Expectations of Late Planted Soybeans

Mother Nature certainly has not done us any favors this growing season.  After a 21 day spell, we have seen rain almost every day since.  Due to all of the rain, saturated soils and poor conditions of crops, many producers are considering replanting soybean fields (if they have not already).

The first question on most minds is “How much yield should I expect from late-planted soybeans?”.  According to UK Extension Grains Specialist Dr. Carrie Knott, based upon a 6-year (2006 to 2011) study that examined two relative maturity groups (late group II and mid group IV) the most recent estimate of Kentucky’s soybean yield loss per day is: 0.50% yield loss per day for mid group IV soybean beginning May 9 and 0.42% yield loss per day for late group II soybean beginning April 20.

To calculate expected soybean yield, based upon planting date:
1.       Calculate the number of days after the optimal planting date
          a.       Optimal Planting Date
                i.      May 9 for mid group IV
                ii.      April 20 for late group II
2.       Calculate expected yield loss
          a.       Multiply the number of days past the optimal planting date by yield loss per day
          b.       Yield Loss per Day
                        i.      0.50% for mid group IV
                        ii.      0.42% for late group II
3.       Multiply average soybean yield by expected yield loss

Additional Considerations
When choosing a cultivar for July or August plantings consider one that is 0.5 to 1.0 relative maturity less than a full season cultivar.  This may help reduce the risk of frost damage in the fall, due to an early frost event. Full-season soybean cultivars range from 3.5 to 5.0 relative maturities in Kentucky.

Be aware that reducing the relative maturity of the soybean cultivar by more than about 1.0 relative maturity may increase the risk that the pods will be near or at the soil level. This is because the internode distances are typically reduced as planting date is delayed, which can have a much more dramatic effect on shorter relative maturities.                                

The calculations above for expected soybean yield assume “normal” weather conditions occur after planting. That means adequate precipitation occurs and no early frost.  If either we get an early frost, drought-like conditions, or other stress events occur, soybean yield may be markedly lower than estimated above.

On a different note, Southern Rust has been confirmed in Webster County.  It was found on one leaf in a variety plot by one of UK Extension Plant Pathologist Dr. Carl Bradley’s interns.  This is about 1 week earlier than when it was detected in KY last year.  Most hybrids are susceptible to southern rust.  Late-planted corn will be the most at risk.  If corn is beyond R3, then probably no need to consider spraying it with a fungicide.  Southern rust may still develop in fields that are beyond R3, and it may look really bad, but any yield reduction at that point in time would be small.  When scouting for Southern rust look for pustules appearing primarily on the upper leaf surface that are orange to light brown, round, and densely packed on the leaf surface.

For more information on late planting of soybeans or if you suspect your corn may have Southern Rust, contact the McLean County Cooperative Extension Office at (270)273-3690. Educational programs of the University of Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability or national origin.


Upcoming Events
July 29th Extension Blood Drive, 11am-4pm
July 30th Farm to Fork Dinner, 6pm at Myer Creek Park
August 4th Forestry Program, Noon
August 9th McLean Co. Beef Field Day, 9am at Cody Robertson’s Farm
August 10th Hay Testing Blitz
August 11th UK Hemp Field Day
August 11th CPH Sale

Farm to Fork Dinner

Be sure to contact the McLean County Extension Office at (270)273-3690 or stop by during office hours to purchase your ticket for $20.  Menu items are produced in McLean County and are a part of the KY Proud program.  There will be live entertainment and a silent auction.  Proceeds go to God's House of Hope. 

Conditions for Corn Diseases are Favorable

With all of the rain that has fallen over McLean County this month, conditions have become favorable for some foliar corn diseases.  The UK Plant Pathology Lab in Princeton has received samples from Western Kentucky of corn with northern leaf blight, gray leaf spot, common rust, and/or Diplodia leaf streak.  As of July 12, southern rust has not been detected in Kentucky however UK Plant Pathology Dr. Carl Bradley warns corn producers to be on the lookout for the following diseases:

Northern Leaf Blight
Northern leaf blight can be a major yield robber in susceptible corn hybrids.  Symptoms of this disease are observed on leaves as elliptical (“cigar-shaped”) lesions that have a light to tan-colored center.  Some hybrids may have excellent resistance to northern leaf blight, while others may be extremely susceptible.  It is important to know how susceptible a hybrid is to this disease to be able to determine the risk of disease occurrence and likelihood of a profitable foliar fungicide application.

This disease may be easily confused with Diplodia leaf streak, which also may appear as elliptical-shaped lesions on leaves.  Lesions of Diplodia leaf streak will contain black pin-sized structures known as “pycnidia” inside lesions, which can help distinguish it from northern leaf blight.  Diplodia leaf streak appears to still be a minor disease in Kentucky, and management of this disease is likely not needed at this time.

Gray Leaf Spot
Gray leaf spot is likely the most commonly-observed foliar disease of corn in Kentucky.  It is observed as rectangular lesions that occur on leaves.  Hybrids can vary greatly in their level of susceptibility to this disease, but no hybrid is completely resistant.  Conditions have been very favorable for gray leaf spot over the last several days.  On susceptible hybrids, expect that gray leaf spot will be very apparent within the next few days.  Disease progress can be “sluggish” with this disease at first, since it can take several days between the time of initial infection and the appearance of symptoms; however, severity can increase suddenly when conditions are favorable.

