THE rain season is on and I am sure the fight to suppress the fall armyworms (FAW) is bearing fruits and we are winning the fight.
Still on our quest to reduce information gaps on the FAW, we continue to impart practical solutions to the readers as we continue from last week’s topic on the pest.
FAW feed on more than 80 plant species which include maize, rice, sorghum, sugar cane and wide grasses such as cynodondactylon (Bermuda grass).
In terms of the biological life cycle the eggs of the FAW are generally laid on the underside of the leaves more especially near the base of the plant.
The eggs are laid close to the nodes attached next to the flag leaf, the reason for the hatched larva is to have access to the leaves and eventually hide on the whorl of the maize plant.
The complete life cycle is as follows, the egg to adult duration takes an average minimum of 32 days.
The eggs take two to three days to hatch. The larva stage will take 14 days in warmer times and 28 days during cold season.
The pupa stage will only take eight to nine days in summer. The female adult moth, lays up to 1500-2000 eggs in its life time, ally army worms are highly reproductive.
Where eggs are laid depends on the population of the moths, when the population is high the eggs are laid on both the upper and lower parts of the plant and the eggs can also be laid in the nearby bushes or vegetation.
To ensure that eggs are not visible moths hide the laid eggs with their scales robbed off from the moth’s abdomen.
The hatched larva will feed on the underside of the leaves, resulting into semi-transparent patches, the damage caused by the larva increases with age of the larva.
The damage will result into perforated leaf reducing the photosynthesis area, meaning less chlorophyll formation will result into low food production of the plant.
However, in tasselled maize plants, the larva will target the area around the cob and will find its way through the bracts of the sheath of the maize cob and feed on the cob kernels.
When the larva feeds on the kernel the droppings will attract the fungal diseases resulting into rotting of the cob.
It must be noted that FAW feed both during day and night time unlike the other caterpillars which feed only in the night.
In terms of description, the female adult moth has a distinct dark vein on the hind wing and the male has a pale orbicular stigma on its forewing, with greyish- brownish in colour.
There is need for scouting which simply means looking out for problems in the crop field, e.g. diseases, pests, orders, irrigation irregularities etc.
There are different methods of scouting, the Zigzag method (making continuous letter W across the field) and the X- method (making crosses from the centre of the field up to the edge).
However, any of the two can be used. For the first step, locate stations in your crop field in a zigzag method or x-method.
This aims at having the general representation of the field condition. The second step includes the selecting of at least 20 plants per station.
However, it is always imperative to look at the economical threshold if at all spraying the all field is necessary, otherwise spot spraying are best to avoid costs.
The spraying can be done when more than five per cent of the sampled plants have the eggs, 50 per cent of the sampled plants are severely damaged and 20 per cent of the plants have leaf damage and have live larva present on the sampled station.
There is surveillances, and insect trapping which is done by the use of pheromone traps and light traps which are some of the best ways of knowing the presence of pests.
Pheromones must be placed throughout the field according to the manufacturing recommended spacing at setting up the traps in the field and should be all year round.
The data collected can now be used for planning ahead.
Look out for fall army worms.
Inclusion early detection of the fall army worm is the best way to avoid crop losses and God willing we will one day look at that.
Generally, for more information on the control methods, visit the extension officers in your areas or contact.
Wishing you a productive week.
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The author is an agricultural consultant at Malangwa Agricultural Innovative Services, with 18 years experience, as farm manager, extension officer and sales agronomist.