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Agronomy


Soybean Cyst Nematode: Public Enemy #1 for Soybeans

Soybean Cyst Nematode (SCN) causes more economic damage than any other pest in U.S. soybean fields, costing the U.S. producer more than billion annual...

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Soybean Cyst Nematode (SCN) causes more economic damage than any other pest in U.S. soybean fields, costing the U.S. producer more than billion annually. Many producers are losing 15-30 percent of their yield to SCN without any above-ground symptoms. SCN has spread to almost all of the Midwest which leads some soybean experts to say there are only two types of soybean fields: those that have SCN or those that will get SCN!

The Soybean Cyst Nematode is a parasitic, microscopic roundworm that invades the soybean root’s vascular system as a juvenile. The female nematode stimulates a specialized feeding cell to form in the root and the nematode feeds from the cell, sapping the plant of nutrients and disrupting water uptake effecting plant growth. The female forms a tough egg sack (cyst) filled with 50-200 eggs that erupts through the root surface forming the white or yellow cyst on the soybean roots of infected plants. There can be 4-6 cycles of nematode development during a growing season, with a cycle completed in 24 days under warm temperatures.

IDENTIFY THE PROBLEM

The easiest method to check for SCN infestation is to check soybean roots from late June until mid August by digging the plant out of the soil with a hand spade and gently removing the dirt from the roots by shaking or by gently swirling in a bucket of water. Infected plants will have small white or yellow cysts about the size of a pin head on the root surface (considerably smaller than the nitrogen nodules). A soil sample can also be used to identify and quantify SCN infection. Collect the sample by normal soil sampling techniques mixing many cores due to the random distribution of the nematode in the soil and then send the sample to a qualified lab.

MANAGEMENT

Using resistant varieties is the best method of managing nematode numbers and most universities recommend resistant soybeans if any soybean cysts are detected in the producer’s field. Genetic resistance involves three recessive genes and is very difficult to incorporate into soybeans. NuTech evaluates all cyst resistant soybeans it sells for cyst resistance by closely monitoring field trials grown in SCN infested areas as well as growing the soybeans in three different infested soils in the lab. These lab experiments allow the creation of a simple index to compare products. The lower the cyst index, the more resistant the variety. The cyst index is not an exact score but is a good indicator of resistance level.

Most Midwest universities have developed cyst nematode management systems for good SCN management for areas under heavy pressure or when new races have developed. These management systems deploy alternating crops and alternating SCN resistance varieties between the common PI 88788 cyst resistance source, Peking cyst resistance source, and SCN susceptible varieties. Alternating sources of cyst resistance is important in cyst nematode management systems and NuTech is one of the few companies with Peking source soybeans to utilize the cyst management systems.

Soybean Diseases

IRON DEFICIENCY CHLOROSIS Iron Deficiency Chlorosis (IDC) is often expressed as a yellowing of the first trifoliate leaves two to five weeks aft...

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IRON DEFICIENCY CHLOROSIS

Iron Deficiency Chlorosis (IDC) is often expressed as a yellowing of the first trifoliate leaves two to five weeks after planting. Problem fields are found in parts of central to north central Iowa, Minnesota, North Dakota and Nebraska on soils with a pH above 7.5. Other soil factors may significantly accentuate the expression of IDC such as high calcium carbonate equivalents (CCE) and soluble salt concentrations (EC). Soybean Cyst Nematode infestation can accentuate IDC symptoms as well.

Control: Management starts with variety selection and NuTech Seed has several outstanding options for IDC tolerance. Higher seeding rates (12+ seeds/ft in 30” rows) can reduce IDC symptoms and improving drainage followed by soil amendments of gypsum and/or sulphur and Iron chelate applied to the young plants at the appropriate stage can all reduce symptoms.

PHYTOPHTHORA ROOT ROT

Phytophthora Root Rot (PRR) is a fungus that can infect plants at any stage of growth and either kill plants or significantly reduce productivity. The disease can be active in cool temperatures but is generally most active in warm conditions with high soil moisture. Although PRR is most frequently associated with fields having poor internal drainage, it can also occur in normally well-drained fields saturated for 10-14 days due to excessive precipitation or irrigation. Symptoms include wilting and yellowing of the upper leaves and a dark brown discoloration that moves up the stem, both externally and internally. The PRR fungus survives and overwinters in soil or buried crop debris.


Control: Fields with a known history of PRR require a soybean with a specific gene for resistance, preferably Rps1c or Rps1k and/or NuTech Seed Smartcote® Extra seed treatment. Some soybeans can also show considerable tolerance to Phytophthora

BROWN STEM ROT

Brown Stem Rot (BSR) is likely to be the most severe in fields that have had optimal moisture in the early vegetative stage and then dry conditions during reproduction. Symptoms are expressed as brown discolorations of the inner stem between nodes, or as a late season leaf symptom consisting of brown interveinal necrosis. Look for unfilled, fully developed pods at harvest. Recent research work indicates that an inverse relationship exists between BSR and soil pH. The data collected to date indicates that the incidents of BSR tend to be significantly reduced in high pH soils and increased in low pH soils.


Control: Resistant soybeans or soybeans with considerable tolerance.

CHARCOAL ROT

Charcoal rot is a root disease caused by a soil borne fungus that attacks young plants when their growth is retarded by unfavorable weather conditions – most normally dry soil conditions. Typical signs of charcoal rot appear after midsummer when hot dry weather slows plant growth and leaves turn yellow and wilt but remain attached to the plant. The best diagnostic symptom is found when the epidermis is peeled away from the stem where numerous small, black sclerotia give infected tissue a grayish-black color resembling a sprinkling of finely powdered charcoal – hence the name charcoal rot. The disease has been an endemic problem in southern soybean growing areas where summers are dry but can also be a problem in the central parts of the Midwest especially Kansas, Nebraska and parts of Missouri. Charcoal rot can be easily misidentified as BSR or SDS.


