Northern Minnesota and northern Wisconsin Walking Your Fields newsletter-Aug


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This August issue of Walking Your Fields contains the following articles for growers in northern WI and northern MN: corn rootworm damage, late season soybean diseases and corn drydown and harvest timing.

Articles are written by DuPont Pioneer agronomists in Minnesota and Wisconsin and are distributed on behalf of DuPont Pioneer account managers and Pioneer sales reps.

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Northern Minnesota and northern Wisconsin Walking Your Fields newsletter-Aug

  1. 1. It has been a challenging growing season with the late start and wet spring conditions. Drought conditions quick- ly took over in mid-season. The August 13th U.S. Drought Monitor Map for the Midwest shows drought affecting var- ious parts of Minnesota and Wisconsin. Luckily, the cool weather in early August allowed crops to survive with minimal rain events but slowed development. At the end of August, crop progress is still variable across the upper Midwest but typically is delayed by 10-14 days. As of Au- gust 18, most of central MN and northern WI accumulat- ed 1500-1600 GDUs since mid May. We currently lag the historical average by 100-200 for the shortened growing season. We need to remain frost free into early October to get the corn crop to naturally black-layer. Producers should monitor fields for root pruning from Corn root- worm (CRW). Often root feeding is discovered after a wind blows over the damaged plants. Dam- aged areas in the field typically are not uniform and will result in patchy areas of lodging next to good standing corn. Rootworm beetles are currently laying eggs that will hatch into the root dam- aging larvae in subsequent years. Northern CRW beetles are green to yellow in color. Western CRW have yellow and black stripes on their wings. Plan ahead for your CRW strategy next year. In a stressful growing season, attack from plant patho- gens may begin to show up late in the year as patches of dying or wilted plants with drooping or diseased leaves. While soybean diseases may become apparent just prior to harvest, the infection may have occurred much earlier in the season. These above-ground symptoms are com- mon to several unique below-ground problems. A quick peek at roots and lower stems can help determine which of these pathogens might be at work in your soybean fields. Proper identification can help with future variety selection and management decisions. Sudden Death Syndrome (Fusarium virguliforme) produces striking leaf symptoms (Figure 1), which alert us to problems in the roots. Affected plants may die rapidly after first leaf symptoms appear due to toxins produced by the root rotting fungus. Split stems will generally show only minor discolora- tion in solid cortex areas, with normal white pith. Cool, moisture conditions early in the growing season often results in higher disease incidence. Stress due to heat and drought may reduce occurrence of SDS in some cases. Brown Stem Rot (Phialophora gregata) produces similar striking leaf symptoms mid-season as SDS, which may cause con- fusion of the two dis- eases. Tissues be- tween veins become yellow and quickly turn brown, except for a narrow band of green tissue outlining the vein. However, BSR is distinguished from SDS and other diseases by brownish discoloration due to an infection of the pith tissue in lower stems (Figure 2). This infection impedes the movement of water and mineral nutrients needed for growth. WALKING YOUR FIELDS® newsletter is brought to you by your local account manager for DuPont Pioneer. It is sent to customers throughout the growing season, courtesy of your Pioneer sales professional. The DuPont Oval Logo is a registered trademark of DuPont. PIONEER® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents. ®, TM, SM Trademarks and service marks of Pioneer. © 2013 PHII. Crop and Weather Update WALKING YOUR FIELDS ® August 28, 2013 - Issue 5 Corn Rootworm Damage Causing Lodging Corn Rootworm Feeding Photo: Clyde Tiffany Late-Season Soybean Diseases Figure 1. Leaf necrosis caused by SDS or BSR. Photo: DuPont Pioneer Figure 2. Brown stem rot. Photo: L. Osborne, DuPont Pioneer <<
  2. 2. Northern Stem Canker (Diaporthe phaseolorum) is a re- emergent soybean disease that begins at points along lower stems, creating brownish-red lesions (cankers) ex- tending part way around and into lower stems (Figure 3). Affected plants often retain dead leaves even up to harvest time. Roots and pith (the soft center are of stems) are generally not affected by stem canker. White Mold (Sclerotinia Rot) Sclerotinia white mold is favored by cooler night temperatures (50-60°F) and moist conditions in the plant canopy. In addition to cool temper- atures, the production of white mold apothecia(mushroom like fruiting bodies) requires moist soil and a closed cano- py. If surface soil moisture is low or the soybean cano- py is not closed during flowering, the fungus would not be able to produce apo- theica. When scouting for this disease, pay attention to the fields that have a history of white mold and fields that have good soil moisture and a closed can- opy. The first evidence of white mold is a chlorotic, girdling lesion covered with white, fluffy mycelium at one of the middle nodes. The evidence of the dis- ease becomes conspicu- ous in August when dead tops start to show up in fields. It is most likely to show up in low spots of the field where plant populations are high, in narrow rows, in tightly closed canopies, where plants become lodged and/or where less tolerant varieties are planted. Many corn fields in the region were planted mid to late May or early June, this corn will likely need until early October to reach maturity (black layer). As growers hope for a late autumn to get field work done before the snow flies, now is the time to weigh the cost of in-field grain drydown versus using artificial drying at harvest. There are three main factors that influence the rate at which corn dries, physiological maturity, weather and the corn hybrid. Corn that matures earlier typically dries fast- er due to more favorable drying conditions earlier in the harvest season. On the same note, later maturing corn has fewer warm days to aid drying and will dry slower. In a typical year, corn that matures on September 15 may require only about 10-15 days to reach 20 percent mois- ture, while corn that matures on September 25 may need 30 days to reach the same moisture level (D.R. Hicks, 2004). Drydown