University of Missouri Extension

Barton County

August 2011 Crop Scouting Reports

Field Scouting Report for August 31…

Corn is Ready, Soybeans are Facing New Pests

Corn fields east of Lamar and in the Milford and Nashville areas are fully mature and many are ready for harvest based on a scouting report done Aug. 31.

“Many fields showed numerous blank ears due to dry weather this season. Others had ears with some tipping back of the kernels,’ said Tim Schnakenberg, the agronomy specialist with University of Missouri Extension who scouted the fields.

Yield reports show very marginal yields and low test weights in corn. According to Schnakenberg, there continues to be concern for aflatoxin in the grain, but most loads have been within the tolerance levels. “That could change if moisture comes back into the forecast,” said Schnakenberg.

Soybeans scouted this week were in R4 and R5 full pod and beginning seed stages of development. Dry weather continues to be the biggest concern to fill pods for the remainder of the season. “There have been some cases of potash deficiency resulting in leaf yellowing and stunting. This is worsened in a dry year,” said Schnakenberg.

The most obvious pests on soybeans currently are soybean podworms and green cloverworms. The larvae will feed on the foliage and the podworms especially cause pod damage.

For podworm, the economic threshold at this stage of development is 20 percent defoliation or when larval numbers exceed one per foot of row and 5 percent or more of the pods are damaged.

For green cloverworm the threshold is 20 percent defoliation and when 10-15 or more half grown or larger larvae are present per foot of row.

“Current market prices and yield potential of the crop must be a consideration for making decisions on spraying,” said Schnakenberg.

For more information on this scouting report or to learn how you can receive it by telephone each week, contact the MU Extension Center in Barton County at (417) 682-3579. These weekly field crop scouting reports are sponsored by MU Extension in Barton County and the Barton County Soil and Water Conservation District.

Photos of the various diseases discussed in this release are also available for viewing or downloading at www.flickr.com/MUExtension417.

Click here for PDF file Audio Report --- http://tinyurl.com/3eptslr

Blank ears

Cloverworm Leaf feeding

Podworm Podworm feeding

Potash Deficiency

Field Scouting Report for August 24…

Penicillium on Corn and Stink Bugs on Soybeans Comprise Main
Concern in Southwest Missouri Crop Fields

Some of the southwest Missouri corn fields are showing signs of penicillium eat rot and the biggest concern for soybeans right now are stink bugs. Brie Menjoulet, agronomy assistant with University of Missouri Extension in Hickory County, scouted fields in southwest Barton County between Lamar and Nashville on Aug. 24.

Corn fields scouted ranged from dent stage to maturity. Penicillium ear rot was found in all the fields scouted this week. Corn earworms were found in several ears of the dent-stage corn. “Because corn earworm feeding damage can increase the chances for penicillium to infect the ears, management strategies that help control corn earworm populations and damage, such as variety selection, tillage practices, and crop rotation, may help reduce infection of penicillium in next year’s crop,” said Menjoulet.

Soybeans scouted this week were in full bloom to R3 pod development stages. “Nearly all plants looked healthy and feeding damage from insects remains minimal so far. However, it is time to start scouting for stink bugs,” said Menjolet. “First, or possibly second, generation stink bugs are reaching maturity and laying eggs.”

Stink bug nymphs and adults feed on soybean stems, blooms, pods, and seeds. Feeding damage can delay maturity, cause abnormal production of leaflets and pods, and can affect seed quality. Eggs can range in color from nearly black to pinkish-white, are barrel-shaped and will be in cluster of 10 to 30. Stink bug distribution within a single field can be patchy.

When scouting for nymphs or adults, use a sweep net or drop cloth at several sites in the field. Insecticide application may be needed if older nymphs or adults reach one per foot of soybean row during the R5 and R6 seed development stages. “I found two clumps of stink bug eggs in one field and have posted the pictures online,” said Menjolet.

Photos of the various diseases discussed in this release are also available for viewing or downloading at www.flickr.com/MUExtension417.

Click here for PDF file Audio Report --- http://tinyurl.com/3ko65va

Corn earworm feeding Penicillium ear rot

Stink bug eggs

Newly hatched stink bugs

Field Scouting Report for August 17…

Several Corn Ear Disorders Spotted Due to Drought

Brie Menjoulet, agronomy assistant with University of Missouri Extension in Hickory County, scouted fields northwest of Lamar and in the Liberal area on Aug. 17.

Corn fields that were scouted were in reproductive stages, 7/8 to maturity.

Several forms of corn ear disorders such as numbed ears, incomplete kernel set, and tassel ear, also known as crazy top, were noticeable in the fields. “The problems are most likely due to the summer drought. The moisture level in some of the harvested corn was at about 17 percent,” said Menjoulet. “A greenish mold was present on several ears and though mold does not necessarily indicate aflatoxins, higher moisture levels coupled with drought can increase the likelihood of these chemicals in the kernels.”

