Original content is great, but sometimes it is unnecessary to reinvent the wheel, or in this case, the YouTube video about armyworm damage in wheat.
We are starting to monitor true armyworm (Mythimna unipuncta) in the PNW, but efforts from Midwest states are much more deliberate because the species can be so damaging to large acreage of grasses and grains.
Today I found this excellent video from Chris DiFonzo at Michigan State University. Chris explains damage to flag leaves, thresholds and how to scout for larvae, and predicted impact on yield. Grab a cup of coffee and watch the 8-minute video here: https://youtu.be/C-Pk0ANkDr4
Soil type and the parameters associated with it (water holding capacity, %OM, etc.) could be important as we continue to investigate armyworm population dynamics. The Web Soil Survey is a useful, interactive tool that is freely available to all.
We are trying to discern why certain sites in our Tillamook trapping effort have 10-20X the amount of armyworm moths detected.
We know that when there is abundant soil moisture, more eggs are laid, and more eggs hatch, which increases the risk for damage by larvae.
Sites less than 5 miles apart have similar pasture management but very different trap counts.
In low-lying areas like coastal Oregon, the distance to the water table might vary between fields
I encourage you to check out the Web Soil Survey tool (link above) and do some “digging” around – there’s a wealth of information available!
60% of monitored locations had a positive catch of true armyworm this week. The average was 0.35 moths per day. The average last year (17 July 2018) was 0.00 moths per day. More info available here: http://beav.es/ZY3
Predicting cutworm and armyworm pressure is difficult. But without predictive tools (monitoring of adult moths, crop scouting, and detection of larvae), cutworm and armyworm attacks are only noticed too late, when the most severe damage has already been done.
Here are some factors that affect activity levels:
Cyclic booms and busts of pest population levels affect the balance of natural enemy regulation, which is one reason why we seem to have ‘bad’ cutworm and armyworm (and looper!) years followed by years where populations seem more normalized.
Some of the cutworm and armyworms we have in this region arrive each year as long-range migrants from southern latitudes. Weather patterns such as el Niño and la Niña can affect migration patterns.
Another predictor of risk is winter moisture level, both locally and in areas where moths overwinter. These, and other abiotic factors contribute to cutworm and armyworm survival and potential damage each year.
Wet Winter = Worms
Okay, so the equation isn’t quite that simple, but we do know that armyworm outbreaks tend to be worse after years with excessive rainfall from Sept-March. Due to recent trends, we will be researching WHY outbreaks happen and if we can better predict them. Stay tuned… (and tell your friends to subscribe for updates!).
Armyworm species, in particular, exhibit moisture dependency. This simply means that the percentage of egg hatch is greater if there is abundant soil moisture. Our regional precipitation was relatively normal from January-March (below, left), but 200% wetter than normal in April (right), and the flooding in May could affect egg hatch as well.
Maps courtesy PRISM program, Oregon State University white=normal; yellow=slightly less; green=approx. 2X increase
Africa looks to biocontrol to reduce fall armyworm problems
Fall armyworm (Spodoptera frugiperda) has been a devastating pest of cereal crops in Africa since 2016, when it was introduced from the Americas. It has since spread to over 20 countries in sub-Saharan Africa. Just this year, it was found in India as well.
Fall armyworm is particularly dangerous because it has a wider host preference than related species (it feeds on 150+ plants including rice, sugarcane, legumes, and cereal crops). Grains like corn, sorghum, and millet are not only a food staple for hundreds of millions of people, they are the root of other commodities like forage and biofuels.
Pests, drought, and extreme poverty already afflict many farmers, and there are both knowledge and income gaps that prevent wide use of pesticides or other control tactics.
Enter: the good news.
Tiny, tiny wasps.
We know that beneficial parasitoid wasps help regulate cutworm and armyworm populations, but on their own, they cannot help in an outbreak situation because there are simply not enough of them to make an impact. Unless – their numbers could be exponentially increased for very little money and people could be trained to ‘raise’ them.
One tiny wasp, in particular, Telenomus remus, already exists in the region, is easy to rear, and is not deterred by the ‘hairy’ covering that protects fall armyworm egg masses. Even better news: the technique of raising the wasps is being taught to local farmers so that the strategy can be implemented large-scale.
