Keep an Eye Out for Stripe Rust in Wheat

Although there have not been any reports about finding stripe rust in Kentucky wheat, the disease is present in Arkansas, Louisiana, Mississippi, and Tennessee. Last night, a storm system rolled through west Kentucky from south to north, and stripe rust spores likely moved into the state. The cool weather will support infection, since the disease likes cool weather. This situation is not cause for great alarm, primarily because temperatures should warm pretty quicky and this will slow further development. Still, some fields might be at risk and it is, therefore, a good idea to scout your wheat throughout the heading period to discern if a rust-targeted fungicide spray is needed. If you choose not to scout and wait until early flowering to apply a fungicide targeting Head Scab, stripe rust may not be adequately controlled.

This is really just a "heads up"; NOT a call to general action. So far, wheat diseases are pretty minimal in KY.

Armyworm Flight Begins

Doug Johnson, Extension Entomologist

 

  Figure 1. Armyworm moth Spring must really be here as armyworm (aka true armyworm) moths have taken flight. Only a few moths have been captured thus far, but it does signal the beginning of insect season in the field crops and the current year’s capture is in line with the outbreak year of 2008. It is still too early to get real excited but important enough to be aware.

In Kentucky, armyworm can be an important pest of corn and wheat. Corn products that contain a Bt trait that provides protection from caterpillar feeding (See: Insecticide recommendations for corn:   http://pest.ca.uky.edu/EXT/Recs/ENT16-Field%20corn.pdf, pages 6-7) will likely be protected. However, non-Bt types including field corn refuge, popcorn, food-grade corns, and sweetcorn along with wheat will be at risk.

We are several weeks from any damage caused by armyworm as the adult moth is not the damaging stage. Monitoring this stage just gives us a “biofix” or heads-up that the pest is about. It is the caterpillar in which we are interested. You may want to check the flight graphs each week for the progress in this population. These may be found at:  http://www.uky.edu/Ag/IPM/ipm.htm. It only takes a few seconds to check and this can give you an idea of the relative risk of this pest for this season. On the graph you can see displayed the current year’s capture (green), the rolling five-year average (blue), and known populations that have resulted in outbreaks (red and/or black) This will give you a rough estimate of the current year’s relative risk. As these graphs represent moth flight, the relative population size can be seen before the damaging stage, the caterpillar, develops.

If populations appear to be indicating an elevated risk, I will use a temperature-based model to predict when the caterpillar stage will appear. This model will NOT predict which fields will be infested. One must scout fields to know if the armyworm is present, but the model will provide an estimate of when the field should be scouted. Remember, the model predictions will be based on the capture and temperatures at the UK-REC in Princeton (Caldwell Co.) KY. In areas to the south and southwest of the UK-REC caterpillar development will be ahead and areas to the north and northeast of the UK-REC will be a bit behind.  I will post, and you may review, the results of these model runs each week in this publication. So, if you are the pest manager for wheat or corn this spring, keep yourself tuned to this outlet for “Early Warnings” about this pest.

Wheat Fungicide Efficacy Chart

Chad Lee, Extension Agronomist, University of Kentucky

A new wheat fungicide efficacy chart is available for producers and crop consultants as wheat fields are scouted this spring. The North Central Regional Committee on Management of Small Grains Diseases, which includes Dr. Don Hershman, compiled the data based on field research across the region. All efficacy values are based on labeled rates of each product. Diseases listed on the chart include Powdery Mildew, Stripe Rust, Head Scab and others. A list of the more common wheat diseases in Kentucky can be accessed here.

Products in the chart include strobilurins, triazoles and mixes of both. Products are listed by the active ingredients and the most common product name. Efficacy ratings range from "E' or excellent to "NR" for not recommended and "NL" for not labeled. The table also includes harvest restrictions.

If you have questions about fungicides, fungicide efficacy or wheat diseases, contact your county extension office.

Fungicide Efficacy for Control of Wheat Diseases

Fusarium Head Blight Prediction Center and Assessment Tool Upgraded

Hot, dry conditions last spring resulted in almost no Fusarium Head Blight (FHB) occurring in Kentucky’s wheat crop.  It is anyone’s guess how severe FHB will be this year, but the time will soon be upon us to decide if spraying a fungicide for FHB (and deoxynivalenol [DON] in grain) is necessary.  As a result, I just wanted to bring your attention to the recently revamped FHB Prediction Center and Risk Assessment Tool webpage (http://www.wheatscab.psu.edu/). Both the appearance of the webpage and its functionality have been substantially improved. Additionally, a mobile version of the tool is available. The site should automatically go to the mobile version if you try to access it from a smart phone or other mobile device.

The purpose of the Assessment Tool is to provide growers and consultants with a FHB risk assessment leading up to and including the all-important time of early flowering (anthesis). This is the time when fungicides targeting FHB/DON must be applied in order to be effective. The Prediction Center also includes extensive and helpful information on how to use the tool (including several important limitations), as well as information on the disease prediction models used.

