Northern Minnesota and northern Wisconsin Walking Your Fields newsletter-July


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This July issue of Walking Your Fields contains the following articles for growers in northern WI and northern MN: a weather and area update, soybean aphids and cyst nematodes, corn root lodging and the role of water in corn development.

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-July

  1. 1. The 2013 planting season will go down as one of the most difficult in many areas of Minnesota and Wisconsin. At this point in the season, we hope the crops develop rapidly enough to produce good quality grain or in some cases enough quality forage for the livestock. Typically it takes 55 to 60 days for grain corn to advance from tassel to physiological maturity (black layer). However, harvest- ing silage corn is earlier. Kernels will be at 50 percent kernel milk about 42 to 47 days after tasseling. The re- cent warm weather has increased optimism of hitting ma- turity before frost. The map below shows the Growing Degree Day accumulation across Minnesota and Wiscon- sin from May 15 to July 15. A typical 95 RM hybrid will need 2200 GDDs from planting to P.M. Pioneer recently realigned territory lines to improve cov- erage; therefore some staff have new territories. No mat- ter their location, our Dairy Specialists, Account Manag- ers, Agronomists and Sales Representatives pledge to provide you with the best information and excellent ser- vice that you have come to expect from Pioneer® . New assignments include: Matt Laubauch– Dairy Specialist for Central MN Ryan Bates – Field Agronomist for NE and Central WI Clyde Tiffany – Field Agronomist for NW WI and C. MN Mark Navara – Account Mgr. for East Central MN Marty Lovrien – Account Mgr. for Central MN Soils with low or- ganic matter levels and fields with ex- cess water satura- tion will benefit from planned or rescue top dress- ing of nitrogen and sulfur. Typically, the biggest re- sponse occurs when applications are done before the corn is 12-18‖ tall. However, weather conditions forced some later applications. Often 30-50 pounds/acre of supplemental N is adequate to offset lost nitrogen. Soybean aphids are right on schedule and were recently report- ed in central Minne- sota. Even if you planted soybean seeds treated with a nicotinoid insecticide to delay aphid popu- lation establishment, you will still want to scout your fields for this pest from V5 through R5. The soybean aphid overwinters in buck- thorn and migrates to legumes (soybeans, alfalfa and clovers) in July. It’s less than 1 mm in length but when left untreated, economic infestations can reduce yields by more than 10 bushels/ acre. Symptoms Aphid-infested soybean plants may look simi- lar to a potassium deficiency: curled leaves, often yellow on the outside. Aphids produce a sugary excrement, Area & Weather Update WALKING YOUR FIELDS ® July 24, 2013 - Issue 4 DuPont Pioneer Territory Adjustments Supplemental Nitrogen Valuable Soybean Aphids Nitrogen and sulfur topdressing were criti- cal this year with the excess precipitation. Photo: Clyde Tiffany, DuPont Pioneer Agronomist Soybean aphids and an ant on a soy- bean leaf. Aphids excrete ―honeydew,‖ a sugary substance that attracts other insects and also results in development of sooty mold. Photo: Marty Lovrien, DuPont Pioneer >> 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.
  2. 2. known as honeydew, on leaves, which promotes soot mold growth and can serve as a feeding ground for ants. Plants infested by the soybean aphid will also appear shorter. Besides a stunted plant with noticeable discolora- tion, you can also detect these oval-shaped, light green pests with black ―tail pipes‖ near the end of the abdomen by doing numerous sweeps through the field. Take Action Count the number of aphids on 30 to 50 plants throughout the entire field and calcu- late the average number of aphids per plant. If aphid pop- ulations reach 250 per plant and are increasing during the R1 – R5 growth stages, consider a foliar insecticide to control the population. Your local Pioneer sales rep can help with product recommendations. There are also sev- eral beneficial insects that feed on soybean aphids and can naturally control the aphid population. They include Asian lady beetles, damsel bugs, green lacewing larvae, and insidious flower bugs. Soybean cyst nema- tode (SCN) race shifts and high cyst counts are an added stress to soybean fields. Planting SCN- resistant soybean varieties that include the Peking and PI88788 source of resistance, along with rotating to a non -host crop are two of the best ways to prevent SCN infesta- tions. Extension spe- cialists have advised that the overuse of any single source of SCN resistance can lead to SCN race shifts over time. Therefore, it is important to switch between varieties and always scout fields. To scout for SCN, dig up soybean roots and gently wash the soil away. If you don’t see a high number of SCN, recheck in two weeks to make sure you are not between production cycles. DuPont Pioneer offers both the Peking and the PI88788 source of resistance. Take time to dig and compare the female cysts numbers between the Peking and PI88788 sources. When SCN becomes prevalent, it also promotes the de- velopment and spread of Sudden Death Syndrome and increases the severity of Brown Stem Rot. Below are recommendations from the Plant Health Initia- tive funded by the Soybean Checkoff on crop and soy- bean resistant variety rotation:  Rotate with non-host crops to reduce SCN numbers.  Rotate with resistant soybean varieties to reduce yield loss due to SCN.  Rotate the resistant varieties you use: don’t use the same one twice in a row.  