Common Rust
Common rust has been widely observed in the state for several weeks now.  In general, most yellow dent corn hybrids have an adequate level of resistance to common rust, and management of common rust with foliar fungicides in yellow dent corn hybrids is not generally needed.

Southern Corn Rust has been confirmed in Webster County.   Since most hybrids are susceptible to southern rust, it is important to be able to be able to differentiate southern rust from common rust.  The timing of southern rust’s appearance in Kentucky relative to corn growth stage is critically important in regards to risk of yield loss.  From Dr. Bradley’s research trials, research results showed the following (in general): if southern rust begins to appear after the R3 (milk) stage, yield loss caused by southern rust will be negligible (although disease levels can still appear to be very severe).
When making decisions about applying a foliar fungicide to corn keep in mind scouting observations, disease risk assessments, and economical considerations.  Also, remember that because of current weather conditions and the amount of precipitation we have had in McLean County in July, conditions are favorable for the development of corn diseases.

For more information on corn diseases, contact the McLean County Cooperative Extension Office at (270)273-3690.  Educational programs of the University of Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability or national origin.


Upcoming Events
July 28th UK Corn, Soybean & Tobacco Field Day, Princeton Research Station
July 29th Extension Blood Drive, 11am-4pm
July 30th Farm to Fork Dinner, 6pm at Myer Creek Park
August 4th Forestry Program, Noon
August 9th McLean Co. Beef Field Day, 9am at Cody Robertson’s Farm
August 10th Hay Testing Blitz
August 11th UK Hemp Field Day

Farm to Fork Dinner

Spotted Wing Drosophila and Small Fruit Production

Cornell University

Spotted wing Drosophila (SWD) is a serious invasive pest of soft-skinned fruits. SWD was first detected in Kentucky in 2012 and has recently been found in Daviess County. This fruit fly lays its eggs in soft-skinned fruits as they soften before harvest; this new pest not only causes issues for the commercial grower but the home gardener as well.

SWD attacks many different soft-skin fruiting crops, but historically the most serious damage has been to raspberries, blackberries, blueberries, and grapes. It also breeds in fruit of native wild plants like pokeweed, mulberries, wild blackberries, and nightshade.

The female SWD uses her serrated egg layer to cut into the skin of otherwise intact soft-skinned fruits to deposit her eggs. Each female deposits 7 to 16 eggs a day and up to 300 eggs during its lifetime. Eggs hatch in 2 to 72 hours, resulting in small larvae in harvested fruit. SWD will overwinter in Kentucky as it survives in states to our north and parts of Canada.

Here are some great tips for checking fruit and management of SWD from UK Extension Entomologist Ric Bessin:

Checking Fruit: When harvesting take the time to thoroughly look over each berry. Externally berries may look unifested but larvae may still be inside. If a berry is very soft, collapsing on itself, or is watery near the cap of the fruit, SWD larvae are most likely present. These berries should be discarded away from the field, and preferably bagged for disposal. We are not aware of any known risk to human health by ingesting SWD eggs and larvae.

Management: Refrigeration- Berries that have no visible damaged should be placed directly in the refrigerator. Placing the berries in the refrigerator will stop the development of the SWD if they are present, both hatched and unhatched. Freezing berries will kill SWD and holding berries at 34F for 72 hrs will kill most of the eggs and larger larvae.

Netting-  Mechanical control maybe an option for homeowners, as with many of the small fruit crops we often use netting to keep the birds from eating the berries. For the SWD the same concept applies except the netting must be a fine mesh, with opening of less than 1 mm. ProTekNet is a brand of netting that provides netting small enough (less than a 1mm square opening) that can exclude SWD, but spun bond row covers should work as well. Netting should be placed over the planting when the earliest berries begin to turn color prior to harvest. Netting may interfere with pollination of later raspberry flowers, but this maybe a sacrifice to save the rest of the crop. The netting must be secured along the ground to prevent any openings for SWD to enter. On larger plantings a structure might be installed to help support the netting and allow a person to pick underneath the netting. The netting will have to remain over the crop until harvest is finished.

Sanitation- It is also important to remove any damaged fruit from the field, as these fruits may contain SWD eggs and larvae. Overripe, damaged, or rotting fruit should be collected, placed in clear bags, and left in the sun.  Burial of infested fruit is ineffective as the larvae can emerge from depths of one foot or more.

If you suspect you have a spotted wing drosophila problem, or would like more information on SWD, please contact the McLean County Cooperative Extension Office at (270)273-3690.  Educational programs of the Cooperative Extension Service serve all people regardless of race, color, sex, religion, disability or national origin.

Upcoming Events
July 13th WKU Hemp Field Day
July 14th-16th Ag Festival
July 28th UK Corn, Soybean & Tobacco Field Day
July 29th Extension Blood Drive
July 30th Farm to Fork Dinner
August 4th Forestry Program
August 9th McLean Co. Beef Field Day
August 10th Hay Testing Blitz
August 11th UK Hemp Field Day

Summer Newsletter

Click the following link to read my summer newsletter:

https://issuu.com/caryhicks/docs/skmbt_c55216070511330/6?e=15773727/30000297