Aflatoxin levels can vary greatly from kernel to kernel and can be patchy throughout a field. The FDA has set an aflatoxin limit of 20 ppb or one contaminated kernel per 5lb of corn.

The University of Iowa has guide on sampling corn for quantitative aflatoxin testing and is available online or at your local Extension office. “Though conditions seem favorable for aflatoxins, no confirmed cases have been reported yet,” said Menjoulet.

Soybeans scouted this week were in the R2 stage. Defoliation was primarily due to grasshopper feeding but it has remained minimal at five percent or less.

“If defoliation reaches 30 percent or more, intervention may be needed to prevent yield loss. I also caught a few scattered fall armyworms in one field but did not observe any stem or root diseases this week,” said Menjoulet

Photos of the various diseases discussed in this release are also available for viewing or downloading at www.flickr.com/MUExtension417.

Click here for PDF file Audio Report --- http://tinyurl.com/3lwwmey

Corn ear disorder (drought damage) Crazy top/tassel ear

Mold on corn ears

University of Iowa guide - "Aflatoxins in Corn"

Field Scouting Report for August 10…

Watch for Aflatoxins on Corn, Insects in Soybeans

Jill Hankins, agronomy assistant with University of Missouri Extension in Barton County, scouted fields southwest of Barton County on Aug. 10.

The corn fields were 7/8 to black layer, or maturity. “Some kernels seemed to have a squishy feel where the kernel connects to the cob. This is likely due to the drought where the kernels were unable to completely fill,” said Hankins.

She also saw a little bit of penicillin ear rot on some tips. Penicillin ear rot usually occurs on ears with mechanical or insect damage. It is a green or blue green mold on or between the kernels, usually at the ear tip. If the grain is stored at high moisture levels greater than 18 percent the fungus may invade the grain and discolor it,” said Hankins. One solution is to separate fields that contain a lot of mold to avoid dockages.

“I also saw leaves with northern corn leaf blight. If the corn is nearing maturity, northern corn leaf blight will not cause any problems. If the corn is young, it can cause yield loss,” said Hankins. Northern corn leaf blight is a fungus that is carried by the wind, so it could spread if someone nearby has it. Aflatoxins in kernels as the recent rains can encourage growth.

According to MU Pathologist Allan Wrather, aflatoxins must be less than 20 parts per billion to be sold. Local grain bins will test for aflatoxin levels.

“It is important to remember that fungicides cannot be applied after silking and fungicides unnecessary once the corn dents,” said Hankins.

The soybeans that were scouted had three to four beans per pod. “The plants I saw were tall and healthy. I saw insect feeding on foliage only,” said Hankins.

Insecticide is justified for soybeans if the defoliation reaches 30 percent before podding and 20 percent defoliation after pods are put on. Pods must show 10 percent damage with insects currently feeding before insecticide should be applied.

Photos of the various diseases discussed in this release are also available for viewing or downloading at www.flickr.com/MUExtension417.

Click here for PDF file Audio Report --- http://tinyurl.com/3qrrhhx

Field Scouting Report for August 3…

Hot Dry Weather Slows Corn and Soybeans

Jill Hankins, agronomy assistant with University of Missouri Extension in Barton County, scouted fields southeast of Lamar and in the Arcola area on Aug. 3.

The corn ranged in those fields from 50 percent pollinated to early dent stage. “I saw grasshopper and corn rootworm feeding, but nothing to cause concern and saw no foliage diseases,” said Hankins. “Some corn was fired up and unable to produce an ear.”

Other corn in early dent stage was smaller than usual and one-eighth of the way to black layer, or maturity. Pollinating corn had skips and ears were very small. Other corn in the same stage filled fine but still had smaller ears than usual.

“If you are considering chopping your corn, test the nitrate level to ensure your cattle will not be poisoned. If silage is put up properly, 50 percent of the nitrate level will lower,” said Hankins.

The silage needs to be chopped when it reaches 60-70 percent moisture. Nitrate levels can be tested at most of the MU Extension offices or at Custom Labs in Golden City.

The soybeans Hankins scouted were in the flowering stage and no foliage diseases were present. “I also saw grasshopper and bean leaf beetle feeding, but not enough to cause concern. Remember that threshold for insects that feed on foliage in soybeans is 30 percent defoliation before podding and 20 percent defoliation after pods are present,” said Hankins.

Soybeans look to be stunted from the heat and progressing at a very slow rate.

“I saw split stems, this is a result to the weather, but usually nothing to worry about because it usually heals. I saw dying blooms, which is a result of the weather also. This can result in less or no pods if the plant has not been pollinated,” said Hankins.

Photos of the various diseases discussed in this release are also available for viewing or downloading at www.flickr.com/MUExtension417.

Click here for PDF file Audio Report --- http://tinyurl.com/3nnfflh

Dying blooms due to pollination completion or hot weather

Splits in stems due to hail or hot weather

Pollination skips or kernel abortion

MU guides to feeding corn silage ---
Corn Silage for Beef Cattle
The Missouri Corn Stalk Nitrate Test Challenge - 2011