Fall Armyworm Moth Flight – Has begun to drop, but still plenty around!

Doug Johnson, Extension Entomologist

Figure 1. 2012 Capture of FAW

The second flight of fall armyworm (FAW) has begun to drop as indexed by the UK-IPM pheromone baited trap in Princeton, KY. Nevertheless, the capture for the trap-week ending Sept. 20, 2012, is still greater than the peak capture during the outbreak of 2007. (See Figure 1.) So, hopefully, we are on the downhill side of this problem, but there will still be plenty of moths to lay eggs over the next couple of weeks.

Producers, consultants and farm service personnel are still calling to report infestations and ask questions. There does not seem to be much problem with obtaining control once an infestation is found, but many folks are still not finding the infestations until considerable damage has already been done. Certainly, most callers are interested in what is coming next. Although the moth capture gives us a heads up and an indication of the level of risk, they will never tell us what is happening in a given field.

Our current weather may tend to extend the time the caterpillars are present. Our cooling temperatures are not cool enough to hamper the worms, but their development may slow down, increasing the days they will be in the damaging stage.

The crops at risk remain the same. Grass crops (pasture, hay, lawns) still remain in danger. Still, soybean problems appear to be coming from the caterpillars “marching” out of grasses in to the beans. Don’t neglect to check a field interior now and again. FAW will lay their eggs in soybeans, but grasses are by far the preferred egg laying site.

Anyone planning to plant wheat, rye, or renovate / restore any “small” grass pasture or hay field should give strong consideration to waiting for a while longer to seed. Experience tells me FAW caterpillars will be around until frost, even if not in the large numbers present now.

Fall Armyworm Moth Counts Continue to Climb!

Doug Johnson, Extension Entomologist

Capture of fall armyworm (FAW) moths has increased for the second week in a row, and this week by a huge margin (Figure 1.). Not only has an unprecedented second distinct FAW flight begun, it has surpassed this year’s previous peak in size. The August flight which reached 549 moths / trap-week for the trap-week ending Thur., Aug 16th, now stands at 675 moths / trap-week for trap-week ending Sept 13, 2012. Will it go higher? Only time will tell.

In addition to the numbers of FAW moths being captured, there is a second situation that gives me pause. This 2nd flight peak will be earlier in the season than we normally see, if one occurs. If the current numbers turn out to be the largest capture, then the peak will be approximately two weeks earlier than we would normally expect. Putting this in perspective, if we have an average frost date of Oct 22nd , this flight has approximately 5 ½ weeks for the caterpillars to develop and feed on our crops as opposed to a more normal 3 weeks. If frost is late this interval could be even longer.

Remember, the graph above represents MOTH flight. Moths are not the damaging stage of this insect. These moths were captured because they were seeking female mates. Once mating and egg lay has occurred, we will begin to see very small FAW caterpillars. This is the beginning of the damaging stage. This will likely take a week, perhaps two, depending on temperatures. Of course, further south and west (toward the upper Mississippi River bottoms) caterpillars will appear sooner. Further north and east (in the western 1/3rd of KY), caterpillars will take longer to appear. Fortunately, the traps in Lexington have just this week captured FAW for the 1st time this year; and the numbers are small. I doubt that there is any unusual risk in central and eastern portions of our field crop / pasture-hay production area.

Remember, as well, that these trap counts will NOT predict what will happen in an individual field. There is really no easy way to detect the presence of this pest. One must go to the field and look for their presence / activity. I would start by sweeping in grasses that have received enough rainfall to start re-growth. This will be a preferred egg laying location. FAW will lay eggs in soybeans, but they are not the preferred host. If this generation acts like the last, most soybean infestations will start with worms moving from grass waterways, roadsides & pasture/hay fields.

Crops primarily at risk will be newly planted wheat, pasture / hay production and very late maturing soybeans.

There is really only one thing that can bring this cycle to a halt….cold weather. FAW is a tropical insect that cannot overwinter in KY. In fact, under historic conditions, FAW cannot overwinter outside the gulf coast areas. So, vigilance will be needed until a hard frost stops their northward migration. Certainly, this is not the year for early planting of wheat.

Also, see Kentucky Pest News No. 1318, Sept. 11, 2012 at:

http://www.ca.uky.edu/agcollege/plantpathology/extension/kpn/current.html

and the Wheat Science News Vol.16, No.5, Sept. 7, 2012 at:

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

for the article: “The Effect of Insects on Wheat Planting Decisions” for a more complete look at FAW and other arthropod pests on our upcoming wheat planting season.

Fall Armyworm Moth Flight Increases, worms sited!

Doug Johnson, Extension Entomologist


Capture of fall armyworm (FAW) moths in UK-IPM pheromone-baited traps has increased substantially over the last week. Until recently, there had been no FAW moths captured at the UK-REC in Princeton (Caldwell Co.) and only small numbers in Cam Kenimer’s trap line in Fulton Co., KY. In the trap week ending 9 Aug. 12, the capture increased from zero to 131 moths / week at the UK-REC, though the Fulton Co. trap counts remain low.

It is difficult to know what the increase at the REC might mean, however, a producer in Caldwell Co. (the county in which the REC is located) has seen a small number of FAW crossing a road. Additionally, reports from counties further east and south report FAW infestations in pastures (they must have gotten some rain!!!). Add to this reports from our colleagues in states to the south, indicating increases in FAW activity in areas that have received recent rains; and I think this adds up to checking to make sure they are not present in your fields.

At this time of year FAW are primarily a risk to soybeans and pasture / grass hay fields. They would also attack corn, but we are too far along for this to happen in our major corn growing area. Nevertheless, this insect can be quite voracious so producers of soybean and pasture / grass hay are encouraged to check your fields to look for this critter.

FAW is a migratory pest in KY and is only an occasional pest of soybeans; but it can cause serious damage if infestations are large. Soybean is not a preferred host crop, but it may be infested especially in years when grass crops are not available. Given our unprecedented drought that is certainly the case this year. This is primarily a defoliating pest but can feed on pods as well.



FAW on corn leaf.



Newly hatched FAW are white with a black head, but the body darkens as it grows. Full-grown larvae are up to 1 1/4“ long, have black bumps, and may be light tan to dark green. The black head will have a distinct inverted “Y”.

Thresholds for this pest in soybean are not well established in KY. Like corn earworm, if sampling in wide row beans with a 3’ shake cloth, the threshold would be an average of 2 worms per row-foot. If sweeping narrow rows with a 15” sweep net, an average of 9 larvae per 25 sweeps would indicate a need for control.

Thresholds for FAW in pastures / grass hay fields are also not established. Clearly the insect can do great damage in some situations. In states further to the south of us 4-6 or 5-7 worms per square foot are used as the economic threshold. Though the season would be earlier and the grass variety different, that is probably as good as starting place as any.

If insecticidal control is required check ENT-13 (for soybeans) or ENT-17 (for pasture / grass hay) for a listing of registered insecticides. These publications may be obtained from your county extension office or on the web at:

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