Traill County Ag Alert Newsletter
June 5, 2008
RAINFALL & GROWING DEGREE DAYS (GDD)
The rains have continued and since May 28th according to NDAWN,
Mayville has received 0.89 inches, Hillsboro 1.28 inches and Galesburg 0.63
inches of rain.
The GDD’s for wheat is at 715 as of June 5 indicating that the wheat planted as of May 1 is in the 4 leaf stage and tillering. The GDD’s for corn is at 299 or 82 behind 2007.
IT’S DECISION TIME FOR
SPRING WHEAT PRODUCERS
Wheat fields are nearing the 4-5 leaf stage. Weather, varietal disease
resistance levels, and the type of crop residue in the field are important
factors to consider when determining the potential for disease development and
whether a fungicide application is needed.
Tan spot is a wheat leaf disease caused by the fungus Pyrenophora teres-repentis. The pathogen survives each winter on aboveground wheat residue and produces spores that infect subsequent wheat crops. Epidemics are common in the RRV during the crop’s early growth stages if certain conditions exist.
Producers are encouraged to scout for tan spot if:
• a susceptible variety of
wheat is grown
• wheat is planted into last year’s wheat residue
• the weather remains wet for extended periods
While some tan spot lesions have been identified in the RRV, with the recent rains NDAWN indicates that the conditions have been right for infection 5 of the last 8 days.
Stripe rust. This disease has been detected on a regular basis during the last few years. Cool temperatures (50-60F) and morning dews promote plant infection and rapid disease development. Luckily, spores of the fungus Puccinia striiformis must be transported by wind from southern states each growing season. The extended cool, spring-like weather we’ve been experiencing will support stripe rust development if spores arrive in our area. Reports from the south indicate that hot spots of inoculum are being produced in Illinois, but other states to our south have normal to light infestations of the disease. This disease is aptly named. Rust pustules appear on leaves in thin, longitudinal stripes. In severe disease cases, pustules can also be found on the glume tissues that cover and protect developing kernels. Disease severity is known to develop rapidly on winter wheat and susceptible spring wheat varieties. Most spring wheat varieties have some resistance to the disease and are not as severely affected as winter wheat.
Fungicide application is an effective means for controlling the disease. The application must be timely to prevent leaf damage caused from erupting pustules. Upper-canopy leaves are important tissues for supporting photosynthates which are used to fill kernels. Protection of upper leaves is key in maintaining production goals.
CANADA THISTLE ON CRP PLOT TOUR – JUNE 25
All are invited to attend a plot tour to view and discuss weed management on
CRP land. The plot tour is 5 miles north of Ada on Highway 9, turn East on
County Road 19 travel 4 miles and turn north on 300th Street for 1.25
miles on Don Andersen Farm.
University and industry speakers will provide demonstrations and discussions on Canada Thistle Management, Brush Control, CRP Re-Enrollment and other topics important to CRP land managers.
The tour runs from 9 a.m.-noon and lunch will be provided. For more information contact: Carlyle Holen @ 218-281-8691 or Jolene Pedersen @ 218-281-8027
CUTWORM ACTIVITY CONTINUING
Field reports are still coming in on cutworm damage to crops - pulse crops,
sugarbeets, sunflowers, and crops in CRP. Late season cutworms are just starting
to become active and still small (<½ inch). These small caterpillars have about
2-3 weeks of feeding before they become mature. The recent cool weather will
delay cutworm development. If cutworms are above action threshold or
significantly reducing plant stands, insecticide should be applied in the
evening, when cutworms are actively feeding.
There are many weeds starting to popup in fields now and early season weed spraying is in full swing. Many of the pyrethroid insecticides used for cutworm control is compatible with tank mixing with herbicides. However, check labels for compatibility or do a simple ‘jar test’ mixing the insecticide and herbicide. With the recent rains, insecticides need a minimum of 3-4 hours of drying time to be rain-fast and provide effective residue for insect control.
CROP SCOUTING
When scouting a field, enter the field at
different points during the summer so the sampling locations will reflect the
whole field. It is important to stop and inspect the crop at multiple locations
in the field away from the head-lands. In order to obtain a good record during
the season write down the observations about weeds, insects and diseases found,
preferably on a map or a drawing with the field boundaries. If problems only
occur in small areas you can consider spot application of pesticides instead of
applying over the whole field. As Global Positioning Systems become more
affordable it may be a good idea to write down the global coordinates of problem
areas. Later in the season a repeat visit to the exact same location can be
made.
When scouting, cover as much of the field as possible. Try to cover areas of the field where indications of a pest are likely. For instance grassy areas at field margins might be the place to find grasshoppers. Weed and insect management decisions are generally evaluated on a plant or insect per square yard basis. Know the density of the pest in order to determine if an economic threshold is reached.
It is important to evaluate the plant stand early in the season. To determine plant stand, make at least 10 random stand counts in an area where the stand is reasonably uniform. Use a tape measure and mark off 1/1000 of an acre for each count.
The lengths of rows equal 1/1000 of an acre with different row widths is indicated below.
