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.
Oftentimes dealing with foliar wheat diseases can be a confusing topic. More often than not, physiological leaf spotting, or genetic leaf spot, can be observed in most wheat fields after flowering stages. However, the leaf spot symptoms are occasionally misdiagnosed as early leaf rust symptoms. But, rarely have I observed a disease epidemic in a situation where the specific “flecking” symptoms are regularly observed.
Scattered reports of wheat diseases have been made over the past two weeks. Limited leaf rust, stripe rust, and Septoria leaf blotch can be observed in some wheat fields. In addition, in some situations bacterial leaf streak can be readily observed on flag leaves in some limited situations. In some cases, bacterial leaf streak and Septoria leaf blotch can appear similar to one another. In most cases, Septoria leaf blotch can be observed in the lower canopy and likely will not move up the plant to the flag leaf. However, bacterial leaf streak can be more readily observed on flag leaves in some fields.
During 2012 fungicide application trials were conducted at a field site west of Greenwood, MS. Following a major wind event that occurred early in June, excessive greensnap was observed in plots that had received V6 foliar fungicide applications. Plots were assessed to determine if fungicides could consistently alleviate the occurrence of greensnap compared to untreated plots.
Oftentimes, deciding whether or not to make a fungicide application to corn in vegetative growth stages is not based on disease. Rarely are foliar diseases an issue in vegetative growth stages (save for extremely rare situations). More often than not, the decision to apply a fungicide at a vegetative timing is based on the theory of “plant health”, or physiological enhancements to the plant as a result of the fungicide that have been difficult to replicate in all situations.
Use the information contained in this blog post to aid in determining the specific disease in field corn. Scouting corn for the presence of disease is difficult and can be confusing since some foliar diseases appear similar to one another such as gray leaf spot and southern corn leaf blight. In addition, particular diseases are more important depending on the particular growth stage when they are encountered.
Wheat disease continue to be discussed throughout MS. Generally speaking, stripe rust has not been near the widespread threat this season as it was during the 2012 wheat crop. Scout wheat fields for the presence of diseased and relate this to the specific variety in each field when determining particular management alternatives. Keep in mind, the general cut off date for fungicides is Feekes 10.5.1.
Please see the attached information regarding the use of products that contain tebuconazole to manage wheat diseases. Note that the label restricts the overall amount of tebuconazole that can be applied to wheat in any one season to 4 fl oz/A.
Stripe rust continues to be observed throughout scattered fields in the Delta. In addition, leaf rust was confirmed in isolated cases over the past week. Keep in mind that not all fields will require a fungicide application to prevent yield loss. Scout wheat fields at this time for stripe rust hot spots (small in size = less than 3 feet in diameter; to large in size = several trucks) and determine the wheat variety present before deciding on a fungicide application.
As we move towards the soybean season we’ve included some information regarding the labeled fungicides for application to prevent yield loss as a result of soybean rust. Soybean rust was able to overwinter in several Gulf Coast states (AL, FL, LA). However, at present, soybean rust has not been detected on kudzu in MS.
Additional stripe rust has been detected throughout the MS Delta over the past two weeks. Scout fields for the presence of stripe rust to determine the extent of the infection in the wheat production area. Keep in mind that stripe rust will appear different on younger wheat plants still in the early vegetative stages than it does on more mature wheat plants.
Throughout the season many ag-related professionals ask questions about particular fungicides. More specifically, sometimes it can be confusing to determine if a particular product falls in the strobilurin class of fungicides or the triazole class of fungicides. The current update includes information to help determine the particular class of fungicides for strobilurin, triazole, and pre-mix products using fungicides labeled for application in soybean as an example.
You must provide numerous resources and management to optimize the opportunity for corn plants to produce high yields. Of course, favorable weather plays a huge role as well. This article describes areas where we can improve corn yield potential.
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