Fall Armyworm Moth Flight Numbers Begin to Rise Again.

Doug Johnson, Extension Entomologist


The number of reports of fall armyworm (FAW) infested fields has slacked off for the present. Unfortunately, I do not think this problem is over for the year. I believe our IPM pheromone- baited traps are supporting this notion with an up-tick in captures this week.

Notice up-tick in green line.

If we look at the FAW moth captures for the year so far (Figure 1.), we can see three telltale signs. All three of these may be found in the relationship of the 2012 flight (Green line) to the 2007 outbreak population (Red line) and the rolling five-year average (Blue line). The 2012 flight of moths is: 1. much earlier, 2. much larger, and 3. appears to be starting to climb, indicating a second moth flight. None of these is absolutely definitive that we will experience a second economically important worm population, but they certainly indicate that we should be watching for one. That certainly seems to be the opinion of my colleagues in states to the south of us, and they experience FAW more often than do we.

We will not know until we see the moth flight numbers for the trap week ending Thursday, Sept 13th, or perhaps even the trap week ending Sept. 20th whether or not we have a second and threatening population. To my knowledge, there is no precedence for this in KY. Certainly we have seen FAW linger until frost, but we have not seen them do this in widespread large numbers.

When viewing these graphs, please remember that you are looking at moth capture. Moths are not the damaging stage in this insect. Moths (adults) are simply responsible for reproduction, dispersal, and egg lay. The resulting worms (damaging stage) will appear after a 1-2 week delay from the moth flight.

See the article: The Affect of Insect on Wheat Planting Decisions, in Kentucky Pest News at:
http://www.ca.uky.edu/agcollege/plantpathology/extension/kpnindex.htm
 for a look at the possible impact of insects, including FAW, and mites on the 2012 wheat crop.

Also see the Wheat Science News Letter at:

http://www2.ca.uky.edu/wheatscience-files/Sept_6_2012_Wheat_Newsletter.pdf

for Insect & other pest considerations and agronomic information related to the 2012 planting season.

Capture of corn earworm moths in IPM pheromone baited traps at UK-REC, Princeton (Caldwell Co.) Ky in 2012.

Doug Johnson, Extension Entomologist

CEW caterpillar and damge on soybean.

Corn ear worm (CEW), also known as soybean podworm, are currently active in soybeans. This is a direct damage pest as it feeds on pods, seeds, & petioles. You are unlikely to detect this pest by checking for defoliation because it does not feed much on leaves. There is no sure way to detect this pest in your soybean crop except to scout for it. This means sweeping or direct visual examination of the pods.

CEW may occur in many color phases. It sometimes appears very dark, almost black, to brown to red and green. The green color phase is most often seen when feeding in soybeans. When fully grown, the larvae are about 1 ½“ long. They are marked by alternating light and dark stripes running the entire length of the body. These stripes are not always the same from one caterpillar to another. Usually a double dark stripe will run down the middle of the back.

You can certainly look for direct damage feeding on the pods to see if they are causing damage. In rows narrower than 30”, sweeping with a 15” sweep net is about the only way to measure this pest. The threshold is 9 worms per 25 sweeps.

Capture of CEW moths at UKREC 2012

We do know that corn earworm moth flight has been increasing and populations are greater than we normally see. Moth capture in our IPM pheromone baited traps at the UK-REC in Princeton is shown in Figure 2. Remember, these are moth counts and moths are NOT the damaging stage. Caterpillars will appear about a week after the moth flight. In 2012, moth numbers (green line) are greater than the rolling five- year average (blue line) so we are at an elevated risk of damage from this pest compared to most years. However, trap captures will NOT tell you what will happen in an individual field. Only field sampling will help you establish whether or not a threshold has been met. Moth flight numbers will give you a week or two heads up on what might happen.

If insecticide control is warranted, you may find products listed for control of CEW in soybeans online at: http://pest.ca.uky.edu/EXT/Recs/welcomerecs.html or from your County Extension Office. Be wary of spraying too early, you may kill the predatory insects that are providing some natural control and miss the actual pest.

Fusarium Ear Rot and Fumonisons

Paul Vincelli, Extension Plant Pathologist, University of Kentucky

Figure 1. Typical symptoms of Fusarium ear and kernel rot.
Note whitish fungal growth.
 Usually damage from Fusarium ear rot affects
scattered kernels or groups of kernels, as shown here.

