Fall Armyworm
Class: Insects
Common Name
Fall armyworm, buckworm, budworm, and maize budworm
Scientific name
Spodoptera frugiperda
Potential Hosts
Fall armyworm affects over 80 different plant species. The following are important hosts: maize, rice, cotton, peanuts, soy, alfalfa, sorghum, sugarcane, bermuda grass, tomatoes, peppers, potatoes, eggplant, and tobacco.
Who am I?
Fall armyworm (FAW) is a species of moth and a member of the Lepidoptera. It feeds on the leaves and stems of more than 80 plant species and causes major damage to economically important crops.
FAW is regarded as a highly invasive species due to its ability to spread and reproduce quickly; female’s can lay over 1000 eggs during her lifespan. The lifecycle of FAW includes: egg, sex larval stages, pupa, and adult moth. The larvae stage is responsible for damaging the crop, and the adult moths move in the direction of the wind, which can reach up to 100 km a day. The adult moth is nocturnal (active at night).
Identification
Adults
The adult moth has dark gray, mottled forewings with light and dark splotches. Identifying the adults is not an easy task and won't be much help regarding treatment decisions since insecticides are not efficient means of killing them.
Larval Stage
To differentiate fall armyworm from other armyworm species, one can use the following characteristics:
The fall armyworm has a distinctive white suture in the form of inverted Y-shape between the eyes.
The last abdominal segment on the fall armyworm’s body has 4 distinct black dots.
The first larval instar is a light green color with a dark head and smooth-skin. It moves around in a looping motion. With time, instars become tan to brown in color and develop white lines lengthwise.
Eggs
Clutches of eggs will contain 100-200 individuals covered in protective scales and are generally found on the underside of leaves. Although they are hard to spot, the appearance of a large amounts of egg clutches is seen as an indication that insecticides are needed.
Feeding Pattern
Visual injury symptoms are what's known as “windowpane” and imply you have a FAW infestation. The first instar stages are too small to chew all the way through the leaves, so only the outer surface of the leaves are chewed off. The results are semi-transparent patches on the leaves.
On Armyworms
“Armyworm” is a descriptive term given for a group of moth species that exhibit large-scale, invasive behaviour. In their larval stage, they advance like a large army that eat every crop they comes across.
Control measures
There isn’t a simple way to control fall armyworm; farmers need to equip themselves with different strategies.
Use of Transgenic Maize:
An effective solution is the use of transgenic plant varieties known as Bt-varieties. The solution produces proteins that are toxic when pests ingest the plant tissues. Note: Bt-varieties aren’t available in some regions of the world.
Cultural
Monitoring: Closely inspect your fields (at least once a week) and look for the presence of caterpillars and feeding signs upon foliage. Early pest detection is crucial since insecticide treatment on young larval stages had higher rates of success
Sanitation: Make an effort to clean and maintain your field’s close surroundings from weeds as often as possible
Crop rotation of non-host plants will aid in reducing pest populations
Organic
Spinosad-based products
Biological
Bacillus thuringiensis aizawai-based products There are no known commercially-available natural enemies at this moment.
Conventional (chemical)
The timing of insecticide applications is critical. There is a necessity to spray when caterpillars are still small. Insecticides will have a difficult time controlling caterpillars bigger than half an inch in length.
The efficiency of applications depends on the stage of development and growth: As time progresses, height and density of the crop canopy can be a limiting factor and obstruct spraying materials from reaching their destination.
How To Know When To Spray?
Some general guidelines: Inspect your field and roughly estimate the infestation level. Consider taking an action when:
Approximately 5% of seedling plants are infested (initial phase of growth)
Approximately 20% of the whorls of small plants show the presence of the pest (first 1.5 months after seeding)
The following are generic names of products divided into separate groups (with respect to their mode of action). These products are found in one or more parts of world:
Group 1: Cypermethrin, lambda cyhalothrin, bifenthrin, betacyflutherine, and Deltamethrin; Group 2: Chlorantraniliprole and Flubendiamide; Group 3: Lufenuron, teflubenzuron, and methoxyfenozide; Group 4: Pyridalyl; Group 5: Indoxacarb; Group 6: Acetamiprid; Group 7: Emamectin benzoate; Group 8: Methomyl; Group 9: Chlorpyrifos
*Names marked in red are considered to be highly poisonous to beneficial insects.
*Names marked in green are considered to be organic and IPM (integrated pest management) compatible.
Careful thought should be taken when planning to use the above chemicals marked in red. What makes the FAW caterpillar so dangerous and difficult to control is that it can build resistance to pesticides quickly. Therefore, rotation between products based on different mode of action is crucial.
If caterpillar populations remain unchanged after a single application of one of the chemicals marked in red, future applications won’t just be inefficient. They will likely wipe out the presence of beneficial insects within the field’s close surroundings and make the situation worse.
Caution and careful notice should be taken when using any plant protection products (insecticides, fungicides, and herbicides). It is the grower’s sole responsibility to keep track of the legal uses and permissions with respect to the laws in their country and destination markets. Always read the instructions written on labels, and in a case of contradiction, work in accordance to the product label. Keep in mind that information written on the label usually applies to local markets. Pest control products intended for organic farming are generally considered to be less effective in comparison to conventional products. When dealing with organic, biologic, and to some extent a small number of conventional chemical products, a complete eradication of a pest or disease will often require several iterations of a specific treatment or combination of treatments.