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Ohio State University Extension

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C.O.R.N. Newsletter: 2017-11

  1. Adult cereal leaf beetles found, look out for larvae in wheat soon

    cereal leaf beetle larva

    Adult cereal leaf beetles have been spotted in a few areas across OH.  Adults do not normally cause yield loss in wheat, but, if present in high numbers, they could lead to heavy larval infestations over the next few weeks.  Adult cereal leaf beetles are shiny, metallic blue and orange and are best found using a sweep net or by walking the field.  Cereal leaf beetle larvae are small, gray and moist, resembling bird droppings, and are easily found on wheat leaves.  Foliar damage on wheat occurs when larvae feed and strip the leaves, causing a “frosted appearance.”  Economic threshold of cereal leaf beetle larvae averages 1 per stem.  As wheat matures, growers should carefully inspect their fields for the presence of cereal leaf beetle larvae. 

    cereal leaf beetle adult

  2. Corn Emergence and Heat Unit Accumulation

    emerged corn
    Author(s): Peter Thomison

    Warm, dry weather promoted significant corn planting last week, especially in western Ohio. According to USDA/NASS estimates (https://www.nass.usda.gov/Statistics_by_State/Ohio/Publications/Crop_Progress_&_Condition/2017/cw1817oh.pdf) as of April 30, 42 percent of the corn crop in Ohio has been planted. However, much cooler temperatures forecast this week may slow germination and emergence of these late April plantings.

    Corn typically requires 100 to 120 growing degree days (GDDs) to emerge (but emergence requirements can vary from 90 to150 GDDs). To determine daily GDD accumulation, calculate the average daily air temperature (high + low)/2 and subtract the base temperature which is 50 degrees F for corn. If the daily low temperature is above 50 degrees, and the high is 86 or less, then this calculation is performed using actual temperatures, but if the low temperature is less than 50 degrees, use 50 degrees as the low in the formula. Similarly, if the high is above 86 degrees, use 86 degrees in the formula. The high cutoff temperature (86 degrees F) is used because growth rates of corn do not increase above 86 degrees F. Growth at the low temperature cutoff (50 degrees F) is already near zero, so it so it does not continue to slow as temperatures drop further.

    If it takes a corn hybrid 110 GDDs to emerge, and daily high and low temperatures average 70 and 50 degrees following planting, 10 GDDs accumulate per day, and corn should emerge in about 11 days (110 GDDs to emerge/10 GDDs per day = 11 days). However, if daily high and low temperatures are cooler, averaging 60 and 45 degrees after planting, 5 GDDs accumulate per day, and it may take more than 3 weeks (110 GDDs to emerge/5 GDDs per day = 22 days) for corn to emerge. In past years, corn planted in mid to late April has taken as much as 3 to 4 weeks to emerge in many fields.

    Temperatures at or below 50 °F may also impact final plant stands, especially when there is protracted period of low temperatures following planting. When such conditions occur, stand loss is usually greater on heavier and poorly drained soils.

    Given the relationship between GDD accumulation and emergence, we should not be too surprised that it sometimes takes early planted corn up to 3 or more weeks to emerge. Seedling emergence is dependent on soil temperature and air temperature. Also, keep in mind that estimates of emergence based on GDDs are approximate and can be influenced by various factors including residue cover, tillage, planting depth, hybrid differences, and soil organic matter (soil "color") and moisture content.

  3. Wet Weather and Evaluating Soybean Stand

    Saturated soils after soybean planting can cause uneven emergence and stand reductions of varying extent depending on the stage of the soybean plant and other environmental factors including temperature and duration of saturated conditions. Additionally, increased disease incidence may further reduce plant stand.

    Saturated Soil Prior to Germination: While soil moisture is necessary for germination, soybean seeds will not germinate when soils are saturated because oxygen is limiting.

    Saturated Soil During Germination: Saturated soils during soybean germination may cause uneven emergence. In a laboratory study, soybean germination was reduced by ~15% after only one hour of flood conditions (Wuebker et al., 2001). After 48 hours of flood conditions, soybean germination was reduced 33-70% depending on when imbibition (seed taking up water) began relative to the flooding conditions. Practically, for Ohio, this means if soybean seeds were further along in the germination process when flooding occurred, the seeds will be more susceptible to flooding stress.