Rotate with tolerant or susceptible soybean varieties only if SCN numbers are low. More information about SCN resistant varieties and SCN damage is available through you local Pioneer sales rep and also available in the Soybean Cyst Nematode Man- agement Guide: SCNGuide_5thEd.pdf Extreme, early-season moisture, strong wind events and corn rootworm feeding all contribute to increased poten- tial of corn root lodging. If root lodging has occurred, take time to assess its cause—don’t just assume it is root- worm feeding. Causes of Root Lodging in Corn  Wet conditions at planting, causing sidewall compac- tion and restricting root growth  Wet conditions early in the growing season  Strong wind and rain events during critical root devel- opment and prior to brace root formation  Reduced root growth due to nitrogen deficiency  Hybrid differences in root formation  Corn rootworm (CRW) feeding Yield loss and lodg- ing due to CRW feeding is affected by the timing of root feeding, weather, soil type and hybrid type. Extreme root lodging often results from root feeding by CRW larvae in June, followed by summer storms. Once rootworm lar- vae have damaged or destroyed roots near the soil sur- face, they work their way down Soybean Cyst Nematodes Root Lodging in Corn Photo: Bruce Carlson Soybean aphid damage on soy- bean leaves. Photo: DuPont Pioneer Female cysts of SCN on plant roots. Photo: Marlin E. Rice Corn rootworm damage reduces a plant’s structural support and makes it more sus- ceptible to lodging. CRW injury to nonBt corn roots on left compared to Bt hybrid on the right. Taken from an Iowa State University research plot.>>
  3. 3. the root system. The later the root lodging occurs in the growing season, the less able corn is to straighten up without pronounced goose-necking. Closely monitor root lodged fields and consider harvesting at higher moistures, if stalk rot becomes an issue. Water is essential to corn growth, especially at tasseling when the corn’s uptake of water increases dramatically. From now through the dent stage, corn demands an aver- age of a ¼ inch of water per day. Inability to receive this amount of water can lead to decreased yields. Root growth can help compensate for the increased water need, as the expansion of the root system reaches deep- er into the soil profile to help the plants extract more soil moisture. However, air temperatures also greatly influ- ence water needs. Temperatures in the 90s during corn growth will double the corn water requirement when com- pared to temperatures in the 60s. Water stress impacts corn yield the most during pollination, followed by grainfill and vegetative growth stages. Irrigation is an option to optimize yields. Checking your fields using probing methods is important as irrigation must be started early enough to fully benefit the crop and increase yield potential. Most irrigation systems cannot keep up with crop water demands during the later critical growth periods (VT to R3). The first priority for irrigation should be a 3-week period starting just before tassel (VT) and ending just after silking. Corn is less susceptible to water stress during later grain-development stages (R3). Soil water levels should be maintained to allow the crop to reach maturity (R6). Understanding Water Usage in Corn Water is acquired, used and lost through evapotranspira- tion (ET). In this process, water is removed directly from the soil surface to the atmosphere by evaporation and through the plant by transpiration. Plant transpiration is the evaporation of water from leaf and other plant surfac- es. For corn, evaporation often accounts for 20 to 30 per- cent and transpiration 70 to 80 percent of total ET over the length of a growing season. The amount of water retained for the plant is affected by the soil texture and organic matter. Soil serves as a reservoir to the plant, even though not all water is acces- sible to the plant. Water held by the soil between field capaci- ty and permanent wilting point is called ―plant-available wa- ter‖ and varies by soil texture. Ranges of available water at fine sandy soil are 0.7 to 1 inch, in- creasing up to clay which holds 1.8 to 2.4 inches. Pioneer® Field360™ Select software is an interactive, web-based subscription service that combines your field data with real-time agronomic and weather information  Track field by field Precipitation and GDUs using Field 360 Select  Scouting 101 with GPS located as-planted Products  On-The-Go organized field applied data Pioneer Field360 Notes pinpoints your field location via satellite imagery so you can record notes or photos on the spot.  Displays field boundaries for DuPont Pioneer custom- ers  Easy to use interface; available for iOS and Android™  Instantly map and organize data with notes and photos  Share your data from the field via email Contact your local Pioneer Professional for more Info! Role of Water in Corn Development Table 1. Estimated Corn Evapotranspiration and Yield Loss per Stress Day During Various Growth Stages Growth Stage Evapo- transpiration* (inches/day) % yield loss per day of stress (min-ave-max) Seedling to 4 leaf 0.06 --- 4 leaf to 8 leaf 0.10 --- 8 leaf to 12 leaf 0.18 --- 12 leaf to 16 leaf 0.21 2.1 - 3.0 - 3.7 16 leaf to tasseling 0.33 2.5 - 3.2 - 4.0 Pollination (R1) 0.33 3.0 - 6.8 - 8.0 Blister (R2) 0.33 3.0 - 4.2 - 6.0 Milk (R3) 0.26 3.0 - 4.2 - 5.8 Dough (R4) 0.26 3.0 - 4.0 - 5.0 Dent (R5) 0.26 2.5 - 3.0 - 4.0 Maturity (R6) 0.23 0.0 Adapted from Rhoads and Bennett (1990) and Shaw (1988). From: What Happens Within The Corn Plant When Drought Occurs? Joe Lauer, Uni- versity of Wisconsin-Extension, 2003. *Evapotranspiration is the total of the water used by the corn plant and water lost to evaporation. Image 1. Evapotranspiration is the sum of evaporation from the land’s surface + transpiration from the plant. Image: