Saving maize crop from armyworm

The armyworm is especially devastating for maize farmers in Kenya and across Africa because it attacks the crop while it is still in the field.

The fall armyworm often invades Kenya’s breadbasket regions of the North Rift and western Kenya maize belt and Meru and Machakos counties.

Integrated pest management is the best way to tackle the risk posed by the ravenous fall armyworm. Awareness campaigns, scientific innovation, quick and coordinated action as well as a multi-agency collaboration is required to tackle the menace.

Nature of threat

Integrated pest management is the best way to tackle the risk posed by the ravenous fall armyworm, experts say. Awareness campaigns, scientific innovation, quick and coordinated action as well as a multi-institutional collaboration will be required to tackle the fall armyworm menace.

This was the message to delegates at a consultative meeting on the pest held in Nairobi recently. The armyworm, which attacks more than 80 different plant species, including grass and maize, a staple food in East Africa, is a threat to regional food security.

“The truly frightening risk of the fall armyworm to food security in Afriintegrated pest management programme,” says Dr Boddupalli Prassana, the director of the Global Maize Programme at the International Maize and Wheat Improvement Centre.

The fall armyworm – Spodoptera frugiperda – has its origin in the Americas, but was first reported in Africa in West and Central Africa, before extensively invading southern Africa. The pest can lay up to 1,000 eggs during its lifetime and produce multiple generations quickly. The larva is spread mainly through wind dispersal on host plants from the eggs laid. It can cause crop losses of up to 73 per cent and becomes difficult to control with pesticides in its advanced larval stage. The worm invades farms in the bread basket counties of Baringo, Bungoma, Busia, Kakamega, Kericho, Nakuru, Nandi, Narok, Siaya and Uasin Gishu.

“We cannot eliminate the pest. Now that it is here to stay, we can only support farmers to manage their crops,” Dr Prassana told a stakeholder consultative meeting in Nairobi. Dr Roger Day, the sanitary and phytosanitary coordinator at the Nairobi-based Centre for Agricultural and Biosciences International (CABI), says the armyworm invasion costs Africa a billions in losses every year. The scientists also fear that the pest could become endemic across the continent. Prof Kenneth Wilson of Britain’s Lancaster University, who has extensive experience working on the African armyworm, predicts that it could spread to the Middle East and eventually Europe.

The moth has been known to fly distances of up to 1,600 kilometres. The meeting noted that Brazil, a tropical country, has battled the pest in the past, and could be a useful benchmark for understanding how to manage it in Africa, which does not have the natural control measure of freezing temperatures. Mr Clement Muyesu, an assistant director in charge of food crops at the Ministry of Agriculture, says: “We still don’t understand it very well and are learning from experts and countries where there have been infestations. We are hopeful that we will combat it.” He says the government has committed an additional Sh320 million to fighting the worm.

“The fall armyworm is bigger than the African armyworm, and behaves like the stalkborer. It burrows into stems and hence, not easily reachable by some pesticides.”

to explore. “Relying only on pesticides is not an option, if we have to eradicate the army worm,” he adds.

Tackling the armyworm, Dr Prassana explains, would also require developing transgenic materials such as Bt maize, which are drought resistant. Research institutions will mobilise vast germ plasm resources and modern breeding tools to speed up the development of transgenic materials resistant to the worm. A combination of methods must be used to curb the spread and damage by the pest.

“The first step is an effective integrated pest management strategy to survey and monitor pest movements, assess yield loss levels and compile data using remote sensing equipment,” says Mr Gabriel Rugalema, FAO’s country representative in Kenya.

The Agriculture ministry has formed a committee to perform several tasks, including creating awareness on the pest and its characteristics. Ms Candace Buzzard, the deputy mission director at the US Agency for International Development (USAid) in Kenya and East Africa, says: “We are building resilience to increase agricultural productivity and regional coordination.”

Though no research has been undertaken in the country to control the fall armyworm (FAW), most experts agree that the best way to tackle the dreadful menace is through integrated pest management (IPM).  They also suggest that to win the war against FAW, there is an urgent need to collaborate Other research and development institutions in Africa must also work together to come up with a long lasting solution. There is a need to strengthen national and county capacity in surveillance, diagnostic skills and management of FAW by training public-private extension service providers, seed inspectors, agrochemical dealers, spraying teams and farmers. A strong communication network on the pest must also be developed to disseminate information. An IPM tool has to be developed to provide a sustainable solution.