30
inch row - 17 feet and 5 inches
20 inch row -
26 feet and 2 inches
15 inch row -
34 feet and 10 inches
10 inch row -
52 feet and 3 inches
7 inch row -
74 feet and 9 inches
Multiply stand count per length of row by 1000 to obtain stand per acre.
Another method used to evaluate plant stands in drilled or narrow row canola, soybean, or other crops is to use a hula hoop. Throw the hoop randomly into the field and count the number of plants inside the hoop. Multiply the number of plants by the multiplication factor as indicated below to obtain the plant population.
Hoop Diameter in Inches Multiplication Factor
30 8,900
32 7,800
34 6,900
36 6,200
38 5,500
Use the average of at least five to ten observations per field to estimate the plant stand. For instance, if a 30 inch hoop is used and 17 plants are counted the stand per acre would be 17 x 8,900 = 151,300 plants per acre.
When the plant stand is low and uneven record the possible causes so next year corrective action can take place. It is very difficult to determine a cause for poor stands at the end of the season. The recorded plant stand will provide baseline information for the remaining of the season. Drought, disease, hail and other factors may reduce the plant stand during the season, but you would not be able to document these plant stand losses without an early season stand count number. Good scouting methods, proper identification of problems and diligent recording of the findings will greatly assist in making the correct management decisions.
MAXIMIZING GLYPHOSATE
ACTIVITY IN GLYPHOSATE-RESISTANT CROPS
The goal of all growers is to maximize glyphosate activity whenever it is
applied to glyphosate resistant crops. These goals maximize profitability and
weed control, and reduce the risk for herbicide resistance. Below are the most
important management strategies for improving glyphosate activity. For
additional information, consult pages 68 and 69 in the 2008 North Dakota Weed
Control Guide.
1. Apply glyphosate to
small (< 4”) annual weeds.
2. Apply glyphosate to
perennial species in the bud to early-flowering stage of development.
3. Apply the most effective rate for the most difficult to control
species in the field. For many annual species the minimum rate of glyphosate
should be 0.75 pounds acid equivalent/acre (lb ae/A). Species such as
lambsquarters, velvetleaf, wild buckwheat, common ragweed, common mallow,
smartweeds, horseweed/marestail, and waterhemp can be difficult to control with
glyphosate. Consider using the maximum single-use rate of glyphosate for these
species, especially if a reduction in control has been observed over time. Rates
of glyphosate greater than 0.75 lb ae/A usually improves control of perennial
species, compared to lower rates. Multiple glyphosate applications can also
improve control of perennial species.
4. Always add ammonium
sulfate (AMS) to glyphosate mixtures. Ammonium sulfate should be added at a
minimum of 4 pounds per 100 gallons of spray mixture (lbs/100 gal) for most of
North Dakota. Add additional AMS if water hardness is greater than 1600 ppm.
5. Allow at least a 6
hour rainfast period for all glyphosate formulations for maximum activity. A
shorter rainfree period can be acceptable for the most susceptible species.
Lambsquarters control is usually reduced if the rainfree period is less than 6
hrs.
6. Apply glyphosate
during the warmest and most humid weather conditions to maximize activity.
7. Most glyphosate
formulations include nonionic surfactant (NIS) at a high enough concentration
for maximum activity. However, some glyphosate formulations do not include NIS.
For these formulations add a quality NIS product at 0.5 to 1.0 % v/v. Some
weed species, especially lambsquarters, may be more effectively controlled with
the addition of NIS at 0.25 %v/v to “loaded” glyphosate formulations. Know
which glyphosate formulations prohibit the use of additional NIS.
8. Glyphosate activity
is influenced by the time of day of the application. Maximum activity occurs
between 10:00 a.m. and 4:00 p.m. Velvetleaf and common ragweed control may be
the most negatively affected by the time of the glyphosate application.
9. Application of
glyphosate in low water volumes improves glyphosate activity. However, when
spraying large weeds and/or dense weed canopies, higher spray volumes usually
improves glyphosate activity.
10.Glyphosate is
strongly and irreversibly absorbed to clay particles and organic matter.
Therefore dust of any amount, especially initiated by the wheels of the
sprayer, will cause a reduction in glyphosate activity. The best methods for
decreasing this problem are to drive slower and put higher volume nozzles in the
boom over the wheels. These solutions will not completely solve the problem and
growers must remember to not apply greater than the single-use rate of
glyphosate when using the higher volume nozzles.
11.When mixing other herbicides with glyphosate, add the most effective adjuvant for that herbicide being added. This strategy will maximize the activity of the herbicide being added to the glyphosate mixture. If the alternative herbicide recommends the addition of an oil adjuvant for maximum activity, add only Superb HC or Destiny HC at 0.5 %v/v to the mixture with glyphosate. The reason for this is that most oil adjuvants antagonize glyphosate activity.
Go to Traill County Agriculture Program Page
Traill County Extension Office
P.O. Box 730
Hillsboro, ND 58045
701-636-5665 or toll-free1-877-843-6383
Contact us at: NDSU.Traill.Extension@ndsu.edu