Black Cutworms and Armyworms Among Concerns for Southwest Missouri Crop Farmers this Week

Contact: Jill Scheidt, agronomy specialist
Tel: (417) 682-3579
E-mail: scheidtjk@missouri.edu

LAMAR, Mo. –Jill Scheidt, agronomy specialist with University of Missouri Extension in Barton County, scouted area fields on June 5 to prepare this week’s field scouting report.

Scheidt says Armyworms are still being seen at threshold level in wheat and fescue fields.

Threshold level for armyworms in wheat and fescue are 4/ sq. ft. or when 2-3 percent of heads are clipped. Mustang Max is recommended to control armyworm because it provides the longest residual effect.

“Armyworms were moving slow, but keep a close eye on them, checking 2-3 times per week for threshold levels, as armyworms at threshold levels can clip heads on half a field in one night. Recent rains may have slowed feeding and may have brought in a fungus that kills armyworms.

BLACK CUTWORMS

Below threshold levels of 1-2 percent of corn plants were clipped above ground due to black cutworm feeding. Threshold levels for black cutworm are when 6-8 percent of plants are clipped above ground or when 2-3 percent of plants are clipped below ground.

“Scout fields for black cutworm until corn reaches the 5-leaf stage. Black cutworms do not feed on corn once it is past the 5-leaf stage,” said Scheidt.

SWITCHING TO SOYBEANS

“If you are thinking about switching from corn to soybeans, soybeans should NOT be planted into fields where applications of atrazine or an atrazine premix have already been made this season,” said Scheidt. “The label says soybeans should not be planted until the following year due to the likelihood of soybean injury from residues of atrazine that may still be present in the soil.”

The average field half-life of atrazine is 60 days. High soil pH’s (>7.5) will also slow the degradation of atrazine, along with cool soil conditions. Fortunately, replanting corn or planting grain sorghum into these damaged areas will still be an option.

MORE INFORMATION

The weekly field scouting report is sponsored by University of Missouri Extension and Barton County Extension.

For more information on this scouting report, or to learn how you can receive it a week earlier by telephone, contact the MU Extension Center in Barton County at (417) 682-3579.

Armyworms Spotted in Southwest Missouri Fescue Fields

Contact: Jill Scheidt, agronomy specialist
Tel: (417) 682-3579
E-mail: scheidtjk@missouri.edu

LAMAR, Mo. – Armyworms were seen in southwest Missouri wheat and fescue fields this week in numbers anywhere from 1 to 7 armyworms per square foot according to Jill Scheidt, agronomy specialist with the University of Missouri Extension in Barton County.

Threshold levels for armyworm in fescue are 4-5 per square foot and before 2-3 percent of heads are clipped.

Scheidt made the discovery while scouting area fields on May 29 to prepare this week’s MU Extension field scouting report.

A very small amount of armyworm feeding was seen in corn fields. Control of armyworm in field corn is justified if 25 percent or more of corn seedlings are significantly damaged through foliage feeding by larvae.

SCOUTING

To scout for armyworms, find a thick area in field or pasture, armyworm moths lay eggs in thick areas first, then beat the heads together and look for armyworms on the ground. “It is best to scout at dusk or early morning, while feeding is taking place,” said Scheidt.

The rate of development for armyworms is temperature related, so it may be hastened by warm weather or slowed down by cool weather. It typically takes two to three weeks from the time the moth lays the egg until they have hatched and grown through the early instars.

Instar is a rating, or size that describes the development or maturity of the larvae. Larvae at the 3rd through 5th instar are the most destructive.

Larvae have a greenish brown body, nearly hairless, with a thin stripe down the center and two orange stripes along each side. Armyworms are identified by four pro-legs at the middle of their body.

According to Wayne Bailey, MU State Entomologist, fescue fields need to be scouted first. “Armyworms typically show up in fescue fields two weeks before they are in wheat fields,” said Bailey.

CONTROLLING

A rate of three to four ounces per acre of Mustang Max is the recommended control for fescue fields with a zero day harvest interval for hay, forage and grazing.

“Armyworms should be treated as soon as threshold levels are seen; armyworms can clip 50 percent of the heads in a pasture in one night when at threshold levels. Larger armyworms cause more damage than full grown armyworms,” said Scheidt.

Prolonged wet weather can be hard on the armyworm larvae by creating conditions whereby a fungus knocks down the population. They prefer cool weather and do not like sun and heat.

“There is also a wasp that can parasitize and kill the armyworm. This is a natural predator, but do not assume this will occur. It is important to check for parasitism when determining threshold levels for spraying. Look for mummified bodies of armyworms clinging to the plant stalks or laying in the plant debris on the ground,” said Scheidt.

MORE INFORMATION

The weekly field scouting report is sponsored by University of Missouri Extension and Barton County Extension.

For more information on this scouting report, or to learn how you can receive it a week earlier by telephone, contact the MU Extension Center in Barton County at (417) 682-3579.

For more information about armyworms or to receive a copy of the Armyworms and their Controls guide go online to http://extension.missouri.edu/webster/webster/agric/armyworms-field.html

Field Scouting Report for May 22: Applying Nitrogen to Wheat Now Will Not Increase Yield; Some Armyworms Spotted This Week

Contact: Jill Scheidt, agronomy specialist
Tel: (417) 682-3579
E-mail: scheidtjk@missouri.edu

LAMAR, Mo. –Jill Scheidt, agronomy specialist with University of Missouri Extension in Barton County, scouted area fields on May 22 to prepare this week’s field scouting report.

According to Peter Scharf, MU Extension state fertility specialist, at this point producers who applied anhydrous on corn ground in January or February have lost no more than 10-20 percent of the nitrogen applied. Dry fertilizer and earlier applied fertilizer have a greater risk for loss.

By going to the website and typing “Nitrogen Watch” into the search engine producers track rainfall and possible nitrogen loss by using the “Nitrogen Watch” web tool.

“It is too late to apply nitrogen to the wheat once 2 nodes are present on the stem. Research has shown that applying nitrogen in the fall then applying nitrogen past the boot stage will not increase yield,” said Scheidt. “It is not economical to apply nitrogen once wheat is in the boot stage because wheat will not efficiently use nitrogen and the increase that could be seen in wheat will not cover the cost of the nitrogen application.”

No diseases were seen this week in wheat. According to Scheidt, weather conditions are still favorable for fusarium head blight. Fungicides do not control head blight, fungicides can only suppress head blight. Fungicides that suppress fusarium should be applied at or during flowering. Remember to read the label for the appropriate timing of fungicide application.

ARMY WORMS

Armyworms were seen in wheat fields around Lamar, just under threshold level. Threshold level for armyworms is 6 per foot. Mustang Max or Hero is recommended to control armyworms. To scout for armyworms bang wheat heads together, then look on the ground for small to medium sized worms.

Armyworm feeding was also seen in corn, but not at threshold level. Armyworms begin feeding in the whorl to the outside of the whorl. Leaves appear as if they had been shot by a shot gun.

MORE INFORMATION

Helpful articles on funguses and fungicide ratings, late corn planting and burndown procedures can be found on the website at extension.missouri.edu or by calling the nearest county extension center.

The weekly field scouting report is sponsored by University of Missouri Extension and Barton County Extension.

For more information on this scouting report, or to learn how you can receive it a week earlier by telephone, contact the MU Extension Center in Barton County at (417) 682-3579.