Tuesday, September 14, 2021

Fall Armyworms Are Back with A Vengeance.

Close-up of a Fall Armyworm on a leaf.
In case you haven’t heard, the always-awful Fall Armyworm (Spodoptera frugiperda) is making its presence known this year in bigger and more voracious numbers than ever before. In fact, according to this article from the Smithsonian, the caterpillars are invading at an unprecedented level. The reason for this is weather-related, like so much else that is plaguing us at this point in the 21st century. And, since the unheard-of weather events we’re seeing are the result of climate change, so all these caterpillars are yet another symptom of climate change. 

A storm over a green and rural place, with lightning striking the ground.
So how do caterpillars and climate change correlate? It takes several steps, each one being more intense than the next as follows: Caterpillar populations boom in drought conditions (which huge parts of the globe are experiencing). The main reason for this is that their natural controls in the form of fungal diseases cannot develop properly when it is too dry. High numbers of caterpillars turn into high numbers of moths. As the moths get flying, they are caught up in storms (and there have been massive storms worldwide recently). Fall Armyworm moths can (and do) survive up in the jet stream, which can take them great distances. Once they finally land in a new place, if there is abundant food they will respond by producing great numbers of larvae (caterpillars). Sometimes this food is carefully planted crops, and other times it’s native grasses. Often, the same storms that brought the moths have caused explosive growth in native plants. Fall Armyworms have traditionally been an issue only in warmer climates as they do not diapause, which means freezing temperatures will kill them. But this distribution is changing as storms move them northward and northern areas warm up. If temperatures stay warm enough through the winter wherever they land, they will just stay there. 

A Nigerian woman in an orange shirt and beige head wrap checking her crops for worms.
The Fall Armyworm is native to the Americas, but this has not stopped it from expanding its reign of
terror elsewhere. In 2016 it reached Africa, and in 2018 it reached Asia. In both areas, it has set upon maize plants (its preferred food) and other essential food  crops with devastating results. The effect that the Fall Armyworm has had in the developing world has been compounded by its resistance to chemical pesticides and its ability to survive in harsh conditions. In just one year (2018) in Nigeria, these pests disrupted the food supply of 1.5 million people. Faced with such a serious problem, scientists have been working overtime trying to find a solution and it looks like they may be on to something. Parasitoid wasps native to East Africa and India have been identified and, they enthusiastically prey on the non-native armyworm eggs. Here is a great article that will tell you more on this. Suffice to say, these wasps provide a speck a hope in a tragic situation. 

A small Fall Armyworm making its way up a leaf.
Fall Armyworms are not just resistant to pesticides and drought, they are efficient and relentless. In fact, they got their name from how they march across fields laying waste to everything in their path, just like an army does. They can devastate a golf course in 48 hours and can wipe out a forage crop in hours. According to this article from Texas A&M, the Fall Armyworm moths can lay up to 2,000 eggs which will hatch out hungry caterpillars in two to three days. Their reproductive cycle is fast enough for at least four to five generations to appear in just one growing season. 

Fall Armyworm moth
Although Fall Armyworms are a formidable foe for growers everywhere, there are some steps that can be taken to gain a measure of control. However, if you have an infestation that is well entrenched already, you may have to scrap the lawn or garden for this season and start over next year. Otherwise, your  best bet for control will always be a multi-pronged approach. The following are some examples of things to use that can get you the help you need. Our Fall Armyworm page has many more suggestions.

Traps and Lures: 

It’s always best to stop an infestation before it starts. With this Scentry Lure, the moths will come right to you and you can monitor how many there are flying about before they turn into ravenous worms (you’ll use it with a Scentry Wing Trap). This will help you plan your next stage of defense. Plus, whatever moths you catch will not be reproducing.

BONIDE® Thuricide

Bacillus thuringiensis:
These beneficial bacteria have proven to be extremely effective against Fall Armyworms, with two caveats: They need to be ingested by the larvae and they work best on newly hatched larvae. We have several species within our inventory for you to choose from. One of our most popular and cost effective products is BONIDE® Thuricide, which is powered by Bacilklus thuringiensis v. kurstaki (Btk).


PFR-97™ 20% WDG
While Fall Armyworms have displayed resistance to conventional insecticides, this is not generally a concern if you use products whose active ingredients are naturally occurring or botanical. These types of products have modes of actions (suffocation, anti-feeding, etc.) that insects cannot develop resistance to. You may want to try Debug® Optimo, Debug® ON or Debug® TrĂ©s, all of which use azadirachtin derived from neem seeds. Or there is Entrust™ SC Naturalyte® Insect Control, whose active ingredient is the soil bacterium spinosad. And then there is  PFR-97™ 20% WDG which utilizes the entomopathogenic fungus Isaria fumosorosea Apopka Strain 97. All of these are excellent choices.

Cartoon worms on the march

Fall Armyworms will continue to be a problem until we as  a species can get a handle on climate change. In the meantime, with a little foresight you can reduce the effects these pests can have on your growing things. 

Take Care.

Submitted by Pam.

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