IPM is an effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices. It is not a single pest control method, but a combination of cultural, biological and biopesticide control measures.

IPM is an effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices.

It is not a single pest control method, but a combination of cultural, biological and biopesticide control measures.

These include developing host plant resistance, use of low cost chemicals, protective clothing and spraying equipment; and developing drought and pest-resistant hybrid crops. Others are identification of predatory insects, pheromone traps to lure moths to target and destroy eggs and larvae as well as use of bio-pesticides from natural distribution by birds or animals.

How Integrated Pest Management works

Intercropping with legumes

According to research, FAW infestations have been reduced by 20-30 per cent on maize intercropped with beans compared to maize alone.

ample, an effective bio-pesticide has been developed against the African armyworm but it needs to go through several registration and commercialisation processes that are costly and time consuming.

Bio-pesticides tend to be effective against a much narrower range of species than chemicals, which is good for the environment. But it means that they can only be used for a limited number of pests, often making them more expensive than chemicals. A similar bio-pesticide has also been developed against the fall armyworm, but again this is not yet registered for use in Africa.

Transgenic materials

In parts of their native range in the Americas, genetically-modified Bt maize has been grown to combat the fall armyworm. This may also be an option for South Africa and some other countries where GM crops are already grown. But many parts of Africa do not allow or welcome GM varieties. Interestingly, fall armyworm has also evolved resistance to some Bt toxins, with some evidence for crops resistance.

Chemical control

Chemical pesticides can be effective against armyworms. However, resistance to many chemicals is an issue. Synthetic pyrethroids have been effective at controlling infestations, but according to CIMMYT; extensive use of synthetic insecticides in South America to control the pest has led to the development of resistance.

Most of the insecticides used are Insect Growth Regulators (IGR). It is not known whether there is pesticide resistance in the fall armyworms blighting southern Africa. But the variable efficacy may be due to genetic resistance, or it might be as a result of the way in which the spray is applied. The application of an insecticide is also usually not economical for control of the fall armyworm but may be necessary if the infestation is extremely severe and/or the plants are under stress. Extensive research, however, is needed to work out which chemical is the best to control the pest in southern Africa.

Insecticides must be applied during the early development stages of larvae because adult larvae may prove to be very difficult to control. They are often inaccessible to insecticides because of their tendency to hide in the whorls and reproductive parts of the host plant. Their excrement also becomes so heavy that it can prevent penetration of the insecticide into the whorls.

Farmers should start their spraying early and ensure good coverage. FAW have a tendency of mutating and developing resistance very fast, thus it is recommended that pesticide groups are rotated with different modes of actions (MoA) and active ingredients. In addition, due to the fact that the FAW moth travels hundreds of kilometres, it is recommended to adopt one spray programme within a wide geographical location to avoid resistance. Spraying should be done late in the evening when caterpillars are most active. Amiran has developed four products to curb the problem.


Grizly is a combination of benzoylureas(IGR) and neonicotinoids with translaminar, systemic and contact activity. It is readily taken up by the plant and further distributed acropetally through the entire crop. Grizly has both ingestion and contact activity on larvae of armyworms and is a growth regulator, thus prevents the FAW from proceeding to the next instar.

Benefits to the Farmer

  • Excellent control of army worms due to its two modes of activity – acts as a stomach poison and growth regulator.
  • Has high absorption rate due to systemic and contact activity.
  • Provides a long protection to cereals because of long residual activity.
  • No cross resistance.
  • Broadspectrum.

Pyrinex Quick

is a unique combination of micro-encapsulated formulation of chlorpyrifos and a pyrethroid. The combination of the two active ingredients bring fumigant action and quick knock down on army worms.

Benefits to the Farmer

  • Unique combination of two active ingredients with excellent knock-down effect.
  • Good combination for resistance
  • Safe and Broad spectrum

3 prove 1.92 EC

A non-systemic insecticide with the ability to penetrate leaf tissues by trans-laminar movement. Once applied on army worms, feeding and egg laying stops and death occurs after a few days.

Prove has a long residual effect and no cross-resistance has been recorded due to its unique mode of action.

Benefits to the Farmer

  • Unmatched solution for control of armyworms.
  • Once applied, armyworms stop feeding immediately.
  • On adult moths, egg laying stops and thus no progressive generation.
  • Prove has a long residual effect.
  • No cross-resistance has been recorded due to its unique mode of action.