The content of this article previously occurred in the Kentucky Pest News, number 1315.

Pre-harvest contamination of corn with fumonisins is a possibility in some lots of this year’s Kentucky corn crop. Fumonisins are a family of mycotoxins produced by the fungus that causes Fusarium ear rot. These natural toxins have the potential to cause lethal diseases of horses and swine (the diseases are equine luekoencephalomalacia and porcine pulmonary edema, respectively). Pre-harvest contamination of corn by fumonisins is most often associated with drought stress at the silking stage, a stress that occurred widely in Kentucky and beyond.

Scouting Corn for Aspergillus Ear Rot

Paul Vincelli, Extension Plant Pathologist, University of Kentucky

Fig. 1 Aspergillus ear rot, 
from University of Illinois

The content of this article previously occurred in the Kentucky Pest News, number 1315.

Aflatoxins are potent, naturally occurring toxins that sometimes develop in corn and certain other crops. Aflatoxins are also among the most carcinogenic substances known. There are well-defined limits on how much aflatoxin is allowable in corn, based on the intended end use. For example, corn intended for human consumption must have less than 20 ppb (parts-per-billion!). More information on aflatoxin can be found in the UK Extension publication, Aflatoxins in Corn, ID-59, at http://www.ca.uky.edu/agc/pubs/id/id59/id59.pdf.

Cutting soybeans for Forage? Consider some Insects!

Doug Johnson and Lee Townsend, Extension Entomologists.

Margined blister beete on soybean.

Some folks have been asking about cutting soybeans to be baled and used for forage. In general most insects in soybean are not a problem. However, blister beetles can be. Blister beetles are commonly found in soybeans thought not in large numbers. In my plots this year the black margined blister beetle has been the most common, though others will occur.

This insect and its close relatives the ash gray and striped blister beetles are infamous as a contaminant of alfalfa hay for their effect on animals, particularly horses. They are found in soybean for the same reason as alfalfa, they are attracted to and feed on blooming weeds.

Soybean Rust Probably Here, But So What?

Don Hershman, Extension Plant Pathologist, University of Kentucky

Spores of the soybean rust pathogen were probably depostited in west Kentucky this weekend as a result of Hurricane Isaac's passing through. Moreover, the weather conditions this weekend were perfect for infection. Now that spores of the SBR fungus have been deposited and infection has likely taken place at some level, it will take approximately 3 weeks for us to find SBR pustules. However, significant disease development will not occur until about 4-6 weeks after spore deposition.  This means we will probably find SBR in Kentucky before the end of September, but the disease will not build-up much until October. By that time, some fields will have already been harvested, many will be near harvest, and even the latest planted doublecrop fields will be well past the point where damage is possible. So, while it is noteworthy and interesting that SBR is probably already here, it is a matter of “too little, too late” to be of any real concern.

Green Cloverworms Appearing in Large Numbers in Soybeans.

Doug Johnson, Extension Entomologist

There are some unusually large populations of green cloverworms on soybeans scattered around the state. This is a very common insect in soybeans which always has the potential for economic damage, but very rarely causes economic damage. The populations I have seen thus far are not at the economic threshold, but were much larger than I am used to seeing. It makes sense to look at your soybeans, especially late planted or slow developing beans.

Green cloverworm caterpillar on soybean stem.

Green cloverworm is easy to find and easy to identify. These worms are light green with two thin white stripes along each side of the body. When fully grown, these slender worms are 1” to 1-1/2“ long. They have only three pair of prologs in the center of their body. Most of the other caterpillars in KY grown soybeans have either 4 or 2 pair of prolegs. Green cloverworm will become very active, wiggling and looping when disturbed.

These pests are foliage feeders. They will strip the leaf tissue from between the veins leaving the veins, petioles and stems behind like a skeleton.

It takes a great many of these caterpillars to cause an economic problem. Economic threshold (ET) depends not only upon the number of green cloverworms, but also on the stage of the plants, the value of the beans, and the cost of treatments. ETs may be found in:

IPM-3, KY IPM Manual for Soybeans at: http://www.uky.edu/Ag/IPM/manuals.htm and

ENT- 13, Insecticide Recommendations for Soybeans at: http://pest.ca.uky.edu/EXT/Recs/welcomerecs.html

These insects are not very hard to kill. It is most important to detect them before they reach threshold and determine if control is needed. If you find them only after the damage has been done, you can kill them, but you can’t put the foliage back on the plants!