I have found the tool to be very useful and mostly accurate.  It is important to note that the tool does not address events after anthesis that impact FHB and DON during grain development. The developers of the tool specifically chose to exclude this period because fungicides applied after anthesis will not control either FHB or DON.  In other words, the FHB Assessment Tool is to be used as a fungicide decision aid and not a final outcome predictive tool.  

If you are interested in signing up for text and/or email alerts for specific states and/or regions of the country, go to http://www.scabusa.org/fhb_alert.php and sign up.

Refuge Requirements for Transgenic Insect Control Traits in Field Corn.

Doug Johnson, Extension Entomologist

2013 is one of those transitional years for changes in refuge requirements for transgenic control traits in field corn. Several changes have been made over the last several years and one can expect for changes to continue as we (likely) move away from large structural refuges and toward refuge in a bag. Generally the % of refuge seed (those seed without transgenic insect control traits) has dropped from 20% to 10% or even 5% depending upon the traits included and the company. In addition those products that  require separate structural refuges (usually as blocks or a series of rows) is giving way to the inclusion of not traited seed within the bag of traited seed; the so called refuge in a bag (RIB). The result is a somewhat confusing situation where products are available that contain different refuge requirements. Obtaining the desired corn genetics which contains the correct transgenic traits to control the likely pests and planting this with the correct refuge in the proper location can be very confusing.

If you follow the link:    http://pest.ca.uky.edu/EXT/Recs/ENT16-Field%20corn.pdf ,    it will take you to ENT-16, the 2013 Insecticide Recommendations for Corn. On pages 6 and 7 of this publication you will find a Bt Trait Table that list the various packages of transgenic insect control traits by trade name, insect toxins, and the event used to include the toxins in the corn plant. This table also includes relative ratings for how well these toxin packages works against the most common and important insect pests of field corn in Kentucky. Additionally, the type (block vs RIB) of refuge and the percent of non-traited seed required to be in the refuge.

In Kentucky producers can expect their greatest and most consistent return on investment from protection against European corn borer (ECB) and southwestern corn borer (SWCB). Traits for control of western corn rootworm (WCRW) are not needed nor recommended in corn fields that are rotated with non-corn crops. Corn that is not rotated (continuous corn) should be planted with products that contain more than one or “stacked” western corn rootworm (WCRW) traits. In any case products containing only the Cry3Bb1 corn rootworm toxin should not be planted in non-rotated corn. Though not yet noted in Kentucky, this is the trait for which resistance has been show in several states to our north. So far this has only occurred in corn planted in the same field for three successive years and using only the Cry3Bb1 trait for protection against western corn rootworm. Black cutworm (BCW), corn earworm (CEW) and fall armyworm (FAW) infestations are very much dependent on the growing year. Very early planting may benefit from BCW traits while very late plantings will likely benefit from control of corn earworm and fall armyworm.

Wheat Yield Contest Forms Available

Chad Lee, Extension Agronomist, University of Kentucky

The 2013 Kentucky Extension Wheat Yield Contest forms are now available online. There are no major changes in the contest from 2012. Entries must be postmarked by July 24, 2013 to be eligible.


Any person who produces at least 10 acres of wheat in Kentucky is eligible to enter the contest. A minimum of 3 acres must be harvested.

Last year, the highest overall wheat yield was 112.07 bu/acre by Double P Farms in a tilled field. The record yield remains a no-tillage entrant from Chad Elkins of 130.61 bu/acre in 2008. The contest first began recognizing no-tillage and tillage divisions in 1997. Since then, the overall high yield has been a tillage entry eight times and a no-tillage entry seven times. Over the past five years, the average highest yield has been 106.71 bu/acre for tillage and 107.61 bu/acre for no-tillage.

For more information about the Kentucky Extension Wheat Yield Contest, contact your county extension agent.

Key Winter Wheat Stages

Chad Lee, Extension Agronomist, University of Kentucky

Wheat at 70 to 100 tillers per square foot is considered an adequate stand.Wheat at the lower end of the range would be a candidate for a low rate of fertilizer nitrogen applied at Feeke's 3, which normally occurs in late February or early March. Wheat above 100 tillers per square foot are at an excessive population and should not have any nitrogen added at Feeke's 3.Instead, a single application should be made a little later at Feeke's 4-5 (around mid-March).

Table 1. Key numbers in wheat.

Crop Stage	Number	Units
Emergence	25	plants/sq.ft.
Tillering	70 to 100	tillers/sq.ft.
Heading	60 to 70	heads/sq.ft.
Heading	35	kernels/head

Use Table 2 as a guide for measuring 1 square foot in a wheat field.

Table 2. Length of Row Needed for One Square Foot.

Row width (inches)	Length of row needed for 1 sq ft (inches)
4	36
6	24
7	20.6
7.5	19.2
8	18
10	14.4
15	9.6

If a split application of nitrogen is to be used, then the first application is applied at Feeke's 3 and the second is applied at about Feeke's 5 (in mid- to late-March). Total N (from both applications) should be in the range of 80 to 120 lbs/acre for no-tillage wheat and about 60 to 100 lbs/acre for tilled wheat.

For more information on stand counts or nitrogen management.