Armyworm Moth Captures are Abnormally Large.

Doug Johnson, Extension Entomologist, University of Kentucky

Armyworm moth.

Recent moth flight of armyworm (AW), in western Kentucky has been much larger than is normal for this time of year. It is not terribly unusual to see problems with this insect on pasture and forage grasses in late June and July, especially in central Kentucky This year’s much larger AW flight during late July and August in western Kentucky is truly unusual. It is difficult to know what to make of this because it has no precedence in our data set. Nevertheless, the fact is they are here.

Generally, I would expect to be looking for fall armyworm (FAW), Spodoptera fugiperda,at this time of year, but our moth captures for this insect in both central and western KY have been quite low, perhaps because the cold winter and spring pushed their overwintering locations farther south, and/or they were later beginning their annual northward migration. Even so we have seen some localized but significant populations in south-central KY.

  The data we see on the armyworm moth flight of course, describes the movement of adults, which are not the damaging stages. It is the juvenile, caterpillar stage that will appear in September that might pose the threat. Moth flights in the earlier portion of the season followed a relatively normal pattern. Our most common problem with AW comes in May on small grains and that is what we saw this year. Also, there is often a small bump in flight in June and July that usually doesn’t amount to much. Those events were relatively normal this year. What is different this year is that following that relatively normal flight in June and July we have another and much larger flight in July and August that will produce caterpillars in September.

Armyworm Caterpillar

AW has a very broad host range; it eats on many plants but really prefers grasses. On the whole, corn and grain sorghum should be too close to maturity for much damage. However, late planted soybeans and forage crops, most especially newly seeded forage crops could be in some danger.

Producers are advised to keep an eye on very late planted / late developing soybeans, along with forage crops, particularly grasses and most especially newly planted grasses, and grass-alfalfa mixes. There is no established threshold for this pest in these circumstances, but populations around 4-6 worms per sq.ft. probably require treatment.

Black Cutworm and Armyworm Caterpillars Should be Evident

Doug Johnson, Extension Entomologist, University of Kentucky

Our insect development estimator, using the insect trap captures as our Biofix and current temperatures from the Princeton weather station indicate that egg hatch has begun and small

Armyworm and Black cutworm Flights Continue

Doug Johnson, Extension Entomologist, University of Kentucky

Capture of armyworm (AW) and black cutworm (BCW) moths continue at a considerable, if slightly lower capture, compared to last week. The AW trap captured 449 moths while the BCW trap

Black Cutworm & Armyworm Moth Captures Show a Big Increase

Doug Johnson, Extension Entomologist, University of Kentucky

Fig. 1 Black cutworm moth.

Black cutworm (BCW) and armyworm (AW) moths captured in the IPM traps at the UK-REC in Princeton, KY show a substantial increase for the trap week ending Friday, April 10th. In the case of BCW, 37 moths were captured when about 8 would be expected. For armyworm, 541 moths were captured when 119 would be average at this time. Captures for both of these pests are significantly greater than their rolling five- year averages. In addition, if the armyworm counts continue to increase at this rate, the population will approach the outbreak levels seen in 2006 & 2008. These are years when known pest problems either caused loss or required extra insecticidal control. See the Insect Trap Graphs on the UK-IPM webpages.

European Corn Borer and Armyworm Active in Central Kentucky

Doug Johnson, Extension Entomologist, University of Kentucky

Fig. 1 Armyworm Damge

I have reports of scattered, mixed infestations of European corn borer (ECB) and armyworm (AW) in central Kentucky. Thus far, all infestations are in corn that does not carry insect foliar and/or stalk GMO traits (rootworm traits would not apply). This falls pretty much in line with the timing after increase (but not a dramatic increase) in moth flights in mid-to late May. I doubt that this insect pressure is large enough to be of importance to corn products carrying the appropriate insect GMO traits. Nevertheless, for those folks producing non- (insect) GMO corn, scouting is certainly in order. I have not heard any reports from western Kentucky, but west Tennessee has reported sprays for AW control on some wheat fields.

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.

Warning, Armyworms Spotted in Pastures!

Doug Johnson, Extension Entomologist, University of Kentucky

Fig. 1. Armyworm

Capture of armyworm (AW) in the IPM pheromone baited traps still remains below average. Nevertheless, this does NOT mean that there are no AWs around. While economically important populations of AW are not (yet) a wide spread problem this year, the fact remains there certainly are infested fields. The question becomes which fields are infested with an economically important population size? There is only one way to know that, and that is to scout. We do know that AW feeding on pasture grass has been reported from Butler Co. and I expect, that if one looks, infested fields will be found in other areas.

