessment is that fields treated with a • Tar spot spreads when spores are carried by wind or rain, and current weather patterns have created a higher risk for widespread infection across the Midwest. Late snow and/or excessive rain in many areas has delayed planting and caused a higher risk for corn diseases. al. practices on tar spot in the United States. Monographella maydis was not detected in any U.S. tar spot samples from 2015 to 2019. Tar spot appears as small, raised, black spots scattered across the upper and lower leaf surfaces. It is unknown how long the fungus will survive in this debris outside a living host or the range of hosts the pathogen can infect, although it is assumed to only infect corn. The authors would like to thank Dr. Kiersten Wise and Gail Ruhl for their contribution to the previous version of this publication (BP-90-W), Nathan Kleczewski and Damon Smith for providing peer-review, and the Indiana Corn Marketing Council for their support. What does tar spot look like? Currently no studies have examined the impacts of these practices on tar spot in the United States. Several fungicides in preliminary fungicide trials may reduce tar spot. The pathogen started appearing in Midwest states over the last few years. Efforts are underway to try to gain a better understanding of the biology and epidemiology of tar spot. “Knowing the weather we’ve had this year, areas that had tar spot last year and counties nearby will be at … “A later fungicide application may be an option for tar spot. In addition, several 2(ee) labels that can manage tar spot will be available starting in 2019. Tar spot was confirmed in 38 Indiana counties in 2018 (Figure 1). Most of the information we have about tar spot originated in Mexico and Central America, where favorable environmental conditions make the disease prevalent. The Tar spot was found on a live oak sample that was sent into the lab from a private residence. The fungus that causes tar spot is an obligate pathogen and requires a living host to grow and reproduce. Heavy infections can also cause early leaf drop. Two of the most common practices for, reducing local disease inoculum include crop rotation, Rotating away from corn allows infested corn residue to, decompose. However, optimum application timing will be critical for a fungicide application to be effective and economical. Tar spot can also be easily confused with the black saprophytic organisms that grow on dead leaf tissue. Plot was evaluated for disease. If tar spot arrives in Nebraska cornfields, it may warrant a later-season fungicide application, Jackson-Ziems says.