DAVID JORDAN
North Carolina State University
Extension Agronomist
Keep Plants Healthy
July will bring issues associated with disease management, cleaning up fields with escaped weeds and the possibility of insect issues. For Virginia market types, it is not too late to apply gypsum. If for some reasons there are delays, applications of gypsum into late July and early August are still advisable.
Also, southern corn rootworm can be an issue in some fields, and while insecticide application in late June or early July would be the most effective, application through July can pay for itself if this insect pest is present.
Applying effective fungicides on time is the key to disease management. These applications should be based initially on growth stage, but generally in the V-C we start around the second week of July. Resistance or tolerance to leaf spot disease and stem rot is relatively good in our newer varieties and that gives us some flexibility in start time. Once we jump in, we need to be on roughly a two-week schedule unless conditions are dry and/or the advisory system suggests application is not needed for a period of time.
Maintaining healthy plants through the entire season gives us the greatest flexibility in digging, and the fungicide programs we implement now can go a long way in keeping disease epidemics from developing. However, we know from the 2015 crop that we must keep our guard up for the entire season, especially as we approach digging and harvesting.
Finally, in July we often have a lot of pests to deal with – weeds, insects and disease. This brings about a lot of questions about tankmixtures with two, three, four or more possible pesticides/fertilizers/PGRs going out at the same time. There are a number of sources of information, such as companies, labels, Extension, research, consultants, farmers, gut feelings, that can help with this decision. However, it is also possible that none of these sources will have information on your specific four-way mixture. A sequential application of some of these will often give you more effective control because you can time things more precisely than getting them out there all at once. Although there are logistical challenges with sequential applications, try to minimize any gunk in the tank, crop injury or poor performance on the target pests.
SCOTT MONFORT
University of Georgia
Extension Agronomist
Scout Weekly For Outbreaks
As we move into the second half of the season, disease and insect management will be the key in maintaining peanuts’ high-yield potential. Scout your fields on a weekly basis in order to stay ahead of any potential problems.
I have had many growers say, “I am on a fungicide program and I add insecticides every time I go across with a fungicide, so I should be okay, right?” The main concern regarding not scouting as part of your disease management program is many growers are using a low-input fungicide program and this type of program may not be the most effective program during severe disease outbreaks.
Scouting is an effective way to monitor for these outbreaks, letting you alter your fungicide programs as needed to maintain a high level of control. Likewise, scouting your fields is the only way to determine when and what to apply to effectively manage insects. Automatic applications of insecticides or applying the wrong products will cost you more than applying insecticides when thresholds are reached or when outbreaks occur. Feel free to contact your local Extension agent if you need information regarding pest management recommendations.
KRIS BALKCOM
Auburn University
Agri-Program Associate
Possible Cause Of Yellowing
Now is the time of season when we sometimes see problems beginning to show up in our fields. Many of us have seen yellowing in spots in our fields before. Often times, it is difficult to know what the problem is because it is only a small area.
What I am referring to is not a disease problem but a micro-nutrient problem. For example, you may see the entire leaf become yellow with the internal veins of the leaves remaining green. The problem is a Manganese (Mn) deficiency, as pictured below, and it results from a high pH ranging from 6.6-6.8. The increased pH ties up the available Mn from the soil solution resulting in the yellow color.
Generally the spots are clay knobs where you would have a higher pH in the field or in an area where the lime was piled before spreading. The problem is usually corrected by spraying manganese sulfate.
I also want to remind everyone to apply their boron applications if they haven’t already. Boron prevents seed damage known as “hollow heart” which reduces seed quality. Boron is applied as a foliar spray due to the fact that it is highly leachable in the soil.
JASON WOODWARD
Texas Agri-Life Extension
Plant Pathologist
Protect Against Pod Rot
An ounce of prevention is worth a pound of cure – While this statement was coined by Benjamin Franklin and is believed to address fire safety, the quote is equally as true when managing peanut disease. Most peanut fields are at peak bloom, and now is a good time to start protecting developing pegs and pods from soilborne disease.
In the Southwest, the pod rot complex is the most common disease affecting peanuts. Numerous fungi can be found in the pegging zone; however, Rhizoctonia solani and several Pythium spp. incite pod rot symptoms. Pods infected by R. solani and Pythium spp. are similar in appearance and often difficult to differentiate.
To further complicate matters, the two can occur simultaneously in the field. Infected pods initially exhibit light brown lesions, which turn dark brown to black as the disease progresses. A subtle difference between the two is that pods infected with Pythium typically have more of a water soaked appearance, whereas pods infected with Rhizoctonia have more of a dry rot appearance. Distinguishing between the two is critical when choosing fungicide options and rates.
Recent research has shown that preventative calendar-based applications made 60 to 70 days after planting are more effective than curative applications made after disease symptoms are readily observed. Similar results were obtained when dealing with other damaging diseases such as Sclerotinia blight.
Management of foliar diseases is no different. Although there are a number of systemic fungicides labeled for use against the leaf spots, applications made prior to infections occurring provide superior control when compared to applications that are made following the onset of symptoms.
Fungicides comprise a large portion of the inputs needed to maximize yield. While proper disease identification, fungicide selection and timing will lead to increased profitability, the effort required proves that “a penny saved is a penny earned.