Rimon Supra

Rimon is a non-systemic highly concentrated benzoylurea with contact and strong stomach activity. Rimon is an insect growth regulator and acts by inhibiting chitin biosynthesis resulting in interference with the normal formation of the cuticle. The insecticide has a unique mode of action and thus can be used for resistance management.

Benefits to the Farmer

  • Pests stop feeding on the crop within 3 hours after exposure.
  • The product has strong stomach activity.
  • Provides prolonged control.
  • Suitable for integrated pest management.
  • Highly selective.

Biological control

Predation: The use of predators as beetles, bugs, birds and rodents consume larvae and pupae readily.

Pheromone traps: Set up 4-6 FAW Pheromone traps per Ha to catch adult male moth, prevent mating and ultimately suppress the moth

How to make your own natural pesticides?

Aside from using synthetic pesticides to control pests, discover natural ways that you can use to halt pests such as thrips, aphids, caterpillars, armyworms and a host of others from attacking your farm. The best time to spray is early in the morning and evening to avoid disintegration from the sun and to killing predators and beneficial insects.


Crush a handful of mature blackjack seeds, add water and boil for 10 minutes then leave it to cool. Alternatively, soak the ground seeds in water for a day. Filter and dilute with an equal amount of soapy water. Use as a general spray for aphids, ants, beetles, cabbage root flies, caterpillars, crickets, mites, termites and whiteflies.

Lantana Camara

Collect leaves of lantana, dry them and spread at the bottom of the storage facility to control storage pests. Place the crop to be stored on top. Helps control cassava weevils, grain weevils and potato weevils.


Crush leaves (about 3kg) and put in four litres of water. Leave for five to eight days or boil for 20 minutes then leave to cool. Filter the liquid and dilute in an equal amount of soapy water made by using bar soap. Spray on the affected crop. Use the large decomposed remains to mulch your vegetables. Inter-planting marigold with crops helps in repelling pests such as ants, caterpillars, cutworms and nematodes. Marigold with chili pepper:

Take 500g of the whole marigold plant and 10 hot chili pods. Soak in 15litres of water and leave overnight. In the morning, dilute in the ratio of 1:2 with water. Add 1 teaspoon of soapy water per litre of the extract. Useful in managing aphids, (Colorado) beetles, grasshoppers, grubs, locust, scales, snails, thrips, weevils, whiteflies.


Neem leaves, fruits, seeds, bark and roots have insecticidal, anti-feed and pest growth inhibiting qualities. The tree takes minerals from deep within the soil.

Anti-feed: Neem repellent does not kill pests immediately, but after tasting it they stop eating and eventually die.

Make a solution from the Neem seed cake powder. Use 500g (three handfuls) of Neem powder and mix it with 10 litres of water and bar soap. Soak it for 12 hours and stir it regularly. Then spread it out on the crops, not forgetting underneath the leaves. Spread it twice a week particularly when pests are rampant. When there are fewer pests, spread every 7 to 10 days. However, don’t spray four days before harvesting. This is used on all vegetables to control all pests.

  • Mix Neem leaves with the crop to be stored. These leaves can also be laid between books or clothes.
  • Mix Neem powder with sawdust and termite clay. Put the mixture in a funnel and throw it in the heart of the maize plant. The rain will spray it. Repeat every eight days. This will help in containing the maize stalkborer.
  • Use this method 10 to 15 days before sowing seeds or planting seedlings. Make the soil loose with a rake. Mix 2kg of Neem powder (eight handfuls) with 10 litres of water. NO SOAP. Leave it overnight. Stir it regularly and apply it the next morning with a watering can on the loosened soil. This helps in killing nematodes in the soil.
  • Use 50g of Neem powder per 1 litre of water. Stir for 10 minutes and add bar soap. For the next six hours keep stirring regularly. Before applying stir for 10 minutes. Spray early in the morning or late in the afternoon. Dip banana suckers overnight in this solution before planting to avoid attacks from the banana weevils.
  • Extract Neem oil from seeds or bark by using a pestle and mortar. Smear seeds with this oil to curb aphids and whiteflies.

Onions, Garlic and Leeks

Useful against many pests, especially: ants, aphids, armyworms, caterpillars and codling moths. Crush leaves or bulbs of the plants, mix in water and allow to stand for two to three days. Filter and dilute in an equal amount of soapy water. Apply on the crops as a spray. These plants have a strong smell, which repel most pests. Intercrop with tomatoes and carrots against carrot fly.


