The fall army-worm (FAW) feeds on more than 80 plant species including vegetable crops, rice, sorghum, maize, sugarcane, cotton and millet.
The origins of FAW can be traced in west & central Africa in 2016 and to date it is still not clear how this notorious worm is capable of adapting to various ecological and biological conditions across the world.
In the absence of any control methods, FAW is a serious threat to the income and food security of millions of small-scale farmers in Kenya.
Today, the fall Army worm is present in over 30 African countries including Kenya where it is a nuisance to thousands of maize farmers.
Fall army-worm control is effective during the egg stage or when the larvae are small, therefore early detection and proper application of the right pesticides are critical.
Spread & movement
Fall Army Worms spread rapidly across huge geographic areas. In fact, in some migrations, the eggs can move over 4oo km before hatching.
These eggs may move longer distances depending on the wind strength. It is also important to note that, FAW generations will be continuous throughout the year wherever as long as the climate is favorable and host plants are available, even if it is irrigated or off-season crops.
The FAW life cycle is completed in about 30 days (at a daily temperature of ~28°C) during the warm summer months but may extend to 60-90 days in cooler temperatures.
Fall Army-worm Life Cycle
Egg Stage (2-3 days)
Female FAW deposit their 150-200 eggs in a single layer although it is not uncommon to find multiple layers of fall armyworm eggs attached to a maize plant. Eggs are typically dome shaped with a flat base and around apex.
Larval Stage (14 days in warm weather and up to 30 days in cooler areas)
The fall army worm larva looks more like the maize earworm, however FAW larva are smooth to the touch and may sometimes appear to be greenish in color with a black head (see figure 1).
The best identifying features of the FAW are a set of four dark spots that are aligned to form a squared shape on the upper parts of the body. The tip of the head also forms a distinct Y shape (See figure 2)
FAW larva usually hide away from direct sunlight therefore it may be difficult to spot them during the day.
Fall Armyworm larva Identification
Pupal Stage (8- 9 days in warm weather but may go up to 20 days in cold weather)
Unless the ground is hard, FAW larva pupates slightly beneath the soil surface (2- 6 cm). If the soil is too hard the caterpillar will cover itself in leaf debris before pupating.
In either case, pupation occurs in an oval brownish cocoon measuring approximately 20 mm. Brown with shades of red is the typical color of the FAW pupa (See figure 1)
In most cases the fall army worm pupa will die in extended periods of extremely cold weather.
Fall Army Moth (Adult Stage: 10- 21 days)
The fall army moth is the last stage of the FAW lifecycle. During this phase, the females lay eggs to restart the cycle.
There are important differences between the female and male FAW, most notably, the male moth’s forewings are shaded brown and gray. The tips and the center of the wings also have triangular white spots.
The female is less distinctively marked and is usually greyish brown in color. Duration of adult life is estimated to average about 10 days, with a range of about 10 to 21 days depending on weather conditions.
Fall Army-worm Damage
The fall armyworm larva is the most devastating stage for farmers. Large larvae destroy maize leaves resulting in loose of aesthetic value and sometimes total damage of the leaf.
Fall Army-worm Control
Which is the best Stage to control fall army-worm?
Farmers need to take control measures as soon as they spot FAW eggs in part or the whole plantation. Applying the right treatment at this stage makes easier to kill the FAW and prevent damage that is caused by the larvae. Remember also that the larvae tend to hide during the day so it may be difficult to control the damage on huge plantations.
Fall Army-worm Insecticides
Agrichem Africa has a broad portfolio of products that can be used to effectively control the Fall Armyworm in many crops, including maize which is the most affected plant.
However it is important to note that in order to effectively control FAW farmers must embrace an integrated approach.
From the choice of good seeds, to the application of the right pesticides and good farming practice, all these are necessary to combat the FAW threat.
This is particularly important given the fact that in some parts fall army worms have become resistant to common insecticides.