As my family and I drove on a mid-July morning, passing field after field of peanuts, I said this time of the season reminded me of the Battle of Gettysburg. One child slumped in his chair and became more intent on his computer game. The other exclaimed softly, “Oh-my-gosh…..” and steeled herself for the analogy to follow.
The Battle of Gettysburg was fought between July 1 and 3 in 1863. Though the Civil War raged for almost another two years, the die was cast for the Confederacy at Gettysburg. On April 9, 1865, General Lee surrendered the Army of Northern Virginia at Appomattox Courthouse and the war was mercifully over. At this point I heard a prolonged sigh and an exasperated question from the back of the truck, “What has THAT got to do with peanuts??”
For me, the analogy is clear and telling. The period from mid-July until mid-August is in the middle of the peanut-growing season for all but the earliest and latest planted fields. It is during this time that important diseases like stem rot (“white mold”), Rhizoctonia limb rot and leaf spot diseases often become established and cause irreversible yield losses if not adequately managed. If white mold, limb rot and leaf spot diseases are not stopped by the middle of the growing season, then there is likely little if anything that can be done to prevent significant yield losses throughout the remainder of the season.
Disease management is different than insect management in a major way. In insect management, growers often are advised to refrain from treating until some threshold level of the insect population is reached. In the case of diseases management, prevention is key; once the disease becomes established in the field it becomes difficult, if not impossible, to control.
Disease management becomes ever more critical during the middle of the season. There are several reasons for this. The first reason has to do with the growth of the peanut crop. It is during the middle part of the season that a significant canopy of foliage develops. Not only are the leaves and stems susceptible to a number of diseases, but the density of this canopy traps humidity and prolongs leaf-wetness periods, creating conditions ideal for disease development. As the plants lap the row middles, conditions become quite favorable for development and spread of disease.
The thick canopy of leaves makes it more difficult for fungicides to penetrate and reach the crown of the plant, an essential target for management of white mold and limb rot. The second reason has to do with weather during the middle part of the season. Increasing temperatures favor development of white mold (stem rot) and rainfall, from afternoon showers or tropical storms, further fuels the development of disease.
Lastly, by the middle of the season, enough time has passed to allow the steady increase of the fungal pathogens causing disease. Not unlike a discarded cigarette smoldering between the cushions on a couch, without adequate protection, fungal diseases can seemingly ignite abruptly within the peanut field.
There are a number of “best management practices” with which to fight diseases in the peanut field. Peanut Rx is an excellent tool by which growers can learn how factors like variety selection, crop rotation, tillage, planting date, seeding rate and row pattern can reduce or increase risk to disease. Peanut Rx is available from local county offices and is now available at no charge as a smart phone app (Google Play: “uga peanut rx” and APP Store: “peanut rx”).
Growers can also get the most out of fungicide applications by taking steps to increase coverage of the peanut plant. These measures include spraying ahead of anticipated rain events or irrigation (so long as there is adequate drying time), increasing spray volumes and spraying the peanut crop at night. There is also importance in choosing fungicides with proven efficacy/improved efficacy in managing diseases like leaf spot, white mold and Rhizoctonia limb rot. A successful fungicide program includes choice of the right product, timeliness (stay ahead of disease) and good coverage.
Protecting yield is only possible if the grower protects his crop against disease and other pests. Losing the battle for control of diseases in the heated months of July and August sets the grower up for significant losses in September and October. Just ask my kids. They can tell you it is a lot like Gettysburg …