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Horticulture under the fall army worm invasion

“Coragen, Avaunt, Fastac and Vantex range from A-D in that order, and any used interchangeably with the other will prevent resistance to the fall army worm.” – Nelson Maina, Elgon Kenya


Although the fall army worm invasion intervention has focused more on the cereals sector notably maize, the country’s staple crop, the horticulture industry has been put on the alert of crops listed as highly susceptible to the pest.“Other susceptible crops include kales, cabbages, legumes, bananas, tomatoes, capsicums, ginger, spinach, amaranths, onions, sugar beet, citrus, cucumber and sunflower”, an statement from the Ministry of Agriculture, Livestock & Fisheries indicates.

Since these crops are at the center of food security being among the most consumed vegetables, the government says, the country is ostensibly staring at a major food security crisis in the face of an invasion by the devastating fall army worms that are devouring maize crops in 13 counties and spreading. The Ministry has sounded the alarm and advised farmers to take immediate action to combat the pest that has capacity to cause up to 100 per cent crop destruction.

Said the Ministry in an alert, “The pest causes massive losses in maize and attacks other cereals crops like sorghum, rice, millet, wheat, barley. Pastures grases like Bermuda, hay and nappier grasses are not spared while other susceptible crops include kales, cabbages, legumes, bananas, tomatoes, capsicums, ginger, spinach, amaranthus, onions, sugar beet, citrus, cucumber and sunflower”.

The invasion complicates a situation already compounded by a prolonged drought as the weatherman warns the long awaited long rains will not be enough. By mid-April the rains were yet to fall as expected. The drought and the army worm are a double tragedy to our food security that’s also taking a knock from skyrocketing prices of basic commodities like Unga and suga, said leading agriculture chemicals distributor Elgon Kenya head of communications Nelson Maina.

The Ministry’s Crops Division has notified all county directors of agriculture on the presence of the worm in the South Rift counties namely;- Baringo, Trans Nzoia, Bungoma, Kakamega, Narok, Uasin Gishu, Nandi, Kericho, Baringo, Nakuru, Busia and Siaya, through Crops Director, Johnson Irungu. The pest is said to be spreading fast across other counties requiring rapid response to keep it at bay.

The Ministry has consequently recommended a list of nine insecticides for the management of the fall army worms. These include;- Vantex, Belt, Coragen, Avaunt, Orthene, Marshall, Fastac, Voliam Targo and Match.

Elgon Kenya says it distributes four of these products – Coragen and Avaunt from Du Pont, Fastac from BASF and Vantex from…..In that order, the products range from A-D and any used interchangeably with the other will prevent resistance, added Mr Maina.

“At Elgon Kenya, we have partnered with multinational agriculture science companies to avail original molecules in the country which makes the nation ready to combat pest invasions like the fall army worm”, he said in an interview with HortiNews.

He added the regiment of products should be used interchangeably to avoid resistance to the fall army worm. Coragen, Avaunt, Fastac and Vantex range from A-D in that order, and any used interchangeably with the other will prevent resistance.

Elgon Kenya has a countrywide stockists network from where the agrochemicals can be purchased, while farmers can also buy online and make inquiries through the company’s information centre. “Through our online shop Hyperlink hppp:// www.ElgonKenya.co.ke farmers can buy and we will deliver to their doorstop through courier. Through our online farm clinic farmers can ask any question and our agronomists will respond immediately and give guidelines on management of the army worm. They can also visit our Information Centre at our offices for assistance”, he said.

The worm

It is a migratory pest which undergoes a full egg-larva-pupa-adult metamorphis. The female lays tiny eggs in masses of 150-200 which are covered in a protein sheath to protect them from attack by natural enemies and pesticides. The larvae is the most destructive phase, feeding on soft plant tissues. Adult moths are most active at night and mates in the evening.

The caterpillars are green, brown or black in colour depending on development stage. A mature caterpillar has a distinct white line between the eyes, which form an inverted ‘Y’ pattern on the face (This is seen when the worm is placed facing you. In addition, they are pronounced four black spots aligned in a square on the top of the eight segment near the black end of the caterpillar.

Farmers are encouraged to use a combination of practices as management options;-

-For early warning and detection of low numbers, farmers should mount at least one pheromone trap per hectare
-Scouting for signs and symptoms should start one week after crop germination
-Deep ploughing exposes the pupae to predators and solar heat
-Planting varieties with hard husk cover provides a physical barrier
-Use hands to squash the caterpillars when infestation is in smack farm plots. In addition, collect and drop caterpillars in hot water to drown them (killing one caterpillar prevents multiplication of more than 1,500 new caterpillars after a period of less than 4 weeks.
-Plant early and adhere to regional planting calendar avoid late off-season planting
-Avoid planting new crop near infested plants
-Use recommended fertilizers and keep fields weed-free to boost plant vigor
-Set up fall army worm pheromone traps per Ha to catch adult male moth, prevent mating and ultimately suppress population build-up
-For effective control (Maize), spray at least three times starting at two weeks after emergence, knee high and just before tussling. Spraying should be done late in the evening when caterpillars are most active.


The adult moth has capacity to fly over 30km in one night drifting through air current. The female lays 1500 -2000 eggs in her lifetime, enabling the pest to quickly establish in new areas, Movement of infested plant materials aid transferring the different stages within the same farm or to distant locations. In Kenya, movement of green maize across locations poses the biggest threat in spreading the pest.

Dr Irungu said in a letter to the affected counties the fall army worm was first reported in September 2016 in West Africa and as spread as far as South Africa where reports indicated it has destroyed more than 100,000 hectares of maize in three African countries.

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