Mark your calendar-- We will again collaborate with A & M Green Power for a Field Day/Harvest Clinic on Wednesday September 1^st.  We will start at 9:00 a.m. and end sometime early afternoon.

 

Here is a sampling of topics discussed this morning.

 

Year in review—Weather, Disease, Weed Control, etc.

Hybrid/Variety review—current data, placement, programs, pricing, etc.

 

We would have one combine on the floor of the seed building for demo and instruction

 

Harvest Tips for Proper combine settings

Hillco

Yield Monitors

Etc.

 

Those topics (among others) would lead us up to lunch---we have a hot dog/hamburger lunch

 

Then we have another combine pick some of the DKC 54-16 just East of the seed building to demonstrate proper settings, harvest loss and corrections to minimize it, etc.  IF we have a “normal” summer that corn should be in the mid 20’s for moisture given it’s planting date and maturity.

 

 

 

 

 

 

 

Source: High Plains Climate Center.

HOW DO I READ THIS? The above table demonstrates 1 planting date for corn between 2600-2800 Growing Degree Days (GDD) emerging on May 1^st and soybeans emerging on May15th at the Nebraska City reporting station.   EXAMPLE: In Nebraska City a 2800 GDD (113 RM) required hybrid emerging on May 1^st has accumulated 1234 GDD as of today (Monday July 5^th)   It is using .21 inches of water per day at the silking stage of development.

Corn Development--The recent heat and moisture have certainly kicked the crops into a growth phase the past couple of weeks. Most of the corn is at or approaching the 12 leaf

to 15 leaf stage V12--V15 and although the ear shoots (potential ears) were formed just prior to tassel formation (V5) the number of ovules (potential kernels) on each ear and the size of the ear are now being determined. The corn is now using up to 0.20" of moisture transpired through the plant on a daily basis.   Rainfall during this portion of development is key at these stages. Some areas have again dealt with hail and green-snap from recent storms. Plant injury (greensnap) at this stage of development in corn is most damaging to yield due to the vulnerability of fast growing plants make stalks weaker at the internodes as well as the plant puts more energy towards the reproductive development phases of growth rather than structural support. 

Stage                                       GDD (Growing Degree Days--base 50)        

Emergence                                                          120

2 leaf-V2                                                              200

V6—tassel initiation                                          475

V10                                                                        740

V14                                                                       1000

VT (tassel emergence)                                       1150

Silking                                                                  1400

R4 (Kernel dough stage)                                   1925

R5 (Kernel dent stage)                                       2450

R6 (physiological maturity—black layer)       2800

*courtesy of Hollinger (University of Nebraska)

 

 

 

 

 

Much of the corn will soon pollinate if it has not already started. Silking and pollen shed is the next critical phase of development in the life of a corn plant that will impact yield potential and results at harvest. Corn is a monoecious species meaning that both the male and female parts of the flower are present on the same plant.

The male part of the plant consists of the tassel, anthers and pollen. Each corn plant produces between two and five million spherical, yellowish-translucent pollen grains. Each of these yellow 'dust-like' pollen grains contains the male genetic material necessary for fertilizing the ovary of one potential kernel. If we multiply plants per acre by potential pollen grains per plant the number of pollen grains produced within a field of corn is astronomical. In general, it takes approximately 7 days for an individual tassel to finish shedding its pollen, although the majority of pollen may be shed during the second and third day of anther emergence. Due to variance within a field, it may take as long as 14 days for a field to complete pollen shed. Pollen is not shed when anthers are wet. Cool, cloudy, humid conditions also delay the onset of pollen shed. Extreme heat stress (100 F or greater) can kill corn pollen, but since pollen maturation and shed is spread out over a period of time ranging from several days to two weeks at least a portion of the pollen in the field will avoid the temperatures, mature, be shed and fertilize the ovules on the ear.

The silks are the functional stigmas of the female flowers. Every potential kernel (ovule) on an ear develops its own silk that must be pollinated in order for the ovary to be fertilized and develop into a kernel. Though we typically harvest only 400 to 600 actual kernels per ear, up to 1000 ovules develop on each ear.

Silk elongation begins 7 to 10 days prior to silk emergence from the husk. Complete silk emergence from an ear generally occurs within two to seven days. Typically, silks from the basal portion of the ear emerge first, while the tip silks generally emerge last. Silks remain receptive to pollen (and fertilization) for up to 10 days.

In order for a kernel to develop, pollen must be transferred to the silk (pollination) and the male gametes must make their way down the silk to combine with the female gametes in the ovule (fertilization). Successful pollination does not necessarily equal successful fertilization and kernel formation. Pollen grains can germinate anywhere along a length of exposed, receptive silk and many pollen grains will germinate and initiate a pollen tube but generally only one will fertilize the ovary.

Silk clipping by certain insects like the corn rootworm beetle not only removes viable silk tissue, but also injures a certain length of the remaining silk. Generally, silk length on these injured ear shoots must be at least 1/2 inch to ensure that a sufficient length of uninjured silk tissue is exposed for pollen germination to occur.

Less than ideal environmental conditions can delay flower development and pollination or result in variable flowering dates. The consequences of delayed or variable flowering dates are 1) the increased risk of poor or uneven kernel set due to insect or weather stress during the later flowering period and 2) greater variability in grain maturation within a field and the subsequent grain moisture at harvest. The greater risk of insect or weather stress during later flowering is due to the attraction of certain insects (e.g., Corn Rootworm) to late flowering corn.

 

Corn Rootworm feeding is currently underway in many areas across Eastern Nebraska. A number of producers are having corn rootworm control problems with insecticide treatments applied at planting. In some cases this has happened where a Rootworm traited hybrid has been used as well as where a non-rootworm hybrid is in place.    In these areas, recent wind damage from storms have goose-necked hybrids that had in-furrow insecticides applied at planting.   Insecticides, much like any other pesticides, need a certain amount of moisture in order to get the active ingredients into soil solution, making them available for pest uptake whether it is a weed, insect, etc. They can also leach through the soil profile if too much rainfall occurs. Now the corn is falling over and lodging with little or no recourse for control unless an aerial application can be watered in. Even then, the damage is already done. Producers plagued with annual rootworm problem might consider transgenic YieldGard rootworm hybrids in

VT3. VT3 offers transgenetic protection for European Corn Borer, Rootworm, and Roundup Ready protected. In addition, hybrids containing SmartStak, VTPro and VT Double Pro also contain transgenic rootworm protection. Contact Mac for more information.

Gray leaf spot (GLS) has begun to infect corn in Eastern Nebraska. About 1 month early this year by calendar. This shouldn’t be surprising given the wet humid weather of the current growing season. GLS thrives in wet conditions and high temperatures. High humidity and frequent rainfall provide the conditions necessary for infection to occur. GLS is more dependent on environmental conditions than on inoculum levels, but reduced tillage and no-till practices also may be a factor, since the pathogen survives readily in corn residue.

GLS lesions initially are pale brown or tan. They first appear on the lower leaves of corn plants as spores are wind-blown or rain-splashed from residue. Lesions may turn gray and move up the plant as the disease progresses. The lesions are ¼ to 2 inches long, narrow and rectangular. In susceptible hybrids, lesions may coalesce, causing extensive leaf tissue damage. If the right environmental conditions exist, GLS may kill entire fields prior to maturity.

High Humidity Invites GLS Infection--Fungal spores infect the host when relative humidity is high. Infection occurs when leaf surfaces are constantly wet for 11 to 13 hours and humidity in the leaf canopy is 90% or above for more than 12 hours. GLS often increases rapidly after summer rains, and is worst in low areas and river bottoms where heavy dew and morning fog keep leaves wet for extended periods. The GLS pathogen has a long latent period (up to 2 to 4 weeks) when no symptoms are evident. Once initial symptoms appear, disease potential already may have reached epidemic proportions.

Select Tolerant Hybrids for GLS--Producers should begin to control GLS by identifying fields where it’s a problem, then selecting resistant or tolerant hybrids for these fields. Aerial Fungicide application once a field has been diagnosed with a problem is a viable option for control. There are many fungicide choices on the market today. Consider selecting fungicides which offer both protective and curative measures of control. Fungicides such as Quilt, Quilt XL, and Headline all offer these measures of control.

 A number of DEKALB hybrids offer above-average tolerance to gray leaf spot. Rotating crops and/or incorporating residue on infected fields also are important steps to reducing GLS inoculum levels.

 

Soybean Development---The soybeans are between the V3 and V5 (third to fifth nodes) and are beginning to bloom. Not much is said about soybean development during the reproductive stages maybe because it is not as flashy as corn is during this stage. Although not as visible as corn, soybeans are now beginning to bloom, and visible pod set and fill are not far away. Physical stress to the plant from herbicide applications, water stress, physical injury from hail, etc. all play a larger role now than any other time of plant development in yield determination. Dependent on variety, a soybean plant has the ability to produce enough blooms to produce yields up to 250 bushels but, 75% typically abort. During the reproductive stage, a soybean plant (much like corn) will require an average of 0.25 inches of water per day. By eliminating any moisture stress during the critical pod set, the percent of pods aborted will decrease.

The soybean flower is self-pollinated which means that the pollen produced within a flower fertilizes the ovary (egg—pod) of that same flower. Unlike corn pollination, studies have shown that little if any cross-pollination occurs in a soybean field   Soybean flowers are often fertilized by the time they are visibly open and few pods are set by the first flowers. Flowering and pod set can last for up to six weeks, however, the majority occurs in a three week time frame.

 

 

 

Insect populations are once again going to pose issues for producers this summer.  Armyworm, Grasshoppers, European Corn Borer are all beginning to increase in population. In some areas, grasshoppers are beginning to approach economic levels of infestations (50-60% defoliation) in which a treatment is justified. European Corn Borer are also present in many non-treated/refuge fields. However, grasshoppers appear to present the largest threat of injury. Grass waterways, ditches, and field margins are where I have found the heaviest of infestations and as the summer wears on, more of them will migrate into the corn and soybean fields as their food source from the ditches etc. is exhausted.   Grasshoppers are best controlled when they are small. Spraying borders of fields, grass waterways and ditches when they are in the nymph stage of development is usually the best approach to gain adequate control. Once they become adult, insecticide rates increase as they need the added rates to control them once they become adults. Insecticides such as Warrior, Asana, Furadan 4F, and Lorsban 4E will provide control for most of these insects and are compatible with Roundup WeatherMax applications.