Numerous questions over the past few weeks regarding how well certain fungicide chemistries are managing frogeye leaf spot. Attached please find preliminary rating data from Starkville and Stoneville on how well particular products are managing observable symptoms of frogeye leaf spot. Additional data to follow as we continue to rate plots.
Numerous diseases continue to be reported from throughout the MS soybean production area. Frogeye leaf spot continues to be the main foliar disease observed. Additional soybean rust was reported from Adams County this past week. However, since low levels of the disease continue to be reported the suggestion remains that farmers wait and watch the available information and allow soybean to get as close to reproductive developmental stages before making a fungicide application.
This last week I found early leaf spot in the Greater Columbus, Mississippi area. For information and images on how to identify early leaf spot, please see: https://www.mississippi-crops.com/2013/08/12/early-leaf-spot-of-peanut/ and https://www.mississippi-crops.com/2012/09/05/early-leaf-spot-found-in-the-greater-aberdeen-area/ Early and late leaf spot are major defoliators of peanuts
Synopsis: Is caused by a fungus, Cercospora arachidicola. Defoliates infected leaflets fairly quickly. Is one of the reasons, along with late leaf spot, for the development of the traditional two week spray schedule in established peanut growing areas (see Figure
Phytotoxicity following a foliar fungicide application is not a commonplace occurrence in our soybean production system. In certain situations, the symptoms that express themselves when a fungicide application is made in the heat of the day can manifest themselves similar to characteristic foliar disease symptoms. Sudden death syndrome (SDS) is a common occurrence from the standpoint that we observe the disease annually but rarely does it impact yield and in fact we normally suggest that SDS simply means you’ve raised some great soybeans in that particular field. Keep in mind that SDS will only occur on light soil texture classes and normally not across an entire field as a situation such as phytotoxicity could.
Blast of rice was positively confirmed in three rice fields on Tuesday afternoon. Blast lesions are specific in that the generally form a diamond-shaped lesion on the leaf.
Cotton leaf spots have been observed in several fields again this year shortly after flowering. Positively confirming the particular disease is the most important event to determine a potential management scenario. The difference between the members of the “potash complex” as well as target spot are distinct, but numerous lesions need to be observed to positively identify the causal organism.
Frogeye leaf spot continues to be one of the main foliar diseases observed in the 2013 soybean crop. In several situations a fungicide has applied and frogeye continues to be an issue. In the current blog post several pieces of information are included to help aid decisions in whether or not a particular variety may be susceptible or resistant to frogeye. In addition, a table of the labeled fungicide products for use to prevent yield loss as a result of frogeye leaf spot are included.
Corn fungicide questions continue to be made even in situations where corn has reached dent. In general, making a fungicide application at dent or later corn growth stages only pays off if excessive disease pressure is observed prior to the fungicide application being made. Moreover, making a fungicide application to a foliar disease tolerant hybrid will likely not pay off since the genes present in the hybrid should be relied on for preventing yield loss as a result of foliar disease.
Over the past two weeks increased reports of soybean diseases have been made from throughout the state. In addition, in southern MS, two more counties have been confirmed to be positive for soybean rust.
The Soybean Minute is a new radio program that can be heard on the Mississippi AgriNews Network. These reports, sponsored by the Mississippi Soybean Promotion Board and the United Soybean Board, offer the latest information on soybean production in Mississippi.
Once again this season soybean rust has been detected early in July. A single infected leaf was discovered in a soybean sentinel plot in Pearl River County on Tuesday, July 9, 2013. Historically this is 4 days earlier than last season (2012) and 2 days earlier than the earliest occurrence of rust in MS that occurred in 2007 on kudzu. At present, no additional management scenarios are necessary. We continue to scout to determine how widespread infection may be across south MS.
Extremely low levels of southern corn rust were observed in a single corn field in Humphreys County on Tuesday afternoon. Southern rust can be a devastating disease if left unchecked and when conducive conditions prevail (hot, humid environment).
Over the past two weeks soybean diseases have become apparent throughout the MS soybean production system. Isolated reports of frogeye leaf spot in reproductive maturity soybean fields as well as Fusarium wilt have been on the rise. Stay tuned to the Mississippi Crop Situation Blog for disease monitoring situations, including maps of counties where soybean rust and strobilurin-resistant frogeye have been made throughout the 2013 season.
Favorable weather conditions continue to help this crop progress. Major problems outside of drift have been few for most of the spring; however, a few different issues have come up this week. Dr. Jeff Gore was called to help address a
Corn diseases continue to be a hot topic throughout the MS corn production area. Most field calls have been regarding common rust as well as northern corn leaf blight. However, over the past two weeks numerous calls regarding nutrient and irrigation stresses have been answered that were initially thought to be disease. In addition, with the recent information from Louisiana regarding the observation of Goss’s wilt in LA (a rare event in their production system) agriculturists should know that disease as well as crop stresses can be initially misdiagnosed as diseases that are not normally present in our production system such as Goss’s wilt.
At this point of the season, we still have some acres of soybean yet to be planted. The majority of those acres will be double cropped soybean behind harvested wheat. Given the environmental conditions that we typically expect during this
Automatic foliar fungicide applications are still widely discussed. However, data from university-based programs suggests waiting for foliar diseases that could ultimately reduce yield before making a foliar fungicide application is more economically advantageous.
Numerous reports of urea injury producing symptoms similar to northern corn leaf blight have been made over the past several weeks. Determining the difference between the two issues on a corn leaf can be difficult. Numerous photos as well as a comparison table of the differences between the two issues are included in the post.
Northern corn leaf blight and common rust continue to be identified in corn fields throughout the south Delta. Determining the specific corn hybrids planted in each field is an important first step every season. For the most part, save for a couple of fields, NCLB has still been detected at extremely low levels (= 1 lesion per leaf per plant).
Over the past week we’ve received two reports of frogeye leaf spot in reproductive soybeans. In both cases, a susceptible variety was planted and frogeye leaf spot symptoms can be clearly distinguished throughout the canopy. Following the observation and reports of strobilurin-resistant frogeye leaf spot in two fields in MS last year, and from adjacent states, it is most important to determine what particular soybean variety is planted in a field prior to making a decision on a specific fungicide product for yield loss prevention.
Several people have asked about a list of fungicides and the specific diseases they may manage best. Included in this post is a table that has been put together by the Corn Disease Working Group of fungicides and how they respond in environments with specific diseases in efficacy trials from throughout the U.S.
Several common diseases have been observed in the MS corn crop over the past week. Common rust and northern corn leaf blight are typical diseases in corn and are likely the result this early in the season due to the cooler than normal temperatures and ample rainfall we’ve received over the past month. But, with the generally atypical environment we’ve experienced this season the likelihood of more non-typical foliar diseases occurring is potentially increased. Proper diagnosis prior to a management decision is therefore increasingly important.
The 2013 Scout School dates have been set. The first will be June 4th from 9:00 a.m -12:00 p.m. at the Delta Research and Extension Center in the auditorium of the main building. The last one will be on the main campus of Mississippi State University in the Clay Lyle Entomology Building conference room.
Within the past week to 10 days, numerous fields have been diagnosed as having “Pythium seedling disease”. In most cases, herbicide injury has resulted in fields appearing to have an uneven stand as a result of seedling disease. Rarely would a seedling disease be responsible for large acreages of dead seedlings. More than likely, a combination of events have occurred to cause the appearance of seedling disease. Preemergence herbicides, cool temperatures, excessive rainfall following planting immediately prior to emergence, light soil texture, and herbicide injury on stressed soybean seedlings have all compounded the stressful situation.
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