Pyrethrum kills most insects including mealy bugs. Boil about half a kilo of pyrethrum flowers in four litres of water to make a ‘strong solution’. Leave to cool and filter. Dilute with an equal amount of soapy water. Apply or spray directly on pests over affected plants. Spray late in the afternoon to avoid killing useful insects, e.g. bees. Dry flowers and grind to a powder and dust over insect pests.

Red peppers and Chilli peppers

Ants, aphids, beetles, caterpillars, cutworms, slugs, snails, mealy bugs, white flies. Crush a handful of pepper fruits (100 gr.) and add 1 l. of water. Leave for one to three days or boil for 20 minutes. Dilute the mixture in an equal amount of soapy water made by using bar soap. Filter and spray on the crops. Apply powdered chillies around the base of crops to repel pests.


Aphids and thrips. Boil water and put the leaves of the rhubarb into the water. Leave it to cool down. Spray by adding 1:3lt of water. Use against soft bodied insects.

Sodom apple

Collect about 50-100 ripe Sodom apple fruits. Extract the juice by squeezing the pierced fruit in 2lt. of water. Then spray immediately. Note: Sodom apple extracts cause irritation so avoid skin contact. Do not spray natural enemies. Put a stick in the apple and then press it in the ground between the pumpkins. The insects which attack the pumpkin flowers, will be attracted to the apple and suck the juice. They will die.

Stinging nettle

This is a fungicide and contains a lot of iron. Use against ants, aphids, armyworms, caterpillars, cutworms, slugs, snails and thrips Take 500 gr. of the plant and 10 hot chilli pods. Soak them in 15lts of water. Leave them in water for a night. The next morning dilute 1:2 with water. Add 1 teaspoon of soap per litre of the extract. Apply the solution as a general spray.

Sun hemp is a trap plant

Plant in a field known to have nematodes. Its roots produce a substance which attracts nematodes and traps them.

Tobacco leaves

Tobacco is poisonous because of its nicotine content. Care must therefore be taken when using it. Against beetles, cabbage worms, caterpillars, cutworms, maize stalk borers, mealy bugs, slugs, snails, thrips.

Crush a handful of fresh leaves (250gs) and add 4litres of water. Boil for 20 min. and allow to cool. Filter and dilute the liquid with 5 equal parts of soapy water. Use as a spray. Crops should only be harvested after 4 days from spraying.

Early planting

Avoidance of offseason agriculture (moths are said to be attracted to extremely late planted/late maturing maize).


Early detection through scouting crops every from the current wind direction, checking borders and centres of crop fields.


  • Restrict movement of infested plant materials from areas where the pest has not been reported.
  • Using habitat manipulation techniques
  • Use trap crops, landscaping and companion plantings to enhance activity of biological control agents

Hand picking

Of caterpillars and egg masses. Killing one caterpillar prevents more than 1,500 and 2,000 new caterpillars after a period of less than four weeks. Tools should be designed to allow farmers to pluck the larvae out of plants and destroy eggs and larvae of the pest.


Adding sand to maize whorls where armyworms are feeding can help control them

Mechanical Control

Deep ploughing exposes the pupae to predators and solar heat.

Pheromone traps

These are used to monitor the presence of insect pests and to lure male moths to disrupt mating and to have them destroyed in designed devices, forest margins and shrub land.

The chemicals in the leaves are called rotenone and classified by the World Health Organisation as a moderately hazardous or Class II pesticide. The extracts of Tephrosia leaves can be used for the control of pests in the field, in storage or on domestic animals. Unlike most synthetic pesticides, it leaves no residues on crops because rotenone breaks down within 3-5 days after application.

Biological control

The first natural line of defence for the fall armyworm is biological control. This is because they have a lot of exotic predators that include wasps, flies, beetles, birds and rodents.

Parasites and pathogenic fungi, bacteria or viruses that would kill or weaken the pest and seed treatment with beneficial soil microbes, which increase the ability of plants to fight off pests, are other measures against the worms that also help plants to adapt to other climate change stressors, including drought.


These are non-chemical, biological pesticides that can also be effective in the eradication of the fall armyworm. These are pesticides derived from natural diseases of insects, such as viruses, fungi and bacteria.

Mr Mathews Matimelo, the principal agriculture research officer in Zambia, who has done extensive research on the impact of the fall armyworm in southern Africa, says botanical control measures are vital. According to Mr Matimelo, laboratory tests have indicated that plants like ‘neem’ are effective in controlling the worm. Use of bio-pesticides is another option

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