    Evaluate Stand: If soybeans were planted shortly before heavy rainfall, it is important to evaluate soybean stands in the next couple of weeks. To quickly estimate stand, count the number of plants in 69’8” of row for 7.5-inch row spacing, 34’10” for 15-inch row spacing, or 17’5” of row for 30-inch row spacing. These counts represent 1/1000th of an acre (i.e., 120 plants in 7.5-inch row spacing = 120,000 plants/acre).

    Keep in mind, the effect of plant population on yield is very small over the normal range of seeding rates. At this time of the year, final populations of 100,000 to 120,000 plants/acre are generally adequate for maximum economic return. For example, in our seeding rate trials in Clark County, 100% yield (77 bu/acre) was achieved with a final plant stand of 125,000 plants/acre. However, 95% yield (73 bu/acre) was achieved with only 77,000 plants/acre. (This trial was planted the second half of May in 15-inch row width.)

    Source:

    Wuebker, E.F., R.E. Mullen, and K. Koehler. 2001. Flooding and temperature effects on soybean germination. Crop Sci. 41:1857-1861.

  4. Impact of recent heavy rains on corn - ponding and flooding

    Author(s): Peter Thomison

    Heavy rains over the weekend resulted in saturated soil conditions across much of the state. Excessive rainfall in some areas resulted in localized ponding and flooding of corn. According to the USDA/NASS  (https://www.nass.usda.gov/Statistics_by_State/Ohio/Publications/Crop_Progress_&_Condition/2017/cw1817oh.pdf) “locally heavy amounts fell in Southwest Ohio, drowning out some recently planted fields.” If the ponding and flooding was of a limited duration, i.e. the water drained off quickly within a few hours, the injury resulting from the saturated soil conditions should be minimal.

    The extent to which ponding injures corn is determined by several factors including: (1) plant stage of development when ponding occurs, (2) duration of ponding and (3) air/soil temperatures. Prior to the 6-leaf collar stage (as measured by visible leaf collars) or when the growing point is at or below the soil surface, corn can usually survive only 2 to 4 days of flooded conditions. Since most of the corn that’s been planted so far is not beyond the VE stage, it’s especially vulnerable to damage from ponding and saturated soil conditions. The oxygen supply in the soil is depleted after about 48 hours in a flooded soil. Without oxygen, the plant cannot perform critical life sustaining functions; e.g. nutrient and water uptake is impaired, root growth is inhibited, etc. If temperatures are warm during ponding (greater than 77 degrees F) plants may not survive 24-hours. Cooler temperatures prolong survival so the cooler than normal forecast this week may limit injury resulting from saturated soil conditions. Once the growing point is above the water level the likelihood for survival improves greatly.

    Even if ponding doesn't kill plants outright, it may have a long term negative impact on crop performance. Excess moisture during the early vegetative stages retards corn root development. As a result, plants may be subject to greater injury during a dry summer because root systems are not sufficiently developed to access available subsoil water. Ponding can also result in losses of nitrogen through denitrification and leaching. Even if water drains quickly, there is the possibility of surface crusts forming as the soil dries that can impact the emergence of recently planted crops. Growers should be prepared to rotary hoe to break up the crust to promote emergence.

    For corn that’s emerged check the color of the growing point to assess plant survival after ponding. It should be white to cream colored, while a darkening and/or softening usually precedes plant death. For corn not yet emerged, evaluate the appearance and integrity of seeds or seedlings that have yet to emerge (likely rotting if discolored and softening). Look for new leaf growth 3 to 5 days after water drains from the field.

    Disease problems that become greater risks due to ponding and cool temperatures include pythium, corn smut, and crazy top. Fungicide seed treatments will help reduce stand loss, but the duration of protection is limited to about 10-14 days. The fungus that causes crazy top depends on saturated soil conditions to infect corn seedlings. There is limited hybrid resistance to these diseases and predicting damage from corn smut and crazy top is difficult until later in the growing season. However, the economic impact of these latter two diseases is usually negligible.

    For more information on the impact of saturated soil conditions on corn, check out the following article written by Dr. Joe Lauer at the University of Wisconsin - Lauer, R.L. 2017. Flooding effects on corn. Univ. of Wisconsin [On-Line]. Available at: http://corn.agronomy.wisc.edu/Management/L038.aspx [verified 5/1/2017].