Fig. 2. Fall Armyworm

Do not confuse armyworm with fall armyworm or for that matter beet armyworm, army cutworm etc. These common names can be misleading as they sound similar but represent completely different insect species, whose ’ common features are only that they often move in large masses (hence the descriptor “Army” worm) and they feed on similar plants,generally grasses such as pastures, and large grasses such as wheat, corn, sorghum, and millet.

Most often confused in Kentucky are armyworm and fall armyworm. Armyworm also called “True armyworm” is a spring pest for Kentucky and most of the eastern U.S. It overwinters as far north as Tennessee and probably southern Kentucky, then migrates northward in the warm months. Fall armyworm (FAW) is a late summer to fall pest in Kentucky. This is due to its’ inability to tolerate cold weather, requiring it to overwinter in Texas, usually south Texas, then migrate to Kentucky and northward in the warmer months. During our current time of year armyworm is the threat to pastures, wheat and corn.

Armyworm Moth Flight Increases in Princeton and Lexington Traps.

Doug Johnson, Extension Entomologist

The capture of armyworm moths in the UK-IPM traps increased significantly in both the Lexington and Princeton traps for the trap week ending Friday May 3^rd. See the Graphics at:

http://www.uky.edu/Ag/IPMPrinceton/counts/taw/tawgraph.htm


In both cases the increase is large and is probably related to the warm weather over this period. Nevertheless, these captures will just bring us back to about average (Lexington) and a bit above average at Princeton. It is too soon to know if these increases point us to an outbreak population.


Even though trap captures have been reduced, and late this year compared to last, we need to remember that these pests are out and about. Just because the trap captures are low and late does not mean that there will not be a problem in some fields. Corn planting and growth are behind as well, and we are (at this writing Fri 5/3/13) about to enter another wet cool period. This type of weather will once again slow down planting and corn growth, and tends to favor armyworm development. Even though the risk is not above average, there is some risk just the same, and corn and wheat should be scouted for this pest.

I have had one report from far west KY that sound like armyworm on struggling 1-2 leaf corn though the diagnosis is not definitive. Just the same, it is best to remain alert for this pest.

Armyworm & Cutworm Moth Flights Rather Ordinary

Doug Johnson, Extension Entomologist, University of Kentucky

Black cutworm moth

Capture of both armyworm and cutworm moths have decreased during the previous trap week. At present the data indicate that neither pest is set for a big outbreak. Of course this can change especially if we get a sustained week of good weather. This does not mean that there are no pests around, there certainly are. Nevertheless, flight patterns compared to the rolling five year average do not show any sign of an elevated risk of outbreak.


 

Armyworm moth

Even though we have a good outlook for the short term we still need to remember that “only about 15 percent of corn has been planted which is well behind last year’s 73 percent and the five year average of 32 percent” (KY Weekly Crop & Weather Report Apr. 22, 2013). Remember, both black cutworm and armyworm are migrating to KY from more southern states, and the timing of their migrations are dependent upon temperature just as are planting and corn development. So it is still very possible that larger populations of either or both of these pests could show up in the early vegetative stages of corn development.So, for the moment things look good, but one best pay attention to future developments.

Tracking moth flights isn’t your only preparation option. With both insects but black cutworm in particular providing a weed free seed bed for at least two weeks prior to planting can make a big difference. Early preplant herbicide programs have shown a positive impact in the prevention of cutworm and common stalk borer infestations. Removing weeds especially grass weeds by whatever mechanism, ahead of planning is a good strategy for these early arriving insects.

Armyworm Flight Begins

Doug Johnson, Extension Entomologist

 

  Figure 1. Armyworm moth Spring must really be here as armyworm (aka true armyworm) moths have taken flight. Only a few moths have been captured thus far, but it does signal the beginning of insect season in the field crops and the current year’s capture is in line with the outbreak year of 2008. It is still too early to get real excited but important enough to be aware.

In Kentucky, armyworm can be an important pest of corn and wheat. Corn products that contain a Bt trait that provides protection from caterpillar feeding (See: Insecticide recommendations for corn:   http://pest.ca.uky.edu/EXT/Recs/ENT16-Field%20corn.pdf, pages 6-7) will likely be protected. However, non-Bt types including field corn refuge, popcorn, food-grade corns, and sweetcorn along with wheat will be at risk.