Control: Any cultural practice that reduces moisture stress helps control the disease. Reduced planting rates and good weed management can help control. The best control is using soybeans with tolerance to the disease.

DAMPING OFF

There are many soil borne pathogens that can cause damping off of soybean seedlings. Pythium is the most common fungus responsible for damping off in cold wet soils and will be the common cause for damping off of soybeans planted in April and early May. As soils warm up, Phytophthora fungus can become a common damping off pathogen, usually in late May and early June. Both pathogens are most damaging in soils that stay saturated for a number of days and will cause the seedling to fall over and the lower stem and roots will be soft and rotted.

Control: Smartcote® Extra seed treatment provide excellent protection against damping off. Resistance to Phytophthora Root Rot can also be helpful. Always use treated seed to replant into soils where damping off has occurred.
 

 

 

 

 

 

 


 

SUDDEN DEATH SYNDROME

Sudden Death Syndrome (SDS) is a fungal disease common to cool, moist growing seasons and has visual symptoms that begin with yellowish lesions forming on upper leaves in interveinal areas. The veins remain green, the lesions spread and eventually the entire interveinal surface of the leaf turns gray-brown. The disease infects the plant early in the soybean development and infection is increased by good  moisture and cool temperatures later in the growing season. Varieties differ in tolerance and the disease is often associated with Soybean Cyst Nematode infested soils. As a rule, the disease is more prevalent in Iowa, Illinois, Indiana and Ohio, but has been spreading the last few years into Nebraska, Kansas, and Missouri. Soybean plants killed by SDS will have often have petioles still attached at harvest maturity to assist in disease identification.


Control: Avoid early planting dates, especially in fields with a significant history of SDS. Variety selection is important as there are varietal differences in SDS tolerance. Controlling SCN populations and maintaining fertility and good drainage with crop rotation is important as SDS yield losses are most severe in continuous soybeans.

WHITE MOLD

White mold thrives in moist, humid and cool conditions. Significant yield losses can occur in soybean monoculture or short rotations of soybeans with other crops susceptible to the disease. White mold infestation occurs during the flowering period in late July and August if cool, moist weather is present. Infected plants will develop white, cottony fungal growth on the plant stem. A sudden yellowing or wilting is usually the first symptom. Leaves of infected plants turn brown, dry and often cling to the dead stem.

Control: Excess lodging, narrow rows and thick canopies reduce air flow and increase the risk of white mold development. NuTech Seed soybeans are rated for white mold tolerance and several soybeans have shown reduced infection of the fungus.

STOP Weeds with Liberty: Best Management Practices

S.T.O.P. WEEDS WITH LIBERTY START early with the first application. Begin soon after emergence when weeds are smaller. TARGET < 3" weeds. Small weed...

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S.T.O.P. Weeds with Liberty

Start early with the first application. Begin soon after emergence when weeds are smaller.
Target < 3" weeds. Small weeds are easier to control. 
Optimize coverage. Follow the correct rate, water volume and droplet size.
Pair with residuals. Use multiple effective sites of action for pre- and post-residuals. 

Why?
Weeds can grow exceptionally fast, such as waterhemp, which grows over an inch a day and can drop hundreds of thousands of seeds. 

Why?
Weeds like Palmer amaranth can be extremely hard to control with any post-emergent herbicide after three inches.

Why?
Liberty® is a contact herbicide, so proper coverage is key to ensure effective control. 

Why?
The key to preventing resistance is to reduce the pressure on single herbicides.

Start early with the first application (Soybean)

LIBERTY® HERBICIDE RECOMMENDATION PROGRAM - TIMING & RATES
PROGRAM PRE-EMERGENCE RESIDUAL FIRST POST APPLICATION SECOND POST APPLICATION SEASONAL MAXIMUM RATE
Guidelines

- Pre-plant
- Pre-plant incorporated
- At planting

- Weeds < 3"
- Use a residual tankmix
- Min. 10 days after first application
- Use a residual tankmix
 
Recommended Program Use pre-emergence residuals Liberty® 29-36 fl. oz./A + residual Liberty 29 fl. oz./A + residual 65 fl. oz./A

Target < 3" weeds

LIBERTY is a CONTACT herbicide

•“Driver” broadleaf weeds have multiple growing points
• Every growing point must be covered to kill
• Spray coverage will be the key in future weed control

For every 2" in height / growing points double!!

Small Weeds - Best Management for all Herbicides

Optimize Coverage

Water Volume

• Liberty is a contact herbicide which requires good coverage with medium-size droplets applied at a minimum of 15 GPA water volume.
• If dense canopy, large weeds or unfavorable growing conditions are present, increase water volume to a minimum of 20 GPA

Spray Tips

• Use nozzles and pressure that generate medium-size spray droplets
- Nozzle recommendations – MEDIUM
- TeeJet®
- Greenleaf Technologies
- Hypro
- Delavan
- Look for medium nozzle recommendations. Refer to nozzle manufacturers’ catalogs, tech sheets or websites for additional guidance.


Palmer Response to Liberty Effects of Different Spray Tips
Pair with Residuals

Soybean National Recommendation

Pre-Emergence Herbicide Post-Emergence Herbicide
Authority MTZ (5, 14) Dual (15)
Authority First (2, 14) Blazer (14)
Boundary (5, 15) Flexstar (14)
Dual (15) Prefix (14, 15)
Envive (2, 14) Warrant (15)
Fierce (14, 15) Zidua (15)
Prefix (14, 15) Select Max (1)
Valor XLT (2, 14) Assure (1)
Zidua (15) Fusilade (1)