  5. First Cutting of Forages is Fast Approaching

    Haybind in grass
    Author(s): Mark Sulc

    The warm temperatures this spring have stimulated growth of hay crops in Ohio and they are well ahead of normal development for early May. The only exception is where spring freezes significantly damaged the crop a few weeks ago. But for most stands, timing for first harvest of high quality forage is coming earlier than normal. Below are the optimal neutral detergent fiber (NDF) targets for high quality forages:

    Forage NDF for high producing and early lactation dairy cows
    Legumes: <44 (<42% is ideal)
    Grasses: < 53% (50% is ideal)
    Mostly legume mix: 42 to 45%
    50/50 Mix: 44 to 48%
    Mostly grass mix: 46 to 49%

    Pure grass stands should be harvested in the late boot stage just before the heads start to peek out. If any heads can be seen, the NDF is probably 55%, past the optimal for dairy cows.

    The neutral detergent fiber (NDF) content of pure alfalfa stands can be estimated quickly and easily based on the stage of the most mature stems and length of the tallest stems. Last week the alfalfa in central Ohio was near 32% NDF already. This method is explained in detail in the factsheet “Estimating Alfalfa Fiber Content in the Field” located on the new forages website (https://forages.osu.edu/forage-management/harvest-storage).

    A timely first and second cutting is critical for high quality forage. Fiber accumulates faster in the first two growth cycles in May and June than it does later in the summer. So for high quality forage, take your first and second harvest early if at all possible.

    Later in the summer (July into August) you can extend the cutting interval because the quality decline with delayed cutting is much less then than it is this time of the year.

    An exception to the above rule of timely first cutting is for forage stands that suffered significant injury this winter or from spring frosts. Those stands should be allowed to recover longer this spring and get into the bloom stage to build up energy reserves. Use that forage for animals having lower nutrient requirements.

    If high quality is not such a concern, a later first harvest will provide more yield. For beef cows or other animals with lower nutrient requirements, you can harvest forage in the heading (grass) or flower (legumes) stages for adequate quality. But don’t get too comfortable waiting. Watch for harvesting weather windows, because forage quality changes fast this time of year.

  6. Some Options for Organic Producers with Alfalfa Weevil

    Alfalfa Weevil
    We have been getting a number of reports about alfalfa weevil damage recently.  A recent newsletter article reviewed basic scouting and management advice (https://agcrops.osu.edu/newsletter/corn-newsletter/2017-09/alfalfa-weevil-early-season-pest).  However, organic producers face a particular challenge in managing this pest due to the limited number of products available for rescue treatment.  Potential options for Ohio organic producers are Pyganic (an organic pyrethrum) at 4.5 oz – 17 oz / acre and  Entrust (a spinosad) at the higher rate of 1.25 oz/acre.  We have not tested these products, but a University of California study found Entrust at the high rate to be moderately effective for alfalfa weevil control.  There is also a Bt product called beetleGONE! Ag (http://www.phyllombioproducts.com/agriculture.html) that has shown some efficacy in a USDA-ARS trial in Montana.  If the weevil infestation is above the action threshold, we recommend treatment even with a high cost product. Why? In the past we have known organic alfalfa producers who lost most of their entire year’s crop as a result of weevil feeding in the spring. If weevil pressure is heavy, the first crop will be lost (unless it is cut before severe defoliation occurs).  The weevil can then survive on the stubble and feed on the crown buds, preventing the crop from regrowing, to the point where the stand never truly recovers during the summer.  Whether organic or not, producers should be careful and attentive to weevil infestations as severe damage can happen quickly.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.

Contributors

Beth Scheckelhoff (Educator, Agriculture and Natural Resources)
Chris Zoller (Educator, Agriculture and Natural Resources)
Ed Lentz, CCA (Educator, Agriculture and Natural Resources)
Elizabeth Hawkins (Field Specialist, Agronomic Systems)
Eric Richer, CCA (Field Specialist, Farm Management)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Jason Hartschuh, CCA (Field Specialist, Dairy & Precision Livestock)
John Barker (Educator, Agriculture and Natural Resources)
Lee Beers, CCA (Educator, Agriculture and Natural Resources)
Les Ober, CCA (Educator, Agriculture and Natural Resources)
Mark Badertscher (Educator, Agriculture and Natural Resources)
Mike Estadt (Educator, Agriculture and Natural Resources)
Mike Gastier, CCA (Educator, Agriculture and Natural Resources)
Pierce Paul (State Specialist, Corn and Wheat Diseases)
Sam Custer (Educator, Agriculture and Natural Resources)
Sarah Noggle (Educator, Agriculture and Natural Resources)
Wayne Dellinger, CCA (Educator, Agriculture and Natural Resources)

Disclaimer

The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

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