Watch for worms in grain sorghum heads

Doug Johnson, Extension Entomologist

Fig. 1. Corn earworm on Corn

Fig. 2. Sorghum webworm
 on sorghum

It is about the time of year for problems with corn earworm (Fig.1.) to begin in grain sorghum. Though I have not seen or heard of any local problems my colleague in VA, Dr. Ames Herbert, is beginning to see some problems. In Kentucky we generally see these problems in the area west of the Pennyrile Parkway and more importantly in LATE planted fields. You are also likely to see a mixture of worm species including the sorghum webworm (Fig. 2.)

Armyworms are sneaky so watch your fields!

 Fig 1. Corn stand with all leaves
below the ear removed

Doug Johnson, UK Extension Entomlolgist and Will Stallard, UK ANR Agent.

Will Stallard, UK ANR agent in Casey Co., KY, came across an odd set of damage on a corn field. It seems that in about a 7-acre area all of the leaves on the corn plants below the ear level were gone, while leaves at and above the ear level suffered only minor damage. There were no pests present at the time of observation so what would eat all the leaves up to the ear, but not cause much damage above the ear? After several iterations of photos and some consultation about what might have caused this unusual damage pattern, and why, we have finally come to a conclusion.

Expect a Later, Wetter Grain Harvest, Get the Driers Ready

Chad Lee, Extension Agronomist, University of Kentucky

Corn was planted late and the cool and cloudy days are slowing development. Most corn hybrids in Kentucky need about 2,700 to about 3,300 GDD’s or heat units to reach black layer (physiological maturity). Looking at the GDD calculator on the UK Ag Weather Center, corn planted April 15, 2013 in Mayfield, Kentucky won’t get to 3,000 GDD’s until Sept. 1.  Corn planted April 15 in Henderson will get to 3,000 on Sept. 3. Corn planted May 15 in Lexington will get to 3,000 GDD’s about Sept. 27.

Kudzu Bug Moves Into Central and West Tennessee

Doug Johnson, UK Extension Entomologist

Kudzu bug continues to be found ever closer to Kentucky (KY). Until just recently, Kudzu bug in Tennessee (TN) was found only in the eastern portion of the state where few soybeans are grown. These infested counties are the closest to KY, but in an area of KY where few soybeans occur. Unfortunately, within the last week, this pest has been found in two additional TN counties. Both of these TN counties are soybean producing areas of central and west TN (See the Map).

Frogeye Leaf Spot of Soybean Active

I continue to get calls  indicating that the occurrence of frogeye leaf spot is pretty severe in some fields east of I-65, and especially in northeast KY.  Most of the fields affected began to show severe symptoms this week, but were relatively clean a week ago.  The main question being asked  is, “should I spray a fungicide?”.  The answer depends on the extent of the disease and the average stage of the plants.

High Day Temperatures and Corn Pollination

Chad Lee, Extension Agronomist, University of Kentucky

Corn pollen drop is
occurring in many fields. 

Much of the corn in the state is going through pollination right as daytime temperatures are the highest for the season. Fortunately, most pollen drop occurs earlier in the morning and some occurs later in the evening. Soon after pollen comes into contact with silks, it begins pollen tube growth in those silks. As long as morning temperatures stay in the low 70's, pollination should occur without much trouble. Last year, morning temperatures were in excess of 90 degrees, relative humidity was low, the soils were extremely dry and the corn was under severe drought stress. This year, humidity is accompanying the hotter temperatures. The higher humidity will help the viability of the pollen grains.

Kudzu Bug – Not Crying Wolf

Doug Johnson, Extension Entomologist, University of Kentucky

Any number of you are aware that I have been talking about the arrival of Kudzu bug in Kentucky for the past two years. Fortunately, so far as I know, this invasive pest has not arrived in the commonwealth. Nevertheless, it approaches ever nearer to our area. Dr. Scott Stewart, my colleague in Tennessee, is now dealing with Kudzu bug infestations in several southeastern Tennessee counties (See his article through the link immediately below).

See: http://news.utcrops.com/2013/06/kudzu-bugs-in-soybean/

Like Kentucky, most of Tennessee’s soybean production is in the western portion of the state. None the less, this activity in eastern Tennessee provides a foothold in our area and represents the infestation closest to Kentucky. In addition, this probably represents establishment (a locally overwintered population) and not introduction because this pest was discovered in eastern Tennessee in previous years.

It is as yet unknown how important this pest will be in Kentucky soybeans. However, it has become a major pest within two years of discovery in the soybean production states to the south of us. I see no reason to believe that this will not be the case in Kentucky. It is therefore important for us to keep a watch out for this pest. My guess is that it will first appear in counties with kudzu along the interstate corridors that handle traffic from east Tennessee, the Carolinas, Georgia and Alabama. This includes I-75, I-65 and I-24. Producers and other interested parties would do well to look for this bug in kudzu and soybeans that border these highways.