Manage to reduce the impact of fall armyworm – know your enemy


By Nan Smith | 18 May 2017
enemy
The fall armyworm has three white stripes down the back and a white inverted Y on the head.

The fall armyworm (FAW) is well named for the devastation it leaves behind as it eats its way through crops –like an army following a scorched earth policy. Unfortunately, there is no permanent peace treaty with this particular enemy.

Dr Anton Chapoto, agricultural economist of the Indaba Agricultural Policy Research Institute (IAPRI) said, “Once it has attacked, it’s here to stay. Don’t think it has gone, it’s only gone to ground.”

It is not to be underestimated, but it should probably not be seen as a precursor to a continental panic attack. As usual in farming, knee-jerk reactions are not a great way to go.

According to FAW expert Prof Kenneth Wilson, (The Conversation 12 February, 2017) of Lancaster University, FAW is native to Central and South America’s tropical and subtropical areas, but with pretty extreme long-distance flying ranges it has migrated as far north as Canada.

The brown moth of the FAW with its grey patterned wings may look innocuous but it is capable of flying long distances and the females are prolific egg layers.

The caterpillar, (or the larval stage) of the innocuous-looking brown moth (Spodoptera frugiperda), is what we call the fall armyworm (FAW).

This caterpillar is a voracious feeder and eats its way through croplands at an alarming rate. As one small-scale farmer from the Zambian Copper Belt put it, “These insects have eaten all my maize.”

Although maize has been the worst affected crop since FAW arrived on the continent about 18 months ago, wheat, soya beans, cotton, rice, sorghum, sugar cane, groundnuts and potatoes are also menu choices.

Because many of these crops are staples, FAW is a definite threat to food shortages in the sub region.

LIFE CYCLE AND CONTROL

The fall armyworm has a 30 day life cycle in the hot season that lengthens to 60 to 90 days during the cooler seasons. FAW does not like frost but in the tropical and sub-tropical areas it can be active all year round.

Moths migrate and lay eggs which hatch into larvae. The larvae (caterpillars) pupate and the pupae metamorphose (change) into moths – that’s the basic life cycle.

Egg packets are found on top of the leaves. The top of the egg packet looks ‘fluffy’.

The FAW can spread easily because the moths are strong fliers with long ranges and highly fertile females. The larval caterpillars can eat a variety of plants and are resistant to many pesticides.

Pesticides only work on young larvae before they penetrate the maize ear in the early stages of development. This is why spotting is so important.

It’s crucial to get your eye in and scout fields so that you are aware of the worms before they start doing damage.

Young larvae hatching from the eggs are candidates for a spraying cycle with the right chemical.

SCOUT, SCOUT, SCOUT

Scout every day and when you scout, look for the egg packets on top of the leaf. Eggs take about four days to hatch – spraying the eggs will kill larvae as they hatch. The early stages (up to the fourth instar) of the larvae are susceptible to the right kind of pesticides.

Once the caterpillars disappear into the whorl of the maize plant or into the ear it is a waste of money spraying them, says South African chemical expert Dr Gerhard Verdoorn of CropLife.

CropLife South Africa advises spraying when 5-10% of the plants have been infected.

For an up to date list of more than 40 chemicals and biologicals to support an integrated pest management programme and detailed information on identifying the fall armyworm go to the CropLife website.

Farmers should be aware that there are a number of spurious remedies punted in the field that do not, not will they ever, work. Spraying FAW caterpillars with washing powder, using ash as a means of control, and other remedies like this is just a waste of money and/or time. This does not mean that biologicals or alternative farming methods should be tossed out, indeed they should not.

But sensible farmers know that the FAW armyworm problem is serious enough to warrant intelligent and diligent attention