is linked to heat units (GDUs). Under ideal weather conditions, corn may lose up to one point of moisture per day. As the days get cooler, GDUs de- crease and drying slows. A rule of thumb is that 30 GDUs are required to lower the grain moisture each point from 30 percent to 25 percent. Forty-five GDUs per moisture point are required from 25 percent to 20 percent. Also consider that we typically expect no more than about 10 GDUs per day in late September, and only about 3-5 GDUs per day in late October. That means that field dry- ing of corn may take two to three times longer for late maturing fields. Drydown is also hybrid specific. The amount, thickness and tightness of husks affect drydown; the more insulated the ear, the longer it takes to dry. Up- right ears are more prone to capture moisture in the husks. Lastly, corn with moderate test weight dries faster than hybrids with heavier test weights. The ideal harvest moisture for corn is between 22-25 per- cent. Waiting for corn to dry to 18 percent moisture in the field certainly saves on the energy bill; but it also increas- es the likelihood of excess harvest losses due to stalk lodging, ear drop and detrimental weather all of which can affect your bottom line. In addition, there may not be enough heat units this fall for in-field drydown. Ohio State University research indicated no additional in-field grain drying occurred after early to mid-November (Minyo, Geyer & Thomison, 2009). “Phantom yield loss” may also encourage growers to har- vest at slightly higher moistures this fall. Growers occa- sionally report harvesting part of a field early and finishing the field when it is dryer, only to discover the later har- vested portion of the field is yielding several bushels less per acre than the first harvested corn. Purdue University confirmed these claims indicating that grain corn dried in the field has the potential to yield one percent less per point of moisture. For example, corn that was 200 bushels/acre at 28 percent moisture would only yield around 180 bushels/acre at 18 percent moisture if left in the field too long. This research also confirmed Figure 3. Northern stem canker. Photo: L. Osborne, DuPont Pioneer Figure 4. White Mold Photo: DuPont Pioneer Corn Drydown & Harvest Timing Delaying harvest may increase risk of lodging, ear drop or kernel loss and result in reduced yields. Photo: DuPont Pioneer >>
  3. 3. that the ideal moisture level for corn grain harvest is 25 percent. Harvesting wetter than that can damage kernels and of course significantly increase drying costs (Nielsen et al., 1996). Artificial drying costs will vary this season depending on LP gas prices, which currently ranges from $1.25 - $1.40 per gallon across Minnesota. Nonetheless, harvesting at a higher moisture level this year may increase grower profitability, specifically when growers anticipate medium to high harvest losses. The table below was developed by Iowa State University, and customized by DuPont Pioneer agronomists to illustrate different drying scenarios and costs based on an average LP price of $1.35/gallon. If you have questions about moisture levels, drydown and harvest, contact your sales representative for assistance. (Sources: Minyo, Geyer & Thomison. 2009. How will delaying corn har- vest affect yield, grain quality and moisture? Ohio State University Ex- tension. Nielsen et al. 1996. Kernel dry weight loss during post-maturity drydown intervals in corn. Purdue University.) What is the ideal harvest moisture for corn grain? Or, to be more specific, what grain moisture will provide the greatest economic return to the grower? This is a question that has been studied and debated over the years, with some growers favoring earlier har- vesting, while others prefer drier grain to minimize artifi- cial drying. While there is no definitive answer to this question, limited research, and some reliable on-farm anecdotes suggest grower’s yield may “disappear” after physiological maturity due to respiring grain in the field. Additionally, field and harvest loss due to ear drop and shelling may also impact harvestable yield. To address this question, DuPont Pioneer is looking for growers to run a simple test in their field this fall, compar- ing a “early harvest” vs. “late harvest.” The test is easy to do, and can be done with any corn hybrid: 1. Select a uniform field near bins or buildings that allow for multiple harvests over time. 2. Harvest a portion of the field early, with grain mois- tures near 25%. 3. Harvest a second time (or more) a week or more lat- er, with final grain moisture targeted less than 20%. 4. Record harvest data with a yield monitor or weigh wagon. 5. Note visible yield loss (dropped ears, etc.) 6. Provide harvest dates, yield & moisture data and notes to your Sales Rep or DuPont Pioneer Agrono- mist. Contact your local Pioneer Sales Representative if you are willing to participate in this test and to answer any questions you may have. Again, we are looking for lots of grower participation to help us address this question. Yield information from monitors and GPS is an extremely important tool that you can use to make deci- sions in your business. However, it is only as accurate as the calibration and taking time to do this will help elimi- nate poor information later. Here are some tips to remem- ber when looking at yield monitor calibration:  Clear memory card and back up previous year’s data  Calibrate multiple times throughout the growing sea- son to ensure consistent data  Make sure the load is enough weight (3,000-6,000 pounds)  Make sure you have multiple loads at different speeds (3.5, 4.5, 5 etc.)  Calibration loads should be in a uniform area of the field, a good representation will improve accuracy  Differences in moisture and grain quality will require a new calibration to be accurate In a year with variability, taking time to calibrate will pay big dividends! AGRONOMY RESOURCES, TOOLS & APPS and Pioneer mobile allow growers to have extensive crop management resources and agronomy information at their fingertips. Check out these apps: Pio- neer® Field360™ Notes and Pioneer® Field360™ Tools! Estimated Cost to Dry Corn to 15% Moisture Harvest Moisture LP gal/bu LP $/gal LP $/bu Drying Cost $/bu* Drying cost $/point* 35 0.472 1.35 0.637 0.645 0.032 30 0.337 1.35 0.455 0.461 0.031 25 0.219 1.35 0.296 0.299 0.030 20 0.109 1.35 0.147 0.149 0.030 Based on: NCH-51 Hybrid Maturity-Energy Relationships in Corn Drying, Iowa State University; *assumes electrical cost of $0.115/kwh Early Harvest Challenge Calibrating Yield Monitors