Scientists have been able to implement a mass-rearing program to enhance native natural enemies that attack fall armyworm eggs and larvae.
Fun fact: Some of our own Beaver emeriti (P. Jepson, D. McGrath) are working towards developing solutions to the fall armyworm crisis in Africa.
Bateman, ML, Day, RK, Luke, B, Edgington, S, Kuhlmann, U, Cock, MJW, ‘Assessment of potential biopesticide options for managing fall armyworm (Spodoptera frugiperda) in Africa,’ J Appl Entomol. 2018;00:1–15.
Virginia Tech Feed the future innovation lab video
Regional trapping of true armyworm (M. unipuncta) in Tillamook county has been ongoing since May. Only 6 of the 15 original monitoring sites remain, but at those sites, we have seen a sharp increase in trap counts.
We know that it is normal for armyworm to have 3 generations per year, which matches the pattern we see here:
This is our first year trapping this species, so these data are invaluable – thanks, Tom!!
Although the traps are in NW Coastal Oregon, it is not unreasonable to assume that activity patterns are similar here in the Valley. More importantly: This recent peak in adult moth trap catches suggests that (larval) armyworm activity THIS FALL is likely.
If there are any grass seed growers out there who haven’t sprayed yet (which I doubt there are), you may want to consider it. Product list here. Or at least hop on the four-wheeler and have a scout around. And remember that insecticides work better on smaller larvae, and by time you see apparent/massive damage, it may be too late for controls to be effective.
A few months ago, a paper was published, confirming that Bogong moths (Agrotis infusa) use geomagnetic fields as a navigational tool for their en-masse aestivation flight.
Say what, now?
Long-range migrations are common in the insect world, the most ‘notable’ (as in..the one in which most people take an interest) is that of the monarch butterfly. The migrations occur each year, are purposeful, and serve some ecological function; to reach breeding sites, etc..
In the case of the Bogong moth, millions of moths leave the plains of Australia and fly towards the high country of the Victorian alps to escape the heat and avoid desiccation. They congregate in such large numbers in the mountainous habitat that indigenous peoples would go there to collect the moths as a food source. They are also a preferred staple for mountain pygmy possums. In autumn, the moths return to the plains to lay eggs and the cycle begins again.
Aestivation is just a fancy word for: reduced state of biological activity that occurs in response to hot and dry conditions. It is a sort of ‘summer hibernation’, if you will.
Closer to home, we have Euxoa auxiliaris that exhibits the same pattern (replace pygmy possums with grizzly bears and Australian Alps with Rocky Mountains). The study found that successful orientation relies on a combination of visual cues and magnetic frequencies emitted by the earth, and that when either cue was missing or altered, their flights became uncoordinated and erratic.
So yes, insects have joined the ranks of migratory songbirds, salmon, sea turtles, and probably many other organisms that use geomagnetic signals to navigate.
Now we just someone to develop the superhero series for these Persistent, Amazing, Perceptive, and Strong …mutants?
No, wait – that name’s already taken:
Author note: not sure why the Dreyer et al. is being referred to as the ‘first’ discovery – 1. Baker, R.R. and J.G. Mather, Magnetic compass sense in the large yellow underwing moth, Noctua pronuba L. Animal Behaviour, 1982. 30(2): p. 543-548.
Other note: concerns of pesticide distribution, bioaccumulation and toxicity levels in this type of system have been raised since at least 2006, and warrant further review, IMO
…Over the past 2 weeks, I have started to detect Noctua pronuba in pheromone traps. There is a commercial lure available, and I have some of those deployed currently, but honestly, have just as good of luck tracking them as non-targets in other armyworm traps.
In 2017, there were 2 apparent activity periods, which matches with published estimates from U. of Idaho, one of the only other places in the country with a documented outbreak of winter cutworm. Click here to see an interactive comparison of trap catches between years, so far.
Keep in mind, these observations are NOT, at this time, part of a full-fledged sampling program for Noctua pronuba. Rather, I am mentioning adult flight because it is an indicator that there is POTENTIAL for winter cutworm activity starting about September 10th.
** Please review the OSU Extension publication for more info about host plants, history, biology, and identification of this species **.