We are several weeks from any damage caused by armyworm as the adult moth is not the damaging stage. Monitoring this stage just gives us a “biofix” or heads-up that the pest is about. It is the caterpillar in which we are interested. You may want to check the flight graphs each week for the progress in this population. These may be found at:  http://www.uky.edu/Ag/IPM/ipm.htm. It only takes a few seconds to check and this can give you an idea of the relative risk of this pest for this season. On the graph you can see displayed the current year’s capture (green), the rolling five-year average (blue), and known populations that have resulted in outbreaks (red and/or black) This will give you a rough estimate of the current year’s relative risk. As these graphs represent moth flight, the relative population size can be seen before the damaging stage, the caterpillar, develops.

If populations appear to be indicating an elevated risk, I will use a temperature-based model to predict when the caterpillar stage will appear. This model will NOT predict which fields will be infested. One must scout fields to know if the armyworm is present, but the model will provide an estimate of when the field should be scouted. Remember, the model predictions will be based on the capture and temperatures at the UK-REC in Princeton (Caldwell Co.) KY. In areas to the south and southwest of the UK-REC caterpillar development will be ahead and areas to the north and northeast of the UK-REC will be a bit behind.  I will post, and you may review, the results of these model runs each week in this publication. So, if you are the pest manager for wheat or corn this spring, keep yourself tuned to this outlet for “Early Warnings” about this pest.

Armyworm / Fall armyworm Problems Increase

Doug Johnson, Extension Entomologist, University of Kentucky

Feeding of one or several “armyworm” species appears to be on the increase. I cannot be completely sure which species are causing the damage, and it is likely that two species, the armyworm also know as True armyworm and the fall armyworm are the most likely culprits.

Fall armyworm moth captures in the IPM pheromone baited traps at Princeton, KY have skyrocketed in the last two weeks, going from 0 to 131 and currently to 550 moths captured in the trap week ending 9/16/12. This problem was reported in TN, AR & MS last week and recently in MO.

Armyworms Active in Corn

Armyworm larvae have been reported feeding in corn. Although armyworm can damage wheat, that very rarely occurs and when it does is usually much later in the season. Certainly this entire season is much earlier than normal because of the warm January – March temperatures. Nonetheless, the general sequence of events is likely to remain the same.

Captures of armyworm moths in the UK-IPM pheromone baited traps have not been very large. Captures did begin very early this year and the first several weeks appeared to be greater than the rolling 5-year average. However, recent counts have dropped below the 5-year average. At this point I don’t expect an unusually large population for 2012. That means that one should probably concentrate their scouting efforts on those situations that are at greatest risk.

Armyworm Flight 2009: No consistent story; but there will be caterpillars!

Doug Johnson, Extension Entomologist
Dept. of Entomology, University of Kentucky

Early captures of armyworm moths appeared to indicate a larger than normal population for 2009. However, after several weeks of monitoring it appears that the capture counts do not indicate an obvious major outbreak situation. This is particularly true of the Princeton, KY trap. We do not yet have enough historic data to know how to interpret the Lexington trap data. However, this does NOT mean that there will not be any problems. [Please see: How to Use Insect Graphs from the UK-IPM Trap Lines at:

http://www.uky.edu/Ag/kpn/kpn_09/pn_090324.html

to review how to use the trap data.]

There will be armyworm caterpillars in susceptible host (corn, small grains, grass forages), as there are every year. In fact if we apply the day degree model to the very first moth captures there are likely caterpillars already appearing in both western and central Kentucky. These will be among the earliest of caterpillars. Remember if you are in a location warmer than where our traps are located then caterpillars will appear earlier. If you are in a cooler location they will appear later. I have received one report of armyworm caterpillars on the heads of wheat (though I have not seen this myself) from a southern Pennyrile area county.

While moth captures in our traps do not indicate a major outbreak year, we certainly have experienced weather that selects for the survival of the caterpillars. Typically armyworm populations do better in cool wet weather. At least in western Kentucky we have certainly seen such weather. Historically, grass forages and corn suffer the most damage from armyworm, but small grains are certainly at risk, particularly if the caterpillars are feeding on the heads.
Scouting techniques and thresholds are available in our IPM Manuals available at:

http://www.uky.edu/Ag/IPM/manuals.htm

If needed, insecticide recommendations are available in our Insect Management Recommendations for field crops available at:

http://pest.ca.uky.edu/EXT/Recs/welcomerecs.html

These publications may also be available at your local County Extension office.

Even though our trap counts do not suggest a big problem, the weather patterns certainly imply that scouting susceptible hosts is still important. I request that anyone that finds an armyworm infestation that requires treatment or should have been treated, please let me know at: doug.johnson@uky.edu.